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4 results on '"Widmann, F."'

1. The GRAVITY young stellar object survey: IV. The CO overtone emission in 51 Oph at sub-au scales

Author

GRAVITY, Collaboration, Koutoulaki, M., Lopez, R. Garcia, Natta, A., Fedriani, R., oGaratti, A. Caratti, Ray, T. P., Coffey, D., Brandner, W., Dougados, C., Garcia, P. J. V, Klarmann, L., Labadie, L., Perraut, K., Sanchez-Bermudez, J., Lin, C. -C., Amorim, A., Bauböck, M., Benisty, M., Berger, J. P., Buron, A., Caselli, P., Clénet, Y., Foresto, V. Coudé Du, De Zeeuw, P. T., Duvert, G., de Wit, W., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Habibi, M., Haubois, X., Haussmann, F., Henning, T., Hippler, S., Hubert, Z., Horrobin, M., Rosales, A. Jimenez, Jocou, L., Kervella, P., Kolb, J., Lacour, S., Bouquin, J. -B. Le, Léna, P., Linz, H., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramírez-Tannus, M. C., Rau, C., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Van Dishoeck, E., Vincent, F., Von fellenberg, S., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Yazici, S., Zins, G., Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Dublin Institute for Advanced Studies (DIAS), School of Physics [UCD Dublin], University College Dublin [Dublin] (UCD), European Southern Observatory (ESO), Chalmers University of Technology [Gothenburg, Sweden], Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Faculdade de Engenharia da Universidade do Porto (FEUP), Universidade do Porto, Centro de Astrofísica e Gravitação (CENTRA), European Southern Observatory [Santiago] (ESO), I. Physikalisches Institut [Köln], Universität zu Köln, Instituto de Astronomía, Univ. Nacional Autónoma de México, Universidad Nacional Autónoma de México (UNAM), Institute for Astronomy, University of Hawai'i at Manoa, Universidade de Lisboa (ULISBOA), Max Planck Institute for Extraterrestrial Physics (MPE), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Sterrewacht Leiden, Universiteit Leiden [Leiden], Max-Planck-Institut für Radioastronomie (MPIFR), Department of Physics [Berkeley], University of California [Berkeley], and University of California-University of California

Subjects
Accretion, Be star, Techniques: Interferometric, Astrophysics::High Energy Astrophysical Phenomena, Overtone, Young stellar object, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, Accretion Disks, 0103 physical sciences, Stars: Pre-Main Sequence, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Image resolution, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Astronomy and Astrophysics, Stars: Individual: 51 Oph, Position angle, Astrophysics - Astrophysics of Galaxies, Interferometry, Wavelength, Stars, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics::Earth and Planetary Astrophysics, Stars: Formation
Abstract

51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 micron, most likely originating in the innermost regions of a circumstellar disc. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc. We used the second-generation VLTI/GRAVITY to spatially resolve the continuum and the CO overtone emission. We obtained data over 12 baselines with the auxiliary telescopes and derive visibilities, and the differential and closure phases as a function of wavelength. We used a simple LTE ring model of the CO emission to reproduce the spectrum and CO line displacements. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of 10.58+-2.65 Rsun.The K-band continuum emission from the disc is inclined by 63+-1 deg, with a position angle of 116+-1 deg, and 4+-0.8 mas (0.5+-0.1 au) across. The visibilities increase within the CO line emission, indicating that the CO is emitted within the dust-sublimation radius.By modelling the CO bandhead spectrum, we derive that the CO is emitted from a hot (T=1900-2800 K) and dense (NCO=(0.9-9)x10^21 cm^-2) gas. The analysis of the CO line displacement with respect to the continuum allows us to infer that the CO is emitted from a region 0.10+-0.02 au across, well within the dust-sublimation radius. The inclination and position angle of the CO line emitting region is consistent with that of the dusty disc. Our spatially resolved interferometric observations confirm the CO ro-vibrational emission within the dust-free region of the inner disc. Conventional disc models exclude the presence of CO in the dust-depleted regions of Herbig AeBe stars. Ad hoc models of the innermost disc regions, that can compute the properties of the dust-free inner disc, are therefore required., Accepted in A&A

Published
2021

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

Author

Jiménez-Rosales, A, Dexter, J, Ressler, S M, Tchekhovskoy, A, Bauböck, M, Dallilar, Y, de Zeeuw, P T, Drescher, A, Eisenhauer, F, von Fellenberg, S, Gao, F, Genzel, R, Gillessen, S, Habibi, M, Ott, T, Stadler, J, Straub, O, and Widmann, F

Subjects
BLACK holes, PHOTONS, GENERAL relativity (Physics), LINEAR polarization, MAGNETIC traps
Abstract

Using general relativistic magnetohydrodynamic simulations of accreting black holes, we show that a suitable subtraction of the linear polarization per pixel from total intensity images can enhance the photon ring feature. We find that the photon ring is typically a factor of ≃2 less polarized than the rest of the image. This is due to a combination of plasma and general relativistic effects, as well as magnetic turbulence. When there are no other persistently depolarized image features, adding the subtracted residuals over time results in a sharp image of the photon ring. We show that the method works well for sample, viable GRMHD models of Sgr A* and M87*, where measurements of the photon ring properties would provide new measurements of black hole mass and spin, and potentially allow for tests of the 'no-hair' theorem of general relativity. [ABSTRACT FROM AUTHOR]

Published
2021
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3. Modeling the orbital motion of Sgr A*’s near-infrared flares

Author

The GRAVITY Collaboration, Baub��ck, M., Dexter, J., Abuter, R., Amorim, A., Berger, J. P., Bonnet, H., Brandner, W., Cl��net, Y., Foresto, V. Coud�� du, de Zeeuw, P. T., Duvert, G., Eckart, A., Eisenhauer, F., Schreiber, N. M. F��rster, Gao, F., Garcia, P., Gendron, E., Genzel, R., Gerhard, O., Gillessen, S., Habibi, M., Haubois, X., Henning, T., Hippler, S., Horrobin, M., Jim��nez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyr��re, V., Bouquin, J. -B. Le, L��na, P., Ott, T., Paumard, T., Perraut, K., Perrin, G., Pfuhl, O., Rabien, S., Coira, G. Rodriguez, Rousset, G., Scheithauer, S., Stadler, J., Sternberg, A., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L. J., Vincent, F., von Fellenberg, S., Waisberg, I., Widmann, F., Wieprecht, E., Wiezorrek, E., Woillez, J., Yazici, S., Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GRAVITY, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Observatoire des Sciences de l'Univers de Grenoble (OSUG), and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Infrared, Event horizon, Astrophysics::High Energy Astrophysical Phenomena, black hole physics, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Gravitation, General Relativity and Quantum Cosmology, accretion, law, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 14. Life underwater, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Galaxy: center, 010308 nuclear & particles physics, accretion disks, Galactic Center, Astronomy and Astrophysics, Light curve, Accretion (astrophysics), [SDU]Sciences of the Universe [physics], Space and Planetary Science, Orbital motion, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Flare
Abstract

Infrared observations of Sgr A* probe the region close to the event horizon of the black hole at the Galactic center. These observations can constrain the properties of low-luminosity accretion as well as that of the black hole itself. The GRAVITY instrument at the ESO VLTI has recently detected continuous circular relativistic motion during infrared flares which has been interpreted as orbital motion near the event horizon. Here we analyze the astrometric data from these flares, taking into account the effects of out-of-plane motion and orbital shear of material near the event horizon of the black hole. We have developed a new code to predict astrometric motion and flux variability from compact emission regions following particle orbits. Our code combines semi-analytic calculations of timelike geodesics that allow for out-of-plane or elliptical motions with ray tracing of photon trajectories to compute time-dependent images and light curves. We apply our code to the three flares observed with GRAVITY in 2018. We show that all flares are consistent with a hotspot orbiting at R$\sim$9 gravitational radii with an inclination of $i\sim140^\circ$. The emitting region must be compact and less than $\sim5$ gravitational radii in diameter. We place a further limit on the out-of-plane motion during the flare., Comment: Accepted in A&A

Published
2020

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

Author

Dexter, J, Jiménez-Rosales, A, Ressler, S M, Tchekhovskoy, A, Bauböck, M, de Zeeuw, P T, Eisenhauer, F, von Fellenberg, S, Gao, F, Genzel, R, Gillessen, S, Habibi, M, Ott, T, Stadler, J, Straub, O, and Widmann, F

Subjects
HOT carriers, LINEAR polarization, ELECTRONS, BLACK holes, FARADAY effect, MAGNETIZATION transfer, ACCRETION (Astrophysics)
Abstract

The Galactic centre black hole candidate Sgr A* is the best target for studies of low-luminosity accretion physics, including with near-infrared (NIR) and submillimetre wavelength long baseline interferometry experiments. Here, we compare images and spectra generated from a parameter survey of general relativistic MHD simulations to a set of radio to NIR observations of Sgr A*. Our models span the limits of weak and strong magnetization and use a range of sub-grid prescriptions for electron heating. We find two classes of scenarios can explain the broad shape of the submillimetre spectral peak and the highly variable NIR flaring emission. Weakly magnetized 'disc-jet' models where most of the emission is produced near the jet wall, consistent with past work, as well as strongly magnetized (magnetically arrested disc) models where hot electrons are present everywhere. Disc-jet models are strongly depolarized at submillimetre wavelengths as a result of strong Faraday rotation, inconsistent with observations of Sgr A*. We instead favour the strongly magnetized models, which provide a good description of the median and highly variable linear polarization signal. The same models can also explain the observed mean Faraday rotation measure and potentially the polarization signals seen recently in Sgr A* NIR flares. [ABSTRACT FROM AUTHOR]

Published
2020
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