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Your search keyword '"accretion, accretion disk"' showing total 32 results
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32 results on '"accretion, accretion disk"'

1. Size matters: are we witnessing super-Eddington accretion in high-redshift black holes from JWST?

Author

Lupi, A, Trinca, A, Volonteri, M, Dotti, M, Mazzucchelli, C, Lupi A., Trinca A., Volonteri M., Dotti M., Mazzucchelli C., Lupi, A, Trinca, A, Volonteri, M, Dotti, M, Mazzucchelli, C, Lupi A., Trinca A., Volonteri M., Dotti M., and Mazzucchelli C.

Abstract

Observations by the James Webb Space Telescope of the Universe at z≳4 have shown that massive black holes (MBHs) appear to be extremely overmassive compared to the local correlation for active galactic nuclei. In some cases, these objects might even reach half the stellar mass inferred for the galaxy. It has become a great challenging for theoretical models to understand how these objects formed and grew to these masses. Different ideas range from heavy seed to super-Eddington accretion phases. We take a different approach and try to infer how accurate these MBH mass estimates are and whether we really need to revise our physical models. By considering how the emerging spectrum (both the continuum and the broad lines) of an accreting MBH changes close to and above the Eddington limit, we infer a much larger uncertainty in the MBH mass estimates relative to that of local counterparts. The uncertainty is up to an order of magnitude. We also infer a potential preference for lower masses and higher accretion rates, which i) moves accreting MBHs closer to the local correlations, and ii) might indicate that we witness a widespread phase of very rapid accretion for the first time.

Published
2024

2. Emission signatures from sub-parsec post-Newtonian binaries embedded in circumbinary discs

Author

Franchini, A, Bonetti, M, Lupi, A, Sesana, A, Franchini A., Bonetti M., Lupi A., Sesana A., Franchini, A, Bonetti, M, Lupi, A, Sesana, A, Franchini A., Bonetti M., Lupi A., and Sesana A.

Abstract

We studied the dynamical evolution of quasi-circular, equal-mass massive black hole binaries embedded in circumbinary discs from separations of ∼100 Rg down to the merger, following the post merger evolution. The binary orbit evolves owing to the presence of the gaseous disc and the addition of post-Newtonian (PN) corrections up to the 2.5 PN order, therefore including the dissipative gravitational wave back reaction. We investigated two cases of relatively cold and warm circumbinary discs, with aspect ratios of H/R = 0.03, 0.1, respectively, employing 3D hyper-Lagrangian resolution simulations with the GIZMO-MFM code. We extracted spectral energy distributions and light curves in different frequency bands (i.e. X-ray, optical, and UV) from the simulations. We find a clear two orders of magnitude drop in the X-ray flux right before merger if the disc is warm, while we identify a significant increase in the UV flux regardless of the disc temperature. The optical flux shows clear distinctive modulations on the binary orbital period and on the cavity edge period, regardless of the disc temperature. We find that the presence of a cold disc can accelerate the coalescence of the binary by up to 130 s over the last five days of inspiral, implying a phase shift accumulation of about 0.14 radians compared to the binary evolution in vacuum. These differences are triggered by the presence of the gaseous disc and might have implications on the waveforms that can be detected in principle. We discuss the implications that these distinctive signatures might have for existing and upcoming time domain surveys and for multi-messenger astronomy.

Published
2024

3. Investigating the coronal structure by studying time lags in the Atoll source 4U 1705-44 using AstroSat.

Author

Malu, S., Harikrishna, S., Sriram, K., and Agrawal, Vivek K.

Subjects
*CORAL reefs & islands, *ACCRETION disks, *NEUTRON stars, *STATISTICAL correlation, *SOLAR corona, *CROSS correlation
Abstract

We performed a detailed timing study of the Atoll source 4U 1705-44 in order to understand the accretion disk geometry. Cross correlation function (CCF) studies were performed between soft (3-5 keV) and hard energy (15-30 keV) bands using the AstroSat LAXPC data. We detected hard as well as soft lags of the order of few ten to hundred seconds. A dynamical CCF study was performed in the same energy bands for one of the light curves and we found smaller lags of few tens of seconds (<50 s) suggesting that the variation is probably originating from the corona. We found a broad noise component around ∼13 Hz in the 3-10 keV band which is absent in 10-20 keV band. We interpret the observed lags as the readjustment timescales of the corona or a boundary layer around the neutron star and constrain the height of this structure to few tens of km. We independently estimated the coronal height to be around 15 km assuming that the 13 Hz feature in the PDS is originating from the oscillation of the viscous shell around the neutron star. [ABSTRACT FROM AUTHOR]

Published
2021
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4. The ionizing and heating power of ultraluminous X-ray sources under the geometrical beaming model

Author

K. Kovlakas, T. Fragos, D. Schaerer, A. Mesinger, Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Kovlakas, K., Fragos, T., Schaerer, D., and Mesinger, A.

Subjects
galaxie [X-rays], High Energy Astrophysical Phenomena (astro-ph.HE), binarie [X-rays], accretion disks, FOS: Physical sciences, Astronomy and Astrophysics, accretion, accretion disk, Astrophysics - Astrophysics of Galaxies, X-rays: ISM, X-rays: binaries, X-rays: galaxies, Settore FIS/05 - Astronomia e Astrofisica, accretion, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ultraviolet: galaxies, ISM [X-rays], galaxie [ultraviolet], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

While there is now a consensus that X-ray binaries (XRBs) are the dominant X-ray sources in the early Universe and play a significant role during the epoch of heating of the intergalactic medium (IGM), recent studies report contradicting results regarding their contribution in the nebular emission of local Universe galaxies. Ultraluminous X-ray sources (ULXs), which dominate the X-ray budget of normal galaxies, may be important interstellar-medium (ISM) ionizing sources. However, their output in the extreme UV (EUV) and soft--X-ray part of the spectrum remains observationally unconstrained. In this paper, we predict the ionizing and heating power from ULX populations under the geometrical beaming scenario, and three models describing the emission from super-critical accretion disks. We find that our theoretical spectra for ULX populations cannot (can) explain the HeII (NeV) emission observed in some galaxies, with their contribution being less (more) important than the underlying stellar population. Stochastic fluctuations in the number of ULXs may allow for equal contributions in the HeII emission, in a fraction of galaxies. We provide average spectra of ULX populations as an input to local, and early-Universe studies. We find that the soft--X-ray emission arising from super-critical accretion is significant for the heating of the IGM, and consistent with recent constraints from the 21-cm cosmic signal. Based on the dependence on the adopted compact-object (CO) mass and accretion model, we encourage efforts in modeling ULX spectra via simulations, and their combination with detailed binary population synthesis models., 8 pages. 6 figures, 1 table. This article has been accepted for publication in the Astronomy & Astrophysics journal. The full Table 1 will be made available via CDS

Published
2022
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5. Reflection component in the Bright Atoll Source GX 9+9

Author

Angelo Gambino, A. Sanna, A. Riggio, A. Marino, T. Di Salvo, R. Iaria, S. M. Mazzola, Luciano Burderi, Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Iaria R., Mazzola S.M., Di Salvo T., Marino A., Gambino A.F., Sanna A., Riggio A., and Burderi L.

Subjects
Photon, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Color temperature, 010502 geochemistry & geophysics, 01 natural sciences, Spectral line, X-rays: binaries, stars: neutron, Accretion, accretion disk, Settore FIS/05 - Astronomia E Astrofisica, accretion, 0103 physical sciences, Black-body radiation, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), accretion disks, Astronomy and Astrophysics, X-rays: binarie, Accretion (astrophysics), Neutron star, Space and Planetary Science, Electron temperature, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Low Mass, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], stars: individual: GX 9+9
Abstract

GX 9+9 (4U 1728-16) is a low mass X-ray binary (LMXB) source harboring a neutron star. Although it belongs to the subclass of the bright Atoll sources together with GX 9+1, GX 3+1, and GX 13+1, its broadband spectrum is poorly studied and apparently does not show reflection features in the spectrum. To constrain the continuum well and verify whether a relativistic smeared reflection component is present, we analyze the broadband spectrum of GX 9+9 using {\it BeppoSAX} and \textit{XMM-Newton} spectra covering the 0.3-40 keV energy band. We fit the spectrum adopting a model composed of a disk-blackbody plus a Comptonized component whose seed photons have a blackbody spectrum (Eastern Model). A statistically equivalent model is composed of a Comptonized component whose seed photons have a disk-blackbody distribution plus a blackbody that mimics a saturated Comptonization likely associated with a boundary layer (Western model). Other trials did not return a good fit. The spectrum of GX 9+9 was observed in a soft state and its luminosity is $2.3 \times 10^{37}$ erg s$^{-1}$ assuming a distance to the source of 5 kpc. In the Eastern Model scenario, we find the seed-photon temperature and electron temperature of the Comptonized component to be $1.14^{+0.10}_{-0.07}$ keV and $2.80^{+0.09}_{-0.04}$ keV, respectively, while the optical depth of the Comptonizing corona is $8.9\pm0.4$. The color temperature of the inner accretion disk is $0.86^{+0.08}_{-0.02}$ keV and $0.82 \pm 0.02$ keV for the {\it BeppoSAX} and \textit{XMM-Newton} spectrum, respectively. In the Western Model scenario, instead, we find that the seed-photon temperature is $0.87 \pm 0.07$ keV and $1.01 \pm 0.08$ keV for the {\it BeppoSAX} and \textit{XMM-Newton} spectrum, respectively. (Abridged abstract), Comment: 10 pages, 8 figures, accepted by Astronomy & Astrophysics

Published
2020
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6. First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Author

Michael Janssen, Joseph Neilsen, Gopal Narayanan, Alexander W. Raymond, Gregory Desvignes, Thomas Bronzwaer, Anne Kathrin Baczko, Alan E. E. Rogers, Ru-Sen Lu, Feryal Özel, Qingwen Wu, Shan Shan Zhao, Monika Moscibrodzka, Chunchong Ni, Michael Titus, Freek Roelofs, Buell T. Jannuzi, Tod R. Lauer, Wen Ping Lo, Geoffrey C. Bower, James M. Moran, Taehyun Jung, Bart Ripperda, Dominique Broguiere, Luciano Rezzolla, Jongsoo Kim, Jirong Mao, Jonathan Weintroub, Colin J. Lonsdale, Laurent Loinard, Daniel Michalik, John Conway, Nicholas R. MacDonald, Olivier Gentaz, Iniyan Natarajan, Izumi Mizuno, Vincent L. Fish, Eduardo Ros, Minfeng Gu, Ilse van Bemmel, Kotaro Moriyama, David J. James, Michael D. Johnson, Vincent Piétu, Daryl Haggard, Richard L. Plambeck, Lynn D. Matthews, Avery E. Broderick, Ilje Cho, Katherine L. Bouman, Karl Friedrich Schuster, Ronald Hesper, Zheng Meyer-Zhao, Daniel C. M. Palumbo, Roman Gold, Koushik Chatterjee, Bong Won Sohn, Makoto Inoue, Rebecca Azulay, Paul Tiede, Alan P. Marscher, Ziri Younsi, Ye-Fei Yuan, Jason Dexter, Venkatessh Ramakrishnan, Michael Lindqvist, Michael Bremer, Carsten Kramer, Ramesh Karuppusamy, Michael Kramer, Chi-kwan Chan, R. P. Eatough, Shiro Ikeda, Jan Wagner, Oliver Porth, Garrett K. Keating, Yi Chen, Tuomas Savolainen, Neil M. Nagar, Chet Ruszczyk, Per Friberg, Michael H. Hecht, Huib Jan van Langevelde, Alan L. Roy, Kazunori Akiyama, Jordy Davelaar, Sang-Sung Lee, Maciek Wielgus, Jason SooHoo, Lei Huang, Hiroshi Nagai, Keiichi Asada, David Ball, Thomas P. Krichbaum, A. Nadolski, Roger Brissenden, Mislav Baloković, Roberto Neri, Svetlana G. Jorstad, Des Small, Shami Chatterjee, Raquel Fraga-Encinas, Michael A. Nowak, Hiroaki Nishioka, Mark G. Rawlings, S. Sánchez, Dominic W. Pesce, Heino Falcke, Roberto Garcia, Luis C. Ho, Yan-Rong Li, Fumie Tazaki, Jessica Dempsey, Sera Markoff, David H. Hughes, Daniel R. van Rossum, Elisabetta Liuzzo, Christian M. Fromm, Cornelia Müller, Yuzhu Cui, Jun Yi Koay, Mahito Sasada, Geoffrey B. Crew, Norbert Wex, Nimesh A. Patel, Ed Fomalont, Chih-Wei Locutus Huang, Lijing Shao, Christiaan D. Brinkerink, David Sánchez-Arguelles, Laura Vertatschitsch, Remo P. J. Tilanus, Andrew Chael, Shuichiro Tsuda, Dan Bintley, Ciriaco Goddi, Ramesh Narayan, Charles F. Gammie, Tyler Trent, Mel Rose, Feng Yuan, Satoki Matsushita, Robert Wharton, Jadyn Anczarski, F. Peter Schloerb, Patrick M. Koch, Kazi L.J. Rygl, Nicolas Pradel, Britton Jeter, Tomohisa Kawashima, Shuo Zhang, John E. Carlstrom, Jae-Young Kim, Junhan Kim, Arash Roshanineshat, Jorge A. Preciado-López, Benjamin R. Ryan, Sara Issaoun, Hector Olivares, Andreas Eckart, Hiroki Okino, Karl M. Menten, Lia Medeiros, Zhiqiang Shen, Mariafelicia De Laurentis, Kuo Liu, Joseph R. Farah, Aristeidis Noutsos, Mark Kettenis, C. Y. Kuo, Wu Jiang, Zhiyuan Li, Boris Georgiev, W. Boland, Ramprasad Rao, Guang-Yao Zhao, Ming-Tang Chen, Mansour Karami, José L. Gómez, André Young, Pablo Torne, John Wardle, Ben Prather, Shoko Koyama, Rurik A. Primiani, Pierre Christian, Walter Alef, Kamal Souccar, Paul T. P. Ho, Andrei P. Lobanov, George N. Wong, Kazuhiro Hada, Ziyan Zhu, Silke Britzen, J. Anton Zensus, Ue-Li Pen, Yosuke Mizuno, Sascha Trippe, Sheperd S. Doeleman, James M. Cordes, John E. Barrett, Peter Galison, Dimitrios Psaltis, Mareki Honma, Daniel P. Marrone, Masanori Nakamura, Frederick K. Baganoff, Aleksandar Popstefanija, Helge Rottmann, Mark Gurwell, Ivan Marti-Vidal, Hung Yi Pu, Tomoaki Oyama, Motoki Kino, Roger Deane, Ken H. Young, Paul Yamaguchi, Lindy Blackburn, Kenji Toma, Do-Young Byun, Antxon Alberdi, Academy of Finland, European Commission, Alexander von Humboldt Foundation, John Templeton Foundation, China Scholarship Council, Comisión Nacional de Investigación Científica y Tecnológica (Chile), Consejo Nacional de Ciencia y Tecnología (México), European Research Council, Generalitat Valenciana, Ministerio de Economía, Industria y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Gordon and Betty Moore Foundation, Istituto Nazionale di Fisica Nucleare, Japan Society for the Promotion of Science, Japanese Government, Chinese Academy of Sciences, Max Planck Society, Ministry of Science and Technology (Taiwan), National Aeronautics and Space Administration (US), National Science Foundation (US), National Natural Science Foundation of China, National Research Foundation of Korea, Netherlands Organization for Scientific Research, Natural Sciences and Engineering Research Council of Canada, Russian Science Foundation, National Research Foundation (South Africa), Ministero dell'Istruzione, dell'Università e della Ricerca, Alberdi, Antxón, Gómez Fernández, J. L., Institut de RadioAstronomie Millimétrique (IRAM), Centre National de la Recherche Scientifique (CNRS), Instituto de RadioAstronomía Milimétrica (IRAM), Event Horizon Telescope, Event Horizon Telescope Collaboration, T., Akiyama, K., Alberdi, A., Alef, W., Asada, K., Azulay, R., Baczko, A. -K., Ball, D., Balokovic, M., Barrett, J., Bintley, D., Blackburn, L., Boland, W., Bouman, K. L., Bower, G. C., Bremer, M., Brinkerink, C. D., Brissenden, R., Britzen, S., Broderick, A. E., Broguiere, D., Bronzwaer, T., Byun, D. -Y., Carlstrom, J. E., Chael, A., Chan, C. -K., Chatterjee, S., Chatterjee, K., Chen, M. -T., Chen, Y., Cho, I., Christian, P., Conway, J. E., Cordes, J. M., Crew, G. B., Cui, Y., Davelaar, J., De Laurentis, M., Deane, R., Dempsey, J., Desvignes, G., Dexter, J., Doeleman, S. S., Eatough, R. P., Falcke, H., Fish, V. L., Fomalont, E., Fraga-Encinas, R., Friberg, P., Fromm, C. M., Gomez, J. L., Galison, P., Gammie, C. F., Garcia, R., Gentaz, O., Georgiev, B., Goddi, C., Gold, R., Gu, M., Gurwell, M., Hada, K., Hecht, M. H., Hesper, R., Ho, L. C., Ho, P., Honma, M., Huang, C. -W. L., Huang, L., Hughes, D. H., Ikeda, S., Inoue, M., Issaoun, S., James, D. J., Jannuzi, B. T., Janssen, M., Jeter, B., Jiang, W., Johnson, M. D., Jorstad, S., Jung, T., Karami, M., Karuppusamy, R., Kawashima, T., Keating, G. K., Kettenis, M., Kim, J. -Y., Kim, J., Kino, M., Koay, J. Y., Koch, P. M., Koyama, S., Kramer, M., Kramer, C., Krichbaum, T. P., Kuo, C. -Y., Lauer, T. R., Lee, S. -S., Li, Y. -R., Li, Z., Lindqvist, M., Liu, K., Liuzzo, E., Lo, W. -P., Lobanov, A. P., Loinard, L., Lonsdale, C., Lu, R. -S., Macdonald, N. R., Mao, J., Markoff, S., Marrone, D. P., Marscher, A. P., Marti-Vidal, I., Matsushita, S., Matthews, L. D., Medeiros, L., Menten, K. M., Mizuno, Y., Mizuno, I., Moran, J. M., Moriyama, K., Moscibrodzka, M., Muller, C., Nagai, H., Nagar, N. M., Nakamura, M., Narayan, R., Narayanan, G., Natarajan, I., Neri, R., Ni, C., Noutsos, A., Okino, H., Olivares, H., Oyama, T., Ozel, F., Palumbo, D. C. M., Patel, N., Pen, U. -L., Pesce, D. W., Pietu, V., Plambeck, R., Popstefanija, A., Porth, O., Prather, B., Preciado-Lopez, J. A., Psaltis, D., Pu, H. -Y., Ramakrishnan, V., Rao, R., Rawlings, M. G., Raymond, A. W., Rezzolla, L., Ripperda, B., Roelofs, F., Rogers, A., Ros, E., Rose, M., Roshanineshat, A., Rottmann, H., Roy, A. L., Ruszczyk, C., Ryan, B. R., Rygl, K. L. J., Sanchez, S., Sanchez-Arguelles, D., Sasada, M., Savolainen, T., Schloerb, F. P., Schuster, K. -F., Shao, L., Shen, Z., Small, D., Sohn, B. W., Soohoo, J., Tazaki, F., Tiede, P., Tilanus, R. P. J., Titus, M., Toma, K., Torne, P., Trent, T., Trippe, S., Tsuda, S., Van Bemmel, I., Van Langevelde, H. J., Van Rossum, D. R., Wagner, J., Wardle, J., Weintroub, J., Wex, N., Wharton, R., Wielgus, M., Wong, G. N., Wu, Q., Young, A., Young, K., Younsi, Z., Yuan, F., Yuan, Y. -F., Zensus, J. A., Zhao, G., Zhao, S. -S., Zhu, Z., Anczarski, J., Baganoff, F. K., Eckart, A., Farah, J. R., Haggard, D., Meyer-Zhao, Z., Michalik, D., Nadolski, A., Neilsen, J., Nishioka, H., Nowak, M. A., Pradel, N., Primiani, R. A., Souccar, K., Vertatschitsch, L., Yamaguchi, P., Zhang, S., Astronomy, High Energy Astrophys. & Astropart. Phys (API, FNWI), Gravitation and Astroparticle Physics Amsterdam, Anne Lähteenmäki Group, Department of Electronics and Nanoengineering, Aalto-yliopisto, Aalto University, Alberdi, Antxón [0000-0002-9371-1033], and Gómez Fernández, J. L. [0000-0003-4190-7613]

Subjects
Magnetohydrodynamics (MHD), 010504 meteorology & atmospheric sciences, individual (M87) [galaxies], Event horizon, galaxies: jet, Astronomy, Strong gravitational lensing, black hole physics, jets [galaxies], galaxies: individual, Astrophysics, accretion, accretion disk, 01 natural sciences, General Relativity and Quantum Cosmology, Galaxies: individual (M87), accretion, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, accretion, accretion disks, accretion disks, high angular resolution [techniques], Accretion disks, (MHD), Astrophysics - High Energy Astrophysical Phenomena, General relativity, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Compact star, galaxies: individual: M87, magnetohydrodynamics (MHD), Techniques: high angular resolution, 0103 physical sciences, (M87), 0105 earth and related environmental sciences, Event Horizon Telescope, Supermassive black hole, Astronomy and Astrophysics, Black hole physics, Astrophysics - Astrophysics of Galaxies, black hole physic, Black hole, Rotating black hole, Space and Planetary Science, magnetohydrodynamics: MHD, Galaxies: jets, Astrophysics of Galaxies (astro-ph.GA), magnetohydrodynamics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.© 2019. The American Astronomical Society., The authors of this Letter thank the following organizations and programs: the Academy of Finland (projects 274477, 284495, 312496); the Advanced European Network of E-infrastructures for Astronomy with the SKA (AENEAS) project, supported by the European Commission Framework Programme Horizon 2020 Research and Innovation action under grant agreement 731016; the Alexander von Humboldt Stiftung; the Black Hole Initiative at Harvard University, through a grant (60477) from the John Templeton Foundation; the China Scholarship Council; Comisión Nacional de Investigación Científica y Tecnológica (CONICYT, Chile, via PIA ACT172033, Fondecyt 1171506, BASAL AFB170002, ALMA-conicyt 31140007); Consejo Nacional de Ciencia y Tecnología (CONACYT, Mexico, projects 104497, 275201, 279006, 281692); the Delaney Family via the Delaney Family John A. Wheeler Chair at Perimeter Institute; Dirección General de Asuntos del Personal Académico-Universidad Nacional 9 The Astrophysical Journal Letters, 875:L1 (17pp), 2019 April 10 The EHT Collaboration et al. Autónoma de México (DGAPA-UNAM, project IN112417); the European Research Council (ERC) Synergy Grant “BlackHoleCam: Imaging the Event Horizon of Black Holes” (grant 610058); the Generalitat Valenciana postdoctoral grant APOSTD/2018/177; the Gordon and Betty Moore Foundation (grants GBMF-3561, GBMF-5278); the Istituto Nazionale di Fisica Nucleare (INFN) sezione di Napoli, iniziative specifiche TEONGRAV; the International Max Planck Research School for Astronomy and Astrophysics at the Universities of Bonn and Cologne; the Jansky Fellowship program of the National Radio Astronomy Observatory (NRAO); the Japanese Government (Monbukagakusho: MEXT) Scholarship; the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Research Fellowship (JP17J08829); JSPS Overseas Research Fellowships; the Key Research Program of Frontier Sciences, Chinese, Academy of Sciences (CAS, grants QYZDJ-SSW-SLH057, QYZDJ-SSW-SYS008); the Leverhulme Trust Early Career Research Fellowship; the Max-Planck-Gesellschaft (MPG); the Max Planck Partner Group of the MPG and the CAS; the MEXT/JSPS KAKENHI (grants 18KK0090, JP18K13594, JP18K03656, JP18H03721, 18K03709, 18H01245, 25120007); the MIT International Science and Technology Initiatives (MISTI) Funds; the Ministry of Science and Technology (MOST) of Taiwan (105-2112-M-001-025-MY3, 106-2112-M001-011, 106-2119-M-001-027, 107-2119-M-001-017, 107- 2119-M-001-020, and 107-2119-M-110-005); the National Aeronautics and Space Administration (NASA, Fermi Guest Investigator grant 80NSSC17K0649); the National Institute of Natural Sciences (NINS) of Japan; the National Key Research and Development Program of China (grant 2016YFA0400704, 2016YFA0400702); the National Science Foundation (NSF, grants AST-0096454, AST-0352953, AST-0521233, AST0705062, AST-0905844, AST-0922984, AST-1126433, AST1140030, DGE-1144085, AST-1207704, AST-1207730, AST1207752, MRI-1228509, OPP-1248097, AST-1310896, AST1312651, AST-1337663, AST-1440254, AST-1555365, AST1715061, AST-1615796, AST-1614868, AST-1716327, OISE1743747, AST-1816420); the Natural Science Foundation of China (grants 11573051, 11633006, 11650110427, 10625314, 11721303, 11725312, 11873028, 11873073, U1531245, 11473010); the Natural Sciences and Engineering Research Council of Canada (NSERC, including a Discovery Grant and the NSERC Alexander Graham Bell Canada Graduate Scholarships-Doctoral Program); the National Youth Thousand Talents Program of China; the National Research Foundation of Korea (grant 2015-R1D1A1A01056807, the Global PhD Fellowship Grant: NRF-2015H1A2A1033752, and the Korea Research Fellowship Program: NRF-2015H1D3A1066561); the Netherlands Organization for Scientific Research (NWO) VICI award (grant 639.043.513) and Spinoza Prize (SPI 78-409); the New Scientific Frontiers with Precision, Radio Interferometry Fellowship awarded by the South African Radio Astronomy Observatory (SARAO), which is a facility of the National Research Foundation (NRF), an agency of the Department of Science and Technology (DST) of South Africa; the Onsala Space Observatory (OSO) national infrastructure, for the provisioning of its facilities/observational support (OSO receives funding through the Swedish Research Council under grant 2017-00648); the Perimeter Institute for Theoretical Physics (research at Perimeter Institute is supported by the Government of Canada through the Department of Innovation, Science and Economic Development Canada and by the Province of Ontario through the Ministry of Economic Development, Job Creation and Trade); the Russian Science Foundation (grant 17-12-01029); the Spanish Ministerio de Economía y Competitividad (grants AYA2015-63939-C2-1-P, AYA2016-80889-P); the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709); the Toray Science Foundation; the US Department of Energy (USDOE) through the Los Alamos National Laboratory (operated by Triad National Security, LLC, for the National Nuclear Security Administration of the USDOE (Contract 89233218CNA000001)); the Italian Ministero dell’Istruzione Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001); the European Unionʼs Horizon 2020 research and innovation programme under grant agreement No 730562 RadioNet; ALMA North America Development Fund; Chandra TM6-17006X

Published
2019
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7. NuSTAR Measurement of Coronal Temperature in Two Luminous, High-redshift Quasars

Author

Francesco Tombesi, Enrico Piconcelli, Roberto Gilli, Massimo Cappi, Francesca Civano, W. N. Brandt, George Chartas, C. Vignali, Giorgio Lanzuisi, Marcella Brusa, Andrea Comastri, Stefano Bianchi, Massimo Gaspari, Mauro Dadina, R. Middei, Andrea Marinucci, Lanzuisi, G., Gilli, R., Cappi, M., Dadina, M., Bianchi, S., Brusa, M., Chartas, G., Civano, F., Comastri, A., Marinucci, A., Middei, R., Piconcelli, E., Vignali, C., Brandt, W. N., Tombesi, F., Gaspari, M., Lanzuisi G., Gilli R., Cappi M., Dadina M., Bianchi S., Brusa M., Chartas G., Civano F., Comastri A., Marinucci A., Middei R., Piconcelli E., Vignali C., Brandt W. N., Tombesi F., Gaspari M., ITA, and USA

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, accretion, accretion disks, black hole physics, X-rays: galaxies, Astrophysics - High Energy Astrophysical Phenomena, Astronomy and Astrophysics, Quasar, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, accretion, accretion disk, black hole physic, Accretion (astrophysics), Redshift, galaxies [X-rays], Accretion disc, Settore FIS/05 - Astronomia e Astrofisica, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

X-ray emission from AGN is believed to be produced via Comptonization of optical/UV seed photons emitted by the accretion disk, up-scattered by hot electrons in a corona surrounding the black hole. A critical compactness vs. temperature threshold is predicted above which any increase in the source luminosity, for a fixed size, would then generate positron-electron pairs rather than continue heating the coronal plasma. Current observations seem to confirm that all AGN populate the region below this critical line. These models, however, have never been probed by observations in the high-luminosity regime, where the critical line is expected to reach low temperatures. To fill this observational gap, we selected two luminous ($log(L_{bol})>47.5$ erg/s) quasars, 2MASSJ1614346+470420 ($z=1.86$) and B1422+231 ($z=3.62$), and obtained XMM-Newton and NuSTAR deep observations for them. We performed detailed spectral analysis of their quasi-simultaneous soft and hard X-ray data, in order to constrain the parameters of their coronae. Using a phenomenological cut-off power-law model, with the inclusion of a reflection component, we derived rest-frame values of the high energy cut-off of $E_{cut}=106^{+102}_{-37}$ keV and $E_{cut}=66^{+17}_{-12}$ keV, respectively. Comptonization models consistently give as best-fit parameters electron temperatures of $\sim45$ keV and $\sim28$ keV, respectively, and optically thick coronae ($��>1$). These low coronal temperatures fall in the limited region allowed at these luminosities to avoid runaway pair production., 8 pages, 2 figures, accepted for publication in ApJ Letter

Published
2019

8. Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4-650224

Author

Carlo Ferrigno, D. de Martino, Alida Odendaal, Alessandro Papitto, Thomas D. Russell, Francesco Coti Zelati, Sergio Campana, David A. H. Buckley, S. M. Mazzola, Mariusz Gromadzki, Jian Li, Diego F. Torres, Simone Migliari, Nanda Rea, Enrico Bozzo, High Energy Astrophys. & Astropart. Phys (API, FNWI), Coti Zelati F., Papitto A., De Martino D., Buckley D.A.H., Odendaal A., Li J., Russell T.D., Torres D.F., Mazzola S.M., Bozzo E., Gromadzki M., Campana S., Rea N., Ferrigno C., Migliari S., DEU, and ESP

Subjects
Photon, X-rays: Binarie, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astrophysics, Methods: Data analysi, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Luminosity, Accretion, accretion disk, Settore FIS/05 - Astronomia E Astrofisica, Pulsar, Methods: Observational, 0103 physical sciences, Emission spectrum, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astronomy and Astrophysics, Stars: neutron, X-rays: Individuals: CXOU J110926.4-650224, Neutron star, 13. Climate action, Space and Planetary Science, Magnitude (astronomy), Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

We report on a multi-wavelength study of the unclassified X-ray source CXOU J110926.4-650224 (J1109). We identified the optical counterpart as a blue star with a magnitude of $\sim$20.1 (3300-10500 $\require{mediawiki-texvc} \AA$). The optical emission was variable on timescales from hundreds to thousands of seconds. The spectrum showed prominent emission lines with variable profiles at different epochs. Simultaneous XMM-Newton and NuSTAR observations revealed a bimodal distribution of the X-ray count rates on timescales as short as tens of seconds, as well as sporadic flaring activity. The average broad-band (0.3-79 keV) spectrum was adequately described by an absorbed power law model with photon index of $\Gamma$=1.63$\pm$0.01 (at 1$\sigma$ c.l.), and the X-ray luminosity was (2.16$\pm$0.04)$\times$10$^{34}$ erg s$^{-1}$ for a distance of 4 kpc. Based on observations with different instruments, the X-ray luminosity has remained relatively steady over the past $\sim$15 years. J1109 is spatially associated with the gamma-ray source FL8Y J1109.8-6500, which was detected with Fermi at an average luminosity of (1.5$\pm$0.2)$\times$10$^{34}$ erg s$^{-1}$ (assuming the distance of J1109) over the 0.1-300 GeV energy band between 2008 and 2016. The source was undetected during ATCA radio observations that were simultaneous with NuSTAR, down to a 3$\sigma$ flux upper limit of 18 $\mu$Jy/beam (at 7.25 GHz). We show that the phenomenological properties of J1109 point to a binary transitional pulsar candidate currently in a sub-luminous accretion disk state, and that the upper limits derived for the radio emission are consistent with the expected radio luminosity for accreting neutron stars at similar X-ray luminosities., Comment: 21 pages, 15 figures, accepted for publication in A&A

Published
2019
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9. New view of the corona of classical T Tauri stars: Effects of flaring activity in circumstellar disks

Author

Fabio Reale, Rosaria Bonito, Giovanni Peres, Costanza Argiroffi, S. Colombo, L. Ibgui, C. Stehlé, Salvatore Orlando, ITA, FRA, Università degli studi di Palermo - University of Palermo, Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Cergy Pontoise (UCP), Université Paris-Seine-Université Paris-Seine-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), INAF - Osservatorio Astronomico di Palermo (OAPa), Istituto Nazionale di Astrofisica (INAF), Politecnico di Milano [Milan] (POLIMI), Colombo, S., Orlando, S., Peres, G., Reale, F., Argiroffi, C., Bonito, R., Ibgui, L., and Stehlé, C.

Subjects
Young stellar object, Stars: flare, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, X-rays: stars, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, accretion, accretion disk, 01 natural sciences, magnetohydrodynamics (MHD), Settore FIS/05 - Astronomia E Astrofisica, accretion, 0103 physical sciences, Radiative transfer, Protostar, Astrophysics::Solar and Stellar Astrophysics, Stars: coronae, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], accretion disks, Stellar magnetic field, Astronomy and Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Corona, Accretion (astrophysics), T Tauri star, Astrophysics - Solar and Stellar Astrophysics, Heat flux, 13. Climate action, Space and Planetary Science, Stars: pre-main sequence, Astrophysics::Earth and Planetary Astrophysics
Abstract

Classical T Tauri stars (CTTSs) are young low-mass stellar objects accreting mass from their circumstellar disks. They are characterized by high levels of coronal activity as revealed by X-ray observations. This activity may affect the disk stability and the circumstellar environment. Here we investigate if an intense coronal activity due to flares occurring close to the accretion disk may perturb the inner disk stability, disrupt the inner part of the disk and, possibly, trigger accretion phenomena with rates comparable with those observed. We model a magnetized protostar surrounded by an accretion disk through 3D magnetohydrodinamic simulations. We explore cases characterized by a dipole plus an octupole stellar magnetic field configuration and different density of the disk or by different levels of flaring activity. As a result of the simulated intense flaring activity, we observe the formation of several loops that link the star to the disk; all these loops build up a hot extended corona with an X-ray luminosity comparable with typical values observed in CTTSs. The intense flaring activity close to the disk can strongly perturb the disk stability. The flares trigger overpressure waves which travel through the disk and modify its configuration. Accretion funnels may be triggered by the flaring activity, thus contributing to the mass accretion rate of the star. Accretion rates synthesized from the simulations are in a range between 10^-10 and 10^-9M_sun yr^-1 The accretion columns can be perturbed by the flares and they can interact with each other, possibly merging together in larger streams. As a result, the accretion pattern can be rather complex: the streams are highly inhomogeneous, with a complex density structure, and clumped, Comment: 12 pages, 9 figures

Published
2019
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11. Discovery of 105 Hz coherent pulsations in the ultracompact binary IGR J16597-3704

Author

Craig O. Heinke, Andrea Possenti, M. Burgay, Enrico Bozzo, Nathalie Degenaar, Thomas J. Maccarone, Gregory R. Sivakoff, T. Di Salvo, R. Iaria, A. Sanna, Rudy Wijnands, A. Riggio, Luciano Burderi, Diego Altamirano, Carlo Ferrigno, Arash Bahramian, Alessandro Papitto, N. D'Amico, Sanna, A., Bahramian, A., Bozzo, E., Heinke, C., Altamirano, D., Wijnands, R., Degenaar, N., Maccarone, T., Riggio, A., Di Salvo, T., Iaria, R., Burgay, M., Possenti, A., Ferrigno, C., Papitto, A., Sivakoff, G.R., D'Amico, N., Burderi, L., and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Photon, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, symbols.namesake, Accretion, accretion disk, Settore FIS/05 - Astronomia E Astrofisica, 0103 physical sciences, Binaries: general, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Accretion (meteorology), 010308 nuclear & particles physics, general, Stars: neutron, X-rays: binaries, Astronomy and Astrophysics, Space and Planetary Science [Accretion, accretion disks, Binaries], Astronomy and Astrophysic, Light curve, Orbital period, X-rays: binarie, Neutron star, Space and Planetary Science, Globular cluster, symbols, Electron temperature, Astrophysics - High Energy Astrophysical Phenomena, Doppler effect
Abstract

We report the discovery of X-ray pulsations at 105.2 Hz (9.5 ms) from the transient X-ray binary IGR J16597-3704 using NuSTAR and Swift. The source was discovered by INTEGRAL in the globular cluster NGC 6256 at a distance of 9.1 kpc. The X-ray pulsations show a clear Doppler modulation implying an orbital period of ~46 minutes and a projected semi-major axis of ~5 lt-ms, which makes IGR J16597-3704 an ultra-compact X-ray binary system. We estimated a minimum companion mass of 0.0065 solar masses, assuming a neutron star mass of 1.4 solar masses, and an inclination angle of, 4 pages, 4 images, Accepted for publication in A&A

Published
2018

12. The Spectral and Environment Properties of z ∼ 2.0-2.5 Quasar Pairs

Author

Joseph F. Hennawi, Jason X. Prochaska, John M. O'Meara, Tom Theuns, Marcel Neeleman, Michele Fumagalli, Marc Rafelski, Elisabeta Lusso, Lusso, E, Fumagalli, M, Rafelski, M, Neeleman, M, Prochaska, J, Hennawi, J, O'Meara, J, and Theuns, T

Subjects
Dark matter, galaxies: active, FOS: Physical sciences, quasars: absorption line, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, accretion, accretion disk, 01 natural sciences, quasars: general, 0103 physical sciences, Lyman continuum photons, Absorption (logic), Emission spectrum, 10. No inequality, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Quasar, Astrophysics - Astrophysics of Galaxies, Redshift, Lyman limit, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), intergalactic medium, Wide Field Camera 3
Abstract

We present the first results from our survey of intervening and proximate Lyman limit systems (LLSs) at $z$$\sim$2.0-2.5 using the Wide Field Camera 3 on-board the Hubble Space Telescope. The quasars in our sample are projected pairs with proper transverse separations $R_\perp$$\leq$150 kpc and line of sight velocity separations $\lesssim$11,000 km/s. We construct a stacked ultraviolet (rest-frame wavelengths 700-2000\AA) spectrum of pairs corrected for the intervening Lyman forest and Lyman continuum absorption. The observed spectral composite presents a moderate flux excess for the most prominent broad emission lines, a $\sim$30% decrease in flux at $\lambda$=800-900\AA\ compared to a stack of brighter quasars not in pairs at similar redshifts, and lower values of the mean free path of the HI ionizing radiation for pairs ($\lambda_{\rm mfp}^{912}=140.7\pm20.2~h_{70}^{-1}$Mpc) compared to single quasars ($\lambda_{\rm mfp}^{912}=213.8\pm28~h_{70}^{-1}$Mpc) at the average redshift $z\simeq2.44$. From the modelling of LLS absorption in these pairs, we find a higher ($\sim$20%) incidence of proximate LLSs with $\log N_{\rm HI}\geq17.2$ at $\delta v$$, Comment: Revised version with minor changes to the text following proof. Some of the references have been amended

Published
2018

13. Active Galactic Nuclei Feedback in an Elliptical Galaxy with the Most Updated AGN Physics (II): High-Angular Momentum Case

Author

Luca Ciotti, Feng Yuan, Ya-Ping Li, Doosoo Yoon, Jeremiah P. Ostriker, Zhao-Ming Gan, Yoon, Doosoo, Yuan, Feng, Gan, Zhao-Ming, Ostriker, Jeremiah P., Li, Ya-Ping, and Ciotti, Luca

Subjects
Angular momentum, Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, accretion, accretion disk, 01 natural sciences, Specific relative angular momentum, 0103 physical sciences, Surface brightness, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Star formation, Astronomy and Astrophysics, Astronomy and Astrophysic, black hole physic, Astrophysics - Astrophysics of Galaxies, Galaxy, Black hole, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: elliptical and lenticular, cD, Elliptical galaxy, galaxies: nuclei, galaxies: evolution, Astrophysics - High Energy Astrophysical Phenomena
Abstract

This is the second paper of our series of works of studying the effects of active galactic nuclei (AGN) feedback on the cosmological evolution of an isolated elliptical galaxy by performing two-dimensional high-resolution hydrodynamical numerical simulations. In these simulations, the inner boundary is chosen so that the Bondi radius is resolved. Physical processes like star formation, SNe Ia and II are taken into account. Compared to previous works, the main improvements is that we adopt the most updated AGN physics, which is described in detail in the first paper of this series (Yuan et al. 2018, Paper I). These improvements include the discrimination of the two accretion modes of the central AGN and the most updated descriptions of the wind and radiation in the two modes. In Paper I, we consider the case that the specific angular momentum of the gas in the galaxy is very low. In this paper, we consider the case that the specific angular momentum of the gas is high. In the galactic scale, we adopt the gravitational torques raised due to non-axisymmetric structure in the galaxy as the mechanism of the transfer of angular momentum of gas, as proposed in some recent works. Since our simulations are axisymmetric, we make use of a parameterized prescription to mimic this mechanism. Same as Paper I, we investigate the AGN light curve, typical AGN lifetime, growth of the black hole mass, AGN duty-cycle, star formation, and the X-ray surface brightness of the galaxy. Special attention is paid to the effects of specific angular momentum of the galaxy on these properties. We find that some results are qualitatively similar to those shown in Paper I, while some results such as star formation and black hole growth do show a significant difference due to the mass concentration in the galactic disk as a consequence of galactic rotation., Comment: 20 pages, 14 figures, accepted for publication to ApJ (Revised to match version published in ApJ)

Published
2018
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14. Upper Limits on Gravitational Waves from Scorpius X-1 from a Model-Based Cross-Correlation Search in Advanced LIGO Data

Author

Ligo, The Scientific Collaboration, the Virgo Collaboration, Abbott, B. P., Abbott, R., Abbott, T. D., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Afrough, M., Agarwal, B., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allen, G., Allocca, A., Altin, P. A., Amato, A., Ananyeva, A., Anderson, S. B., Anderson, W. G., Antier, S., Appert, S., Arai, K., Araya, M. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Aultoneal, K., Avila-Alvarez, A., Babak, S., Bacon, P., Bader, M. K. M., Bae, S., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Banagiri, S., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bawaj, M., Bazzan, M., B Ecsy, B., Beer, C., Bejger, M., Belahcene, I., Bell, A. S., Berger, B. K., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Billman, C. R., Birch, J., Birney, R., Birnholtz, O., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blackman, J., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bode, N., Boer, M., Bogaert, G., Bohe, A., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Broida, J. E., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Brunett, S., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cabero, M., Cadonati, L., Cagnoli, G., Cahillane, C., Calder On Bustillo, J., Callister, T. A., Calloni, E., Camp, J. B., Canepa, M., Priscilla Canizares, Cannon, K. C., Cao, H., Cao, J., Capano, C. D., Capocasa, E., Carbognani, F., Caride, S., Carney, M. F., Casanueva Diaz, J., Casentini, C., Caudill, S., Cavagli A, M., Cavalier, F., Cavalieri, R., Cella, G., Cepeda, C. B., Cerboni Baiardi, L., Cerretani, G., Cesarini, E., Chamberlin, S. J., Chan, M., Chao, S., Charlton, P., Chassande-Mottin, E., Chatterjee, D., Chatziioannou, K., Cheeseboro, B. D., Chen, H. Y., Chen, Y., Cheng, H. -P, Chincarini, A., Chiummo, A., Chmiel, T., Cho, H. S., Cho, M., Chow, J. H., Christensen, N., Chu, Q., Chua, A. J. K., Chua, S., Chung, A. K. W., Chung, S., Ciani, G., Ciolfi, R., Cirelli, C. E., Cirone, A., Clara, F., Clark, J. A., Cleva, F., Cocchieri, C., Coccia, E., Cohadon, P. -F, Colla, A., Collette, C. G., Cominsky, L. R., Constancio, M., Conti, L., Cooper, S. J., Corban, P., Corbitt, T. R., Corley, K. R., Cornish, N., Corsi, A., Cortese, S., Costa, C. A., Coughlin, M. W., Coughlin, S. B., Coulon, J. -P, Countryman, S. T., Couvares, P., Covas, P. B., Cowan, E. E., Coward, D. M., Cowart, M. J., Coyne, D. C., Coyne, R., Creighton, J. D. E., Creighton, T. D., Cripe, J., Crowder, S. G., Cullen, T. J., Cumming, A., Cunningham, L., Cuoco, E., Dal Canton, T., Danilishin, S. L., D Antonio, S., Danzmann, K., Dasgupta, A., Da Silva Costa, C. F., Dattilo, V., Dave, I., Davier, M., Davis, D., Daw, E. J., Day, B., De, S., Debra, D., Deelman, E., Degallaix, J., Laurentis, M., Del Eglise, S., Del Pozzo, W., Denker, T., Dent, T., Dergachev, V., Rosa, R., Derosa, R. T., Desalvo, R., Devenson, J., Devine, R. C., Dhurandhar, S., D Iaz, M. C., Di Fiore, L., Di Giovanni, M., Di Girolamo, T., Di Lieto, A., Di Pace, S., Di Palma, I., Di Renzo, F., Doctor, Z., Dolique, V., Donovan, F., Dooley, K. L., Doravari, S., Dorrington, I., Douglas, R., Dovale Alvarez, M., Downes, T. 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M., Magana Hernandez, I., Magana-Sandoval, F., Magana Zertuche, L., Magee, R. M., Majorana, E., Maksimovic, I., Man, N., Mandic, V., Mangano, V., Mansell, G. L., Manske, M., Mantovani, M., Marchesoni, F., Marion, F., M Arka, S., M Arka, Z., Markakis, C., Markosyan, A. S., Maros, E., Martelli, F., Martellini, L., Martin, I. W., Martynov, D. V., Mason, K., Masserot, A., Massinger, T. J., Masso-Reid, M., Mastrogiovanni, S., Matas, A., Matichard, F., Matone, L., Mavalvala, N., Mayani, R., Mazumder, N., Mccarthy, R., Mcclelland, D. E., Mccormick, S., Mcculler, L., Mcguire, S. C., Mcintyre, G., Mciver, J., Mcmanus, D. J., Mcrae, T., Mcwilliams, S. T., Meacher, D., Meadors, G. D., Meidam, J., Mejuto-Villa, E., Melatos, A., Mendell, G., Mercer, R. A., Merilh, E. L., Merzougui, M., Meshkov, S., Messenger, C., Messick, C., Metzdorff, R., Meyers, P. M., Mezzani, F., Miao, H., Michel, C., Middleton, H., Mikhailov, E. E., Milano, L., Miller, A. L., Miller, A., Miller, B. 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P., Abbott, R., Abbott, T. D., Acernese, F., Ackley, K., Adams, C., Adams, T., Addesso, P., Adhikari, R. X., Adya, V. B., Affeldt, C., Afrough, M., Agarwal, B., Agathos, M., Agatsuma, K., Aggarwal, N., Aguiar, O. D., Aiello, L., Ain, A., Ajith, P., Allen, B., Allen, G., Allocca, A., Altin, P. A., Amato, A., Ananyeva, A., Anderson, S. B., Anderson, W. G., Antier, S., Appert, S., Arai, K., Araya, M. C., Areeda, J. S., Arnaud, N., Arun, K. G., Ascenzi, S., Ashton, G., Ast, M., Aston, S. M., Astone, P., Aufmuth, P., Aulbert, C., Aultoneal, K., Avila-Alvarez, A., Babak, S., Bacon, P., Bader, M. K. M., Bae, S., Baker, P. T., Baldaccini, F., Ballardin, G., Ballmer, S. W., Banagiri, S., Barayoga, J. C., Barclay, S. E., Barish, B. C., Barker, D., Barone, F., Barr, B., Barsotti, L., Barsuglia, M., Barta, D., Bartlett, J., Bartos, I., Bassiri, R., Basti, A., Batch, J. C., Baune, C., Bawaj, M., Bazzan, M., Bécsy, B., Beer, C., Bejger, M., Belahcene, I., Bell, A. S., Berger, B. K., Bergmann, G., Berry, C. P. L., Bersanetti, D., Bertolini, A., Betzwieser, J., Bhagwat, S., Bhandare, R., Bilenko, I. A., Billingsley, G., Billman, C. R., Birch, J., Birney, R., Birnholtz, O., Biscans, S., Bisht, A., Bitossi, M., Biwer, C., Bizouard, M. A., Blackburn, J. K., Blackman, J., Blair, C. D., Blair, D. G., Blair, R. M., Bloemen, S., Bock, O., Bode, N., Boer, M., Bogaert, G., Bohe, A., Bondu, F., Bonnand, R., Boom, B. A., Bork, R., Boschi, V., Bose, S., Bouffanais, Y., Bozzi, A., Bradaschia, C., Brady, P. R., Braginsky, V. B., Branchesi, M., Brau, J. E., Briant, T., Brillet, A., Brinkmann, M., Brisson, V., Brockill, P., Broida, J. E., Brooks, A. F., Brown, D. A., Brown, D. D., Brown, N. M., Brunett, S., Buchanan, C. C., Buikema, A., Bulik, T., Bulten, H. J., Buonanno, A., Buskulic, D., Buy, C., Byer, R. L., Cabero, M., Cadonati, L., Cagnoli, G., Cahillane, C., Bustillo, J. Calderón, Callister, T. A., Calloni, E., Camp, J. B., Canepa, M., Canizares, P., Cannon, K. 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Z., Wang, M., Wang, Y. -F., Wang, Y., Ward, R. L., Warner, J., Was, M., Watchi, J., Weaver, B., Wei, L. -W., Weinert, M., Weinstein, A. J., Weiss, R., Wen, L., Wessel, E. K., Wessels, P., Westphal, T., Wette, K., Whelan, J. T., Whiting, B. F., Whittle, C., Williams, D., Williams, R. D., Williamson, A. R., Willis, J. L., Willke, B., Wimmer, M. H., Winkler, W., Wipf, C. C., Wittel, H., Woan, G., Woehler, J., Wofford, J., Wong, K. W. K., Worden, J., Wright, J. L., Wu, D. S., Wu, G., Yam, W., Yamamoto, H., Yancey, C. C., Yap, M. J., Yu, Hang, Yu, Haocun, Yvert, M., Zanolin, M., Zelenova, T., Zendri, J. -P., Zevin, M., Zhang, L., Zhang, M., Zhang, T., Zhang, Y. -H., Zhao, C., Zhou, M., Zhou, Z., Zhu, X. J., Zucker, M. E., Zweizig, J., Steeghs, D., Wang, L., The LIGO Scientific Collaboration, The Virgo Collaboration, Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Annecy de Physique des Particules ( LAPP/Laboratoire d'Annecy-le-Vieux de Physique des Particules ), Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Université Savoie Mont Blanc ( USMB [Université de Savoie] [Université de Chambéry] ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire des matériaux avancés ( LMA ), Université Claude Bernard Lyon 1 ( UCBL ), Université de Lyon-Université de Lyon-Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de l'Accélérateur Linéaire ( LAL ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), AstroParticule et Cosmologie ( APC - UMR 7164 ), Centre National de la Recherche Scientifique ( CNRS ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Commissariat à l'énergie atomique et aux énergies alternatives ( CEA ), Astrophysique Relativiste Théories Expériences Métrologie Instrumentation Signaux ( ARTEMIS ), Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de la Côte d'Azur, Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Physique de Rennes ( IPR ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Kastler Brossel ( LKB (Lhomond) ), 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 ) -Centre National de la Recherche Scientifique ( CNRS ), (Astro)-Particles Physics, Massachusetts Institute of Technology. Department of Physics, LIGO (Observatory : Massachusetts Institute of Technology), MIT Kavli Institute for Astrophysics and Space Research, Aggarwal, Nancy, Barsotti, Lisa, Biscans, Sebastien, Buikema, Aaron, Donovan, Frederick J, Eisenstein, Robert Alan, Essick, Reed Clasey, Evans, Matthew J, Fernandez Galiana, Alvaro-Miguel, Fritschel, Peter K, Gras, Slawomir, Katsavounidis, Erotokritos, Kontos, Antonios, Lanza Jr, Robert K, Libson, Adam A., Lynch, Ryan Christopher, MacInnis, Myron E, Martynov, Denis, Mason, Kenneth R, Matichard, Fabrice, Mavalvala, Nergis, McCuller, Lee P, Miller, John, Mittleman, Richard K, Ray Pitambar Mohapatra, Satyanarayan, Oelker, Eric Glenn, Shoemaker, David H, Tse, Maggie, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)

Subjects
accretion, accretion disks, gravitational waves, stars: neutron, X-rays: binaries, Astronomy and Astrophysics, Space and Planetary Science, Astronomy, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], accretion, accretion disk, spin, 01 natural sciences, General Relativity and Quantum Cosmology, neutron, accretion, accretion,accretion disks, Range (statistics), LIGO, neutron star, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, gravitational wave, QC, QB, Physics, astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), accretion disks, SDG 10 - Reduced Inequalities, X-rays: binarie, Amplitude, X-ray: binary, Astrophysics - High Energy Astrophysical Phenomena, stars, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), 1ST SEARCH, Accretion, neutron [stars], 0103 physical sciences, Continuous signal, Orbital elements, Cross-correlation, 010308 nuclear & particles physics, Gravitational wave, Physique, gravitational radiation, Astronomy and Astrophysic, gravitational radiation detector, Computational physics, coherence, detector: sensitivity, Neutron star, Physics and Astronomy, gravitational radiation: emission, RADIATION, binaries [X-rays], neutron, X-rays: binaries [accretion, accretion disks, gravitational waves, stars], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

We present the results of a semicoherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using data from the first Advanced LIGO observing run. The search method uses details of the modeled, parametrized continuous signal to combine coherently data separated by less than a specified coherence time, which can be adjusted to trade off sensitivity against computational cost. A search was conducted over the frequency range 25-2000 Hz, spanning the current observationally constrained range of binary orbital parameters. No significant detection candidates were found, and frequency-dependent upper limits were set using a combination of sensitivity estimates and simulated signal injections. The most stringent upper limit was set at 175 Hz, with comparable limits set across the most sensitive frequency range from 100 to 200 Hz. At this frequency, the 95% upper limit on the signal amplitude h0 is 2.3 × 10-25 marginalized over the unknown inclination angle of the neutron star's spin, and 8.0 × 10-26 assuming the best orientation (which results in circularly polarized gravitational waves). These limits are a factor of 3-4 stronger than those set by other analyses of the same data, and a factor of ∼ 7 stronger than the best upper limits set using data from Initial LIGO science runs. In the vicinity of 100 Hz, the limits are a factor of between 1.2 and 3.5 above the predictions of the torque balance model, depending on the inclination angle; if the most likely inclination angle of 44° is assumed, they are within a factor of 1.7., 0, info:eu-repo/semantics/published

Published
2017
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15. The fine line between total and partial tidal disruption events

Author

Alessandro Lupi, Sergio Campana, Enrico Ramirez-Ruiz, Deborah Mainetti, Monica Colpi, James Guillochon, Eric R. Coughlin, Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ITA, USA, FRA, Mainetti, D, Lupi, A, Campana, S, Colpi, M, Coughlin, E, Guillochon, J, Ramirez Ruiz, E, Institut d'Astrophysique de Paris ( IAP ), and Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS )

Subjects
Critical distance, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, black hole physics, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Star (graph theory), Fine line, 01 natural sciences, methods: numerical, Black hole physic, General Relativity and Quantum Cosmology, Accretion, accretion disk, Accretion disc, accretion, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Finite mass, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Accretion, accretion disks, Black hole physics, Galaxies: nuclei, Hydrodynamics, Methods: numerical, Astronomy and Astrophysics, Space and Planetary Science, Accretion (meteorology), 010308 nuclear & particles physics, Hydrodynamic, Astronomy and Astrophysic, Galaxy, Polytrope, hydrodynamics, Astrophysics::Earth and Planetary Astrophysics, galaxies: nuclei, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Flares from tidal disruption events are unique tracers of quiescent black holes at the centre of galaxies. The appearance of these flares is very sensitive to whether the star is totally or partially disrupted, and in this paper we seek to identify the critical distance of the star from the black hole (r_d) that enables us to distinguish between these two outcomes. We perform here Mesh-free Finite Mass, traditional, and modern Smoothed Particle Hydrodynamical simulations of star-black hole close encounters, with the aim of checking if the value of r_d depends on the simulation technique. We find that the critical distance (or the so-called critical disruption parameter beta_d) depends only weakly on the adopted simulation method, being beta_d=0.92\pm 0.02 for a gamma=5/3 polytrope and beta_d=2.01\pm 0.01 for a gamma=4/3 polytrope., 8 pages, 8 figures, 2 tables; accepted to A&A

Published
2017
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16. Hydrodynamic Modeling of Accretion Impacts in Classical T Tauri Stars: Radiative Heating of the Pre-shock Plasma

Author

Costanza Argiroffi, Rosaria Bonito, Giovanni Peres, G. Costa, Salvatore Orlando, ITA, Costa, G., Orlando, S., Peres, G., Argiroffi, C., and Bonito, R.

Subjects
Shock wave, Radiative cooling, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Accretion, accretion disk, Settore FIS/05 - Astronomia E Astrofisica, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, X-rays: star, Irradiation, Emission spectrum, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Hydrodynamic, Plasma, Astronomy and Astrophysic, Thermal conduction, Accretion (astrophysics), T Tauri star, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Stars: pre-main sequence, Astrophysics::Earth and Planetary Astrophysics
Abstract

Context. It is generally accepted that, in classical T Tauri stars, the plasma from the circumstellar disc accretes onto the stellar surface with free-fall velocity and the impact generates a shock. The impact region is expected to contribute to emission in different spectral bands; many studies have confirmed that the X-rays arise from the post-shock plasma but, otherwise, there are no studies in the literature investigating the origin of the observed UV emission which is apparently correlated to accretion. Aims: We investigated the effect of radiative heating of the infalling material by the post-shock plasma at the base of the accretion stream, with the aim to identify in which region a significant part of the UV emission originates. Methods: We developed a one-dimensional hydrodynamic model describing the impact of an accretion stream onto the stellar surface; the model takes into account the gravity, the radiative cooling of an optically thin plasma, the thermal conduction, and the heating due to absorption of X-ray radiation. The latter term represents the heating of the infalling plasma due to the absorption of X-rays emitted from the post-shock region. Results: We found that the radiative heating of the pre-shock plasma plays a non-negligible role in the accretion phenomenon. In particular, the dense and cold plasma of the pre-shock accretion column is gradually heated up to a few 105K due to irradiation of X-rays arising from the shocked plasma at the impact region. This heating mechanism does not affect significantly the dynamics of the post-shock plasma. On the other hand, a region of radiatively heated gas (that we consider a precursor) forms in the unshocked accretion column and contributes significantly to UV emission. Our model naturally reproduces the luminosity of UV emission lines correlated to accretion and shows that most of the UV emission originates from the precursor....

Published
2016

17. Angular momentum, accretion and radial flows in chemodynamical models of spiral galaxies

Author

Pezzulli, G., Fraternali, F., Pezzulli, G., Fraternali, F., and Astronomy

Subjects
accretion disks, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy and Astrophysic, accretion, accretion disk, Astrophysics - Astrophysics of Galaxies, Galaxy: abundance, accretion, galaxies: abundance, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Galaxy: abundances, Astrophysics::Solar and Stellar Astrophysics, galaxies: abundances, intergalactic medium, Astrophysics::Earth and Planetary Astrophysics, galaxies: evolution, galaxies: ISM, Astrophysics::Galaxy Astrophysics
Abstract

Gas accretion and radial flows are key ingredients of the chemical evolution of spiral galaxies. They are also tightly linked to each other (accretion drives radial flows, due to angular momentum conservation) and should therefore be modelled simultaneously. We summarise an algorithm that can be used to consistently compute accretion profiles, radial flows and abundance gradients under quite general conditions and we describe illustrative applications to the Milky Way. We find that gas-phase abundance gradients strongly depend on the angular momentum of the accreting material and, in the outer regions, they are significantly affected by the choice of boundary conditions., 4 pages, 2 figures. Proceedings of the 592 WE-Heraeus Seminar. To appear in Astronomische Nachricthen, special issue "Reconstructing the Milky Way's history: spectroscopic surveys, asteroseismology and chemodynamical models", Guest Editors C. Chiappini, J. Montalban and M. Steffen

Published
2016

18. A broadband spectral analysis of 4U 1702-429 using XMM-Newton and BeppoSAX data

Author

A. Segreto, T. Di Salvo, Alessandro Riggio, N. D'Amico, Andrea Santangelo, Andrea Sanna, Angelo Gambino, S. M. Mazzola, M. Del Santo, R. Iaria, Luciano Burderi, Mazzola, S.M., Iaria, R., Di Salvo, T., Del Santo, M., Sanna, A., Gambino, A.F., Riggio, A., Segreto, A., Burderi, L., Santangelo, A., and D'Amico, N.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, X-rays: Binarie, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Binary number, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Corona, Stars: neutron, Spectral line, Neutron star, Accretion, accretion disk, Space and Planetary Science, Ionization, Stars: Individual: 4U 1702-429, 0103 physical sciences, Reflection (physics), Black-body radiation, Astrophysics - High Energy Astrophysical Phenomena, Low Mass, 010303 astronomy & astrophysics
Abstract

Most of the X-ray binary systems containing neutron stars classified as Atoll sources show two different spectral states, called soft and hard. Moreover, a large number of these systems show a reflection component relativistically smeared in their spectra, which gives information on the innermost region of the system. Our aim is to investigate the poorly studied broadband spectrum of the low mass X-ray binary system 4U 1702-429, which was recently analysed combining XMM-Newton and INTEGRAL data. The peculiar value of the reflection fraction brought us to analyse further broadband spectra of 4U 1702-429. We re-analysed the spectrum of the XMM-Newton/INTEGRAL observation of 4U 1702-429 in the 0.3-60 keV energy range and we extracted three 0.1-100 keV spectra of the source analysing three observations collected with the BeppoSAX satellite. We find that the XMM-Newton/INTEGRAL spectrum is well fitted using a model composed of a disc blackbody plus a Comptonised component and a smeared reflection component. We used the same spectral model for the BeppoSAX spectra, finding out that the addition of a smeared reflection component is statistically significant. The best-fit values of the parameters are compatible to each other for the BeppoSAX spectra. We find that the reflection fraction is $0.05^{+0.03}_{-0.01}$ for the XMM-Newton/INTEGRAL spectrum and between 0.15 and 0.4 for BeppoSAX ones. The relative reflection fraction and the ionisation parameter are incompatible between the XMM-Newton/INTEGRAL and the BeppoSAX observations and the characteristics of the Comptonising corona suggest that the source was in a soft state in the former observation and in a hard state in the latter., 10 pages, 14 figures, submitted to A&A

Published
2019
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19. Short Gamma-Ray Bursts from the Merger of Two Black Holes

Author

Rosalba Perna, Bruno Giacomazzo, Davide Lazzati, Perna, R, Lazzati, D, and Giacomazzo, B

Subjects
Astrophysics::High Energy Astrophysical Phenomena, gamma-ray burst: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, general [gamma-ray burst], accretion, accretion disk, 01 natural sciences, massive [stars], accretion, 0103 physical sciences, general, gravitational waves, stars black holes, stars: massive, Space and Planetary Science, Astronomy and Astrophysics [accretion, accretion disks, gamma-ray burst], stars black hole, 010303 astronomy & astrophysics, gravitational wave, accretion disk, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Gravitational wave, accretion disks, Astronomy and Astrophysics, Accretion (astrophysics), Black hole, Neutron star, Supernova, Stars, Astrophysics::Earth and Planetary Astrophysics, Gamma-ray burst, Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

Short Gamma-Ray Bursts (GRBs) are explosions of cosmic origin believed to be associated with the merger of two compact objects, either two neutron stars, or a neutron star and a black hole. The presence of at least one neutron star has long been thought to be an essential element of the model: its tidal disruption provides the needed baryonic material whose rapid accretion onto the post-merger black hole powers the burst. The recent tentative detection by the Fermi satellite of a short GRB in association with the gravitational wave signal GW150914 produced by the merger of two black holes has challenged this standard paradigm. Here we show that the evolution of two high-mass, low-metallicity stars with main sequence rotational speeds a few tens of percent of the critical speed eventually undergoing a weak supernova explosion {\em can} produce a short gamma-ray burst. The outer layers of the envelope of the last exploding star remain bound and circularize at large radii. With time, the disk cools and becomes neutral, suppressing the magneto-rotational instability, and hence the viscosity. The disk remains 'long-lived dead' until tidal torques and shocks during the pre-merger phase heat it up and re-ignite accretion, rapidly consuming the disk and powering the short gamma-ray burst., Matches version accepted to ApJL

Published
2016

20. Broadband observations of the X-ray burster 4U1705-44 with Beppo SAX

Author

P. Kaaret, T. Di Salvo, R. Iaria, E. Egron, Andrea Santangelo, B. Mück, S. Piraino, Antonino D'Ai, Piraino, S., Santangelo, A., Mück, B., Kaaret, P., Di Salvo, T., D'Aì, A., Iaria, R., Egron, E., ITA, USA, and DEU

Subjects
X-ray burster, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), Astrophysics, X-rays: general, 01 natural sciences, Spectral line, Accretion, accretion disk, Stars: individual: 4U 1705-44, Settore FIS/05 - Astronomia E Astrofisica, 0103 physical sciences, Black-body radiation, X-rays: star, 010303 astronomy & astrophysics, Line (formation), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Accretion (meteorology), 010308 nuclear & particles physics, Astronomy and Astrophysics, Astronomy and Astrophysic, X-rays: binarie, Stars: neutron, Neutron star, Space and Planetary Science, Reflection (physics), individual: 4U 1705-44, X-rays: binaries, X-rays: stars, Space and Planetary Science [Accretion, accretion disks, Stars], Astrophysics - High Energy Astrophysical Phenomena
Abstract

4U 1705-44 is one of the most-studied type I X-ray burster and Atoll sources. This source represents a perfect candidate to test different models proposed to self-consistently track the physical changes occurring between different spectral states because it shows clear spectral state transitions. The broadband coverage, the sensitivity and energy resolution of the BeppoSAX satellite offers the opportunity to disentangle the components that form the total X-ray spectrum and to study their changes according to the spectral state. Using two BeppoSAX observations carried out in August and October 2000, respectively, for a total effective exposure time of about 100 ks, we study the spectral evolution of the source from a soft to hard state. Energy spectra are selected according to the source position in the color-color diagram (CCD) Results. We succeeded in modeling the spectra of the source using a physical self-consistent scenario for both the island and banana branches (the double Comptonization scenario). The components observed are the soft Comptonization and hard Comptonization, the blackbody, and a reflection component with a broad iron line. When the source moves from the banana state to the island state, the parameters of the two Comptonization components change significantly and the blackbody component becomes too weak to be detected. We interpret the soft Comptonization component as emission from the hot plasma surrounding the neutron star, hard Comptonization as emission from the disk region, and the blackbody component as emission from the inner accretion disk. The broad feature in the iron line region is compatible with reflection from the inner accretion disk., Comment: 8 pages, 10 figures, accepted for publication by A&A

Published
2016

21. A TEST of the NATURE of the FE K LINE in the NEUTRON STAR LOW-MASS X-RAY BINARY SERPENS X-1

Author

Jeroen Homan, Luciano Burderi, Sudip Bhattacharyya, Tiziana Di Salvo, Chia-Ying Chiang, Michael Parker, Jon M. Miller, Elise Egron, R. Iaria, Antonino D'Ai, Edward M. Cackett, Didier Barret, Dacheng Lin, Andrew C. Fabian, M. Coleman Miller, Chiang, C., Cackett, E., Miller, J., Barret, D., Fabian, A., D'Aì, A., Parker, M., Bhattacharyya, S., Burderi, L., Di Salvo, T., Egron, E., Homan, J., Iaria, R., Lin, D., Miller, M., ITA, USA, GBR, FRA, and IND

Subjects
Serpens, Astrophysics::High Energy Astrophysical Phenomena, X-ray binary, FOS: Physical sciences, Astrophysics, accretion, accretion disk, 01 natural sciences, Spectral line, stars: neutron, Settore FIS/05 - Astronomia E Astrofisica, 0103 physical sciences, Emission spectrum, 010303 astronomy & astrophysics, Line (formation), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, profiles, X-rays: binaries, Space and Planetary Science [accretion, accretion disks, line], Astronomy and Astrophysic, K-line, X-rays: binarie, Black hole, Neutron star, line: profile, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena
Abstract

Broad Fe K emission lines have been widely observed in the X-ray spectra of black hole systems, and in neutron star systems as well. The intrinsically narrow Fe K fluorescent line is generally believed to be part of the reflection spectrum originating in an illuminated accretion disk, and broadened by strong relativistic effects. However, the nature of the lines in neutron star LMXBs has been under debate. We therefore obtained the longest, high-resolution X-ray spectrum of a neutron star LMXB to date with a 300 ks Chandra HETGS observation of Serpens X-1. The observation was taken under the "continuous clocking" mode and thus free of photon pile-up effects. We carry out a systematic analysis and find that the blurred reflection model fits the Fe line of Serpens X-1 significantly better than a broad Gaussian component does, implying that the relativistic reflection scenario is much preferred. Chandra HETGS also provides highest spectral resolution view of the Fe K region and we find no strong evidence for additional narrow lines., Accepted for publication in ApJ

Published
2016

22. NuSTAR reveals the extreme properties of the super-Eddington accreting supermassive black hole in PG 1247+267

Author

Duncan Farrah, Franz E. Bauer, M. Cappi, W. N. Brandt, W. W. Zhang, Giorgio Lanzuisi, M. Dadina, Enrico Piconcelli, Fausto Vagnetti, Andrea Comastri, C. J. Hailey, William W. Craig, S. E. Boggs, Fiona A. Harrison, Giorgio Matt, Claudio Ricci, A. C. Fabian, Dom Walton, Andrea Marinucci, F. E. Christensen, Michele Perna, S. Puccetti, David R. Ballantyne, Alberto Masini, D. Stern, C. Vignali, Cristian Saez, B. Luo, Marcella Brusa, Lanzuisi, G., Perna, M., Comastri, A., Cappi, M., Dadina, M., Marinucci, Andrea, Masini, A., Matt, Giorgio, Vagnetti, F., Vignali, C., Ballantyne, D. R., Bauer, F. E., Boggs, S. E., Brandt, W. N., Brusa, M., Christensen, F. E., Craig, W. W., Fabian, A. C., Farrah, D., Hailey, C. J., Harrison, F. A., Luo, B., Piconcelli, E., Puccetti, S., Ricci, C., Saez, C., Stern, D., Walton, D. J., Zhang, W. W., Marinucci, A., Matt, G., Ballantyne, D.R., Bauer, F.E., Boggs, S.E., Brandt, W.N., Christensen, F.E., Craig, W.W., Fabian, A.C., Hailey, C.J., Harrison, F.A., Walton, D.J., and Zhang, W.W.

Subjects
Accretion, active [Galaxies], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Power law, Relativistic disk, Quasars: individual: PG 1247+267, Accretion, accretion disk, Settore FIS/05 - Astronomia e Astrofisica, individual: PG 1247+267 [Quasars], Ionization, 0103 physical sciences, Cutoff, Emission spectrum, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Galaxies: nuclei, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, Quasar, Plasma, Galaxies: active, Astronomy and Astrophysic, Redshift, Space and Planetary Science, nuclei [Galaxies], Accretion disks
Abstract

PG1247+267 is one of the most luminous known quasars at z similar to 2 and is a strongly super-Eddington accreting supermassive black hole (SMBH) candidate. We obtained NuSTAR data of this intriguing source in December 2014 with the aim of studying its high-energy emission, leveraging the broad band covered by the new NuSTAR and the archival XMM-Newton data. Several measurements are in agreement with the super-Eddington scenario for PG1247+267: the soft power law (Gamma = 2.3 +/- 0.1); the weak ionized Fe emission line; and a hint of the presence of outflowing ionized gas surrounding the SMBH. The presence of an extreme reflection component is instead at odds with the high accretion rate proposed for this quasar. This can be explained with three different scenarios; all of them are in good agreement with the existing data, but imply very different conclusions: i) a variable primary power law observed in a low state, superimposed on a reflection component echoing a past, higher flux state; ii) a power law continuum obscured by an ionized, Compton thick, partial covering absorber; and iii) a relativistic disk reflector in a lamp-post geometry, with low coronal height and high BH spin. The first model is able to explain the high reflection component in terms of variability. The second does not require any reflection to reproduce the hard emission, while a rather low high-energy cutoff of similar to 100 keV is detected for the first time in such a high redshift source. The third model require a face-on geometry, which may affect the SMBH mass and Eddington ratio measurements. Deeper X-ray broad-band data are required in order to distinguish between these possibilities.

Published
2016
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23. XMMSL1J063045.9-603110: a tidal disruption event fallen into the back burner

Author

Sergio Campana, Monica Colpi, Deborah Mainetti, ITA, Mainetti, D, Campana, S, and Colpi, M

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, X-rays:galaxie, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Compact star, 01 natural sciences, law.invention, Tidal disruption event, Accretion, accretion disk, law, 0103 physical sciences, Tidal force, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, galaxies:dwarf, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Galaxies: dwarf, 010308 nuclear & particles physics, Astronomy and Astrophysics, Accretion (astrophysics), Galaxy, Black hole, Space and Planetary Science, Globular cluster, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, X-rays: galaxie, Flare
Abstract

Black holes at the centre of quiescent galaxies can be switched on when they accrete gas that is gained from stellar tidal disruptions. A star approaching a black hole on a low angular momentum orbit may be ripped apart by tidal forces, which triggers raining down of a fraction of stellar debris onto the compact object through an accretion disc and powers a bright flare. In this paper we discuss XMMSL1J063045.9-603110 as a candidate object for a tidal disruption event. The source has recently been detected to be bright in the soft X-rays during an XMM-Newton slew and later showed an X-ray flux decay by a factor of about 10 in twenty days. We analyse XMM-Newton and Swift data. XMMSL1J063045.9-603110 shows several features typical of tidal disruption events: the X-ray spectrum shows the characteristics of a spectrum arising from a thermal accretion disc, the flux decay follows a t^-5/3 law, and the flux variation is > 350. Optical observations testify that XMMSL1J063045.9-603110 is probably associated with an extremely small galaxy or even a globular cluster, which suggests that intermediate-mass black holes are located in the cores of (at least) some of them., 8 pages, 4 figures; accepted to A&A

Published
2016

24. Retrograde binaries of massive black holes in circumbinary accretion discs

Author

Massimo Dotti, Cristián Maureira-Fredes, Monica Colpi, Pau Amaro-Seoane, Amaro Seoane, P, Maureira Fredes, C, Dotti, M, and Colpi, M

Subjects
Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Binary number, Astrophysics, 01 natural sciences, Gravitation, General Relativity and Quantum Cosmology, Accretion, accretion disk, Accretion disc, 0103 physical sciences, Roche lobe, Methods: analytical, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Methods: numerical, 010308 nuclear & particles physics, Astronomy and Astrophysics, Hydrodynamic, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Black hole, Density distribution, Drag, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Circumbinary planet, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

We explore the hardening of a massive black hole binary embedded in a circum-binary gas disc when the binary and the gas are coplanar and the gas is counter-rotating. The secondary black hole, revolving in the direction opposite to the gas, experiences a drag from gas-dynamical friction and from direct accretion of part of it. Using two-dimensional (2D) hydrodynamical grid simulations we investigate the effect of changing the accretion prescriptions on the dynamics of the secondary black hole which in turn affect the binary hardening and eccentricity evolution. We find that realistic accretion prescriptions lead to results that differ from those inferred assuming accretion of all the gas within the Roche Lobe of the secondary black hole. Different accretion prescriptions result in different disc's surface densities which alter the black hole's dynamics back. Full 3D SPH realizations of a number of representative cases, run over a shorter interval of time, validate the general trends observed in the less computationally demanding 2D simulations. Initially circular black hole binaries increase only slightly their eccentricity which then oscillates around small values (, abridged. Accepted for publication A&A

Published
2016

25. High-energy monitoring of Seyfert galaxies: The case of NGC 4593

Author

Ursini, F., Petrucci, P. -O., Matt, G., Bianchi, S., Cappi, M., De Marco, B., De Rosa, A., Malzac, J., Ponti, G., Ursini, Francesco, Petrucci, P. O., Matt, Giorgio, Bianchi, Stefano, Cappi, M., De Marco, B., De Rosa, A., Malzac, J., Ponti, G., Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-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), Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), galaxie [X-rays], Seyfert [Galaxies], Accretion, accretion disk, active [Galaxies], Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, individuals (NGC 4593) [X-rays], content, Astronomy and Astrophysic, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

We discuss preliminary results from a joint XMM-Newton and NuSTAR monitoring program on the active galactic nucleus NGC 4593, consisting of 5x20 ks observations, spaced by two days, performed in January 2015. The source is found to be variable, both in flux and spectral shape, on time scales as short as a few ks. The spectrum clearly softens when the source brightens. A simple timing analysis suggests the presence of a variable soft excess that correlates with the primary continuum., Proceedings of the XMM Science Workshop 2015; to appear in Astronomische Nachrichten

Published
2016
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26. The coronal parameters of local Seyfert galaxies

Author

Marinucci, A., Tortosa, A., Marinucci, A., and Tortosa, A.

Subjects
galaxie [X-rays], High Energy Astrophysical Phenomena (astro-ph.HE), Seyfert [Galaxies], active [Galaxies], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy and Astrophysic, Accretion, accretion disk, Space and Planetary Science, nuclei [Galaxies], Astrophysics::Solar and Stellar Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract

One of the open problems for AGN is the nature of the primary X-ray emission: it is likely due to Comptonization of soft UV photons, but the optical depth and temperature of the emitting corona were largely unknown before the launch of the Nuclear Spectroscopic Telescope Array (NuSTAR). It is the first focusing hard X-ray telescope on orbit, 100 times more sensitive in the 10-79 keV band compared to previous observatories, enabling the study of AGN at high energies with high precision. We present and discuss the results on the hot corona parameters of Active Galactic Nuclei that have been recently measured with NuSTAR (often in coordination with XMM-Newton, Suzaku or Swift) with unprecedented accuracy, in a number of local Seyfert galaxies., 6 pages, 3 figures, accepted for publication on Astronomische Nachrichten/Astronomical Notes, proceedings of "The Extremes of Black Hole Accretion"

Published
2015

27. High ionisation absorption in low mass X-ray binaries

Author

PONTI, GABRIELE, Bianchi, S., Muñoz-Darias, T., De, K., Fender, R., Merloni, A., Ponti, G, Bianchi, Stefano, Muñoz Darias, T., De, K., Fender, R., and Merloni, A.

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), binarie [X-rays], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astronomy and Astrophysic, individuals (AX J1745.6-2901, EXO0748-676) [X-rays], spectroscopic [Techniques], Accretion, accretion disk, Space and Planetary Science, Astrophysics::Solar and Stellar Astrophysics, winds, outflow [Stars], Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics
Abstract

The advent of the new generation of X-ray telescopes yielded a significant step forward in our understanding of ionised absorption generated in the accretion discs of X-ray binaries. It has become evident that these relatively weak and narrow absorption features, sporadically present in the X-ray spectra of some systems, are actually the signature of equatorial outflows, which might carry away more matter than that being accreted. Therefore, they play a major role in the accretion phenomenon. These outflows (or ionised atmospheres) are ubiquitous during the softer states but absent during the power-law dominated, hard states, suggesting a strong link with the state of the inner accretion disc, presence of the radio-jet and the properties of the central source. Here, we discuss the current understanding of this field., Accepted for publication in Astronomical Notes (Proceedings of "The Extremes of Black Hole Accretion" workshop, held at ESAC, Madrid, in June 2015)

Published
2015

28. Pan-STARRS1 variability of XMM-COSMOS AGN. II. Physical correlations and power spectrum analysis

Author

Roberto P. Saglia, Giorgio Lanzuisi, Kirpal Nandra, Gabriele Ponti, Mara Salvato, Benny Trakhtenbrot, T. Simm, Ralf Bender, Simm, T., Salvato, M., Saglia, R., Ponti, G., Lanzuisi, G., Trakhtenbrot, B., Nandra, K., and Bender, R.

Subjects
Active galactic nucleus, Hubble Deep Field, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, Black hole physic, Accretion, accretion disk, 0103 physical sciences, 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astronomy and Astrophysics, Quasar, Galaxies: active, Astronomy and Astrophysic, Light curve, Astrophysics - Astrophysics of Galaxies, Redshift, Black hole, Quasars: general, Amplitude, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena, X-rays: galaxie, Methods: data analysi
Abstract

[Abbreviated] We search for scaling relations between the fundamental AGN parameters and rest-frame UV/optical variability properties for a sample of $\sim$90 X-ray selected AGNs covering a wide redshift range from the XMM-COSMOS survey, with optical light curves in four bands provided by the Pan-STARRS1 (PS1) Medium Deep Field 04 survey. To estimate the variability amplitude we utilize the normalized excess variance ($\sigma_{\mathrm{rms}}^{2}$) and probe variability on rest-frame timescales of several months and years by calculating $\sigma_{\mathrm{rms}}^{2}$ from different parts of our light curves. In addition, we derive the rest-frame optical PSD for our sources using continuous-time autoregressive moving average (CARMA) models. We observe that the excess variance and the PSD amplitude are strongly anti-correlated with wavelength, bolometric luminosity and Eddington ratio. There is no evidence for a dependency of the variability amplitude on black hole mass and redshift. These results suggest that the accretion rate is the fundamental physical quantity determining the rest-frame UV/optical variability amplitude of quasars on timescales of months and years. The optical PSD of all of our sources is consistent with a broken power law showing a characteristic bend at rest-frame timescales ranging between $\sim$100 and $\sim$300 days. The break timescale exhibits no significant correlation with any of the fundamental AGN parameters. The low frequency slope of the PSD is consistent with a value of $-1$ for most of our objects, whereas the high frequency slope is characterized by a broad distribution of values between $\sim-2$ and $\sim-4$. These findings unveil significant deviations from the simple "damped random walk" model, frequently used in previous optical variability studies. We find a weak tendency for AGNs with higher black hole mass having steeper high frequency PSD slopes., Comment: Accepted by A&A, 23 pages, 19 figures

Published
2015

29. XMMSL1J063045.9-603110: A tidal disruption event fallen into the back burner

Author

Mainetti, D, Campana, S, Colpi, M, MAINETTI, DEBORAH, COLPI, MONICA, Mainetti, D, Campana, S, Colpi, M, MAINETTI, DEBORAH, and COLPI, MONICA

Abstract

Black holes at the centre of quiescent galaxies can be switched on when they accrete gas that is gained from stellar tidal disruptions. A star approaching a black hole on a low angular momentum orbit may be ripped apart by tidal forces, which triggers raining down of a fraction of stellar debris onto the compact object through an accretion disc and powers a bright flare. In this paper we discuss XMMSL1J063045.9-603110 as a candidate object for a tidal disruption event. The source has recently been detected to be bright in the soft X-rays during an XMM-Newton slew and later showed an X-ray flux decay by a factor of about 10 in twenty days. We analyse XMM-Newton and Swift data. XMMSL1J063045.9-603110 shows several features typical of tidal disruption events: the X-ray spectrum shows the characteristics of a spectrum arising from a thermal accretion disc, the flux decay follows a t-5/3 law, and the flux variation is >350. Optical observations testify that XMMSL1J063045.9-603110 is probably associated with an extremely small galaxy or even a globular cluster, which suggests that intermediate-mass black holes are located in the cores of (at least) some of them.

Published
2016

30. SHORT GAMMA-RAY BURSTS from the MERGER of TWO BLACK HOLES

Author

Perna, R, Lazzati, D, Giacomazzo, B, Perna, Rosalba, Lazzati, Davide, Giacomazzo, Bruno, Perna, R, Lazzati, D, Giacomazzo, B, Perna, Rosalba, Lazzati, Davide, and Giacomazzo, Bruno

Abstract

Short gamma-ray bursts (GRBs) are explosions of cosmic origins believed to be associated with the merger of two compact objects, either two neutron stars or a neutron star and a black hole (BH). The presence of at least one neutron star has long been thought to be an essential element of the model: its tidal disruption provides the needed baryonic material whose rapid accretion onto the post-merger BH powers the burst. The recent tentative detection by the Fermi satellite of a short GRB in association with the gravitational wave signal GW150914 produced by the merger of two BHs has challenged this standard paradigm. Here, we show that the evolution of two high-mass, low-metallicity stars with main-sequence rotational speeds a few tens of percent of the critical speed eventually undergoing a weak supernova explosion can produce a short GRB. The outer layers of the envelope of the last exploding star remain bound and circularize at large radii. With time, the disk cools and becomes neutral, suppressing the magnetorotational instability, and hence the viscosity. The disk remains "long-lived dead" until tidal torques and shocks during the pre-merger phase heat it up and re-ignite accretion, rapidly consuming the disk and powering the short GRB.

Published
2016

31. Retrograde binaries of massive black holes in circumbinary accretion discs

Author

Amaro Seoane, P, Maureira Fredes, C, Dotti, M, Colpi, M, DOTTI, MASSIMO, COLPI, MONICA, Amaro Seoane, P, Maureira Fredes, C, Dotti, M, Colpi, M, DOTTI, MASSIMO, and COLPI, MONICA

Abstract

Context. We explore the hardening of a massive black hole binary embedded in a circumbinary gas disc under a specific circumstance: when the binary and the gas are coplanar and the gas is counter-rotating. The binary has unequal mass and the interaction of the gas with the lighter secondary black hole is the main cause of the braking torque on the binary that shrinks with time. The secondary black hole, revolving in the direction opposite to the gas, experiences a drag from gas-dynamical friction and from direct accretion of part of it. Aims. In this paper, using two-dimensional (2D) hydrodynamical grid simulations we investigate the effect of changing the accretion prescriptions on the dynamics of the secondary black hole, which in turn affect the binary hardening and eccentricity evolution. Methods. We find that realistic accretion prescriptions lead to results that differ from those inferred assuming accretion of all the gas within the Roche Lobe of the secondary black hole. Results. When considering gas accretion within the gravitational influence radius of the secondary black hole (which is smaller than the Roche Lobe radius) to better describe gas inflows, the shrinking of the binary is slower. In addition, in this case, a smaller amount of accreted mass is required to reduce the binary separation by the same amount. Different accretion prescriptions result in different discs' surface densities, which alter the black hole's dynamics back. Full 3D Smoothed-particle hydrodynamics realizations of a number of representative cases, run over a shorter interval of time, validate the general trends observed in the less computationally demanding 2D simulations. Conclusions. Initially circular black hole binaries increase their eccentricity only slightly, which then oscillates around small values (<0.1) while they harden. By contrast, initially eccentric binaries become more and more eccentric. A semi-analytical model describing the black hole's dynamics under accretion, Context. We explore the hardening of a massive black hole binary embedded in a circumbinary gas disc under a specific circumstance: when the binary and the gas are coplanar and the gas is counter-rotating. The binary has unequal mass and the interaction of the gas with the lighter secondary black hole is the main cause of the braking torque on the binary that shrinks with time. The secondary black hole, revolving in the direction opposite to the gas, experiences a drag from gas-dynamical friction and from direct accretion of part of it. Aims. In this paper, using two-dimensional (2D) hydrodynamical grid simulations we investigate the effect of changing the accretion prescriptions on the dynamics of the secondary black hole, which in turn affect the binary hardening and eccentricity evolution. Methods. We find that realistic accretion prescriptions lead to results that differ from those inferred assuming accretion of all the gas within the Roche Lobe of the secondary black hole. Results. When considering gas accretion within the gravitational influence radius of the secondary black hole (which is smaller than the Roche Lobe radius) to better describe gas inflows, the shrinking of the binary is slower. In addition, in this case, a smaller amount of accreted mass is required to reduce the binary separation by the same amount. Different accretion prescriptions result in different discs' surface densities, which alter the black hole's dynamics back. Full 3D Smoothed-particle hydrodynamics realizations of a number of representative cases, run over a shorter interval of time, validate the general trends observed in the less computationally demanding 2D simulations. Conclusions. Initially circular black hole binaries increase their eccentricity only slightly, which then oscillates around small values (<0.1) while they harden. By contrast, initially eccentric binaries become more and more eccentric. A semi-analytical model describing the black hole's dynamics under accretion

Published
2016

32. Accretion disk coronae of intermediate polar cataclysmic variables

Author

Enrico Barbera, Giovanni Peres, Salvatore Orlando, ITA, Barbera, E., Orlando, S., and Peres, G.

Subjects
Magnetohydrodynamics (MHD), Stars: flare, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Astrophysics, 01 natural sciences, law.invention, Accretion, accretion disk, Settore FIS/05 - Astronomia E Astrofisica, Intermediate polar, law, 0103 physical sciences, Radiative transfer, Astrophysics::Solar and Stellar Astrophysics, Stars: coronae, X-rays: star, 0101 mathematics, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Novae, cataclysmic variable, White dwarf, Astronomy and Astrophysics, Astronomy and Astrophysic, Thermal conduction, Accretion (astrophysics), 010101 applied mathematics, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Astrophysics::Earth and Planetary Astrophysics, Magnetohydrodynamics, Astrophysics - High Energy Astrophysical Phenomena, Flare
Abstract

Context. Intermediate polar cataclysmic variables (IPCV) contain a magnetic, rotating white dwarf surrounded by a magnetically truncated accretion disk. To explain their strong flickering X-ray emission, accretion has been successfully taken into account. Nevertheless, observations suggest that accretion phenomena might not be the only process behind it. An intense flaring activity occurring on the surface of the disk may generate a corona, contribute to the thermal X-ray emission, and influence the system stability. Aims. Our purposes are: investigating the formation of an extended corona above the accretion disk, due to an intense flaring activity occurring on the disk surface; studying the effects of flares on the disk and stellar magnetosphere; assessing its contribution to the observed thermal X-ray flux. Methods. We have developed a 3D magnetohydrodynamic (MHD) model of a IPCV system. The model takes into account gravity, disk viscosity, thermal conduction, radiative losses, and coronal flare heating through heat injection at randomly chosen locations on the disk surface. To perform a parameter space exploration, several system conditions have been considered, with different magnetic field intensity and disk density values. From the results of the evolution of the model, we have synthesized the thermal X-ray emission. Results. The simulations show the formation of an extended corona, linking disk and star. The flaring activity is capable of strongly influencing the disk configuration and possibly its stability, effectively deforming the magnetic field lines. Hot plasma evaporation phenomena occur in the layer immediately above the disk. The flaring activity gives rise to a thermal X-ray emission in both the [0.1-2.0] keV and the [2.0-10] keV X-ray bands. Conclusions. An intense coronal activity occurring on the disk surface of an IPCV can affect the structure of the disk depending noticeably on the density of the disk and the magnetic field of the central object. Moreover, the synthesis of the thermal X-ray fluxes shows that this flaring activity may contribute to the observed flickering thermal X-ray emission.

Published
2017
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