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V. Coudé du Foresto

Bio: V. Coudé du Foresto is an academic researcher from Max Planck Society. The author has contributed to research in topics: Stars & Exoplanet. The author has an hindex of 27, co-authored 75 publications receiving 3553 citations. Previous affiliations of V. Coudé du Foresto include Pierre-and-Marie-Curie University.
Topics: Stars, Exoplanet, Interferometry, Planet, CHARA array


Papers
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Journal ArticleDOI
R. Abuter, António Amorim, Narsireddy Anugu, M. Bauböck, Myriam Benisty, Jean-Philippe Berger, Nicolas Blind, H. Bonnet, Wolfgang Brandner, A. Buron, C. Collin, F. Chapron, Yann Clénet, V. Coudé du Foresto, P. T. de Zeeuw, Casey Deen, F. Delplancke-Ströbele, Roderick Dembet, Jason Dexter, Gilles Duvert, Andreas Eckart, Frank Eisenhauer, G. Finger, N. M. Förster Schreiber, P. Fédou, Paulo J. V. Garcia, R. J. García López, Feng Gao, Eric Gendron, Reinhard Genzel, Stefan Gillessen, Paulo Gordo, Maryam Habibi, Xavier Haubois, M. Haug, F. Haußmann, Th. Henning, Stefan Hippler, Matthew Horrobin, Z. Hubert, N. Hubin, A. Jimenez Rosales, Lieselotte Jochum, Laurent Jocou, Andreas Kaufer, S. Kellner, Sarah Kendrew, Pierre Kervella, Yitping Kok, Martin Kulas, Sylvestre Lacour, Vincent Lapeyrere, B. Lazareff, J.-B. Le Bouquin, Pierre Léna, Magdalena Lippa, Rainer Lenzen, Antoine Mérand, Ewald Müller, Udo Neumann, Thomas Ott, L. Palanca, Thibaut Paumard, Luca Pasquini, Karine Perraut, Guy Perrin, O. Pfuhl, P. M. Plewa, Sebastian Rabien, Andres J. Ramirez, Juan-Luis Ramos, C. Rau, G. Rodríguez-Coira, R.-R. Rohloff, G. Rousset, J. Sanchez-Bermudez, Silvia Scheithauer, Markus Schöller, N. Schuler, Jason Spyromilio, Odele Straub, Christian Straubmeier, Eckhard Sturm, Linda J. Tacconi, Konrad R. W. Tristram, F. H. Vincent, S. von Fellenberg, Imke Wank, Idel Waisberg, Felix Widmann, Ekkehard Wieprecht, M. Wiest, Erich Wiezorrek, Julien Woillez, Senol Yazici, D. Ziegler, Gérard Zins 
TL;DR: In this article, the authors detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z ~ 200 km/s / c with different statistical analysis methods.
Abstract: The highly elliptical, 16-year-period orbit of the star S2 around the massive black hole candidate Sgr A* is a sensitive probe of the gravitational field in the Galactic centre. Near pericentre at 120 AU, ~1400 Schwarzschild radii, the star has an orbital speed of ~7650 km/s, such that the first-order effects of Special and General Relativity have now become detectable with current capabilities. Over the past 26 years, we have monitored the radial velocity and motion on the sky of S2, mainly with the SINFONI and NACO adaptive optics instruments on the ESO Very Large Telescope, and since 2016 and leading up to the pericentre approach in May 2018, with the four-telescope interferometric beam-combiner instrument GRAVITY. From data up to and including pericentre, we robustly detect the combined gravitational redshift and relativistic transverse Doppler effect for S2 of z ~ 200 km/s / c with different statistical analysis methods. When parameterising the post-Newtonian contribution from these effects by a factor f, with f = 0 and f = 1 corresponding to the Newtonian and general relativistic limits, respectively, we find from posterior fitting with different weighting schemes f = 0.90 +/- 0.09 (stat) +\- 0.15 (sys). The S2 data are inconsistent with pure Newtonian dynamics.

639 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a 0.16% precise and 0.27% accurate determination of R 0, the distance to the Galactic center using the star S2 on its 16-year orbit around the massive black hole Sgr A* that they followed astrometrically and spectroscopically for 27 years.
Abstract: We present a 0.16% precise and 0.27% accurate determination of R 0 , the distance to the Galactic center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 μ as in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km s−1 , this yields a geometric distance estimate of R 0 = 8178 ± 13stat. ± 22sys. pc. This work updates our previous publication, in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20σ with f redshift = 1.04 ± 0.05.

507 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented a 0.16% precise and 0.27% accurate determination of R0, the distance to the Galactic Center using the star S2 on its 16-year orbit around the massive black hole Sgr A* that they followed astrometrically and spectroscopically for 27 years.
Abstract: We present a 0.16% precise and 0.27% accurate determination of R0, the distance to the Galactic Center. Our measurement uses the star S2 on its 16-year orbit around the massive black hole Sgr A* that we followed astrometrically and spectroscopically for 27 years. Since 2017, we added near-infrared interferometry with the VLTI beam combiner GRAVITY, yielding a direct measurement of the separation vector between S2 and Sgr A* with an accuracy as good as 20 micro-arcsec in the best cases. S2 passed the pericenter of its highly eccentric orbit in May 2018, and we followed the passage with dense sampling throughout the year. Together with our spectroscopy, in the best cases with an error of 7 km/s, this yields a geometric distance estimate: R0 = 8178 +- 13(stat.) +- 22(sys.) pc. This work updates our previous publication in which we reported the first detection of the gravitational redshift in the S2 data. The redshift term is now detected with a significance level of 20 sigma with f_redshift = 1.04 +- 0.05.

479 citations

Journal ArticleDOI
R. Abuter, Matteo Accardo, António Amorim, Narsireddy Anugu, G. Avila, N. Azouaoui, Myriam Benisty, Jean-Philippe Berger, Nicolas Blind, H. Bonnet, Pierre Bourget, Wolfgang Brandner, R. Brast, A. Buron, Leonard Burtscher, Frédéric Cassaing, F. Chapron, Elodie Choquet, Y. Clénet, C. Collin, V. Coudé du Foresto, W. J. de Wit, P. T. de Zeeuw, Casey Deen, F. Delplancke-Ströbele, Roderick Dembet, Frederic Derie, Jason Dexter, Gilles Duvert, M. Ebert, Andreas Eckart, Frank Eisenhauer, Michael Esselborn, P. Fédou, G. Finger, Paulo J. V. Garcia, C. E. Garcia Dabo, R. J. García López, Eric Gendron, R. Genzel, Stefan Gillessen, Frédéric Gonté, Paulo Gordo, M. Grould, Ulrich Grözinger, S. Guieu, P. Haguenauer, O. Hans, Xavier Haubois, M. Haug, F. Haussmann, Th. Henning, Stefan Hippler, Matthew Horrobin, Armin Huber, Z. Hubert, N. Hubin, Christian A. Hummel, Gerd Jakob, A. Janssen, Lieselotte Jochum, Laurent Jocou, Andreas Kaufer, S. Kellner, L. Kern, Pierre Kervella, Mario Kiekebusch, Ralf Klein, Yitping Kok, Johann Kolb, Martin Kulas, Sylvestre Lacour, Vincent Lapeyrere, B. Lazareff, J.-B. Le Bouquin, Pierre Léna, Rainer Lenzen, Samuel Lévêque, Magdalena Lippa, Yves Magnard, Leander Mehrgan, M. Mellein, Antoine Mérand, J. Moreno-Ventas, Thibaut Moulin, Ewald Müller, F. Müller, Udo Neumann, S. Oberti, T. Ott, L. Pallanca, Johana Panduro, Luca Pasquini, T. Paumard, Isabelle Percheron, K. Perraut, Guy Perrin, A. Pflüger, O. Pfuhl, T. Phan Duc, P. M. Plewa, Dan Popovic, Sebastian Rabien, A. Ramirez, Juan-Luis Ramos, C. Rau, M. Riquelme, R.-R. Rohloff, G. Rousset, J. Sanchez-Bermudez, Silvia Scheithauer, Markus Schöller, Nicolas Schuhler, Jason Spyromilio, Christian Straubmeier, Eckhard Sturm, Marcos Suarez, Konrad R. W. Tristram, N. Ventura, F. H. Vincent, Idel Waisberg, Imke Wank, J. Weber, Ekkehard Wieprecht, M. Wiest, Erich Wiezorrek, Markus Wittkowski, Julien Woillez, Burkhard Wolff, Senol Yazici, D. Ziegler, Gérard Zins 
TL;DR: GRAVITY as mentioned in this paper is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m$^2$.
Abstract: GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m$^2$. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual beam operation and laser metrology [...]. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase tracking on stars as faint as m$_K$ ~ 10 mag, phase-referenced interferometry of objects fainter than m$_K$ ~ 15 mag with a limiting magnitude of m$_K$ ~ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25 %, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than 10 microarcseconds ({\mu}as). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 {\mu}as when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic Center supermassive black hole and its fast orbiting star S2 for phase referenced dual beam observations and infrared wavefront sensing, the High Mass X-Ray Binary BP Cru and the Active Galactic Nucleus of PDS 456 for few {\mu}as spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, {\xi} Tel and 24 Cap for high accuracy visibility observations, and {\eta} Car for interferometric imaging with GRAVITY.

391 citations

Journal ArticleDOI
TL;DR: In this article, the authors reported the detection of continuous positional and polarization changes of SgrA* in high states of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument.
Abstract: We report the detection of continuous positional and polarization changes of the compact source SgrA* in high states ('flares') of its variable near- infrared emission with the near-infrared GRAVITY-Very Large Telescope Interferometer (VLTI) beam-combining instrument. In three prominent bright flares, the position centroids exhibit clockwise looped motion on the sky, on scales of typically 150 micro-arcseconds over a few tens of minutes, corresponding to about 30% the speed of light. At the same time, the flares exhibit continuous rotation of the polarization angle, with about the same 45(+/-15)-minute period as that of the centroid motions. Modelling with relativistic ray tracing shows that these findings are all consistent with a near face-on, circular orbit of a compact polarized 'hot spot' of infrared synchrotron emission at approximately six to ten times the gravitational radius of a black hole of 4 million solar masses. This corresponds to the region just outside the innermost, stable, prograde circular orbit (ISCO) of a Schwarzschild-Kerr black hole, or near the retrograde ISCO of a highly spun-up Kerr hole. The polarization signature is consistent with orbital motion in a strong poloidal magnetic field.

272 citations


Cited by
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Journal Article
TL;DR: The first direct detection of gravitational waves and the first observation of a binary black hole merger were reported in this paper, with a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ.
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

4,375 citations

Journal ArticleDOI
Kazunori Akiyama, Antxon Alberdi1, Walter Alef2, Keiichi Asada3  +403 moreInstitutions (82)
TL;DR: In this article, the Event Horizon Telescope was used to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87.
Abstract: When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter of 42 +/- 3 mu as, which is circular and encompasses a central depression in brightness with a flux ratio greater than or similar to 10: 1. The emission ring is recovered using different calibration and imaging schemes, with its diameter and width remaining stable over four different observations carried out in different days. Overall, the observed image is consistent with expectations for the shadow of a Kerr black hole as predicted by general relativity. The asymmetry in brightness in the ring can be explained in terms of relativistic beaming of the emission from a plasma rotating close to the speed of light around a black hole. We compare our images to an extensive library of ray-traced general-relativistic magnetohydrodynamic simulations of black holes and derive a central mass of M = (6.5 +/- 0.7) x 10(9) M-circle dot. Our radio-wave observations thus provide powerful evidence for the presence of supermassive black holes in centers of galaxies and as the central engines of active galactic nuclei. They also present a new tool to explore gravity in its most extreme limit and on a mass scale that was so far not accessible.

2,589 citations

Journal ArticleDOI
TL;DR: In this article, a review describes the theoretical framework within which debris disk evolution takes place and shows how that framework has been constrained by observations, including infrared photometry of large numbers of debris disks, providing snapshots of the dust present at different evolutionary phases.
Abstract: Circumstellar dust exists around several hundred main sequence stars. For the youngest stars, that dust could be a remnant of the protoplanetary disk. Mostly it is inferred to be continuously replenished through collisions between planetesimals in belts analogous to the Solar System’s asteroid and Kuiper belts, or in collisions between growing protoplanets. The evolution of a star’s debris disk is indicative of the evolution of its planetesimal belts and may be influenced by planet formation processes, which can continue throughout the first gigayear as the planetary system settles to a stable configuration and planets form at large radii. Evidence for that evolution comes from infrared photometry of large numbers of debris disks, providing snapshots of the dust present at different evolutionary phases, as well as from images of debris disk structure. This review describes the theoretical framework within which debris disk evolution takes place and shows how that framework has been constrained by observations.

985 citations

Journal ArticleDOI
Kazunori Akiyama, Antxon Alberdi1, Walter Alef2, Keiichi Asada3  +259 moreInstitutions (62)
TL;DR: In this article, a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by GRS was constructed and compared with the observed visibilities.
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.

808 citations

Journal ArticleDOI
Kazunori Akiyama, Antxon Alberdi1, Walter Alef2, Keiichi Asada3  +394 moreInstitutions (78)
TL;DR: The Event Horizon Telescope (EHT) as mentioned in this paper is a very long baseline interferometry (VLBI) array that comprises millimeter and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth.
Abstract: The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of the Earth. At a nominal operating wavelength of ~1.3 mm, EHT angular resolution (λ/D) is ~25 μas, which is sufficient to resolve nearby supermassive black hole candidates on spatial and temporal scales that correspond to their event horizons. With this capability, the EHT scientific goals are to probe general relativistic effects in the strong-field regime and to study accretion and relativistic jet formation near the black hole boundary. In this Letter we describe the system design of the EHT, detail the technology and instrumentation that enable observations, and provide measures of its performance. Meeting the EHT science objectives has required several key developments that have facilitated the robust extension of the VLBI technique to EHT observing wavelengths and the production of instrumentation that can be deployed on a heterogeneous array of existing telescopes and facilities. To meet sensitivity requirements, high-bandwidth digital systems were developed that process data at rates of 64 gigabit s^(−1), exceeding those of currently operating cm-wavelength VLBI arrays by more than an order of magnitude. Associated improvements include the development of phasing systems at array facilities, new receiver installation at several sites, and the deployment of hydrogen maser frequency standards to ensure coherent data capture across the array. These efforts led to the coordination and execution of the first Global EHT observations in 2017 April, and to event-horizon-scale imaging of the supermassive black hole candidate in M87.

756 citations