Author: "Oliver Pfuhl" - Searchworks@Jio Institute Digital Library Search Results

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84 results on '"Oliver Pfuhl"'

1. Infrared detectors for first generation extremely large telescope instruments and their characterization program

Author: Naidu Bezawada, Elizabeth George, Derek Ives, Domingo Alvarez, Benoit Serra, Leander Mehrgan, Eric Müller, Marcus Haug, Serban Leveratto, Oliver Pfuhl, Ronald Guzman, Ivan Guidolin, Andreas Jost, Dan Popovic, Christophe Moins, Barbara Klein, Ralf Conzelmann, Matteo Accardo, and Martin Brinkmann
Subjects: Space and Planetary Science, Astronomy and Astrophysics
Published: 2023
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2. The young stars in the Galactic center

Author: Sebastiano D. von Fellenberg, Stefan Gillessen, Julia Stadler, Michi Bauböck, Reinhard Genzel, Tim de Zeeuw, Oliver Pfuhl, Pau Amaro Seoane, Antonia Drescher, Frank Eisenhauer, Maryam Habibi, Thomas Ott, Felix Widmann, and Alice Young
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - astrophysics of galaxies, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - high energy astrophysical phenomena, Astrophysics - solar and stellar astrophysics, Galactic center, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract: We present a large ${\sim 30" \times 30"}$ spectroscopic survey of the Galactic Center using the SINFONI IFU at the VLT. Combining observations of the last two decades we compile spectra of over $2800$ stars. Using the Bracket-$\gamma$ absorption lines we identify $195$ young stars, extending the list of known young stars by $79$. In order to explore the angular momentum distribution of the young stars, we introduce an isotropic cluster prior. This prior reproduces an isotropic cluster in a mathematically exact way, which we test through numerical simulations. We calculate the posterior angular momentum space as function of projected separation from Sgr~A*. We find that the observed young star distribution is substantially different from an isotropic cluster. We identify the previously reported feature of the clockwise disk and find that its angular momentum changes as function of separation from the black hole, and thus confirm a warp of the clockwise disk ($p \sim 99.2\%$). At large separations, we discover three prominent overdensities of angular momentum. One overdensity has been reported previously, the counter-clockwise disk. The other two are new. Determining the likely members of these structures, we find that as many as $75\%$ of stars can be associated with one of these features. Stars belonging to the warped clockwise-disk show a top heavy K-band luminosity function, while stars belonging to the larger separation features do not. Our observations are in good agreement with the predictions of simulations of in-situ star formation, and argue for common formation of these structures., Comment: Accepted for Publication in APJL
Published: 2022

3. A geometric distance to the supermassive black Hole of NGC 3783

Author: N. M. Förster Schreiber, M. L. Bolzer, Pierre-Olivier Petrucci, E. Sturm, Jason Dexter, Thibaut Paumard, Florentin Millour, Christopher A. Onken, Christian Straubmeier, Sebastian F. Hönig, Daniel Rouan, Makoto Kishimoto, Reinhard Genzel, Yann Clénet, P. T. de Zeeuw, Julien Woillez, Ric Davies, D. Kaltenbrunner, António Amorim, A. Drescher, Jinyi Shangguan, S. von Fellenberg, D. Gratadour, Misty C. Bentz, Linda J. Tacconi, J. Stadler, Karine Perraut, Felix Widmann, P. Vermot, Amiel Sternberg, Thomas Ott, Paulo J. V. Garcia, Rachel Street, Wolfgang Brandner, Odele Straub, Dieter Lutz, Hagai Netzer, Mercedes Prieto, Taro Shimizu, Stefan Gillessen, Konrad R. W. Tristram, Oliver Pfuhl, M. Bauböck, Frank Eisenhauer, Andreas Eckart, Guy Perrin, Sylvestre Lacour, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and GRAVITY
Subjects: Length scale, Gravity (chemistry), Cosmology and Nongalactic Astrophysics (astro-ph.CO), Galaxies: Seyfert, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, symbols.namesake, Angular diameter, 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Galaxies: nuclei, Physics, Supermassive black hole, Distance scale, Quasars: individual: NGC 3783, Astronomy and Astrophysics, Galaxies: active, Light curve, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), symbols, Reverberation mapping, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Hubble's law, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The angular size of the broad line region (BLR) of the nearby active galactic nucleus (AGN) NGC 3783 has been spatially resolved by recent observations with VLTI/GRAVITY. A reverberation mapping (RM) campaign has also recently obtained high quality light curves and measured the linear size of the BLR in a way that is complementary to the GRAVITY measurement. The size and kinematics of the BLR can be better constrained by a joint analysis that combines both GRAVITY and RM data. This, in turn, allows us to obtain the mass of the supermassive black hole in NGC3783 with an accuracy that is about a factor of two better than that inferred from GRAVITY data alone. We derive $M_\mathrm{BH}=2.54_{-0.72}^{+0.90}\times 10^7\,M_\odot$. Finally, and perhaps most notably, we are able to measure a geometric distance to NGC 3783 of $39.9^{+14.5}_{-11.9}$ Mpc. We are able to test the robustness of the BLR-based geometric distance with measurements based on the Tully-Fisher relation and other indirect methods. We find the geometric distance is consistent with other methods within their scatter. We explore the potential of BLR-based geometric distances to directly constrain the Hubble constant, $H_0$, and identify differential phase uncertainties as the current dominant limitation to the $H_0$ measurement precision for individual sources., 9 pages and 5 figures in main text, Accepted for publication in A&A
Published: 2021
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4. Constraining particle acceleration in Sgr A⋆ with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations

Author: Wolfgang Brandner, A. Jiménez-Rosales, Mark Gurwell, Stefan Hippler, Christian Straubmeier, Th. Henning, Fiona A. Harrison, Jason Dexter, N. M. Förster Schreiber, F. Vincent, Pierre Kervella, Daryl Haggard, S. Yazici, Silvia Scheithauer, Oliver Pfuhl, Y. Dallilar, T. Taro Shimizu, Idel Waisberg, Odele Straub, K. Foster, Felix Widmann, Sera Markoff, Dieter Lutz, J.-B. Le Bouquin, M. Bauböck, Matthew Horrobin, Yann Clénet, P. T. de Zeeuw, Gabriele Ghisellini, Howard A. Smith, Frederick K. Baganoff, Daniel Stern, Thibaut Paumard, Eckhard Sturm, Ric Davies, M. Nowak, Andreas Eckart, Andreas Kaufer, Sebastian Rabien, Laurent Jocou, Paulo J. V. Garcia, Ekkehard Wieprecht, Reinhard Genzel, Jinyi Shangguan, G. Rodríguez-Coira, Patrick Lowrance, C. J. Hailey, Thomas Ott, S. Zhang, A. Drescher, G. Ponti, Giovanni G. Fazio, Steven P. Willner, S. D. von Fellenberg, Linda J. Tacconi, Maryam Habibi, H. Bonnet, Julien Woillez, V. Lapeyrère, Sylvestre Lacour, António Amorim, Erich Wiezorrek, Xavier Haubois, Guy Perrin, J. Neilsen, K. Mori, Eric Gendron, Frank Eisenhauer, G. Heißel, Pierre Léna, Joseph L. Hora, Karine Perraut, Charles F. Gammie, Feng Gao, G. Witzel, Gérard Zins, Mark Morris, André Young, Julia Stadler, Jean-Phillipe Berger, Hope Boyce, Stefan Gillessen, Lieselotte Jochum, Roberto Abuter, High Energy Astrophys. & Astropart. Phys (API, FNWI), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Accretion, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Electron, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - high energy astrophysical phenomena, law.invention, Luminosity, symbols.namesake, law, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), Galaxy: center, 010308 nuclear & particles physics, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astronomy and Astrophysics, Black hole physics, Synchrotron, ddc, Particle acceleration, Lorentz factor, 13. Climate action, Space and Planetary Science, Accretion disks, symbols, Spectral energy distribution, Flare
Abstract: We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare of Sgr A*. We obtained light curves in the $M$-, $K$-, and $H$-bands in the mid- and near-infrared and in the $2-8~\mathrm{keV}$ and $2-70~\mathrm{keV}$ bands in the X-ray. The observed spectral slope in the near-infrared band is $\nu L_\nu\propto \nu^{0.5\pm0.2}$; the spectral slope observed in the X-ray band is $\nu L_\nu \propto \nu^{-0.7\pm0.5}$. We tested synchrotron and synchrotron self-Compton (SSC) scenarios. The observed near-infrared brightness and X-ray faintness, together with the observed spectral slopes, pose challenges for all models explored. We rule out a scenario in which the near-infrared emission is synchrotron emission and the X-ray emission is SSC. A one-zone model in which both the near-infrared and X-ray luminosity are produced by SSC and a model in which the luminosity stems from a cooled synchrotron spectrum can explain the flare. In order to describe the mean SED, both models require specific values of the maximum Lorentz factor $\gamma_{max}$, which however differ by roughly two orders of magnitude: the SSC model suggests that electrons are accelerated to $\gamma_{max}\sim 500$, while cooled synchrotron model requires acceleration up to $\gamma_{max}\sim5\times 10^{4}$. The SSC scenario requires electron densities of $10^{10}~\mathrm{cm^{-3}}$ much larger than typical ambient densities in the accretion flow, and thus require in an extraordinary accretion event. In contrast, assuming a source size of $1R_s$, the cooled synchrotron scenario can be realized with densities and magnetic fields comparable with the ambient accretion flow. For both models, the temporal evolution is regulated through the maximum acceleration factor $\gamma_{max}$, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare., Comment: accepted for publication in Astronomy & Astrophysics; preview abstract shortened due to arXiv requirements
Published: 2021
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5. Detection of faint stars near Sagittarius A* with GRAVITY

Author: Christian Straubmeier, Stefan Hippler, Th. Henning, Feng Gao, Gérard Zins, Maryam Habibi, Linda J. Tacconi, Oliver Pfuhl, V. Lapeyrère, Xavier Haubois, Guy Perrin, A. Jiménez-Rosales, Felix Widmann, G. Heißel, António Amorim, Stefan Gillessen, Yann Clénet, P. T. de Zeeuw, H. Bonnet, Jason Dexter, Paulo J. V. Garcia, Julien Woillez, Ric Davies, Lieselotte Jochum, Eric Gendron, G. Rodríguez-Coira, Eckhard Sturm, Laurent Jocou, Jinyi Shangguan, S. Yazici, T. Taro Shimizu, Thibaut Paumard, M. Nowak, M. Bauböck, Karine Perraut, Reinhard Genzel, N. M. Förster Schreiber, Wolfgang Brandner, Matthew Horrobin, Julia Stadler, Thomas Ott, Idel Waisberg, A. Drescher, S. von Fellenberg, Sebastian Rabien, Ekkehard Wieprecht, F. Vincent, Pierre Kervella, Jean-Philippe Berger, Odele Straub, Dieter Lutz, J.-B. Le Bouquin, Sylvestre Lacour, Silvia Scheithauer, Y. Dallilar, Andreas Kaufer, Frank Eisenhauer, Pierre Léna, Erich Wiezorrek, Roberto Abuter, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and GRAVITY
Subjects: Astrophysics - instrumentation and methods for astrophysics, Stars: imaging, Proper motion, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics - astrophysics of galaxies, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Supermassive black hole, Galaxy: center, 010308 nuclear & particles physics, Galactic Center, Astronomy and Astrophysics, Infrared: stars, Stars, Sagittarius A, 13. Climate action, Space and Planetary Science, Magnitude (astronomy), Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Radio astronomy, Gravitational redshift
Abstract: International audience; The spin of the supermassive black hole that resides at the Galactic Center can, in principle, be measured by accurate measurements of the orbits of stars that are much closer to Sgr A* than S2, the orbit of which recently provided the measurement of the gravitational redshift and the Schwarzschild precession. The GRAVITY near-infrared interferometric instrument combining the four 8m telescopes of the VLT provides a spatial resolution of 2–4 mas, breaking the confusion barrier for adaptive-optics-assisted imaging with a single 8–10m telescope. We used GRAVITY to observe Sgr A* over a period of six months in 2019 and employed interferometric reconstruction methods developed in radio astronomy to search for faint objects near Sgr A*. This revealed a slowly moving star of magnitude 18.9 in the K-band within 30 mas of Sgr A*. The position and proper motion of the star are consistent with the previously known star S62, which is at a substantially greater physical distance, but in projection passes close to Sgr A*. Observations in August and September 2019 detected S29 easily, with K-magnitude of 16.6, at approximately 130 mas from Sgr A*. The planned upgrades of GRAVITY, and further improvements in the calibration, offer greater chances of finding stars fainter than K-magnitude of 19.Key words: Galaxy: center / stars: imaging / infrared: stars⋆ GRAVITY was developed as part of a collaboration by the Max Planck Institute for extraterrestrial Physics, LESIA of the Observatoire de Paris/Université PSL/CNRS/Sorbonne Université/Université de Paris and IPAG of Université Grenoble Alpes/CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the CENTRA – Centro de Astrofisica e Gravitação, and the European Southern Observatory.⋆⋆ Corresponding authors: F. Gao, e-mail: fgao@mpe.mpg.de; T. Paumard, e-mail: thibaut.paumard@obspm.fr
Published: 2021
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6. Improved GRAVITY astrometric accuracy from modeling of optical aberrations

Author: Stefan Hippler, Maryam Habibi, S. Yazici, Paulo J. V. Garcia, T. Taro Shimizu, Roberto Abuter, F. Vincent, Linda J. Tacconi, M. Bauböck, Pierre Kervella, Guy Perrin, Idel Waisberg, G. Heißel, Karine Perraut, Eckhard Sturm, Laurent Jocou, Lieselotte Jochum, Sebastian Rabien, Julien Woillez, A. Jiménez-Rosales, Gérard Zins, M. Nowak, Odele Straub, Dieter Lutz, J.-B. Le Bouquin, Ekkehard Wieprecht, Julia Stadler, Reinhard Genzel, Wolfgang Brandner, Feng Gao, Thomas Ott, A. Drescher, N. M. Förster Schreiber, S. von Fellenberg, Christian Straubmeier, Silvia Scheithauer, Ric Davies, Y. Dallilar, Th. Henning, H. Bonnet, Jinyi Shangguan, Eric Gendron, Andreas Eckart, Yann Clénet, P. T. de Zeeuw, Thibaut Paumard, Jason Dexter, Andreas Kaufer, Felix Widmann, Frank Eisenhauer, Pierre Léna, V. Lapeyrère, Xavier Haubois, Erich Wiezorrek, Matthew Horrobin, Sylvestre Lacour, António Amorim, Jean-Philippe Berger, G. Rodríguez-Coira, Oliver Pfuhl, Stefan Gillessen, André Young, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Astrophysics - instrumentation and methods for astrophysics, Field (physics), Astrophysics - astrophysics of galaxies, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, 010309 optics, Telescope, law, Methods: data analysis, 0103 physical sciences, Binary star, Calibration, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Physics, Galaxy: center, Galactic Center, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrometry, Galaxy: fundamental parameters, Interferometry, Space and Planetary Science, Instrumentation: interferometers, Astrophysics of Galaxies (astro-ph.GA), Instrumentation: high angular resolution, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: The GRAVITY instrument on the ESO VLTI pioneers the field of high-precision near-infrared interferometry by providing astrometry at the 10−100 μas level. Measurements at this high precision crucially depend on the control of systematic effects. We investigate how aberrations introduced by small optical imperfections along the path from the telescope to the detector affect the astrometry. We develop an analytical model that describes the effect of these aberrations on the measurement of complex visibilities. Our formalism accounts for pupil-plane and focal-plane aberrations, as well as for the interplay between static and turbulent aberrations, and it successfully reproduces calibration measurements of a binary star. The Galactic Center observations with GRAVITY in 2017 and 2018, when both Sgr A* and the star S2 were targeted in a single fiber pointing, are affected by these aberrations at a level lower than 0.5 mas. Removal of these effects brings the measurement in harmony with the dual-beam observations of 2019 and 2020, which are not affected by these aberrations. This also resolves the small systematic discrepancies between the derived distance R0 to the Galactic Center that were reported previously.
Published: 2021
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7. Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole

Author: Wolfgang Brandner, Thomas Ott, S. von Fellenberg, Thibaut Paumard, Jason Dexter, S. Yazici, V. Lapeyrère, Reinhard Genzel, Andreas Eckart, Xavier Haubois, Gérard Zins, Karine Perraut, Odele Straub, Stefan Hippler, Christian Straubmeier, Jean-Philippe Berger, António Amorim, M. Bauböck, J.-B. Le Bouquin, Th. Henning, Yann Clénet, P. T. de Zeeuw, Idel Waisberg, Eckhard Sturm, Sylvestre Lacour, Laurent Jocou, H. Bonnet, Jinyi Shangguan, Linda J. Tacconi, Silvia Scheithauer, Eric Gendron, Guy Perrin, M. Nowak, Maryam Habibi, Ekkehard Wieprecht, Felix Widmann, Andreas Kaufer, Julien Woillez, Matthew Horrobin, N. M. Förster Schreiber, Erich Wiezorrek, Frank Eisenhauer, Pierre Léna, Paulo J. V. Garcia, A. Jiménez-Rosales, G. Rodríguez-Coira, F. Vincent, Pierre Kervella, Oliver Pfuhl, Feng Gao, Vitor Cardoso, Lieselotte Jochum, Julia Stadler, Stefan Gillessen, Roberto Abuter, Observatoire de Paris, Université Paris sciences et lettres (PSL), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), GRAVITY, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Astrophysics and Astronomy, gr-qc, astro-ph.GA, black hole physics, Highly elliptical orbit, FOS: Physical sciences, Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, General Relativity and Quantum Cosmology, symbols.namesake, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, relativistic processes, Physics, Galaxy: nucleus, 010308 nuclear & particles physics, General Relativity and Cosmology, Astronomy and Astrophysics, Orbital period, Astrophysics - Astrophysics of Galaxies, Black hole, Radial velocity, Orbit, Space and Planetary Science, gravitation, [SDU]Sciences of the Universe [physics], Kepler orbit, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Precession, symbols, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Schwarzschild radius, astro-ph.IM
Abstract: The star S2 orbiting the compact radio source Sgr A* is a precision probe of the gravitational field around the closest massive black hole (candidate). Over the last 2.7 decades we have monitored the star's radial velocity and motion on the sky, mainly with the SINFONI and NACO adaptive optics (AO) instruments on the ESO VLT, and since 2017, with the four-telescope interferometric beam combiner instrument GRAVITY. In this paper we report the first detection of the General Relativity (GR) Schwarzschild Precession (SP) in S2's orbit. Owing to its highly elliptical orbit (e = 0.88), S2's SP is mainly a kink between the pre-and post-pericentre directions of motion ~ +- 1 year around pericentre passage, relative to the corresponding Kepler orbit. The superb 2017-2019 astrometry of GRAVITY defines the pericentre passage and outgoing direction. The incoming direction is anchored by 118 NACO-AO measurements of S2's position in the infrared reference frame, with an additional 75 direct measurements of the S2-Sgr A* separation during bright states ('flares') of Sgr A*. Our 14-parameter model fits for the distance, central mass, the position and motion of the reference frame of the AO astrometry relative to the mass, the six parameters of the orbit, as well as a dimensionless parameter f_SP for the SP (f_SP = 0 for Newton and 1 for GR). From data up to the end of 2019 we robustly detect the SP of S2, del phi = 12' per orbital period. From posterior fitting and MCMC Bayesian analysis with different weighting schemes and bootstrapping we find f_SP = 1.10 +- 0.19. The S2 data are fully consistent with GR. Any extended mass inside S2's orbit cannot exceed ~ 0.1% of the central mass. Any compact third mass inside the central arcsecond must be less than about 1000 M_sun., accepted to A&A
Published: 2020
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8. 3D AMR hydrosimulations of a compact-source scenario for the Galactic Centre cloud G2

Author: Elizabeth George, Maryam Habibi, Stefan Gillessen, R. Genzel, P. M. Plewa, A. Ballone, Andreas Burkert, T. Ott, Marc Schartmann, Frank Eisenhauer, and Oliver Pfuhl
Subjects: Physics, 010308 nuclear & particles physics, Adaptive mesh refinement, business.industry, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Cloud computing, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Accretion (astrophysics), T Tauri star, Compact space, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Outflow, Astrophysics::Earth and Planetary Astrophysics, business, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: The nature of the gaseous and dusty cloud G2 in the Galactic Centre is still under debate. We present three-dimensional hydrodynamical adaptive mesh refinement (AMR) simulations of G2, modeled as an outflow from a "compact source" moving on the observed orbit. The construction of mock position-velocity (PV) diagrams enables a direct comparison with observations and allow us to conclude that the observational properties of the gaseous component of G2 could be matched by a massive ($\dot{M}_\mathrm{w}=5\times 10^{-7} \;M_{\odot} \mathrm{yr^{-1}}$) and slow ($50 \;\mathrm{km \;s^{-1}}$) outflow, as observed for T Tauri stars. In order for this to be true, only the material at larger ($>100 \;\mathrm{AU}$) distances from the source must be actually emitting, otherwise G2 would appear too compact compared to the observed PV diagrams. On the other hand, the presence of a central dusty source might be able to explain the compactness of G2's dust component. In the present scenario, 5-10 years after pericentre the compact source should decouple from the previously ejected material, due to the hydrodynamic interaction of the latter with the surrounding hot and dense atmosphere. In this case, a new outflow should form, ahead of the previous one, which would be the smoking gun evidence for an outflow scenario., resubmitted to MNRAS after referee report, 16 pages, 11 figures
Published: 2018
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9. Probing the gas density in our Galactic Centre: moving mesh simulations of G2

Author: Stefan Gillessen, Elad Steinberg, Maryam Habibi, Frank Eisenhauer, Jason Dexter, Oliver Pfuhl, Alejandra Rosales, P. M. Plewa, Orly Gnat, Re'em Sari, Reinhard Genzel, M. Bauböck, Idel Waisberg, Thomas Ott, and Sebastiano von Fellenberg
Subjects: Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, FOS: Physical sciences, High resolution, Astronomy and Astrophysics, Astrophysics, Radiation, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Accretion (astrophysics), Redshift, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Ionization, 0103 physical sciences, Size ratio, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Spherical shape
Abstract: The G2 object has recently passed its pericenter passage in our Galactic Center. While the $Br_\gamma$ emission shows clear signs of tidal interaction, the change in the observed luminosity is only of about a factor of 2, in contention with all previous predictions. We present high resolution simulations performed with the moving mesh code, RICH, together with simple analytical arguments that reproduce the observed $Br_\gamma$ emission. In our model, G2 is a gas cloud that undergoes tidal disruption in a dilute ambient medium. We find that during pericenter passage, the efficient cooling of the cloud results in a vertical collapse, compressing the cloud by a factor of $\sim5000$. By properly taking into account the ionization state of the gas, we find that the cloud is UV starved and are able to reproduce the observed $Br_\gamma$ luminosity. For densities larger than $\approx500\;\mathrm{cm}^{-3}$ at pericenter, the cloud fragments, due to cooling instabilities and the emitted radiation is inconsistent with observations. For lower densities, the cloud survives the pericenter passage intact and its emitted radiation matches the observed lightcurve. From the duration of $Br_\gamma$ emission which contains both redshifted and blueshifted components, we show that the cloud is not spherical but rather elongated with a size ratio of 4 at year 2001. The simulated cloud's elongation grows as it travels towards pericenter and is consistent with observations, due to viewing angles. The simulation is also consistent with having a spherical shape at apocenter.
Published: 2017
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10. Peering into the formation history of β Pictoris b with VLTI/GRAVITY long-baseline interferometry

Author: Gérard Rousset, N. M. Förster Schreiber, E. F. van Dishoeck, Laurent Pueyo, Frank Eisenhauer, Pierre Léna, H. Bonnet, Jingxiu Wang, Eric Gendron, Stefan Gillessen, Anne-Lise Maire, Yann Clénet, P. T. de Zeeuw, Hervé Beust, Jinyi Shangguan, S. Yazici, Julien Woillez, Thibaut Paumard, Claudia Paladini, C. Collin, M. Nowak, Sylvestre Lacour, Thomas Ott, D. Ziegler, F. Chapron, António Amorim, Erich Wiezorrek, Oliver Pfuhl, Feng Gao, A. Buron, P. Fédou, Z. Hubert, R. Garcia Lopez, Reinhard Genzel, Wolfgang Brandner, Odele Straub, J.-B. Le Bouquin, Ekkehard Wieprecht, Jean-Phillipe Berger, Stefan Hippler, Benjamin Charnay, Eckhard Sturm, F. Vincent, Pierre Kervella, Faustine Cantalloube, Laurent Jocou, G. Rodríguez-Coira, Sebastian Rabien, Roberto Abuter, Anne-Marie Lagrange, Mickael Bonnefoy, C. Rau, Linda J. Tacconi, Guy Perrin, Andreas Eckart, Silvia Scheithauer, Felix Widmann, Karine Perraut, V. Lapeyrère, P. Mollière, Gilles Duvert, Christian Straubmeier, F. Haußmann, Th. Henning, Jason Dexter, V. Coudé du Foresto, R. Dembet, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: Planetesimal, 010504 meteorology & atmospheric sciences, planets and satellites, formation -planets and satellites, atmospheres -techniques, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, β Pictoris, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, individual, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Orbital elements, Physics, [PHYS]Physics [physics], Earth and Planetary Astrophysics (astro-ph.EP), Very Large Telescope, Giant planet, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astrometry, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics::Earth and Planetary Astrophysics, interferometricstars, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Planetary mass, Astrophysics - Earth and Planetary Astrophysics
Abstract: Our objective is to estimate the C/O ratio in the atmosphere of beta Pictoris b and obtain an estimate of the dynamical mass of the planet, as well as to refine its orbital parameters using high-precision astrometry. We used the GRAVITY instrument with the four 8.2 m telescopes of the Very Large Telescope Interferometer to obtain K-band spectro-interferometric data on $\beta$ Pic b. We extracted a medium resolution (R=500) K-band spectrum of the planet and a high-precision astrometric position. We estimated the planetary C/O ratio using two different approaches (forward modeling and free retrieval) from two different codes (ExoREM and petitRADTRANS, respectively). Finally, we used a simplified model of two formation scenarios (gravitational collapse and core-accretion) to determine which can best explain the measured C/O ratio. Our new astrometry disfavors a circular orbit for $\beta$ Pic b ($e=0.15^{+0.05}_{-0.04}$). Combined with previous results and with Hipparcos/GAIA measurements, this astrometry points to a planet mass of $M = 12.7\pm{}2.2\,M_\mathrm{Jup}$. This value is compatible with the mass derived with the free-retrieval code petitRADTRANS using spectral data only. The forward modeling and free-retrieval approches yield very similar results regarding the atmosphere of beta Pic b. In particular, the C/O ratios derived with the two codes are identical ($0.43\pm{}0.05$ vs $0.43^{+0.04}_{-0.03}$). We argue that if the stellar C/O in $\beta$ Pic is Solar, then this combination of a very high mass and a low C/O ratio for the planet suggests a formation through core-accretion, with strong planetesimal enrichment., Comment: 14 pages + 7 page appendix, 7 figures, accepted for pulication
Published: 2020
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11. The GRAVITY Young Stellar Object survey I. Probing the disks of Herbig Ae/Be stars in terrestrial orbits

Author: S. Yazici, Oliver Pfuhl, Thomas Henning, J. Bouvier, Stefan Hippler, V. Coudé du Foresto, Thomas Ott, J. Sanchez-Bermudez, Lucas Labadie, E. F. van Dishoeck, Myriam Benisty, Sebastian Rabien, Stefan Gillessen, Frank Eisenhauer, Frederic H. Vincent, A. Caratti o Garatti, Karine Perraut, Chien-Cheng Lin, Laurent Jocou, Andreas Eckart, Jaime E. Pineda, Matthew Horrobin, Christian Straubmeier, Roberto Abuter, Idel Waisberg, Feng Gao, L. Klarmann, Catherine Dougados, Imke Wank, Antoine Mérand, C. Rau, Gérard Rousset, Felix Widmann, Sarah Kendrew, Guy Perrin, A. Buron, P. T. de Zeeuw, Thomas P. Ray, R. Grellmann, Wolfgang Brandner, António Amorim, Bernard Lazareff, Dominique Segura-Cox, Paulo Gordo, Erich Wiezorrek, Henri Bonnet, F. Eupen, Eric Gendron, F. Haussmann, M. Koutoulaki, Yann Clénet, Silvia Scheithauer, Xavier Haubois, Paola Caselli, M. Wiest, Paulo J. V. Garcia, Gilles Duvert, Reinhard Genzel, Julien Woillez, Thibaut Paumard, E. Sturm, Jason Dexter, Jean-Philippe Berger, Z. Hubert, Sylvestre Lacour, Odele Straub, J.-B. Le Bouquin, Pierre Léna, R. Garcia-Lopez, Ekkehard Wieprecht, Pierre Kervella, Faustine Cantalloube, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)
Subjects: stars, Young stellar object, Population, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Thermal, Astrophysics::Solar and Stellar Astrophysics, high angular resolutiontechniques, education, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Earth and Planetary Astrophysics (astro-ph.EP), education.field_of_study, Very Large Telescope, 010308 nuclear & particles physics, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), formation -circumstellar matter -infrared, interferometric, Closure phase, Terrestrial planet, Astrophysics::Earth and Planetary Astrophysics, ISM -techniques, Astrophysics - Earth and Planetary Astrophysics
Abstract: The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. The processes of disk evolution and planet formation are intrinsically linked. We spatially resolve with GRAVITY/VLTI in the K-band the sub au-scale region of 27 stars to gain statistical understanding of their properties. We look for correlations with stellar parameters, such as luminosity, mass, temperature and age. Our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data. Our best models correspond to smooth and wide rings, implying that wedge-shaped rims at the dust sublimation edge are favored, as found in the H-band. The closure phases are generally non-null with a median value of ~10 deg, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20-25 deg but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to ~1e4 Lsun and confirm the significant spread around the mean relation observed in the H-band. Gapped sources exhibit a large N-to-K band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the 2 Ms mass range, we observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the N-to-K size ratio. However, the size of the current sample does not yet permit us to invoke a clear universal evolution mechanism across the HAeBe mass range. The measured locations of the K-band emission suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation., Comment: Accepted for publication in A&A; 23 pages, 16 figures, 7 tables
Published: 2019
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12. NAOMI: the adaptive optics system of the Auxiliary Telescopes of the VLTI

Author: E. Cottalorda, C. Heritier, F. Delplancke-Ströbele, S. Zúñiga-Fernández, S. Guieu, Javier Reyes, M. Seidel, Alexander Meister, Laurent Jocou, Johan Kosmalski, G. Santos Tomás, Oliver Pfuhl, Pierre Bourget, Marcos Suarez, Christophe Verinaud, J. L. Beuzit, Anthony Meilland, Philippe B. Gitton, Andreas Haimerl, J.-B. Le Bouquin, Eric Stadler, C. Frank, Christophe Dupuy, Lorenzo Pettazzi, Pascaline Darré, Xavier Haubois, Gérard Zins, Frédéric Gonté, Jaime Alonso, Bruno Lopez, R. Donaldson, Peter Krempl, H. Bonnet, Pavel Shchekaturov, Johann Kolb, Frank Eisenhauer, Pablo Gutierrez, Thibaut Guerlet, Paul Lilley, Julien Woillez, J. P. Berger, Gerhard Fischer, M. Todorovic, Sebastien Egner, A. Mérand, Thibaut Moulin, Luis Caniguante, Christian Stephan, J. P. Kirchbauer, Luigi Andolfato, Guillermo Valdes, N. Hubin, D. Phan, Eloy Fuenteseca, Stewart McLay, M. Riedel, Isabelle Percheron, A. Delboulbe, Jerome Paufique, W. Pirani, Christian Schmid, Christian Soenke, J. Dupeyron, Jose Abad, Andrew Rakich, M. Le Louarn, Pablo Barriga, Stefan Huber, P. Haguenauer, Paul Jolley, G. Bourdarot, E. Aller Carpentier, R. Brast, Nicolas Schuhler, B. Delabre, Reinhold J. Dorn, Roderick Dembet, Sylvain Rochat, Roberto Abuter, Yves Magnard, J. Quentin, Luca Pasquini, R. Ridings, European Southern Observatory (ESO), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre Spatial Universitaire de Grenoble ( CSUG), CRLCC Eugène Marquis (CRLCC), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Wavefront, Coupling, Very Large Telescope, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, Tracking (particle physics), 01 natural sciences, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010309 optics, Interferometry, Optics, Space and Planetary Science, 0103 physical sciences, Astronomical seeing, Astrophysics::Solar and Stellar Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, business, Adaptive optics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics
Abstract: The tip-tilt stabilisation system of the 1.8 m Auxiliary Telescopes of the Very Large Telescope Interferometer was never dimensioned for robust fringe tracking, except when atmospheric seeing conditions are excellent. Increasing the level of wavefront correction at the telescopes is expected to improve the coupling into the single-mode fibres of the instruments, and enable robust fringe tracking even in degraded conditions. We deployed a new adaptive optics module for interferometry (NAOMI) on the Auxiliary Telescopes. We present its design, performance, and effect on the observations that are carried out with the interferometric instruments., Comment: 10 pages, 18 figures, 2 tables, A&A forthcoming
Published: 2019
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13. The GRAVITY fringe tracker

Author: Christian Straubmeier, Oliver Pfuhl, Elodie Choquet, Wolfgang Brandner, Xavier Haubois, P. Fédou, Roderick Dembet, Sylvestre Lacour, Guy Perrin, Burkhard Wolff, Julien Woillez, Karine Perraut, A. Ramirez, António Amorim, Konrad R. W. Tristram, Ekkehard Wieprecht, Roberto Abuter, Frédéric Cassaing, T. Ott, Erich Wiezorrek, Frank Eisenhauer, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, University of Cambridge [UK] (CAM), European Southern Observatory (ESO), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), DOTA, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Universität zu Köln, Max-Planck-Institut für Astronomie (MPIA), SIM/IDL Faculdade de Ciências da Universidade de Lisboa (FCUL), University of Lisboa, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), DOTA, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Universität zu Köln = University of Cologne
Subjects: Time delay and integration, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Context (language use), Astrophysics, Tracking (particle physics), 01 natural sciences, Optics, Optical path, Control theory, 0103 physical sciences, instrumentation: interferometers, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, business.industry, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, techniques: high angular resolution, Astronomy and Astrophysics, Kalman filter, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Space and Planetary Science, Integrator, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, business
Abstract: The GRAVITY instrument has been commissioned on the VLTI during 2016 and is now available to the astronomical community. It is the first optical interferometer capable of observing sources as faint as magnitude 19 in K-band. This is possible thanks to the fringe tracker which compensates the differential piston based on measurements of a brighter off-axis astronomical reference source. The goal of this paper is to consign the main developments made in the context of the GRAVITY fringe tracker. This could serve as basis for future fringe tracking systems. The paper therefore covers all aspects of the fringe tracker, from hardware, to control software and on-sky observations. Special emphasis is placed on the interaction between the group delay controller and the phase delay controller. The group delay control loop is a simple but robust integrator. The phase delay controller is a state-space control loop based on an auto-regressive representation of the atmospheric and vibrational perturbations. A Kalman filter provides optimal determination of the state of the system. The fringe tracker shows good tracking performance on sources with coherent K magnitudes of 11 on the UTs and 9.5 on the ATs. It can track fringes with an SNR level of 1.5 per DIT, limited by photon and background noises. On the ATs, during good seeing conditions, the optical path delay residuals can be as low as 75 nm root mean square. On the UTs, the performance is limited to around 250 nm because of structural vibrations., Accepted in A&A. 18 pages
Published: 2019
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14. NU Ori: a hierarchical triple system with a strongly magnetic B-type star

Author: Paulo J. V. Garcia, Gregg A. Wade, Evelyne Alecian, Feng Gao, J.-B. Le Bouquin, Véronique Petit, Oleg Kochukhov, Sylvestre Lacour, R. Grellmann, M. Karl, Matt Shultz, Th. Rivinius, Chien-Cheng Lin, Oliver Pfuhl, Department of Physics and Astronomy [Uppsala], Uppsala University, Department of Physics and Astronomy, University of Delaware, University of Delaware [Newark], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Royal Military College of Canada (RMCC), Royal Military College of Canada, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Physikalisches Institut [Köln], Universität zu Köln, Max Planck Institute for Astrophysics [Heidelberg], Max Planck Institute, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Max-Planck-Institut, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Rotation period, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Spectral line, symbols.namesake, 0103 physical sciences, Orion Nebula, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Visual binary, Physics, Zeeman effect, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Orbital period, Radial velocity, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, symbols, Astrophysics::Earth and Planetary Astrophysics
Abstract: NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with 4 components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer (VLTI) dataset. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution we show that the Zeeman Stokes $V$ signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding $M_{\rm Aa} = 14.9 \pm 0.5 M_\odot$, $M_{\rm Ab} = 3.9 \pm 0.7 M_\odot$, and $M_{\rm C} = 7.8 \pm 0.7 M_\odot$. The rotational period obtained from longitudinal magnetic field $\langle B_z \rangle$ measurements is $P_{\rm rot} = 1.09468(7)$ d, consistent with previous results. Modeling of $\langle B_z \rangle$ indicates a surface dipole magnetic field strength of $\sim 8$ kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric H$\alpha$ emission, and we find marginal evidence of emission at the expected level ($\sim$1% of the continuum)., Comment: 17 pages, 14 figures, 7 tables, accepted for publication in MNRAS
Published: 2019
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15. A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty

Author: Idel Waisberg, Thibaut Paumard, Julien Woillez, Jason Dexter, Oliver Pfuhl, Stefan Gillessen, Thomas Henning, Senol Yazici, Matthew Horrobin, Stefan Hippler, Christian Straubmeier, Karine Perraut, Odele Straub, J.-B. Le Bouquin, Sebastian Rabien, Amiel Sternberg, F. Vincent, António Amorim, Laurent Jocou, Vincent Lapeyrere, Reinhard Genzel, V. Coudé du Foresto, Feng Gao, Xavier Haubois, Gilles Duvert, Ekkehard Wieprecht, Jean-Philippe Berger, Paulo J. V. Garcia, Maryam Habibi, Thomas Ott, A. Jiménez-Rosales, Ortwin Gerhard, S. von Fellenberg, Linda J. Tacconi, G. Rousset, Eric Gendron, Guy Perrin, Pierre Kervella, Frank Eisenhauer, G. Rodriguez Coira, R. Abuter, Felix Widmann, Pierre Léna, Eckhard Sturm, Silvia Scheithauer, N. M. Förster Schreiber, Erich Wiezorrek, Henri Bonnet, Andreas Eckart, M. Bauböck, Sylvestre Lacour, Yann Clénet, P. T. de Zeeuw, Wolfgang Brandner, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Physics, Galaxy: nucleus, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Galactic Center, black hole physics, FOS: Physical sciences, Astronomy and Astrophysics, Orbital eccentricity, Astrometry, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Redshift, Black hole, Orbit, Interferometry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, astrometry, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Gravitational redshift
Abstract: We present a 0.16% precise and 0.27% accurate determination of R0, the distance to the Galactic Center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 micro-arcsec in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km/s, this yields a geometric distance estimate: R0 = 8178 +- 13(stat.) +- 22(sys.) pc. This work updates our previous publication in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20 sigma with f_redshift = 1.04 +- 0.05., Comment: 9 pages, 7 figures, submitted to A&A
Published: 2019
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16. Scalar field effects on the orbit of S2 star

Author: Andreas Eckart, A. Jiménez-Rosales, Thibaut Paumard, Odele Straub, J.-B. Le Bouquin, V. Coudé Du Forest, Eckhard Sturm, Feng Gao, Maryam Habibi, Pierre Kervella, T. de Zeeuw, G. Rodriguez Coira, Jason Dexter, Laurent Jocou, Idel Waisberg, Myriam Benisty, Oliver Pfuhl, T. Ott, Christian Straubmeier, António Amorim, Paulo Gordo, Frank Eisenhauer, S. von Fellenberg, Pierre Léna, M. Bauböck, M. Pössel, Gilles Duvert, Sylvestre Lacour, Stefan Gillessen, Jean-Philippe Berger, R. Genzel, Yann Clénet, G. Rousset, F. Vincent, Paulo J. V. Garcia, Karine Perraut, Guy Perrin, Felix Widmann, M. Ferreira, Eric Gendron, Matthew Horrobin, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Field (physics), Dark matter, black hole physics, FOS: Physical sciences, torus, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Compact star, mass: scalar, 01 natural sciences, General Relativity and Quantum Cosmology, dark matter, Gravitation, precession, black hole: Kerr, energy: rotation, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, central region, Astronomy and Astrophysics, hair, star: orbit, celestial mechanics, Astrophysics - Astrophysics of Galaxies, mass: coupling, Galaxy: centre, Galaxy, field theory: scalar, Black hole, Rotating black hole, 13. Climate action, Space and Planetary Science, gravitation, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], galaxy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Scalar field, superradiance, signature
Abstract: Precise measurements of the S-stars orbiting SgrA* have set strong constraints on the nature of the compact object at the centre of the Milky Way. The presence of a black hole in that region is well established, but its neighboring environment is still an open debate. In that respect, the existence of dark matter in that central region may be detectable due to its strong signatures on the orbits of stars: the main effect is a Newtonian precession which will affect the overall pericentre shift of S2, the latter being a target measurement of the GRAVITY instrument. The exact nature of this dark matter (e.g., stellar dark remnants or diffuse dark matter) is unknown. This article assumes it to be an scalar field of toroidal distribution, associated with ultra-light dark matter particles, surrounding the Kerr black hole. Such a field is a form of "hair" expected in the context of superradiance, a mechanism that extracts rotational energy from the black hole. Orbital signatures for the S2 star are computed and shown to be detectable by GRAVITY. The scalar field can be constrained because the variation of orbital elements depends both on the relative mass of the scalar field to the black hole and on the field mass coupling parameter., Comment: 17 pages, 6 figures. v2: added some references and fixed minor typos to match version in press in MNRAS
Published: 2019
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17. Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole

Author: N. M. Förster Schreiber, Karine Perraut, Ekkehard Wieprecht, Christian Straubmeier, Stefan Hippler, Th. Henning, Thibaut Paumard, Frank Eisenhauer, Felix Widmann, Pierre Kervella, Laurent Jocou, Paulo J. V. Garcia, Pierre Léna, Silvia Scheithauer, Matthew Horrobin, M. Bauböck, Thomas Ott, Maryam Habibi, Oliver Pfuhl, Jason Dexter, Linda J. Tacconi, S. von Fellenberg, A. Jimenez Rosales, Yann Clénet, P. T. de Zeeuw, Sylvestre Lacour, Gilles Duvert, Andreas Eckart, Guy Perrin, Amiel Sternberg, Senol Yazici, Eckhard Sturm, Erich Wiezorrek, Eric Gendron, Idel Waisberg, M. Ebert, Reinhard Genzel, F. Vincent, António Amorim, Sebastian Rabien, G. Rodríguez-Coira, Z. Hubert, Xavier Haubois, Vincent Lapeyrere, Odele Straub, J.-B. Le Bouquin, Wolfgang Brandner, G. Rousset, Feng Gao, V. Coudé du Foresto, Jean-Philippe Berger, Stefan Gillessen, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
Subjects: General Physics and Astronomy, FOS: Physical sciences, Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Gravitation and Astrophysics, 7. Clean energy, 01 natural sciences, General Relativity and Quantum Cosmology, Gravitational potential, 0103 physical sciences, Equivalence principle, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, Supermassive black hole, Galactic Center, White dwarf, Astrophysics - Astrophysics of Galaxies, Redshift, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Black hole, Sagittarius A, Astrophysics of Galaxies (astro-ph.GA), Physics::Space Physics, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: During its orbit around the four million solar mass black hole Sagittarius A* the star S2 experiences significant changes in gravitational potential. We use this change of potential to test one part of the Einstein equivalence principle: the local position invariance (LPI). We study the dependency of different atomic transitions on the gravitational potential to give an upper limit on violations of the LPI. This is done by separately measuring the redshift from hydrogen and helium absorption lines in the stellar spectrum during its closest approach to the black hole. For this measurement we use radial velocity data from 2015 to 2018 and combine it with the gravitational potential at the position of S2, which is calculated from the precisely known orbit of S2 around the black hole. This results in a limit on a violation of the LPI of $|\beta_{He}-\beta_{H}| = (2.4 \pm 5.1) \cdot 10^{-2}$. The variation in potential that we probe with this measurement is six magnitudes larger than possible for measurements on Earth, and a factor ten larger than in experiments using white dwarfs. We are therefore testing the LPI in a regime where it has not been tested before., Comment: Accepted for publication in Physical Review Letters
Published: 2019
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18. An image of the dust sublimation region in the nucleus of NGC 1068

Author: Sebastian F. Hönig, António Amorim, Idel Waisberg, N. M. Förster Schreiber, Feng Gao, Wolfgang Brandner, Paulo J. V. Garcia, T. Taro Shimizu, Linda J. Tacconi, Amiel Sternberg, D. Gratadour, Guy Perrin, Konrad R. W. Tristram, Jason Dexter, Felix Widmann, Andreas Eckart, Mercedes Prieto, P.-O. Petrucci, Bradley M. Peterson, Karine Perraut, Oliver Pfuhl, Sylvestre Lacour, Eckhard Sturm, Frank Eisenhauer, Julien Woillez, Stefan Gillessen, Ric Davies, Jinyi Shangguan, Odele Straub, Dieter Lutz, Makoto Kishimoto, Yann Clénet, P. T. de Zeeuw, Hagai Netzer, P. Vermot, Thibaut Paumard, Thomas Ott, Florentin Millour, Daniel Rouan, Marc Schartmann, Reinhard Genzel, Christian Straubmeier, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)
Subjects: 010504 meteorology & atmospheric sciences, galaxies: active, FOS: Physical sciences, Astrophysics, 01 natural sciences, Observatory, 0103 physical sciences, medicine, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Physics, Very Large Telescope, Astronomy and Astrophysics, Position angle, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies: Seyfert, Interferometry, medicine.anatomical_structure, Space and Planetary Science, techniques: interferometric, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Sublimation (phase transition), galaxies: nuclei, Nucleus
Abstract: We present near-infrared interferometric data on the Seyfert 2 galaxy NGC 1068, obtained with the GRAVITY instrument on the European Southern Observatory Very Large Telescope Interferometer. The extensive baseline coverage from 5 to 60 M\lambda allowed us to reconstruct a continuum image of the nucleus with an unrivaled 0.2 pc resolution in the K-band. We find a thin ring-like structure of emission with a radius r = 0.24+/-0.03 pc, inclination i = 70+/-5 deg, position angle PA = -50+/-4 deg, and h/r < 0.14, which we associate with the dust sublimation region. The observed morphology is inconsistent with the expected signatures of a geometrically and optically thick torus. Instead, the infrared emission shows a striking resemblance to the 22 GHz maser disc, which suggests they share a common region of origin. The near-infrared spectral energy distribution indicates a bolometric luminosity of (0.4-4.7) x 10^45 erg/s, behind a large A_K ~ 5.5 (A_V ~ 90) screen of extinction that also appears to contribute significantly to obscuring the broad line region., Comment: Accepted for publication in Astronomy and Astrophysics. 13 pages with 7 figures
Published: 2019
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19. Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

Author: Linda J. Tacconi, Eckhard Sturm, Laurent Jocou, Julien Woillez, Guy Perrin, Bernard Lazareff, Christian Straubmeier, P. M. Plewa, Stefan Hippler, H. Bonnet, Feng Gao, Eric Gendron, Th. Henning, Gérard Rousset, N. M. Förster Schreiber, Thomas Ott, Johana Panduro, Jean-Philippe Berger, P. Guajardo, Frank Eisenhauer, Karine Perraut, S. von Fellenberg, Yann Clénet, P. T. de Zeeuw, Felix Widmann, Pierre Léna, Thibaut Paumard, Oliver Pfuhl, Xavier Haubois, Erich Wiezorrek, V. Coudé du Foresto, Casey Deen, Sylvestre Lacour, Stefan Gillessen, Jason Dexter, Amiel Sternberg, Gilles Duvert, Matthew Horrobin, Odele Straub, J.-B. Le Bouquin, Armin Huber, Reinhard Genzel, Paulo J. V. Garcia, Sebastian Rabien, António Amorim, G. Rodríguez-Coira, Wolfgang Brandner, Frederic H. Vincent, Roberto Abuter, V. Lapeyrère, Idel Waisberg, Andreas Eckart, S. Yazici, Maryam Habibi, M. Bauböck, Pierre Kervella, Magdalena Lippa, A. Jiménez-Rosales, Ekkehard Wieprecht, European Southern Observatory (ESO), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), Laboratoire de Physique Statistique de l'ENS (LPS), Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Transport et Environnement (INRETS/LTE), Institut National de Recherche sur les Transports et leur Sécurité (INRETS), Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Swedish Space Corporation (SSC), School of Physics and Astronomy [Tel Aviv], Tel Aviv University [Tel Aviv], Laboratoire Univers et Théories (LUTH (UMR_8102)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Universität zu Köln, AUTRES, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Paris Diderot - Paris 7 (UPD7)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Gravitation, Telescope, General Relativity and Quantum Cosmology, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Circular orbit, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Solar mass, 010308 nuclear & particles physics, Astronomy and Astrophysics, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Interferometry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Orbital motion, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Schwarzschild radius
Abstract: We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-15)-minute period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized 'hot spot' of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field., Comment: accepted by A&A; 16 pages
Published: 2018
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20. Physical parameters and ±0.2% parallax of the detached eclipsing binary V923 Scorpii

Author: Matthew Horrobin, Casey Deen, W. W. Weiss, A. F. J. Moffat, Slavek M. Rucinski, Paulo J. V. Garcia, Oliver Pfuhl, J. M. Matthews, Odele Straub, Pierre Kervella, A. Mérand, C. Cameron, T. Pribulla, European Southern Observatory (ESO), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), School of engineering sciences, University of Southampton, Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Department of Physics and Astronomy [Toronto], York University [Toronto], Laboratoire Univers et Théories (LUTH (UMR_8102)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 010309 optics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Parallax, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), ComputingMilieux_MISCELLANEOUS
Abstract: V923 Sco is a bright ($V$ = 5.91), nearby ($\pi$ = 15.46$\pm$0.40 mas) southern eclipsing binary. Because both components are slow rotators, the minimum masses of the components are known with 0.2% precision from spectroscopy. The system seems ideal for very precise mass, radius, and luminosity determinations and, owing to its proximity and long orbital period ($\sim$ 34.8 days), promises to be resolved with long-baseline interferometry. The principal aim is very accurate determinations of absolute stellar parameters for both components of the eclipsing binary and a model-independent determination of the distance.} New high-precision photometry of both eclipses of V923 Sco with the MOST satellite was obtained. The system was spatially resolved with the VLTI AMBER, PIONIER, and GRAVITY instruments at nine epochs. Combining the projected size of the spectroscopic orbit (in km) and visual orbit (in mas) the distance to the system is derived. Simultaneous analysis of photometric, spectroscopic, and interferometric data was performed to obtain a robust determination of the absolute parameters. Very precise absolute parameters of the components were derived in spite of the parameter correlations. The primary component is found to be overluminous for its mass. Combining spectroscopic and interferometric observations enabled us to determine the distance to V923 Sco with better than 0.2% precision, which provides a stringent test of Gaia parallaxes. It is shown that combining spectroscopic and interferometric observations of nearby eclipsing binaries can lead to extremely accurate parallaxes and stellar parameters., Comment: 10 pages, 4 figures, A&A in press
Published: 2018
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21. Improving GRAVITY towards observations of faint targets

Author: Markus Schöller, P. M. Plewa, Oliver Pfuhl, Felix Widmann, Wolfgang Brandner, Christian Straubmeier, Feng Gao, Stefan Gillessen, Reinhard Genzel, Sylvestre Lacour, M. Karl, Guy Perrin, Frank Eisenhauer, António Amorim, Karin Perraut, Magdalena Lippa, Idel Waisberg, and Thomas Ott
Subjects: Physics, Gravity (chemistry), Very Large Telescope, 010308 nuclear & particles physics, Galactic Center, First light, Astrophysics, 01 natural sciences, Black hole, Interferometry, Sagittarius A, 0103 physical sciences, 010303 astronomy & astrophysics, Data reduction
Abstract: Since its first light at the Very Large Telescope Interferometer (VLTI), GRAVITY has reached new regimes in optical interferometry, in terms of accuracy as well as sensitivity. 1 GRAVITY is routinely doing phase referenced interferometry of objects fainter than K > 17 mag, which makes for example the galactic center black hole Sagittarius A* 2 detectable 90 % of the times. However from SNR calculations we are confident that even a sensitivity limit of K ~ 19 mag is possible. We therefore try to push the limits of GRAVITY by improving the observations as well as the calibration and the data reduction. This has further improved the sensitivity limit to K > 18 mag in the beginning of this year. Here we present some work we are currently doing in order to reach the best possible sensitivity.
Published: 2018
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22. What stellar orbit is needed to measure the spin of the Galactic center black hole from astrometric data?

Author: Maryam Habibi, Thomas Ott, Phillip M Plewa, Jason Dexter, Idel Waisberg, Feng Gao, A. Jiménez-Rosales, Felix Widmann, Oliver Pfuhl, M. Bauböck, Frank Eisenhauer, Stefan Gillessen, Sebastiano von Fellenberg, and Reinhard Genzel
Subjects: Physics, Supermassive black hole, Stellar population, 010308 nuclear & particles physics, Star (game theory), Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, FOS: Physical sciences, Sigma, Astronomy and Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, General Relativity and Quantum Cosmology, Radial velocity, Black hole, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Astrometric and spectroscopic monitoring of individual stars orbiting the supermassive black hole in the Galactic Center offer a promising way to detect general relativistic effects. While low-order effects are expected to be detected following the periastron passage of S2 in Spring 2018, detecting higher-order effects due to black hole spin will require the discovery of closer stars. In this paper, we set out to determine the requirements such a star would have to satisfy to allow the detection of black hole spin. We focus on the instrument GRAVITY, which saw first light in 2016 and which is expected to achieve astrometric accuracies $10-100 \mu$as. For an observing campaign with duration $T$ years, $N_{obs}$ total observations, astrometric precision $\sigma_x$ and normalized black hole spin $\chi$, we find that $a_{orb}(1-e^2)^{3/4} \lesssim 300 R_S \sqrt{\frac{T}{4 \text{years}}} \left(\frac{N_{obs}}{120}\right)^{0.25} \sqrt{\frac{10 \mu as}{\sigma_x}} \sqrt{\frac{\chi}{0.9}}$ is needed. For $\chi=0.9$ and a potential observing campaign with $\sigma_x = 10 \mu$as, 30 observations/year and duration 4-10 years, we expect $\sim 0.1$ star with $K, Comment: Accepted to MNRAS
Published: 2018

23. Single-mode waveguides for GRAVITY: I. The cryogenic 4-telescope integrated optics beam combiner

Author: S. Guieu, F. Patru, C. Scibetta, Sylvestre Lacour, Y. Gambérini, A. Delboulbé, Christian Straubmeier, Guy Perrin, A. Chabli, Laurent Jocou, Stefan Gillessen, Cyprien Lanthermann, E. Stadler, A. Nolot, P. Noël, S. Pocas, Thibaut Moulin, Karine Perraut, G. Chamiot-Maitral, P. Labeye, C. Vizioz, R. Templier, J.-B. Le Bouquin, Wolfgang Brandner, F. Haußmann, Frank Eisenhauer, Pierre Kervella, Oliver Pfuhl, Magdalena Lippa, V. Cardin, Yves Magnard, Marcus Haug, Noel Ventura, António Amorim, F. Joulain, J. Guerrero, S. Poulain, V. Lapras, Jean-Philippe Berger, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information (CEA-LETI), Direction de Recherche Technologique (CEA) (DRT (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Istituto Nazionale di Geofisica e di Oceanografia Sperimentale (OGS), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Département d'Optronique (DOPT), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Technologique (CEA) (DRT (CEA)), Institut de biologie et chimie des protéines [Lyon] (IBCP), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Le Verre Fluoré, Institute Patology and Imunology Molecular, Fac Ciencias, Universidade do Porto, Max-Planck-Institut für Astronomie (MPIA), Universität zu Köln, Universidade do Porto = University of Porto, and Universität zu Köln = University of Cologne
Subjects: Cryostat, FRONT SENSORS, Context (language use), Astrophysics, Astronomy & Astrophysics, 01 natural sciences, 7. Clean energy, Computer Science::Digital Libraries, VLTI, law.invention, 010309 optics, Telescope, Optics, law, K band, ASTRONOMICAL INTERFEROMETRY, 0103 physical sciences, 010303 astronomy & astrophysics, Physics, Very Large Telescope, Science & Technology, business.industry, high angular resolution [techniques], Astrophysics::Instrumentation and Methods for Astrophysics, techniques: high angular resolution, Astronomy and Astrophysics, H band, K-BAND, CIAO, Physics::History of Physics, interferometric [techniques], Interferometry, Space and Planetary Science, techniques: interferometric, Physical Sciences, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Beam (structure)
Abstract: Context. Within the framework of the second-generation instrumentation of the Very Large Telescope Interferometer of the European Southern Observatory we have developed the four-telescope beam combiner in integrated optics. Aims. We optimized the performance of such beam combiners, for the first time in the near-infrared K band, for the GRAVITY instrument dedicated to the study of the close environment of the galactic centre black hole by precision narrow-angle astrometry and interferometric imaging. Methods. We optimized the design of the integrated optics chip and the manufacturing technology as well, to fulfil the very demanding throughput specification. We also designed an integrated optics assembly able to operate at 200 K in the GRAVITY cryostat to reduce thermal emission. Results. We manufactured about 50 beam combiners by silica-on-silicon etching technology. We glued the best combiners to single-mode fluoride fibre arrays that inject the VLTI light into the integrated optics beam combiners. The final integrated optics assemblies have been fully characterized in the laboratory and through on-site calibrations: their global throughput over the K band is higher than 55% and the instrumental contrast reaches more than 95% in polarized light, which is well within the GRAVITY specifications. Conclusions. While integrated optics technology is known to be mature enough to provide efficient and reliable beam combiners for astronomical interferometry in the H band, we managed to successfully extend it to the longest wavelengths of the K band and to manufacture the most complex integrated optics beam combiner in this specific spectral band.
Published: 2018
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24. Learnings from the use of fiber optics in GRAVITY

Author: Erich Wiezorrek, A. Buron, Guy Perrin, Sylvestre Lacour, Thomas Ott, Frank Eisenhauer, Nicolas Blind, F. Haußmann, Laurent Jocou, Ekkehard Wieprecht, António Amorim, Markus Plattner, Oliver Pfuhl, Stefan Gillessen, Reinhard Genzel, Karine Perraut, C. Rau, O. Hans, M. Haug, Christian Straubmeier, Magdalena Lippa, Yitping Kok, Stefan Kellner, Eckhard Sturm, and Wolfgang Brandner
Subjects: Physics, Optical fiber, business.industry, Scattering, Physics::Optics, Ranging, Inelastic scattering, Polarization (waves), law.invention, Astronomical instrumentation, Metrology, Optics, law, High transmission, business
Abstract: The use of optical fibers in astronomical instrumentation has been becoming more and more common. High transmission, polarization control, compact and easy routing are just a few of the advantages in this respect. But fibers also bring new challenges for the development of systems. During the assembly of the VLTI beam combiner GRAVITY different side effects of the fiber implementation had to be taken into account. In this work we summarize the corresponding phenomena ranging from the external factors influencing the fiber performance, like mechanical and temperature effects, to inelastic scattering within the fiber material.
Published: 2018

25. A Detection of Sgr A* in the far infrared

Author: Felix Widmann, Feng Gao, Gabriele Ponti, Idel Waisberg, Maryam Habibi, A. Jiménez-Rosales, Sebastiano von Fellenberg, Reinhard Genzel, T. K. Fritz, P. M. Plewa, Stefan Gillessen, Javier Graciá-Carpio, Jason Dexter, Thomas Ott, Oliver Pfuhl, M. Bauböck, and Frank Eisenhauer
Subjects: Physics, Astrophysics::High Energy Astrophysical Phenomena, Theoretical models, Flux, FOS: Physical sciences, Astronomy and Astrophysics, Electron, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, On board, Black hole, Accretion disc, Far infrared, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We report the first detection of the Galactic Centre massive black hole, Sgr~A*, in the far infrared. Our measurements were obtained with PACS on board the \emph{Herschel} satellite at $100~\mathrm{\mu m}$ and $160~\mathrm{\mu m}$. While the warm dust in the Galactic Centre is too bright to allow for a direct detection of Sgr~A*, we measure a significant and simultaneous variation of its flux of $\Delta F_{\nu\widehat{=}160 ~\mathrm{\mu m}} = (0.27\pm0.06)~\mathrm{Jy}$ and $\Delta F_{\nu\widehat{=}100 ~\mathrm{\mu m}}= (0.16\pm0.10)~\mathrm{Jy}$ during one observation. The significance level of the $160 ~\mathrm{\mu m}$ band variability is $4.5\sigma$ and the corresponding $100 ~\mathrm{\mu m}$ band variability is significant at $1.6\sigma$. We find no example of an equally significant false positive detection. Conservatively assuming a variability of $25\%$ in the FIR, we can provide upper limits to the flux. Comparing the latter with theoretical models we find that 1D RIAF models have difficulties explaining the observed faintness. However, the upper limits are consistent with modern ALMA and VLA observations. Our upper limits provide further evidence for a spectral peak at $\sim 10^{12} ~ \mathrm{Hz}$ and constrain the number density of $\gamma \sim 100$ electrons in the accretion disk and or outflow., Comment: accepted for publication in APJ
Published: 2018
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26. Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

Author: R.-R. Rohloff, Andreas Eckart, Sarah Kendrew, Maryam Habibi, Joany Andreina Manjarres Ramos, S. Kellner, Nicolas Blind, D. Ziegler, Wolfgang Brandner, Casey Deen, Bernard Lazareff, Jean-Philippe Berger, Gérard Zins, M. Haug, A. Ramirez, Eric Gendron, F. Haußmann, Thomas Ott, E. Müler, Silvia Scheithauer, Jason Spyromilio, Andreas Kaufer, Xavier Haubois, Markus Schöller, Eckhard Sturm, C. Collin, Stefan Hippler, Laurent Jocou, Myriam Benisty, Julien Woillez, Linda J. Tacconi, A. Buron, Imke Wank, S. von Fellenberg, M. Wiest, Paulo Gordo, Luca Pasquini, Pierre Kervella, L. Palanca, Magdalena Lippa, Martin Kulas, Roderick Dembet, Gilles Duvert, Z. Hubert, Jason Dexter, Yann Clénet, P. T. de Zeeuw, C. Rau, A. Jimenez Rosales, H. Bonnet, Sylvestre Lacour, Guy Perrin, Odele Straub, P. Fédou, J.-B. Le Bouquin, Christian Straubmeier, S. Yazici, Ekkehard Wieprecht, Gérard Rousset, V. Lapeyrère, N. M. Förster Schreiber, Sebastian Rabien, Felix Widmann, Th. Henning, F. Delplancke-Ströbele, M. Bauböck, F. Chapron, Frank Eisenhauer, Gert Finger, R. Garcia Lopez, G. Rodríguez-Coira, Reinhard Genzel, Frederic H. Vincent, Pierre Léna, Thibaut Paumard, Narsireddy Anugu, Idel Waisberg, J. Sanchez-Bermudez, N. Schuler, Karine Perraut, P. M. Plewa, Paulo J. V. Garcia, António Amorim, Yitping Kok, Oliver Pfuhl, Lieselotte Jochum, V. dCoudé u Foresto, Matthew Horrobin, Udo Neumann, Rainer Lenzen, Erich Wiezorrek, Antoine Mérand, Konrad R. W. Tristram, Norbert Hubin, Feng Gao, Stefan Gillessen, Roberto Abuter, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), and Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)
Subjects: General relativity, black hole physics, FOS: Physical sciences, Astrophysics, Physics - Classical Physics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, General Relativity and Quantum Cosmology, Gravitation, Gravitational field, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, Very Large Telescope, Galaxy: center, 010308 nuclear & particles physics, Classical Physics (physics.class-ph), Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], Black hole, Space and Planetary Science, gravitation, Astrophysics of Galaxies (astro-ph.GA), [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Schwarzschild radius, Gravitational redshift
Abstract: The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU, ~1400 Schwarzschild radii, the star has an orbital speed of ~7650 km/s, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z ~ 200 km/s / c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 (stat) +\- 0.15 (sys). The S2 data are inconsistent with pure Newtonian dynamics., Comment: Accepted for publication in A&A Letters, 29 June 2018, 10 pages, 6 figures, corresponding author: F. Eisenhauer
Published: 2018
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27. Twelve years of spectroscopic monitoring in the Galactic Center: the closest look at S-stars near the black hole

Author: Stefan Gillessen, S. von Fellenberg, Maryam Habibi, Jason Dexter, Reinhard Genzel, A. Jiménez-Rosales, M. Bauböck, Elizabeth George, Oliver Pfuhl, Idel Waisberg, Fabrice Martins, T. Ott, Frank Eisenhauer, P. M. Plewa, Laboratoire Univers et Particules de Montpellier (LUPM), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Stellar evolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, Supermassive black hole, Star formation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Galactic Center, Astronomy and Astrophysics, Effective temperature, Surface gravity, Astrophysics - Astrophysics of Galaxies, Galaxy, Stars, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics
Abstract: We study the young S-stars within a distance of 0.04 pc from the supermassive black hole in the center of our Galaxy. Given how inhospitable the region is for star formation, their presence is more puzzling the younger we estimate their ages. In this study, we analyse the result of 12 years of high resolution spectroscopy within the central arcsecond of the Galactic Center (GC). By co-adding between 55 and 105 hours of spectra we have obtained high signal to noise H- and K-band spectra of eight stars orbiting the central supermassive black hole. Using deep H-band spectra, we show that these stars must be high surface gravity (dwarf) stars. We compare these deep spectra to detailed model atmospheres and stellar evolution models to infer the stellar parameters. Our analysis reveals an effective temperature of 21000-28500 K, a rotational velocity of 60-170 km/s, and a surface gravity of 4.1-4.2. These parameters imply a spectral type of B0-B3V for these stars. The inferred masses lie within 8-14 Msun. We derive an age of 6.6^{+3.4}{-4.7} Myr for the star S2, which is compatible with the age of the clockwise rotating young stellar disk in the GC. We estimate the age of all other studied S-stars to be less than 15 Myr, which are compatible with the age of S2 within the uncertainties. The relatively low ages for these S-stars favor a scenario in which the stars formed in a local disk rather than the field-binary-disruption scenario throughout a longer period of time., Accepted for publication in ApJ
Published: 2017
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28. The nuclear cluster of the Milky Way: total mass and luminosity

Author: Reinhard Genzel, Thomas Ott, Stefan Gillessen, Sotiris Chatzopoulos, Ortwin Gerhard, Frank Eisenhauer, Sandro Tacchella, Tobias K. Fritz, and Oliver Pfuhl
Subjects: Proper motion, Milky Way, FOS: Physical sciences, Flux, Astrophysics::Cosmology and Extragalactic Astrophysics, Star count, Astrophysics, 01 natural sciences, Luminosity, 0103 physical sciences, Cluster (physics), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Component (thermodynamics), Isotropy, Astronomy and Astrophysics, Radius, Astrophysics - Astrophysics of Galaxies, Galaxy, Radial velocity, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics
Abstract: IAU Symposium, 9 (S303), ISSN:0074-1809, ISSN:1743-9213
Published: 2013
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29. On the origin of young stars at the Galactic center

Author: Yuri Levin, Reinhard Genzel, Ann-Marie Madigan, Oliver Pfuhl, Hagai B. Perets, and Stefan Gillessen
Subjects: Physics, Orbital elements, education.field_of_study, Galactic Center, Population, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, Early type, Black hole, Stars, Star cluster, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, education, Astrophysics::Galaxy Astrophysics
Abstract: The center of our galaxy is home to a massive black hole, SgrA*, and a nuclear star cluster containing stellar populations of various ages. While the late type stars may be too old to have retained memory of their initial orbital configuration, and hence formation mechanism, the kinematics of the early type stars should reflect their original distribution. In this contribution we present a new statistic which uses directly-observable kinematical stellar data to infer orbital parameters for stellar populations, and is capable of distinguishing between different origin scenarios. We use it on a population of B-stars in the Galactic center that extends out to large radii (0.5 pc) from the massive black hole. We find that the high K-magnitude population form an eccentric distribution, suggestive of a Hills binary-disruption origin., Comment: 4 pages, 2 figures, Proceedings of IAU Symposium No. 303: The Galactic Center: Feeding and Feedback in a Normal Galactic Nucleus
Published: 2013
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30. Observations of the gas cloud G2 in the Galactic center

Author: Alessandro Ballone, T. Ott, Oliver Pfuhl, Frank Eisenhauer, Reinhard Genzel, Marc Schartmann, Tobias K. Fritz, Andreas Burkert, and Stefan Gillessen
Subjects: Physics, business.industry, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Cloud computing, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, Luminosity, Black hole, General Relativity and Quantum Cosmology, Orbit, Accretion rate, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Falling (sensation), business, Astrophysics::Galaxy Astrophysics
Abstract: In 2011, we discovered a compact gas cloud ("G2") with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic Center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus., Comment: Proceedings of IAU Symposium #303, "The Galactic Center: Feeding and Feedback in a Normal Galactic Nucleus"; 30 Sep - 4 Oct 2013, Santa Fe / NM (USA)
Published: 2013
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31. A powerful flare from Sgr A* confirms the synchrotron nature of the X-ray emission

Author: Nathalie Degenaar, Maryam Habibi, Stefan Gillessen, Idel Waisberg, Fiona A. Harrison, Reinhard Genzel, Jason Dexter, Elizabeth George, Gabriele Ponti, Andrea Goldwurm, Maïca Clavel, P. M. Plewa, C. J. Hailey, Andrea Merloni, K. Mori, Shuang-Nan Zhang, Simone Scaringi, Chichuan Jin, Oliver Pfuhl, T. Ott, Kirpal Nandra, Frank Eisenhauer, Regis Terrier, Daryl Haggard, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Département de Physique des Particules (ex SPP) (DPP), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), AstroParticule et Cosmologie ( APC - UMR 7164 ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Département de Physique des Particules (ex SPP) ( DPP ), Institut de Recherches sur les lois Fondamentales de l'Univers ( IRFU ), Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ) -Université Paris-Saclay, Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Département de Physique des Particules (ex SPP) (DPhP), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Milky Way, Astrophysics::High Energy Astrophysical Phenomena, black hole physics, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 7. Clean energy, law.invention, law, 0103 physical sciences, Spectral slope, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, 010308 nuclear & particles physics, Astronomy, Astronomy and Astrophysics, Magnetic reconnection, methods: data analysis, Galaxy: centre, Synchrotron, Magnetic field, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Flare
Abstract: We present the first fully simultaneous fits to the NIR and X-ray spectral slope (and its evolution) during a very bright flare from Sgr A*, the supermassive black hole at the Milky Way's center. Our study arises from ambitious multi-wavelength monitoring campaigns with XMM-Newton, NuSTAR and SINFONI. The average multi-wavelength spectrum is well reproduced by a broken power-law with $\Gamma_{NIR}=1.7\pm0.1$ and $\Gamma_X=2.27\pm0.12$. The difference in spectral slopes ($\Delta\Gamma=0.57\pm0.09$) strongly supports synchrotron emission with a cooling break. The flare starts first in the NIR with a flat and bright NIR spectrum, while X-ray radiation is detected only after about $10^3$ s, when a very steep X-ray spectrum ($\Delta\Gamma=1.8\pm0.4$) is observed. These measurements are consistent with synchrotron emission with a cooling break and they suggest that the high energy cut-off in the electron distribution ($\gamma_{max}$) induces an initial cut-off in the optical-UV band that evolves slowly into the X-ray band. The temporal and spectral evolution observed in all bright X-ray flares are also in line with a slow evolution of $\gamma_{max}$. We also observe hints for a variation of the cooling break that might be induced by an evolution of the magnetic field (from $B\sim30\pm8$ G to $B\sim4.8\pm1.7$ G at the X-ray peak). Such drop of the magnetic field at the flare peak would be expected if the acceleration mechanism is tapping energy from the magnetic field, such as in magnetic reconnection. We conclude that synchrotron emission with a cooling break is a viable process for Sgr A*'s flaring emission., Comment: Accepted for publication in MNRAS
Published: 2017
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32. BlackHoleCam: Fundamental physics of the galactic center

Author: Robert Laing, Monika Moscibrodzka, Roman Konoplya, I. van Bemmel, Luciano Rezzolla, M. Janßen, Gregory Desvignes, Yosuke Mizuno, Christiaan D. Brinkerink, Ru-Sen Lu, Ziri Younsi, Oliver Pfuhl, Alexander Zhidenko, Jordy Davelaar, Raquel Fraga-Encinas, Roger Deane, Hector Olivares, Remo P. J. Tilanus, Frank Eisenhauer, K. F. Schuster, Heino Falcke, H. J. van Langevelde, M. De Laurentis, Arne Grenzebach, Michael Kramer, Oliver Porth, Christian M. Fromm, Ralph Eatough, Norbert Wex, Thomas Bronzwaer, Thomas P. Krichbaum, Sara Issaoun, Pablo Torne, Ciriaco Goddi, Cornelia Müller, Stefan Gillessen, Eduardo Ros, Freek Roelofs, Kang Liu, Goddi, C., Falcke, H., Kramer, M., Rezzolla, L., Brinkerink, C., Bronzwaer, T., Davelaar, J. R. J., Deane, R., De Laurentis, M., Desvignes, G., Eatough, R. P., Eisenhauer, F., Fraga-Encinas, R., Fromm, C. M., Gillessen, S., Grenzebach, A., Issaoun, S., Janßen, M., Konoplya, R., Krichbaum, T. P., Laing, R., Liu, K., Lu, R. -S., Mizuno, Y., Moscibrodzka, M., Müller, C., Olivares, H., Pfuhl, O., Porth, O., Roelofs, F., Ros, E., Schuster, K., Tilanus, R., Torne, P., Van Bemmel, I., Van Langevelde, H. J., Wex, N., Younsi, Z., Zhidenko, A., and Bianchi, M.
Subjects: Field (physics), General relativity, Event horizon, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, General Relativity and Quantum Cosmology (gr-qc), high energy astrophysical phenomena, 7. Clean energy, 01 natural sciences, General Relativity and Quantum Cosmology, Radio telescope, Tests of general relativity, 0103 physical sciences, black hole, Mathematical Physic, 010303 astronomy & astrophysics, Mathematical Physics, Astrophysics::Galaxy Astrophysics, pulsar, Physics, Event Horizon Telescope, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Gravitational wave, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Astronomy and Astrophysic, LIGO, tests of general relativity, Sagittarius A, Space and Planetary Science, Fundamental physics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Einstein's General Theory of Relativity (GR) successfully describes gravity. The most fundamental predictions of GR are black holes (BHs), but in spite of many convincing BH candidates in the Universe, there is no conclusive experimental proof of their existence using astronomical observations in the electromagnetic spectrum. Are BHs real astrophysical objects? Does GR hold in its most extreme limit or are alternatives needed? The prime target to address these fundamental questions is in the center of our own Galaxy, which hosts the closest and best-constrained supermassive BH candidate in the Universe, Sagittarius A* (Sgr A*). Three different types of experiments hold the promise to test GR in a strong-field regime using observations of Sgr A* with new-generation instruments. The first experiment aims to image the relativistic plasma emission which surrounds the event horizon and forms a "shadow" cast against the background, whose predicted size (~50 microarcseconds) can now be resolved by upcoming VLBI experiments at mm-waves such as the Event Horizon Telescope (EHT). The second experiment aims to monitor stars orbiting Sgr A* with the upcoming near-infrared interferometer GRAVITY at the Very Large Telescope (VLT). The third experiment aims to time a radio pulsar in tight orbit about Sgr A* using radio telescopes (including the Atacama Large Millimeter Array or ALMA). The BlackHoleCam project exploits the synergy between these three different techniques and aims to measure the main BH parameters with sufficient precision to provide fundamental tests of GR and probe the spacetime around a BH in any metric theory of gravity. Here, we review our current knowledge of the physical properties of Sgr A* as well as the current status of such experimental efforts towards imaging the event horizon, measuring stellar orbits, and timing pulsars around Sgr A*., Comment: review paper, 36 pages, 12 figures (v2 is the published version)
Published: 2017

33. Submilliarcsecond Optical Interferometry of the High-mass X-Ray Binary BP Cru with VLTI/GRAVITY

Author: Christian Straubmeier, Th. Henning, Stefan Hippler, Gert Finger, Antoine Mérand, W. J. de Wit, H. Bonnet, Stefan Gillessen, R.-R. Rohloff, T. Ott, F. Haussmann, Eckhard Sturm, Laurent Jocou, Andreas Eckart, Yann Clénet, Martin Kulas, Oliver Pfuhl, Nicolas Blind, Jean-Philippe Berger, Pierre Léna, Jason Dexter, Senol Yazici, Markus Schöller, Julien Woillez, R. Genzel, Lieselotte Jochum, Sebastian Rabien, Gérard Rousset, Silvia Scheithauer, C. Rau, Z. Hubert, Frederic H. Vincent, Joany Andreina Manjarres Ramos, P. Fédou, V. Lapeyrère, Marcus Haug, Guy Perrin, Laurent Pallanca, Wolfgang Brandner, Ewald Müller, R. Garcia Lopez, Imke Wank, Roberto Abuter, F. Delplancke-Ströbele, Sylvestre Lacour, Karine Perraut, J.-B. Le Bouquin, Frank Eisenhauer, A. Buron, Idel Waisberg, Yitping Kok, Matthew Horrobin, Paulo J. V. Garcia, J. Sanchez-Bermudez, Erich Wiezorrek, Casey Deen, R. Dembet, Pierre Kervella, Magdalena Lippa, A. Ramirez, Ekkehard Wieprecht, Markus Wittkowski, Johana Panduro, Thibaut Paumard, Narsireddy Anugu, António Amorim, Eric Gendron, Xavier Haubois, M. Wiest, Gilles Duvert, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), GRAVITY, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Planétologie et d'Astrophysique de Grenoble ( IPAG ), Observatoire des Sciences de l'Univers de Grenoble ( OSUG ), and Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS )
Subjects: Physics, Final version, Gravity (chemistry), 010308 nuclear & particles physics, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], X-ray binary, techniques: high angular resolution, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, circumstellar matter, Interferometry, X-rays: binaries, 13. Climate action, Space and Planetary Science, techniques: interferometric, 0103 physical sciences, High mass, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, X-rays: individual
Abstract: International audience; We observe the high-mass X-ray binary (HMXB) BP Cru using interferometry in the near-infrared K band with VLTI/GRAVITY. Continuum visibilities are at most partially resolved, consistent with the predicted size of the hypergiant. Differential visibility amplitude (${\rm{\Delta }}| V| \sim 5 \% $) and phase (${\rm{\Delta }}\phi \sim 2^\circ $) signatures are observed across the He i $2.059\,\mu {\rm{m}}$ and Brγ lines, the latter seen strongly in emission, unusual for the donor star’s spectral type. For a baseline $B\sim 100$ m, the differential phase rms $\sim 0\buildrel{\circ}\over{.} 2$ corresponds to an astrometric precision of $\sim 2\,\mu \mathrm{as}$. We generalize expressions for image centroid displacements and variances in the marginally resolved limit of interferometry to spectrally resolved data, and use them to derive model-independent properties of the emission such as its asymmetry, extension, and strong wavelength dependence. We propose geometric models based on an extended and distorted wind and/or a high-density gas stream, which has long been predicted to be present in this system. The observations show that optical interferometry is now able to resolve HMXBs at the spatial scale where accretion takes place, and therefore to probe the effects of the gravitational and radiation fields of the compact object on its environment.
Published: 2017
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34. An Update on Monitoring Stellar Orbits in the Galactic Center

Author: Elizabeth George, Jason Dexter, Maryam Habibi, Oliver Pfuhl, Stefan Gillessen, S. von Fellenberg, T. Ott, Frank Eisenhauer, Idel Waisberg, P. M. Plewa, Reinhard Genzel, and Re'em Sari
Subjects: Physics, 010308 nuclear & particles physics, media_common.quotation_subject, Coordinate system, Galactic Center, FOS: Physical sciences, Astronomy and Astrophysics, Astrometry, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Star (graph theory), 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Orbit (dynamics), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Eccentricity (behavior), Parallax, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common
Abstract: Using 25 years of data from uninterrupted monitoring of stellar orbits in the Galactic Center, we present an update of the main results from this unique data set: A measurement of mass of and distance to SgrA*. Our progress is not only due to the eight year increase in time base, but also due to the improved definition of the coordinate system. The star S2 continues to yield the best constraints on the mass of and distance to SgrA*; the statistical errors of 0.13 x 10^6 M_sun and 0.12 kpc have halved compared to the previous study. The S2 orbit fit is robust and does not need any prior information. Using coordinate system priors, also the star S1 yields tight constraints on mass and distance. For a combined orbit fit, we use 17 stars, which yields our current best estimates for mass and distance: M = 4.28 +/- 0.10|stat. +/. 0.21|sys. x 10^6 M_sun and R_0 = 8.32 +/- 0.07|stat. +/- 0.14|sys. kpc. These numbers are in agreement with the recent determination of R_0 from the statistical cluster parallax. The positions of the mass, of the near-infrared flares from SgrA* and of the radio source SgrA* agree to within 1mas. In total, we have determined orbits for 40 stars so far, a sample which consists of 32 stars with randomly oriented orbits and a thermal eccentricity distribution, plus eight stars for which we can explicitly show that they are members of the clockwise disk of young stars, and which have lower eccentricity orbits., submitted to ApJ, 19 pages, 14 figures
Published: 2016

35. 3D AMR simulations of G2 as an outflow

Author: Reinhard Genzel, Maryam Habibi, Frank Eisenhauer, Andreas Burkert, P. M. Plewa, Stefan Gillessen, Marc Schartmann, A. Ballone, Thomas Ott, Elizabeth George, and Oliver Pfuhl
Subjects: Physics, Accretion (meteorology), Star (game theory), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Flow (mathematics), Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Outflow, Orbit (control theory), Astrophysics::Galaxy Astrophysics
Abstract: We study the evolution of G2 in a \textit{Compact Source Scenario}, where G2 is the outflow from a low-mass central star moving on the observed orbit. This is done through 3D AMR simulations of the hydrodynamic interaction of G2 with the surrounding hot accretion flow. A comparison with observations is done by means of mock position-velocity (PV) diagrams. We found that a massive ($\dot{M}_\mathrm{w}=5\times 10^{-7} \;M_{\odot} \; \mathrm{yr^{-1}}$) and slow ($v_\mathrm{w}=50 \;\mathrm{km\; s^{-1}}$) outflow can reproduce G2's properties. A faster outflow ($v_\mathrm{w}=400 \;\mathrm{km\; s^{-1}}$) might also be able to explain the material that seems to follow G2 on the same orbit., 2 pages, 1 figure, Proceedings of IAU Symposium 322: The Multi-Messenger Astrophysics of the Galactic Centre
Published: 2016

36. GRAVITY acquisition camera: characterization results

Author: Christian Straubmeierfan, Oliver Pfuhl, Paulo J. V. Garcia, Erich Wiezorrek, Karine Perraut, Thomas Ott, António Amorim, Wolfgang Brandner, Paulo Gordo, Narsireddy Anugu, Frank Eisenhauer, Guy Perrin, and Ekkehard Wieprecht
Subjects: Very Large Telescope, business.industry, Computer science, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Lenslet, 01 natural sciences, Pupil, law.invention, 010309 optics, Telescope, Interferometry, Optics, law, 0103 physical sciences, Astrophysics - Instrumentation and Methods for Astrophysics, business, Secondary mirror, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Data reduction
Abstract: GRAVITY acquisition camera implements four optical functions to track multiple beams of Very Large Telescope Interferometer (VLTI): a) pupil tracker: a $2 \times 2$ lenslet images four pupil reference lasers mounted on the spiders of telescope secondary mirror; b) field tracker: images science object; c) pupil imager: reimages telescope pupil; d) aberration tracker: images a Shack-Hartmann. The estimation of beam stabilization parameters from the acquisition camera detector image is carried out, for every 0.7 s, with a dedicated data reduction software. The measured parameters are used in: a) alignment of GRAVITY with the VLTI; b) active pupil and field stabilization; c) defocus correction and engineering purposes. The instrument is now successfully operational on-sky in closed loop. The relevant data reduction and on-sky characterization results are reported., Comment: SPIE, Optical and Infrared Interferometry and Imaging V, Proceedings Volume 9907, 990727, 2016, "See, https://doi.org/10.1117/12.2233315"
Published: 2016
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37. The distance to the Galactic Center

Author: Stefan Gillessen, Frank Eisenhauer, Tobias K. Fritz, Reinhard Genzel, Thomas Ott, and Oliver Pfuhl
Subjects: Physics, Black hole, Galactic halo, Space and Planetary Science, Milky Way, Galactic Center, Satellite galaxy, Astronomy, Astronomy and Astrophysics, Astrophysics, Galactic plane, Galaxy, Dwarf galaxy
Abstract: One of the Milky Way's fundamental parameters is the distance of the Sun from the Galactic Center, R0. This article reviews the various ways of estimating R0, placing special emphasis on methods that have become possible recently. In particular, we focus on the geometric distance estimate made possible thanks to observations of individual stellar orbits around the massive black hole at the center of the Galaxy. The specific issues of concern there are the degeneracies with other parameters, most importantly the mass of the black hole and the definition of the reference frame. The current uncertainty is nevertheless only a few percent, with error bars shrinking every year.
Published: 2012
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38. Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii

Author: Feng Gao, Maryam Habibi, Oliver Pfuhl, M. Bauböck, Jason Dexter, Andreas Burkert, Frank Eisenhauer, Thomas Ott, A. Jimenez Rosales, P. M. Plewa, Stefan Gillessen, I. Waisberg, S. von Fellenberg, Marc Schartmann, Reinhard Genzel, P. T. de Zeeuw, and Felix Widmann
Subjects: Physics, Number density, 010504 meteorology & atmospheric sciences, Accretion (meteorology), Event horizon, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Radius, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Black hole, Space and Planetary Science, Drag, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Schwarzschild radius, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract: The Galactic Center black hole Sgr A* is the archetypical example of an underfed massive black hole. The extremely low accretion rate can be understood in radiatively inefficient accretion flow models. Testing those models has proven to be difficult due to the lack of suitable probes. Radio and submm polarization measurements constrain the flow very close to the event horizon. X-ray observations resolving the Bondi radius yield an estimate roughly four orders of magnitude further out. Here, we present a new, indirect measurement of the accretion flow density at intermediate radii. We use the dynamics of the gas cloud G2 to probe the ambient density. We detect the presence of a drag force slowing down G2 with a statistical significance of approx 9 {\sigma}. This probes the accretion flow density at around 1000 Schwarzschild radii and yields a number density of approx. 4 x 10^3 cm^-3. Self-similar accretion models where the density follows a power law radial profile between the inner zone and the Bondi radius have predicted similar values., Comment: accepted by ApJ, 15 pages, 6 figures
Published: 2019
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39. Optical Distortion in the NACO Imager

Author: P. M. Plewa, Stefan Gillessen, Felix Widmann, Reinhard Genzel, A. Jiménez-Rosales, Jason Dexter, S. von Fellenberg, Thomas Ott, Feng Gao, I. Waisberg, Maryam Habibi, Oliver Pfuhl, M. Bauböck, and Frank Eisenhauer
Subjects: Physics, Optics, business.industry, Optical distortion, Computer Science::Computer Vision and Pattern Recognition, Distortion, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, General Medicine, Astrophysics - Instrumentation and Methods for Astrophysics, business, Adaptive optics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: In this research note, we present a set of distortion solutions that may be used to correct geometric optical distortion in images taken with the S13 camera of the NACO adaptive optics imager., published in the RNAAS
Published: 2018
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40. 3D AMR simulations of the evolution of the diffuse gas cloud G2 in the Galactic Centre

Author: Marc Schartmann, Maryam Habibi, Reinhard Genzel, P. M. Plewa, Frank Eisenhauer, Oliver Pfuhl, Stefan Gillessen, Andreas Burkert, A. Ballone, Elizabeth George, and Thomas Ott
Subjects: Physics, business.industry, FOS: Physical sciences, Astronomy and Astrophysics, Cloud computing, Astrophysics, Parameter space, Astrophysics - Astrophysics of Galaxies, Diffuse cloud, Accretion (astrophysics), Stars, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, business, Astrophysics::Galaxy Astrophysics
Abstract: With the help of 3D AMR hydrodynamical simulations we aim at understanding G2's nature, recent evolution and fate in the coming years. By exploring the possible parameter space of the diffuse cloud scenario, we find that a starting point within the disc of young stars is favoured by the observations, which may hint at G2 being the result of stellar wind interactions., Comment: Proceedings IAU Symposium No. 322, The Multi-Messenger Astrophysics of the Galactic Centre, 2016, S. Longmore, G. Bicknell & R. Crocker, eds
Published: 2016
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41. Pinpointing the near-infrared location of Sgr A* by correcting optical distortion in the NACO imager

Author: Reinhard Genzel, Elizabeth George, Oliver Pfuhl, T. Ott, Frank Eisenhauer, Maryam Habibi, Karl M. Menten, Jason Dexter, M. J. Reid, P. M. Plewa, and Stefan Gillessen
Subjects: Physics, Red giant, Infrared, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, Astrometry, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, law.invention, Black hole, Stars, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Maser, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Reference frame
Abstract: Near-infrared observations of stellar orbits at the Galactic Center provide conclusive evidence for a massive black hole associated with the compact radio source Sgr A*. The astrometric reference frame for these observations is tied to a set of red giant stars, which are also detectable at radio wavelengths through SiO maser emission in their envelopes. We have improved the precision and long-term stability of this reference frame, in which Sgr A* is localized to within a factor 5 better than previously: ~0.17 mas in position (in 2009) and ~0.07 mas/yr in velocity. This improvement is the result of modeling and correcting optical distortion in the VLT/NACO imager to a sub-mas level and including new infrared and radio measurements, which now both span more than a decade in time. A further improvement will follow future observations and facilitate the detection of relativistic orbital effects., 12 pages, 8 figures, 5 tables. MNRAS in press
Published: 2015

42. Dust within the old nuclear star cluster in the Milky Way

Author: Frank Eisenhauer, Ortwin Gerhard, Sotiris Chatzopoulos, Christopher Wegg, Tobias K. Fritz, Oliver Pfuhl, and Stefan Gillessen
Subjects: Physics, Extinction, media_common.quotation_subject, Milky Way, Galactic Center, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Asymmetry, Astrophysics - Astrophysics of Galaxies, Stars, Star cluster, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Longitude, Parallax, Astrophysics::Galaxy Astrophysics, media_common
Abstract: The mean absolute extinction towards the central parsec of the Milky Way is A_K~3 mag, including both foreground and Galactic center dust. Here we present a measurement of dust extinction within the Galactic old nuclear star cluster (NSC), based on combining differential extinctions of NSC stars with their u_l proper motions along Galactic longitude. Extinction within the NSC preferentially affects stars at its far side, and because the NSC rotates, this causes higher extinctions for NSC stars with negative u_l, as well as an asymmetry in the u_l-histograms. We model these effects using an axisymmetric dynamical model of the NSC in combination with simple models for the dust distribution. Comparing the predicted asymmetry to data for ~7100 stars in several NSC fields, we find that dust associated with the Galactic center mini-spiral with extinction A_K~=0.15-0.8 mag explains most of the data. The largest extinction A_K~=0.8 mag is found in the region of the Western arm of the mini-spiral. Comparing with total A_K determined from stellar colors, we determine the extinction in front of the NSC. Finally, we estimate that for a typical extinction of A_K~=0.4 the statistical parallax of the NSC changes by ~0.4%., Comment: 14 pages, 13 figures, 2 tables, submitted to MNRAS
Published: 2015
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43. The Post-pericenter Evolution of the Galactic Center Source G2

Author: Elizabeth George, Jason Dexter, Frank Eisenhauer, S. von Fellenberg, Maryam Habibi, Andreas Burkert, P. M. Plewa, Stefan Gillessen, Thomas Ott, Reinhard Genzel, I. Waisberg, and Oliver Pfuhl
Subjects: Physics, Supermassive black hole, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Spatially resolved, Galactic Center, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Radial velocity, Integral field spectrograph, Space and Planetary Science, Homogeneous, Drag, Astrophysics of Galaxies (astro-ph.GA), Ionization, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: In early 2014 the fast-moving near-infrared source G2 reached its closest approach to the supermassive black hole Sgr A* in the Galactic Center. We report on the evolution of the ionized gaseous component and the dusty component of G2 immediately after this event, revealed by new observations obtained in 2015 and 2016 with the SINFONI integral field spectrograph and the NACO imager at the ESO VLT. The spatially resolved dynamics of the Br$\gamma$ line emission can be accounted for by the ballistic motion and tidal shearing of a test-particle cloud that has followed a highly eccentric Keplerian orbit around the black hole for the last 12 years. The non-detection of a drag force or any strong hydrodynamic interaction with the hot gas in the inner accretion zone limits the ambient density to less than a few 10$^3$ cm$^{-3}$ at the distance of closest approach (1500 $R_s$), assuming G2 is a spherical cloud moving through a stationary and homogeneous atmosphere. The dust continuum emission is unresolved in L'-band, but stays consistent with the location of the Br$\gamma$ emission. The total luminosity of the Br$\gamma$ and L' emission has remained constant to within the measurement uncertainty. The nature and origin of G2 are likely related to that of the precursor source G1, since their orbital evolution is similar, though not identical. Both object are also likely related to a trailing tail structure, which is continuously connected to G2 over a large range in position and radial velocity., Comment: 17 pages, 12 figures; accepted for publication in ApJ
Published: 2017
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44. GRAVITY: The impact of non-common optical paths within the metrology system

Author: A. Janssen, Reinhard Genzel, Magdalena Lippa, Stefan Gillessen, O. Hans, Leonard Burtscher, Sylvestre Lacour, Ekkehard Wieprecht, Frank Eisenhauer, Oliver Pfuhl, Christian Straubmeier, Yitping Kok, Marcus Haug, Eckhard Sturm, Stefan Kellner, Thomas Ott, J. Weber, Karine Perraut, Guy Perrin, N. Blind, Wolfgang Brandner, F. Haussmann, António Amorim, Max-Planck-Institut für Extraterrestrische Physik (MPE), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Haute résolution angulaire en astrophysique, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Univ. zu Koln (Germany), Max-Planck-Institut fur Astronomie (Germany), and Lisboa
Subjects: Physics, Gravity (chemistry), Optics, Path length, business.industry, Measure (physics), Astrometry, business, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Differential phase, Optical path length, Starlight, Metrology
Abstract: International audience; The laser metrology system in the GRAVITY instrument plays a crucial role in an attempt at high-precision narrow-angle astrometry. With a design goal of achieving 10 microarcseconds precision in astrometry, the system must measure the optical path difference between two beam combiners within GRAVITY to an accuracy of better than 5nm. However in its current design, some parts of the optical paths of the metrology system are not common to the optical paths of starlight (the science path) which it must measure with high accuracy. This state of the design is true for most but not all the baselines which will be used by the GRAVITY instrument. The additional non-common optical paths could produce inaccurate path length measurements and consequently inaccurate measurements of the differential phase between fringe packets of two nearby celestial objects, which is the main astrometric observable of the instrument. With reference to the stability and the sensitivity of the non-common paths, this paper describes the impact of a biased differential phase measurement on the narrowangle astrometry and the image reconstruction performance of the GRAVITY instrument. Several alternative designs are also discussed.
Published: 2014
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45. GCIRS 7, a pulsating M1 supergiant at the Galactic centre. Physical properties and age

Author: J.-U. Pott, J. Breitfelder, Wolfgang Brandner, Oliver Pfuhl, Thibaut Paumard, J.-B. Le Bouquin, Xavier Haubois, Stefan Gillessen, Leonard Burtscher, Guy Perrin, Pierre Kervella, Fabrice Martins, Thomas Ott, Laboratoire Univers et Particules de Montpellier (LUPM), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
Subjects: Physics, Photosphere, Very Large Telescope, Stellar population, 010308 nuclear & particles physics, Star formation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Effective temperature, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 01 natural sciences, Galaxy, Luminosity, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, 0103 physical sciences, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Luminosity function (astronomy)
Abstract: The stellar population in the central parsec of the Galaxy is dominated by an old (several Gyr) population, but young, massive stars dominate the luminosity function. We have studied the most luminous of these stars, GCIRS 7, in order to constrain the age of the recent star formation event in the Galactic Centre and to characterise it as an interferometric reference for observations of the Galactic Centre with the instrument GRAVITY, which will equip the Very Large Telescope Interferometer in the near future. We present the first H-band interferometric observations of GCIRS 7, obtained using the PIONIER visitor instrument on the VLTI using the four 8.2-m unit telescopes. In addition, we present unpublished K-band VLTI/AMBER data, build JHKL light-curves based on data spanning 4 decades, and measured the star's effective temperature using SINFONI spectroscopy. GCIRS 7 is marginally resolved at H-band (in 2013: uniform-disk diameter=1.076+/-0.093mas, R=960+/-92Rsun at 8.33+/-0.35kpc). We detect a significant circumstellar contribution at K-band. The star and its environment are variable in brightness and in size. The photospheric H-band variations are well modelled with two periods: P0~470+/-10 days (amplitude ~0.64mag) and long secondary period LSP~2700-2850 days (~1.1mag). As measured from CO equivalent width, =3600+/-195K. The size, periods, luminosity (=-8.44+/-0.22) and effective temperature are consistent with an M1 supergiant with an initial mass of 22.5+/-2.5Msun and an age of 6.5-10Myr (depending on rotation). This age is in remarkable agreement with most estimates for the recent star formation event in the central parsec. Caution should be taken when using this star as an interferometric reference as it is variable in size, is surrounded by a variable circumstellar environment and large convection cells may form on its photosphere., Comment: Accepted for publication in A&A. 10 pages, 12 figures
Published: 2014
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46. Integration and testing of the GRAVITY infrared camera for multiple telescope optical beam analysis

Author: M. Duarte Naia, Frank Eisenhauer, Oliver Pfuhl, Eckhard Sturm, M. Guimarães, Narsireddy Anugu, Christian Straubmeier, Karine Perraut, Ekkehard Wieprecht, António Amorim, Paulo Gordo, Paulo J. V. Garcia, Guy Perrin, Jorge Abreu, Marcus Haug, and Wolfgang Brandner
Subjects: Physics, Spectrum analyzer, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Physics::Optics, Strehl ratio, law.invention, Telescope, Interferometry, Optics, Optical path, law, Optoelectronics, Laser beam quality, business, Beam splitter, Beam (structure)
Abstract: The GRAVITY Acquisition Camera was designed to monitor and evaluate the optical beam properties of the four ESO/VLT telescopes simultaneously. The data is used as part of the GRAVITY beam stabilization strategy. Internally the Acquisition Camera has four channels each with: several relay mirrors, imaging lens, H-band filter, a single custom made silica bulk optics (i.e. Beam Analyzer) and an IR detector (HAWAII2-RG). The camera operates in vacuum with operational temperature of: 240k for the folding optics and enclosure, 100K for the Beam Analyzer optics and 80K for the detector. The beam analysis is carried out by the Beam Analyzer, which is a compact assembly of fused silica prisms and lenses that are glued together into a single optical block. The beam analyzer handles the four telescope beams and splits the light from the field mode into the pupil imager, the aberration sensor and the pupil tracker modes. The complex optical alignment and focusing was carried out first at room temperature with visible light, using an optical theodolite/alignment telescope, cross hairs, beam splitter mirrors and optical path compensator. The alignment was validated at cryogenic temperatures. High Strehl ratios were achieved at the first cooldown. In the paper we present the Acquisition Camera as manufactured, focusing key sub-systems and key technical challenges, the room temperature (with visible light) alignment and first IR images acquired in cryogenic operation.
Published: 2014
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47. The interferometric baselines and GRAVITY astrometric error budget

Author: A. Amorin, Sylvestre Lacour, Christian Straubmeier, Guy Perrin, Oliver Pfuhl, Frank Eisenhauer, Stefan Gillessen, Yitping Kok, H. Bonnet, Julien Woillez, Wolfgang Brandner, K. Rousselet-Perraut, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Haute résolution angulaire en astrophysique, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Max-Planck-Institut für Extraterrestrische Physik (MPE), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Univ. zu Koln (Germany), Max-Planck-Institut fur Astronomie (Germany), Lisboa, and European Southern Observatory (Germany)
Subjects: Gravity (chemistry), Interferometry, Computer science, FOS: Physical sciences, Astrometry, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Focus (optics), Baseline (configuration management), Instrumentation and Methods for Astrophysics (astro-ph.IM), Beam (structure), Remote sensing
Abstract: GRAVITY is a new generation beam combination instrument for the VLTI. Its goal is to achieve microarsecond astrometric accuracy between objects separated by a few arcsec. This $10^6$ accuracy on astrometric measurements is the most important challenge of the instrument, and careful error budget have been paramount during the technical design of the instrument. In this poster, we will focus on baselines induced errors, which is part of a larger error budget., Comment: SPIE Meeting 2014 -- Montreal
Published: 2014
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48. GRAVITY: the Calibration Unit

Author: Wolfgang Brandner, N. Blind, J. Weber, E. Wieprecht, E. Sturm, Thomas Ott, Oliver Pfuhl, Christian Straubmeier, S. Kellner, António Amorim, F. Haussmann, Frank Eisenhauer, Stefan Gillessen, Yitping Kok, Karine Perraut, O. Hans, S. Huber, Marcus Haug, Guy Perrin, Leonard Burtscher, A. Janssen, and Magdalena Lippa
Subjects: Gravity (chemistry), Computer science, business.industry, FOS: Physical sciences, Metrology, Interferometry, Stars, Optics, Calibration, business, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Beam (structure), Diode
Abstract: We present in this paper the design and characterisation of a new sub-system of the VLTI 2nd generation instrument GRAVITY: the Calibration Unit. The Calibration Unit provides all functions to test and calibrate the beam combiner instrument: it creates two artificial stars on four beams, and dispose of four delay lines with an internal metrology. It also includes artificial stars for the tip-tilt and pupil guiding systems, as well as four metrology pick-up diodes, for tests and calibration of the corresponding sub-systems. The calibration unit also hosts the reference targets to align GRAVITY to the VLTI, and the safety shutters to avoid the metrology light to propagate in the VLTI-lab. We present the results of the characterisation and validtion of these differrent sub-units., 12 pages, 11 figures. Proceeding of SPIE 9146 "Optical and Infrared Interferometry IV"
Published: 2014

49. The GRAVITY metrology system: narrow-angle astrometry via phase-shifting interferometry

Author: N. Blind, Markus Schöller, Stefanie Senftleben, Marcus Haug, A. Janssen, Magdalena Lippa, A. Pflüger, O. Hans, S. Huber, Roland Greßmann, Christian Straubmeier, Leonard Burtscher, Stefan Gillessen, António Amorim, Reiner Hofmann, Guy Perrin, Thomas Ott, David M. Huber, J. Weber, F. Haußmann, Stefan Kellner, Reinhard Genzel, E. Sturm, E. Wieprecht, Frank Eisenhauer, Yitping Kok, Oliver Pfuhl, Wolfgang Brandner, and Karine Perraut
Subjects: Physics, business.industry, Angular distance, Astrophysics::Instrumentation and Methods for Astrophysics, Measure (physics), Phase (waves), FOS: Physical sciences, Astrometry, Metrology, Interferometry, Optics, Astronomical interferometer, Astrophysics - Instrumentation and Methods for Astrophysics, business, Instrumentation and Methods for Astrophysics (astro-ph.IM), Optical path length
Abstract: The VLTI instrument GRAVITY will provide very powerful astrometry by combining the light from four telescopes for two objects simultaneously. It will measure the angular separation between the two astronomical objects to a precision of 10 microarcseconds. This corresponds to a differential optical path difference (dOPD) between the targets of few nanometers and the paths within the interferometer have to be maintained stable to that level. For this purpose, the novel metrology system of GRAVITY will monitor the internal dOPDs by means of phase-shifting interferometry. We present the four-step phase-shifting concept of the metrology with emphasis on the method used for calibrating the phase shifts. The latter is based on a phase-step insensitive algorithm which unambiguously extracts phases in contrast to other methods that are strongly limited by non-linearities of the phase-shifting device. The main constraint of this algorithm is to introduce a robust ellipse fitting routine. Via this approach we are able to measure phase shifts in the laboratory with a typical accuracy of lambda/2000 or 1 nanometer of the metrology wavelength., Comment: 11 pages, 7 figures
Published: 2014
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50. The GRAVITY metrology system: modeling a metrology in optical fibers

Author: Karine Perraut, Thomas Ott, Wolfgang Brandner, Stefan Gillessen, Marcus Haug, O. Hans, E. Wieprecht, S. Huber, Oliver Pfuhl, S. Kellner, Guy Perrin, Frank Eisenhauer, H. Huber, Yitping Kok, N. Blind, António Amorim, F. Haussmann, Christian Straubmeier, J. Weber, E. Sturm, A. Janssen, Magdalena Lippa, and Leonard Burtscher
Subjects: Gravity (chemistry), Optical fiber, business.industry, Computer science, Measure (physics), FOS: Physical sciences, Astrometry, Systems modeling, law.invention, Metrology, Interferometry, Optics, law, Astrophysics - Instrumentation and Methods for Astrophysics, business, Instrumentation and Methods for Astrophysics (astro-ph.IM), Optical path length
Abstract: GRAVITY is the second generation VLT Interferometer (VLTI) instrument for high-precision narrow-angle astrometry and phase-referenced interferometric imaging. The laser metrology system of GRAVITY is at the heart of its astrometric mode, which must measure the distance of 2 stars with a precision of 10 micro-arcseconds. This means the metrology has to measure the optical path difference between the two beam combiners of GRAVITY to a level of 5 nm. The metrology design presents some non-common paths that have consequently to be stable at a level of 1 nm. Otherwise they would impact the performance of GRAVITY. The various tests we made in the past on the prototype give us hints on the components responsible for this error, and on their respective contribution to the total error. It is however difficult to assess their exact origin from only OPD measurements, and therefore, to propose a solution to this problem. In this paper, we present the results of a semi-empirical modeling of the fibered metrology system, relying on theoretical basis, as well as on characterisations of key components. The modeling of the metrology system regarding various effects, e.g., temperature, waveguide heating or mechanical stress, will help us to understand how the metrology behave. The goals of this modeling are to 1) model the test set-ups and reproduce the measurements (as a validation of the modeling), 2) determine the origin of the non-common path errors, and 3) propose modifications to the current metrology design to reach the required 1nm stability., Comment: 20 pages, 19 figures. Proceeding of SPIE 9146 "Optical and Infrared Interferometry IV"
Published: 2014
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