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1. Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

Author: A Jiménez-Rosales, J Dexter, S M Ressler, A Tchekhovskoy, M Bauböck, Y Dallilar, P T de Zeeuw, A Drescher, F Eisenhauer, S von Fellenberg, F Gao, R Genzel, S Gillessen, M Habibi, T Ott, J Stadler, O Straub, and F Widmann
Published: 2021
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2. A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating

Author: J Dexter, A Jiménez-Rosales, S M Ressler, A Tchekhovskoy, M Bauböck, P T de Zeeuw, F Eisenhauer, S von Fellenberg, F Gao, R Genzel, S Gillessen, M Habibi, T Ott, J Stadler, O Straub, and F Widmann
Published: 2020
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3. Constraining particle acceleration in Sgr A? with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations

Author: R. Abuter, A. Amorim, M. Bauböck, F. Baganoff, J. P. Berger, H. Boyce, H. Bonnet, W. Brandner, Y. Clénet, R. Davies, P. T. de Zeeuw, J. Dexter, Y. Dallilar, A. Drescher, A. Eckart, F. Eisenhauer, G. G. Fazio, N. M. Förster Schreiber, K. Foster, C. Gammie, P. Garcia, F. Gao, E. Gendron, R. Genzel, G. Ghisellini, S. Gillessen, M. A. Gurwell, M. Habibi, D. Haggard, C. Hailey, F. A. Harrison, X. Haubois, G. Heißel, T. Henning, and S. Hippler
Subjects: Astrophysics
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 keV and 2 − 70 keV bands in the X-ray. The observed spectral slope in the near-infrared band is νLν ∝ ν0.5 ± 0.2; the spectral slope observed in the X-ray band is νLν ∝ ν−0.7 ± 0.5. Using a fast numerical implementation of a synchrotron sphere with a constant radius, magnetic field, and electron density (i.e., a one-zone model), we tested various synchrotron and synchrotron self-Compton 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 synchrotron self-Compton. Two realizations of the one-zone model can explain the observed flare and its temporal correlation: one-zone model in which the near-infrared and X-ray luminosity are produced by synchrotron self-Compton and a model in which the luminosity stems from a cooled synchrotron spectrum. Both models can describe the mean spectral energy distribution (SED) and temporal evolution similarly well. In order to describe the mean SED, both models require specific values of the maximum Lorentz factor γmax, which differ by roughly two orders of magnitude. The synchrotron self-Compton model suggests that electrons are accelerated to γmax ∼ 500, while cooled synchrotron model requires acceleration up to γmax ∼ 5 × 104. The synchrotron self-Compton scenario requires electron densities of 1010 cm−3 that are much larger than typical ambient densities in the accretion flow. Furthermore, it requires a variation of the particle density that is inconsistent with the average mass-flow rate inferred from polarization measurements and can therefore only be realized in an extraordinary accretion event. In contrast, assuming a source size of 1 RS, 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 γmax, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare.
Published: 2021
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4. 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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5. GRAVITY upgrade with high-performance grisms with factor >2 enhanced throughput

Author: Guy Perrin, Alejandra Rosales, Christian Straubmeier, Odele Straub, Eckhard Sturm, Laurent Jocou, Frank Eisenhauer, Ekkehard Wieprecht, Karine Perraut, M. Riquelme, O. Pfuhl, Andreas Eckart, Tim de Zeeuw, Jinyi Shangguan, Erich Wiezorrek, M. Bauböck, António Amorim, P. Guajardo, V. Lapeyrere, C. Rau, Martin G. F. Mayer, Kateryna Kravchenko, Takashi Sukegawa, Thomas Ott, Maryam Habibi, Felix Widmann, A. Buron, F. Haussmann, Julia Stadler, Sebastiano von Fellenberg, Sylvestre Lacour, Yukinobu Okura, Wolfgang Brandner, Reinhard Genzel, L. Barl, Senol Yazici, Stefan Gillessen, Feng Gao, Thibaut Paumard, David M. Huber, Paolo Garcia, Laurent Pallanca, Tuthill, P.G., Mérand, A., and Sallum, S.
Subjects: Grism, Physics, Interferometry, Gravity (chemistry), Optics, Upgrade, Spectrometer, business.industry, Instrumentation, Astrometry, business, Throughput (business)
Abstract: During the past years, the VLTI-instrument GRAVITY has made spectacular discoveries with phase-referenced interferometric imaging with milliarcsecond resolution and ten microarcsecond astrometry. Here, we report on the upgrade of the GRAVITY science spectrometer with two new grisms in October 2019, increasing the instrument throughput by a factor > 2. This improvement was made possible by using a high refractive index Germanium substrate, which reduces the grism and groove angles, and by successfully applying an anti-reflection coating to the ruled surface to overcome Fresnel losses. We present the design, manufacturing, and laboratory testing of the new grisms, as well as the results from the re-commissioning on sky.
Published: 2021

6. 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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7. Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

Author: Feng Gao, P. T. de Zeeuw, Julia Stadler, Maryam Habibi, Y. Dallilar, M. Bauböck, A. Jiménez-Rosales, Jason Dexter, T. Ott, Frank Eisenhauer, Alexander Tchekhovskoy, Reinhard Genzel, A. Drescher, S. von Fellenberg, Felix Widmann, Stefan Gillessen, S M Ressler, and Odele Straub
Subjects: Accretion, Photon, MHD, General relativity, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, 01 natural sciences, Polarization, 0103 physical sciences, Radiative transfer, 010303 astronomy & astrophysics, Spin-½, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Ring (mathematics), 010308 nuclear & particles physics, Linear polarization, Astronomy and Astrophysics, Black hole physics, Polarization (waves), Computational physics, Black hole, Space and Planetary Science, Relativistic quantum chemistry, Astrophysics - High Energy Astrophysical Phenomena, Accretion discs
Abstract: Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring features. We find that the photon ring is typically a factor of $\simeq 2$ less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the "no-hair" theorem of general relativity., Comment: 13 pages, 12 figures, accepted for publication in MNRAS
Published: 2021

8. The GRAVITY Young Stellar Object survey VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

Author: R. Grellmann, O. Pfuhl, V. Ganci, Eric Gendron, Feng Gao, Stefan Hippler, V. Coudé du Foresto, Guy Perrin, Gérard Rousset, Thibaut Paumard, Frederic H. Vincent, Catherine Dougados, A. Wojtczak, R. Genzel, A. Drescher, A. de Valon, Lucas Labadie, Gilles Duvert, E. F. van Dishoeck, G. Heissel, S. D. von Fellenberg, V. Lapeyrère, Mercedes E. Filho, Christian Straubmeier, Karine Perraut, Julia Stadler, Th. Henning, Paola Caselli, Felix Widmann, Z. Hubert, Stefan Gillessen, Matthew Horrobin, António Amorim, Odele Straub, R. Garcia Lopez, J.-B. Le Bouquin, L. Klarmann, Paulo J. V. Garcia, Jean-Phillipe Berger, G. Heißel, J. Sanchez-Bermudez, Andreas Eckart, Pierre Kervella, Silvia Scheithauer, Sylvestre Lacour, T. Ott, Frank Eisenhauer, Pierre Léna, T. Taro Shimizu, M. Bauböck, A. Caratti o Garatti, A. Jiménez-Rosales, Myriam Benisty, F. Eupen, Julien Woillez, Eckhard Sturm, Laurent Jocou, Wolfgang Brandner, Yann Clénet, P. T. de Zeeuw, and Jinyi Shangguan
Subjects: Physics, Protoplanetary disks, Earth and Planetary Astrophysics (astro-ph.EP), Young stellar object, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Planetary system, Stars, Infrared: planetary systems, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Techniques: interferometric, Radiative transfer, Spectral energy distribution, Astrophysics::Solar and Stellar Astrophysics, Emission spectrum, Astrophysics::Earth and Planetary Astrophysics, Spectral resolution, Stars: individual: HD 141569, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Line (formation), Astrophysics - Earth and Planetary Astrophysics
Abstract: The formation and evolution of planetary systems impact the primordial accretion disk. HD141569 is the only known pre-main sequence star characterized by a hybrid disk. Observations probed the outer-disk structure showing a complex system of rings and interferometric observations attempted to characterize its inner 5 au region, but derived limited constraints. The goal of this work was to explore with new high-resolution interferometric observations the properties of the dust and gas in the internal regions of HD141569. We observed HD141569 on mas scales with GRAVITY/VLTI in the near-infrared at low and high spectral resolution. We interpreted the visibilities and spectral energy distribution with geometrical models and radiative transfer techniques to constrain the dust emission. We analyzed the high spectral resolution quantities to investigate the properties of the Br-Gamma line emitting region. Thanks to the combination of three different epochs, GRAVITY resolves the inner dusty disk in the K band. Data modeling shows that an IR excess of about 6% is spatially resolved and that the origin of this emission is confined in a ring of material located at a radius of 1 au from the star with a width smaller than 0.3 au. The MCMax modeling suggests that this emission could originate from a small amount of QHPs, while large silicate grain models cannot reproduce at the same time the observational constraints on the properties of near-IR and mid-IR fluxes. The differential phases in the Br-Gamma line clearly show an S-shape that can be best reproduced witha gas disk in Keplerian rotation, confined within 0.09 au. This is also hinted at by the double-peaked Br-Gamma emission line shape. The modeling of the continuum and gas emission shows that the inclination and position angle of these two components are consistent with a system showing relatively coplanar rings on all scales., Comment: Accepted for publication in A&A; 25 pages, 15 figures, 5 tables
Published: 2021
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9. MOLsphere and pulsations of the Galactic Center’s red supergiant GCIRS 7 from VLTI/GRAVITY

Author: Karine Perraut, Xavier Haubois, Jason Dexter, Christian Straubmeier, Th. Henning, F. H. Vincent, Linda J. Tacconi, Eckhard Sturm, Idel Waisberg, Stefan Hippler, Guy Perrin, Vincent Lapeyrere, J. Sanchez-Bermudez, Felix Widmann, Andreas Kaufer, Thomas Ott, A. Drescher, O. Pfuhl, Julien Woillez, G. Rodríguez-Coira, Laurent Jocou, Jean-Philippe Berger, Eric Gendron, Lieselotte Jochum, Gérard Zins, S. von Fellenberg, Paulo J. V. Garcia, Sylvestre Lacour, Stefan Gillessen, M. Nowak, N. M. Förster Schreiber, Julia Stadler, Matthew Horrobin, Feng Gao, António Amorim, Frank Eisenhauer, Pierre Léna, Odele Straub, J.-B. Le Bouquin, Erich Wiezorrek, M. Habibi, Reinhard Genzel, Silvia Scheithauer, H. Bonnet, Thibaut Paumard, Pierre Kervella, A. Jiménez-Rosales, Andreas Eckart, Ekkehard Wieprecht, S. Yazici, T. Taro Shimizu, M. Bauböck, Roberto Abuter, Jinyi Shangguan, Wolfgang Brandner, Yann Clénet, P. T. de Zeeuw, 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), 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), Département de Chimie Moléculaire - Ingéniérie et Intéractions BioMoléculaires (DCM - I2BM), Département de Chimie Moléculaire (DCM), Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), 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), Wageningen University and Research [Wageningen] (WUR), European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Poznan Technical University, Max Planck Institute for Astronomy (MPIA), GRAVITY Collaboration, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics [LESIA], Récepteurs nucléaires, maladies cardiovasculaires et diabète - U 1011 [RNMCD], Département de Chimie Moléculaire - Ingéniérie et Intéractions BioMoléculaires [DCM - I2BM], Max-Planck-Institut für Extraterrestrische Physik [MPE], Laboratoire d'études spatiales et d'instrumentation en astrophysique [LESIA], Wageningen University and Research [Wageningen] [WUR], European Southern Observatory [Santiago] [ESO], European Southern Observatory [ESO], Institut Européen des membranes [IEM], Institut de Planétologie et d'Astrophysique de Grenoble [IPAG], Max Planck Institute for Astronomy [MPIA], 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), Universidade de Lisboa = University of Lisbon (ULISBOA), Centro de Astrofísica e Gravitação (CENTRA), Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, 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)-Météo-France -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)-Météo-France, Leiden University, University of Colorado [Boulder], Universität zu Köln = University of Cologne, Max Planck Institute for Radio Astronomy, Universidade do Porto = University of Porto, University of California [Berkeley] (UC Berkeley), University of California (UC), Institute of Astronomy [Cambridge], University of Cambridge [UK] (CAM), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Weizmann Institute of Science [Rehovot, Israël], Sciences, EDP, Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut Européen des membranes (IEM), and Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Galaxy: nucleus, techniques: interferometric, stars: individual: GCIRS 7, stars: fundamental parameters, supergiants, Astrophysics - astrophysics of galaxies, Extinction (astronomy), Continuum (design consultancy), FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, Astrophysics - solar and stellar astrophysics, 0103 physical sciences, Red supergiant, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, Photosphere, 010308 nuclear & particles physics, Galactic Center, Astronomy and Astrophysics, Stars, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Supergiant, [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: GCIRS 7, the brightest star in the Galactic central parsec, formed $6\pm2$ Myr ago together with dozens of massive stars in a disk orbiting the central black-hole. It has been argued that GCIRS 7 is a pulsating body, on the basis of photometric variability. We present the first medium-resolution ($R=500$), K-band spectro-interferometric observations of GCIRS 7, using the GRAVITY instrument with the four auxiliary telescopes of the ESO VLTI. We looked for variations using two epochs, namely 2017 and 2019. We find GCIRS 7 to be moderately resolved with a uniform-disk photospheric diameter of $\theta^*_\text{UD}=1.55 \pm 0.03$ mas ($R^*_\text{UD}=1368 \pm 26$ $R_\odot$) in the K-band continuum. The narrow-band uniform-disk diameter increases above 2.3 $\mu$m, with a clear correlation with the CO band heads in the spectrum. This correlation is aptly modeled by a hot ($T_\text{L}=2368\pm37$ K), geometrically thin molecular shell with a diameter of $\theta_\text{L}=1.74\pm0.03$ mas, as measured in 2017. The shell diameter increased ($\theta_\text{L}=1.89\pm0.03$ mas), while its temperature decreased ($T_\text{L}=2140\pm42$ K) in 2019. In contrast, the photospheric diameter $\theta^*_\text{UD}$ and the extinction up to the photosphere of GCIRS 7 ($A_{\mathrm{K}_\mathrm{S}}=3.18 \pm 0.16$) have the same value within uncertainties at the two epochs. In the context of previous interferometric and photo-spectrometric measurements, the GRAVITY data allow for an interpretation in terms of photospheric pulsations. The photospheric diameter measured in 2017 and 2019 is significantly larger than previously reported using the PIONIER instrument ($\theta_*=1.076 \pm 0.093$ mas in 2013 in the H band). The parameters of the photosphere and molecular shell of GCIRS 7 are comparable to those of other red supergiants that have previously been studied using interferometry., Comment: 12 pages, 11 figures, 3 tables. Accepted for publication in Astronomy and Astrophysics (A&A)
Published: 2021
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10. 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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11. Static phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distanceStatic phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distance

Author: M. Nowak, Reinhard Genzel, Wolfgang Brandner, K. Rousselet-Perraut, Julien Woillez, Christian Straubmeier, Eckhard Sturm, Sylvestre Lacour, Felix Widmann, Sebastiano von Fellenberg, M. Bauböck, Guy Perin, Jinyi Shangguan, Odele Straub, Frank Eisenhauer, A. Jiménez-Rosales, Paulo J. V. Garcia, António Amorim, Stefan Gillessen, Julia Stadler, Feng Gao, O. Pfuhl, and Thomas Ott
Subjects: Physics, Gravity (chemistry), business.industry, Zernike polynomials, Galactic Center, Phase (waves), Astrometry, Interferometry, symbols.namesake, Optics, Optical path, symbols, Calibration, business
Abstract: The GRAVITY instrument has revolutionized optical/IR interferometry: fringe-tracking and phase-referencing allow for 30 micro-arcsecond astrometry in a dual beam mode, and for spectro-differential astrometry better than 10 micro-arcseconds. The control of systematic effects is essential to fully exploit this technological advancement. Among those systematics are static phase aberrations, introduced along the instrument's optical path, which in particular affect the inferred separation of two unresolved objects within the same FOV. Here, we present how the aberrations can be measured, characterized by low-order Zernike polynomials and, most importantly, how their impact on the astrometry is corrected. The resulting astrometry corrections are verified with calibration observations of a binary before we discuss how they affect GRAVITY's measurement of the galactic center distance.
Published: 2020
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12. Polarization analysis of GRAVITY and the VLTI

Author: Feng Gao, Christian Straubmeier, Nicolas Schuhler, O. Pfuhl, António Amorim, Jinyi Shangguan, M. Bauböck, Paulo J. V. Garcia, Eckhard Sturm, Jason Dexter, Wolfgang Brandner, Sylvestre Lacour, K. Rousselet-Perraut, Stefan Gillessen, Guy Perrin, Sebastiano von Fellenberg, Thomas Ott, Felix Widmann, A. Jiménez-Rosales, Xavier Haubois, Frank Eisenhauer, Odele Straub, and Reinhard Genzel
Subjects: Physics, Brewster's angle, Astrophysics::High Energy Astrophysical Phenomena, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics, Polarization (waves), law.invention, General Relativity and Quantum Cosmology, symbols.namesake, Interferometry, law, symbols, Astrophysics::Solar and Stellar Astrophysics, Flare
Abstract: Instrumental polarization can have large effects on measurements with the VLTI, as it can alter measured polarization and introduce uncertainties. To understand these effects we measured and simulated the instrumental polarization of the VLTI and of GRAVITY. We are able to provide a calibration model for GRAVITY observations and quantify systematic uncertainties due to instrumental polarization. This work has shown to be crucial to measure the polarization of the galactic center black hole Sgr A* where we detect a swing in the polarization angle during flare events. While the analysis was done for GRAVITY, it also gives an important basis for the design of future near-infrared instruments at the VLTI.
Published: 2020
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13. The GRAVITY young stellar object survey: III. The dusty disk of RY Lup

Author: Christian Straubmeier, V. Coudé du Foresto, T. Ott, Th. Henning, Guy Perrin, Z. Hubert, Frank Eisenhauer, E. F. van Dishoeck, Pierre Léna, Mercedes E. Filho, Stefan Hippler, Yann Clénet, P. T. de Zeeuw, O. Pfuhl, Odele Straub, J.-B. Le Bouquin, A. Caratti o Garatti, Karine Perraut, F. Vincent, Pierre Kervella, Eckhard Sturm, Julia Stadler, Feng Gao, Laurent Jocou, Catherine Dougados, Jinyi Shangguan, R. Genzel, R. Garcia-Lopez, M. Wiest, Thibaut Paumard, Gilles Duvert, Paola Caselli, Wing-Fai Thi, Wolfgang Brandner, Y.-I. Bouarour, Silvia Scheithauer, R. Grellmann, Francois Menard, S. D. von Fellenberg, Paulo J. V. Garcia, Stefan Gillessen, F. Eupen, Sylvestre Lacour, J. Sanchez-Bermudez, Andreas Eckart, Eric Gendron, A. Natta, Felix Widmann, Matthew Horrobin, Jean-Phillipe Berger, A. Jiménez-Rosales, L. Klarmann, Myriam Benisty, M. Bauböck, António Amorim, Lucas Labadie, Gérard Rousset, 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 Franco-Chilien d'Astronomie (LFCA), Universidad de Concepción [Chile]-Pontificia Universidad Católica de Chile (UC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Universidad de Chile, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, INAF - Osservatorio Astrofisico di Arcetri (OAA), Istituto Nazionale di Astrofisica (INAF), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Physikalisches Institut [Köln], Universität zu Köln, Faculty of Agronomy, University of Parakou, European Southern Observatory (ESO), SIM/IDL Faculdade de Ciências da Universidade de Lisboa (FCUL), University of Lisboa, 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), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), University of Brasilia [Brazil] (UnB), Universitat Politècnica de València (UPV), Galaxies, Etoiles, Physique, Instrumentation (GEPI), 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), Laboratoire Transport et Environnement (INRETS/LTE), Institut National de Recherche sur les Transports et leur Sécurité (INRETS), Swedish Space Corporation (SSC), HELMHOLTZ CENTRE FOR ENVIRONMENTAL RESEARCH UFZ HALLE SUR SAALE DEU, Partenaires IRSTEA, Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), GRAVITY Collaboration, 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, 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 [2007-2019] (Grenoble INP [2007-2019])-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 [2007-2019] (Grenoble INP [2007-2019])-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 National de la Recherche Scientifique (CNRS)-Universidad de Concepción [Chile]-Pontificia Universidad Católica de Chile (UC)-Universidad de Chile-Institut national des sciences de l'Univers (INSU - CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble [2020-....] (OSUG [2020-....]), 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 [2020-....] (UGA [2020-....])-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 [2020-....] (UGA [2020-....]), Environnement Ville Société (EVS), École normale supérieure - Lyon (ENS Lyon)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université Lumière - Lyon 2 (UL2)-Université Jean Moulin - Lyon 3 (UJML), Université de Lyon-Université de Lyon-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université Jean Monnet [Saint-Étienne] (UJM)-École Nationale des Travaux Publics de l'État (ENTPE)-École nationale supérieure d'architecture de Lyon (ENSAL)-Centre National de la Recherche Scientifique (CNRS), Universitat Politecnica de Valencia (UPV), 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: Young stellar object, variables, Extinction (astronomy), FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, stars: pre-main sequence, Herbig Ae/Be -stars, T Tauri, 01 natural sciences, circumstellar matter, Luminosity, stars: low-mass, stars: individual: RY Lup, protoplanetary disks -stars, 0103 physical sciences, low-mass, Astrophysics::Solar and Stellar Astrophysics, individual, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, stars: variables: T Tauri, Very Large Telescope, 010308 nuclear & particles physics, protoplanetary disks, Herbig Ae/Be, Astronomy and Astrophysics, Radius, Effective temperature, Astrophysics - Astrophysics of Galaxies, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), pre-main sequencestars, Spectral energy distribution, Astrophysics::Earth and Planetary Astrophysics, RY Lup -circumstellar matter -stars, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the Spectral Energy Distribution and match the interferometric observations. To match the SED , our model requires a stellar luminosity of 2.5 Lsun, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 Rsun. These revised fundamental parameters, when combined with the mass estimates available , lead to an age of 0.5-2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12~au from the central star. This model corresponds to an inclination of the inner disk of 50deg, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70 deg in NIR) and ALMA(67 $\pm$5 deg) images, but consistent with the inclination determination from the ALMA CO spectra (55$\pm$5deg). Increasing the inclination of the inner disk to 70 deg leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 Lsun to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13~Rsun, leading to an age of 2-3~Ma, and a stellar mass of about 2 Msun, in disagreement with the observed dynamical mass estimate of 1.3-1.5 Msun. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY., Accepted for publication in A&A; 11 pages, 5 figures, 3 tables
Published: 2020
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14. Direct confirmation of the radial-velocity planet β Pictoris c

Author: Benjamin Charnay, Feng Gao, Antoine Mérand, L. Rodet, H. Bonnet, Tyler Gardner, Jean-Phillipe Berger, E. F. van Dishoeck, Anthony Boccaletti, Stefan Gillessen, Felix Widmann, Eric Gendron, Hervé Beust, Karine Perraut, Wolfgang Brandner, A. Cridland, J. Rameau, Sasha Hinkley, R. Asensio-Torres, Stefan Hippler, Roderick Dembet, Thibaut Paumard, John D. Monnier, Claudia Paladini, Valentin Christiaens, Julien Woillez, Linda J. Tacconi, Gilles Otten, Z. Hubert, V. Lapeyrère, Xavier Haubois, António Amorim, Guy Perrin, Jinyi Shangguan, Jingxiu Wang, R. Garcia Lopez, David Mouillet, Erich Wiezorrek, M. Nowak, Reinhard Genzel, Sylvestre Lacour, P. Rubini, G. Heißel, Gilles Duvert, Odele Straub, J.-B. Le Bouquin, Thomas Ott, Jens Kammerer, Anne-Lise Maire, A. Drescher, Laura Kreidberg, G. Rodríguez-Coira, O. Pfuhl, Paulo J. V. Garcia, Laurent Pueyo, A. Grandjean, Frank Eisenhauer, Yann Clénet, P. T. de Zeeuw, Pierre Léna, Matthew Horrobin, V. Coudé du Foresto, Roberto Abuter, Anne-Marie Lagrange, S. D. von Fellenberg, Tomas Stolker, Gérard Rousset, F. Vincent, Pierre Kervella, Faustine Cantalloube, Julien Girard, Andreas Eckart, Arthur Vigan, Mickael Bonnefoy, Paul Mollière, Silvia Scheithauer, André Müller, Miriam Keppler, Ekkehard Wieprecht, E. Nasedkin, Christian Straubmeier, Th. Henning, Jason Dexter, Sarah Blunt, Myriam Benisty, M. Houllé, K. Ward-Duong, Julia Stadler, A. Jiménez-Rosales, Eckhard Sturm, Laurent Jocou, M. Kulikauskas, M. Bauböck, Elodie Choquet, Laboratoire d'Astrophysique de Marseille (LAM), 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), 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), and 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)
Subjects: planets and satellites, Astrophysics, 01 natural sciences, Luminosity, formation -techniques, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, detection -planets and satellites, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Planetary core, Giant planet, Astronomy and Astrophysics, Orbital period, Exoplanet, Accretion (astrophysics), Radial velocity, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], interferometric, Astrophysics::Earth and Planetary Astrophysics
Abstract: Context.Methods used to detect giant exoplanets can be broadly divided into two categories: indirect and direct. Indirect methods are more sensitive to planets with a small orbital period, whereas direct detection is more sensitive to planets orbiting at a large distance from their host star. This dichotomy makes it difficult to combine the two techniques on a single target at once.Aims.Simultaneous measurements made by direct and indirect techniques offer the possibility of determining the mass and luminosity of planets and a method of testing formation models. Here, we aim to show how long-baseline interferometric observations guided by radial-velocity can be used in such a way.Methods.We observed the recently-discovered giant planetβPictoris c with GRAVITY, mounted on the Very Large Telescope Interferometer.Results.This study constitutes the first direct confirmation of a planet discovered through radial velocity. We find that the planet has a temperature ofT = 1250 ± 50 K and a dynamical mass ofM = 8.2 ± 0.8 MJup. At 18.5 ± 2.5 Myr, this putsβPic c close to a ‘hot start’ track, which is usually associated with formation via disk instability. Conversely, the planet orbits at a distance of 2.7 au, which is too close for disk instability to occur. The low apparent magnitude (MK = 14.3 ± 0.1) favours a core accretion scenario.Conclusions.We suggest that this apparent contradiction is a sign of hot core accretion, for example, due to the mass of the planetary core or the existence of a high-temperature accretion shock during formation.
Published: 2020
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15. 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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16. The GRAVITY young stellar object survey

Author: Paola Caselli, E. F. van Dishoeck, Feng Gao, Jaime E. Pineda, Karine Perraut, Lucas Labadie, Stefan Gillessen, Catherine Dougados, Felix Widmann, E. Sturm, Odele Straub, Eric Gendron, J.-B. Le Bouquin, Christian Straubmeier, L. Klarmann, Mercedes E. Filho, A. Eckart, Thomas Ott, J. Sanchez-Bermudez, Th. Henning, A. Drescher, V. Lapeyrère, Gérard Rousset, Zoltan Hubert, Matthew Horrobin, Paulo J. V. Garcia, Gilles Duvert, Julien Woillez, G. Heissel, Thibaut Paumard, Jean-Phillipe Berger, G. Rodríguez-Coira, R. Grellmann, Frederic H. Vincent, Laurent Jocou, J. Stadler, S. D. von Fellenberg, Sylvestre Lacour, António Amorim, Guy Perrin, Pierre Kervella, V. Coudé du Foresto, Frank Eisenhauer, R. Garcia Lopez, Reinhard Genzel, Dominique Segura-Cox, Pierre Léna, M. Bauböck, Myriam Benisty, T. Taro Shimizu, A. Caratti o Garatti, A. Jiménez-Rosales, Yann Clénet, P. T. de Zeeuw, Wolfgang Brandner, and Jinyi Shangguan
Subjects: Young stellar object, FOS: Physical sciences, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Angular resolution, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Earth and Planetary Astrophysics (astro-ph.EP), Physics, Very Large Telescope, 010308 nuclear & particles physics, Astronomy and Astrophysics, Accretion (astrophysics), Vortex, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures, etc.) of stars and planets. Understanding such physical processes is one of the main astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. This study aims at characterizing the morphology of the inner disk in HD 163296 with multi-epoch near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer (VLTI). Our goal is to depict the K-band (lambda_0 ~ 2.2 um) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival PIONIER (H-band; lambda_0 ~ 1.65 um) data of the source. We performed a Gradient Descent parametric model fitting to recover the sub-au morphology of our source. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H- and K-bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and persistence of this asymmetric structure on timescales of several years, we argue that it is a dusty feature (e.g., a vortex or dust clouds), probably, made by a mixing of sillicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk., Accepted to be published in Astronomy and Astrophysics; main-body: 11 pages, 3 figures and 3 tables
Published: 2021
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17. 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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18. A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating

Author: Maryam Habibi, T. Ott, Jason Dexter, Frank Eisenhauer, M. Bauböck, A. Jiménez-Rosales, Odele Straub, Feng Gao, Stefan Gillessen, Reinhard Genzel, Julia Stadler, S. von Fellenberg, S M Ressler, Felix Widmann, Alexander Tchekhovskoy, and P. T. de Zeeuw
Subjects: Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, symbols.namesake, 0103 physical sciences, Faraday effect, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Linear polarization, Astronomy and Astrophysics, Polarization (waves), Astrophysics - Astrophysics of Galaxies, Accretion (astrophysics), Wavelength, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, Magnetohydrodynamics, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The Galactic center black hole candidate Sgr A* is the best target for studies of low-luminosity accretion physics, including with near-infrared and submillimeter wavelength long baseline interferometry experiments. Here we compare images and spectra generated from a parameter survey of general relativistic MHD simulations to a set of radio to near-infrared observations of Sgr A*. Our models span the limits of weak and strong magnetization and use a range of sub-grid prescriptions for electron heating. We find two classes of scenarios can explain the broad shape of the submillimeter spectral peak and the highly variable near-infrared flaring emission. Weakly magnetized "disk-jet" models where most of the emission is produced near the jet wall, consistent with past work, as well as strongly magnetized (magnetically arrested disk) models where hot electrons are present everywhere. Disk-jet models are strongly depolarized at submillimeter wavelengths as a result of strong Faraday rotation, inconsistent with observations of Sgr A*. We instead favor the strongly magnetized models, which provide a good description of the median and highly variable linear polarization signal. The same models can also explain the observed mean Faraday rotation measure and potentially the polarization signals seen recently in Sgr A* near-infrared flares., 20 pages, 17 figures, MNRAS in press
Published: 2020

19. The GRAVITY young stellar object survey

Author: Y.-I. Bouarour, K. Perraut, F. Ménard, W. Brandner, A. Caratti o Garatti, P. Caselli, E. van Dishoeck, C. Dougados, R. Garcia-Lopez, R. Grellmann, T. Henning, L. Klarmann, L. Labadie, A. Natta, J. Sanchez-Bermudez, W.-F. Thi, P. T. de Zeeuw, A. Amorim, M. Bauböck, M. Benisty, J.-P. Berger, Y. Clenet, V. Coudé du Foresto, G. Duvert, A. Eckart, F. Eisenhauer, F. Eupen, M. Filho, F. Gao, P. Garcia
Published: 2020
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20. 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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21. 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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22. 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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23. 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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24. 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

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. 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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29. 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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30. Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way.

Author: M. Habibi, S. Gillessen, O. Pfuhl, F. Eisenhauer, P. M. Plewa, S. von Fellenberg, F. Widmann, T. Ott, F. Gao, I. Waisberg, M. Bauböck, A. Jimenez-Rosales, J. Dexter, P. T. de Zeeuw, and R. Genzel
Published: 2019
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31. Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii.

Author: S. Gillessen, P. M. Plewa, F. Widmann, S. von Fellenberg, M. Schartmann, M. Habibi, A. Jimenez Rosales, M. Bauböck, J. Dexter, F. Gao, I. Waisberg, F. Eisenhauer, O. Pfuhl, T. Ott, A. Burkert, P. T. de Zeeuw, and R. Genzel
Subjects: DRAG force, GALACTIC center, BLACK holes, SUBMILLIMETER astronomy, SCHWARZSCHILD radius, ACCRETION (Astrophysics), STELLAR orbits
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 submillimeter 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 ≈9σ. This probes the accretion flow density at around 1000 Schwarzschild radii and yields a number density of ≈4 × 103 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. [ABSTRACT FROM AUTHOR]
Published: 2019
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32. The resolved size and structure of hot dust in the immediate vicinity of AGN

Author: A. Jiménez-Rosales, Feng Gao, Reinhard Genzel, N. M. Förster Schreiber, T. Taro Shimizu, António Amorim, Julien Woillez, M. Bauböck, Sylvestre Lacour, Jason Dexter, Marc Schartmann, Christian Straubmeier, Wolfgang Brandner, R. L. Davies, Idel Waisberg, P. Vermot, Stefan Gillessen, Paulo J. V. Garcia, Mercedes Prieto, Konrad R. W. Tristram, K. Perraut, T. Paumard, Felix Widmann, Andreas Eckart, Jinyi Shangguan, Oliver Pfuhl, Linda J. Tacconi, Guy Perrin, Makoto Kishimoto, P. T. de Zeeuw, T. Ott, B. M. Peterson, Frank Eisenhauer, D. Rouan, P.-O. Petrucci, Sebastian F. Hönig, Eckhard Sturm, Damien Gratadour, Amiel Sternberg, F. Millour, Y. Clénet, Odele Straub, Dieter Lutz, Hagai Netzer, 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), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-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), GRAVITY, Max-Planck-Institut für Extraterrestrische Physik (MPE), Department of Earth Sciences [Oxford], University of Oxford [Oxford], Max Planck Institute for Extraterrestrial Physics (MPE), Max-Planck-Gesellschaft, Institute Patology and Imunology Molecular, Fac Ciencias, Universidade do Porto [Porto], Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Institut für Radioastronomie (MPIFR), Institut Européen des membranes (IEM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Columbia University [New York], 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), Institut of Physics - Riga, Latvian Academy of Sciences, Universität zu Köln, 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), 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), Universidade do Porto, 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), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), 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), 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 sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-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)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble [2020-....] (IPAG [2020-....]), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble [2020-....] (OSUG [2020-....]), 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 [2020-....] (UGA [2020-....])-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 [2020-....] (UGA [2020-....])
Subjects: media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asymmetry, law.invention, law, quasars: general, 0103 physical sciences, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Astrophysics::Galaxy Astrophysics, media_common, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Bolometer, Astronomy and Astrophysics, Quasar, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies: Seyfert, Full width at half maximum, Interferometry, Space and Planetary Science, techniques: interferometric, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), Sublimation (phase transition), Astrophysics::Earth and Planetary Astrophysics, galaxies: nuclei, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We use VLTI/GRAVITY near-infrared interferometry measurements of 8 bright, Type 1 AGN to study the size and structure of hot dust heated by the central engine. We partially resolve each source, and report Gaussian FWHM sizes in the range 0.3-0.8 milliarcseconds. In all but one object, we find no evidence for significant elongation or asymmetry (closure phases < 1 deg). The effective physical radius increases with bolometric luminosity as found from past reverberation and interferometry measurements. The measured sizes for Seyfert galaxies are systematically larger than for the two quasars in our sample when measured relative to the previously reported R ~ L^1/2 relationship explained by emission at the sublimation radius. This could be evidence of evolving near-infrared emission region structure as a function of central luminosity., 13 pages, 9 figures, submitted to A&A
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33. Twelve Years of Spectroscopic Monitoring in the Galactic Center: The Closest Look at S-stars near the Black Hole.

Author: M. Habibi, S. Gillessen, F. Martins, F. Eisenhauer, P. M. Plewa, O. Pfuhl, E. George, J. Dexter, I. Waisberg, T. Ott, S. von Fellenberg, M. Bauböck, A. Jimenez-Rosales, and R. Genzel
Subjects: BLACK holes, GALACTIC center, GRAVITY, SPECTRUM analysis, STARS
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 analyze 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 hr 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 21,000–28,500 K, a rotational velocity of 60–170 km s−1, 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 . We derive an age of Myr for the star S2, which is compatible with the age of the clockwise-rotating young stellar disk in the GC. We estimate the ages of all other studied S-stars to be less than 15 Myr, which is 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 a field binary-disruption scenario that occurred over a longer period of time. [ABSTRACT FROM AUTHOR]
Published: 2017
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34. Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole.

Author: Amorim A, Bauböck M, Berger JP, Brandner W, Clénet Y, Coudé du Foresto V, de Zeeuw PT, Dexter J, Duvert G, Ebert M, Eckart A, Eisenhauer F, Förster Schreiber NM, Garcia P, Gao F, Gendron E, Genzel R, Gillessen S, Habibi M, Haubois X, Henning T, Hippler S, Horrobin M, Hubert Z, Jiménez Rosales A, Jocou L, Kervella P, Lacour S, Lapeyrère V, Le Bouquin JB, Léna P, Ott T, Paumard T, Perraut K, Perrin G, Pfuhl O, Rabien S, Rodríguez-Coira G, Rousset G, Scheithauer S, Sternberg A, Straub O, Straubmeier C, Sturm E, Tacconi LJ, Vincent F, von Fellenberg S, Waisberg I, Widmann F, Wieprecht E, Wiezorrek E, and Yazici S
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 |β_{He}-β_{H}|=(2.4±5.1)×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 of 10 larger than in experiments using white dwarfs. We are therefore testing the LPI in a regime where it has not been tested before.
Published: 2019
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34 results on '"M. Bauböck"'

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2. A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating

3. Constraining particle acceleration in Sgr A? with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations

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

5. GRAVITY upgrade with high-performance grisms with factor >2 enhanced throughput

6. Detection of faint stars near Sagittarius A* with GRAVITY

7. Relative depolarization of the black hole photon ring in GRMHD models of Sgr A* and M87*

8. The GRAVITY Young Stellar Object survey VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

9. MOLsphere and pulsations of the Galactic Center’s red supergiant GCIRS 7 from VLTI/GRAVITY

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11. Static phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distanceStatic phase aberrations in near-IR interferometry and GRAVITY's determination of the galactic center distance

12. Polarization analysis of GRAVITY and the VLTI

13. The GRAVITY young stellar object survey: III. The dusty disk of RY Lup

14. Direct confirmation of the radial-velocity planet β Pictoris c

15. Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole

16. The GRAVITY young stellar object survey

17. Probing the gas density in our Galactic Centre: moving mesh simulations of G2

18. A parameter survey of Sgr A* radiative models from GRMHD simulations with self-consistent electron heating

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20. A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty

21. Scalar field effects on the orbit of S2 star

22. Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole

23. Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*

24. What stellar orbit is needed to measure the spin of the Galactic center black hole from astrometric data?

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

26. Detection of the gravitational redshift in the orbit of the star S2 near the Galactic centre massive black hole

27. Twelve years of spectroscopic monitoring in the Galactic Center: the closest look at S-stars near the black hole

28. Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii

29. Optical Distortion in the NACO Imager

30. Spectroscopic Detection of a Cusp of Late-type Stars around the Central Black Hole in the Milky Way.

31. Detection of a Drag Force in G2's Orbit: Measuring the Density of the Accretion Flow onto Sgr A* at 1000 Schwarzschild Radii.

32. The resolved size and structure of hot dust in the immediate vicinity of AGN

33. Twelve Years of Spectroscopic Monitoring in the Galactic Center: The Closest Look at S-stars near the Black Hole.

34. Test of the Einstein Equivalence Principle near the Galactic Center Supermassive Black Hole.

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