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1. The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE

Author

A. Chiavassa, K. Kravchenko, M. Montargès, F. Millour, A. Matter, B. Freytag, M. Wittkowski, V. Hocdé, P. Cruzalèbes, F. Allouche, B. Lopez, S. Lagarde, R. G. Petrov, A. Meilland, S. Robbe-Dubois, K.-H. Hofmann, G. Weigelt, P. Berio, P. Bendjoya, F. Bettonvil, A. Domiciano de Souza, M. Heininger, Th. Henning, J. W. Isbell, W. Jaffe, L. Labadie, M. Lehmitz, K. Meisenheimer, A. Soulain, J. Varga, J.-C. Augereau, R. van Boekel, L. Burtscher, W. C. Danchi, C. Dominik, J. Drevon, V. Gámez Rosas, M. R. Hogerheijde, J. Hron, L. Klarmann, E. Kokoulina, E. Lagadec, J. Leftley, L. Mosoni, N. Nardetto, C. Paladini, E. Pantin, D. Schertl, P. Stee, L. Szabados, R. Waters, S. Wolf, and G. Yoffe

Subjects
Astronomy, Astrophysics
Abstract

Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification. Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment. Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3–4 μm), M (4.5–5 μm), and N (8–13 μm) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with CO5BOLD and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively. Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration. Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr’s stellar surface and circumstellar environment across a very large spectral domain for the first time.

Published
2022
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2. The Asymmetric Inner Disk of the Herbig Ae Star HD 163296 in the Eyes of VLTI/MATISSE: Evidence for a Vortex?

Author

J Varga, M Hogerheijde, R van Boekel, L Klarmann, R Petrov, L B F M Waters, S Lagarde, E Pantin, Ph Berio, G Weigelt, S Robbe-Dubois, B Lopez, F Millour, J-C Augereau, H Meheut, A Meilland, Th Henning, W Jaffe, F Bettonvil, P Bristow, K-H Hofmann, A Matter, G Zins, S Wolf, F Allouche, F Donnan, D Schertl, C Dominik, M Heininger, M Lehmitz, P Cruzalebes, A Glindermann, K Meisenheimer, C Paladini, M Scholler, J Woillez, L Venema, E Kokoulina, G Yoffe, P Abraham, S Abadie, R Abuter, M Accardo, T Adler, T Agocs, P Antonelli, A Bohm, C Bailet, G Bazin, U Beckmann, J Beltran, W Boland, P Bourget, R Brast, Y Bresson, L Burtscher, R Castillo, A Chelli, C Cid, J-M Clausse, C Connot, R D Conzelmann, W-C Danchi, M De Hann, M Delbo, M Ebert, E Elswijk, Y Fantei, R Frahm, V Gamez Rosas, A Gabasch, A Gallenne, E Garces, P Girard, F Y J Gonte, J C Gonzalez Herrera, U Graser, P Guajardo, F Guitton, X Haubois, J Hron, N Hubin, R Huerta, J W Isbell, D Ives, G Jakob, A Jasko, L Jochum, R Klein, J Kragt, G Kroes, S Kuindersma, L Labadie, W Laun, R Le Poole, C Leinert, J-L Lizon, M Lopez, A Merand, A Marcotto, N Mauclert, T Maurer, L H Mehrgan, J Meisner, K Meixner, M Mellein, L Mohr, S Morel, L Mosoni, R Navarro, U Neumann, E NuBbaum, L Pallanca, L Pasquini, I Percheron, J-U Pott, E Ponza, A Ridinger, F Rigal, M Riquelme, Th Rivinius, R Roelfsema, R-R Rohloff, S Rousseau, N Schuhler, M Schuil, A Soulain, P Stee, C Stephan, R ter Horst, N Tromp, F Vakili, A van Duin, J Vinther, M Wittkowski, and F Wrhel

Subjects
Astronomy
Abstract

Context.A complex environment exists in the inner few astronomical units of planet-forming disks. High-angular-resolution observa-tions play a key role in our understanding of the disk structure and the dynamical processes at work.Aims.In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-massstar HD 163296 from early VLTI/MATISSE observations taken in theL- andN-bands. We put special emphasis on the detection ofpotential disk asymmetries.Methods.We use simple geometric models to fit the interferometric visibilities and closure phases. Our models include a smoothedring, a flat disk with an inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetriesas well. We also perform numerical hydrodynamical simulations of the inner edge of the disk.Results.Our modeling reveals a significant brightness asymmetry in theL-band disk emission. The brightness maximum of the asym-metry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio inthe azimuthal variation is3.5±0.2. Comparing our result on the location of the asymmetry with other interferometric measurements,we confirm that the morphology of ther<0.3au disk region is time-variable. We propose that this asymmetric structure, located in ornear the inner rim of the dusty disk, orbits the star. To find the physical origin of the asymmetry, we tested a hypothesis where a vortexis created by Rossby wave instability, and we find that a unique large-scale vortex may be compatible with our data. The half-lightradius of theL-band-emitting region is0.33±0.01au, the inclination is52◦+5◦−7◦, and the position angle is143◦±3◦. Our models predictthat a non-negligible fraction of theL-band disk emission originates inside the dust sublimation radius forμm-sized grains. Refractorygrains or large (&10μm-sized) grains could be the origin of this emission.N-band observations may also support a lack of smallsilicate grains in the innermost disk (r.0.6au), in agreement with our findings fromL-band data.

Published
2021
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3. The dusty heart of Circinus: I. Imaging the circumnuclear dust in N-band

Author

J. W. Isbell, K. Meisenheimer, J.-U. Pott, M. Stalevski, K. R. W. Tristram, J. Sanchez-Bermudez, K.-H. Hofmann, V. Gámez Rosas, W. Jaffe, L. Burtscher, J. Leftley, R. Petrov, B. Lopez, T. Henning, G. Weigelt, F. Allouche, P. Berio, F. Bettonvil, P. Cruzalebes, C. Dominik, M. Heininger, M. Hogerheijde, S. Lagarde, M. Lehmitz, A. Matter, A. Meilland, F. Millour, S. Robbe-Dubois, D. Schertl, R. van Boekel, J. Varga, J. Woillez, and Low Energy Astrophysics (API, FNWI)

Subjects
instrumentation, galaxies, galaxies, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, active, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Seyfert, instrumentation, interferometers, interferometers, Astrophysics - Astrophysics of Galaxies, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies, Seyfert, infrared, Astrophysics::Earth and Planetary Astrophysics, active, galaxies, Astrophysics::Galaxy Astrophysics
Abstract

Active galactic nuclei play a key role in the evolution of galaxies, but their inner workings and physical connection to the host are poorly understood due to a lack of angular resolution. Infrared interferometry makes it possible to resolve the circumnuclear dust in the nearby Seyfert 2 galaxy, Circinus. Previous observations have revealed complex structures and polar dust emission but interpretation was limited to simple models. MATISSE makes it possible to image these structures for the first time. We observed the Circinus Galaxy with VLTI/MATISSE, producing 150 correlated flux spectra and 100 closure phase spectra. We reconstructed images in the N-band at ~10 mas resolution. We fit blackbody functions with dust extinction to several aperture-extracted fluxes from the images to produce a temperature distribution of central dusty structures. We find significant substructure in the circumnuclear dust: central unresolved flux of ~0.5 Jy, a thin disk 1.9 pc in diameter oriented along ~45 deg,and a ~4x1.5 pc polar emission extending orthogonal to the disk. The polar emission exhibits patchiness, which we attribute to clumpy dust. Flux enhancements to the east and west of the disk are seen for the first time. We distinguish the temperature profiles of the disk and of the polar emission: the disk shows a steep temperature gradient indicative of denser material; the polar profile is flatter, indicating clumpiness and/or lower dust density. The unresolved flux is fitted with a high temperature, ~370 K. The polar dust remains warm (~200 K) out to 1.5 pc from the disk. The recovered morphology and temperature distribution resembles modeling of accretion disks with radiation-driven winds at large scales, but we placed new constraints on the subparsec dust. The subparsec features imaged here place new constraints on the physical modeling of circumnuclear dust in active galaxies., Comment: Accepted for publication in A&A

Published
2022
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4. VLTI-MATISSE chromatic aperture-synthesis imaging of η Carinae's stellar wind across the Brα line: Periastron passage observations in February 2020

Author

Th. Rivinius, C. M. P. Russell, A. Domiciano de Souza, Uwe Beckmann, Lucas Labadie, F. Allouche, P. Cruzalèbes, Sylvie Robbe-Dubois, Antoine Mérand, William C. Danchi, A. F. J. Moffat, Kenji Hamaguchi, Michael F. Corcoran, József Varga, Alexis Matter, Thomas I. Madura, Stephane Lagarde, Sebastian Wolf, Anthony Meilland, Walter Jaffe, Paul Bristow, T. R. Gull, Felix Bettonvil, D. A. Espinoza-Galeas, Jose H. Groh, J. C. Augereau, Carsten Dominik, W. J. de Wit, Markus Schöller, J. Leftley, V. Hocdé, Uwe Graser, R. van Boekel, F. Navarete, L. Klarmann, K. Ohnaka, Leonard Burtscher, Th. Henning, Karl-Heinz Hofmann, Augusto Damineli, Ian R. Stevens, C. Connot, Klaus Meisenheimer, Stefan Kraus, Patrick W. Morris, G. Yoffe, Michiel R. Hogerheijde, Romain Petrov, Ph. Berio, M. Heininger, Henrik Hartman, J. W. Isbell, Markus Wittkowski, Eric Pantin, E. Kokoulina, J. Drevon, Julien Woillez, L. B. F. M. Waters, E. Nußbaum, Dieter Schertl, Bruno Lopez, Alexander Kreplin, Gerd Weigelt, Florentin Millour, D. J. Hillier, J. Hron, M. Lehmitz, V. Gámez Rosas, J. Sanchez-Bermudez, Noel D. Richardson, C. A. Hummel, Claudia Paladini, Andrea Mehner, Farrokh Vakili, Andreas Glindemann, P. Antonelli, C. Leinert, Gérard Zins, Philippe Stee, and Low Energy Astrophysics (API, FNWI)

Subjects
Interferometric, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Continuum (design consultancy), individual: eta Carinae [stars], Context (language use), Outflows, Individual, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Winds, 01 natural sciences, Spectral line, outflows, Mass-Loss, general [binaries], massive [stars], Astronomi, astrofysik och kosmologi, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astronomy, Astrophysics and Cosmology, winds [stars], General, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation), O-type star, Physics, 010308 nuclear & particles physics, Binaries, Astronomy and Astrophysics, mass-loss [stars], Radius, Stars, Techniques, interferometric [techniques], Luminous blue variable, 13. Climate action, Space and Planetary Science, Massive, Astrophysics::Earth and Planetary Astrophysics, η Carinae
Abstract

Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis ~15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, η Car A, is a luminous blue variable (LBV); the secondary, η Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV η Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of η Car’s WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Brα imaging of η Car’s distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of η Car A’s stellar windin several spectral channels distributed across the Brα 4.052 μm line (spectral resolving power R ~ 960). Our observations were performed close to periastron passage in February 2020 (orbital phase ~ 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (~14 au). The radius of the faintest outer wind regions is ~26 mas (~60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 ± 0.06 mas (6.54 ± 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.

Published
2021

5. First MATISSE L-band observations of HD 179218

Author

Dieter Schertl, Th. Henning, Gerd Weigelt, Florentin Millour, József Varga, Stephane Lagarde, J. Hron, Walter Jaffe, J. Leftley, Karl-Heinz Hofmann, L. Klarmann, G. Yoffe, A. Soulain, M. Heininger, V. Hocdé, Marco Delbo, Felix C. M. Bettonvil, Paul Bristow, Anthony Meilland, Uwe Beckmann, F. Allouche, A. Bensberg, M. Lehmitz, J. C. Augereau, C. A. Hummel, Lucas Labadie, Gérard Zins, Philippe Berio, Uwe Graser, Farrokh Vakili, P. Antonelli, Markus Wittkowski, Pierre Cruzalèbes, Nathalie Ysard, C. Leinert, Carsten Dominik, L. B. F. M. Waters, Claudia Paladini, Isabelle Percheron, J. Duprat, Anthony P. Jones, Michiel R. Hogerheijde, E. Habart, Sylvie Robbe-Dubois, J. W. Isbell, Eric Pantin, R. van Boekel, Klaus Meisenheimer, Julien Woillez, Bruno Lopez, Alexis Matter, Péter Ábrahám, E. Kokoulina, Romain Petrov, V. Gámez Rosas, Emmanuel Dartois, Ph. Stee, Sebastian Wolf, J. Drevon, M. Dannhoff, William C. Danchi, Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut d'astrophysique spatiale (IAS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Low Energy Astrophysics (API, FNWI), and Ysard, Nathalie

Subjects
Interferometric, 010504 meteorology & atmospheric sciences, Infrared, Astronomy, Continuum (design consultancy), chemistry.chemical_element, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Spectral resolution, General, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Very Large Telescope, Protoplanetary Disks, Astronomy and Astrophysics, Techniques, Astrophysics - Solar and Stellar Astrophysics, Amorphous carbon, chemistry, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Circumstellar Matter, Spectral energy distribution, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics::Earth and Planetary Astrophysics, [SDU.ASTR.GA] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA], Astrophysics - Solar and Stellar Astrophysic, Carbon, Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. Carbon is one of the most abundant components in the Universe. While silicates have been the main focus of solid phase studies in protoplanetary discs (PPDs), little is known about the solid carbon content especially in the planet-forming regions (~0.1–10 au). Fortunately, several refractory carbonaceous species present C-H bonds (such as hydrogenated nano-diamond and amorphous carbon as well as polycyclic aromatic hydrocarbons), which generate infrared (IR) features that can be used to trace the solid carbon reservoirs. The new mid-IR instrument MATISSE, installed at the Very Large Telescope Interferometer (VLTI), can spatially resolve the inner regions (~1–10 au) of PPDs and locate, down to the au-scale, the emission coming from carbon grains. Aims. Our aim is to provide a consistent view on the radial structure, down to the au-scale, as well as basic physical properties and the nature of the material responsible for the IR continuum emission in the inner disk region around HD 179218. Methods. We implemented a temperature-gradient model to interpret the disk IR continuum emission, based on a multiwavelength dataset comprising a broadband spectral energy distribution and VLTI H-, L-, and N-bands interferometric data obtained in low spectral resolution. Then, we added a ring-like component, representing the carbonaceous L-band features-emitting region, to assess its detectability in future higher spectral resolution observations employing mid-IR interferometry. Results. Our temperature-gradient model can consistently reproduce our dataset. We confirmed a spatially extended inner 10 au emission in H- and L-bands, with a homogeneously high temperature (~1700 K), which we associate with the presence of stochastically heated nano-grains. On the other hand, the N-band emitting region presents a ring-like geometry that starts at about 10 au with a temperature of 400 K. Moreover, the existing low resolution MATISSE data exclude the presence of aromatic carbon grains (i.e., producing the 3.3 μm feature) in close proximity tothe star (≲1 au). Future medium spectral resolution MATISSE data will confirm their presence at larger distances. Conclusions. Our best-fit model demonstrates the presence of two separated dust populations: nano-grains that dominate the near- to mid-IR emission in the inner 10 au region and larger grains that dominate the emission outward. The presence of such nano-grains in the highly irradiated inner 10 au region of HD 179218 requires a replenishment process. Considering the expected lifetime of carbon nano-grains from The Heterogeneous dust Evolution Model for Interstellar Solids (THEMIS model), the estimated disk accretion inflow of HD 179218 could significantly contribute to feed the inner 10 au region in nano-grains.Moreover, we also expect a local regeneration of those nano-grains by the photo-fragmentation of larger aggregates.

Published
2021
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6. The asymmetric inner disk of the Herbig Ae star HD 163296 in the eyes of VLTI/MATISSE: evidence for a vortex?

Author

William C. Danchi, Luca Pasquini, Lars Venema, Leonard Burtscher, Josef Hron, Markus Wittkowski, J. Beltran, H. Méheut, Antoine Mérand, Sylvie Robbe-Dubois, A. Jaskó, Th. Henning, Farrokh Vakili, F. Guitton, Anthony Meilland, J. Vinther, Carsten Dominik, A. Gabasch, S. Rousseau, E. Kokoulina, M. Ebert, P. Antonelli, J.-U. Pott, N. Tromp, J.-L. Lizon, F. Rigal, J. Kragt, Markus Schöller, Ronald Roelfsema, Romain Petrov, L. Klarmann, P. Guajardo, Karl Heinz Hofmann, R. Frahm, Klaus Meisenheimer, Alexis Matter, F. Wrhel, Nicolas Schuhler, Gerd Jakob, Gerd Weigelt, Ph. Stee, Laurent Pallanca, A. Marcotto, Pierre Cruzalèbes, A. Chelli, I. Percheron, J. C. González Herrera, Andreas Glindemann, Claudia Paladini, Jean-Michel Clausse, M. de Haan, Eddy Elswijk, K. Meixner, Felix Bettonvil, S. Morel, R. Castillo, Uwe Graser, E. Nußbaum, Paul Bristow, Péter Ábrahám, J. W. Isbell, Eric Pantin, T. Maurer, R. ter Horst, Bruno Lopez, R. van Boekel, T. Adler, A. van Duin, L. Mosoni, Alexandre Gallenne, Udo Neumann, Ralf Conzelmann, Jean-Charles Augereau, Yves Bresson, Ramón Navarro, Norbert Hubin, M. Accardo, E. Garces, F. Allouche, Julien Woillez, Th. Rivinius, Y. Fantei, S. Abadie, A. Ridinger, Derek Ives, F. Donnan, G. Bazin, Ralf Klein, Udo Beckmann, M. Mellein, Roberto Abuter, Eszter Pozna, Sebastian Wolf, Tibor Agócs, J. Meisner, D. Schertl, L. Mohr, Marcelo Lopez, L. Jochum, Ralf-Rainer Rohloff, C. Connot, A. Soulain, Claudia Cid, W. Laun, C. Stephan, M. Heininger, R. Brast, V. Gámez Rosas, W. Boland, Michiel R. Hogerheijde, Ph. Berio, Marco Delbo, Christoph Leinert, S. Kuindersma, L. Labadie, A. Böhm, Xavier Haubois, N. Mauclert, Leander Mehrgan, F. Y. J. Gonté, M. Schuil, L. B. F. M. Waters, G. Zins, P. Bourget, R. S. Le Poole, P. Girard, M. Riquelme, József Varga, Florentin Millour, Stephane Lagarde, Walter Jaffe, R. Huerta, M. Lehmitz, G. Kroes, G. Yoffe, C. Bailet, foreign laboratories (FL), CERN [Genève], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 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), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Max-Planck-Institut für Radioastronomie (MPIFR), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Konkoly Observatory, Research Centre for Astronomy and Earth Sciences [Budapest], Hungarian Academy of Sciences (MTA)-Hungarian Academy of Sciences (MTA), Anton Pannenkoek Institute for Astronomy [University of Amsterdam], Max Planck Institute for Astronomy (MPIA), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Low Energy Astrophysics (API, FNWI), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Observatoire de la Côte d'Azur (OCA), and Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Brightness, Interferometric, Astronomy, media_common.quotation_subject, Astronomical unit, [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP], FOS: Physical sciences, Astrophysics, 01 natural sciences, Asymmetry, Instability, 0103 physical sciences, Surface brightness, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, media_common, Physics, Earth and Planetary Astrophysics (astro-ph.EP), Pre-Main Sequence, Protoplanetary Disks, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Research Programm of Institute for Mathematics, Astrophysics and Particle Physics, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Position angle, Stars, Techniques, Vortex, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Azimuth, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Circumstellar Matter, Astrophysics::Earth and Planetary Astrophysics, Infrared, Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. The inner few au region of planet-forming disks is a complex environment. High angular resolution observations have a key role in understanding the disk structure and the dynamical processes at work. Aims. In this study we aim to characterize the mid-infrared brightness distribution of the inner disk of the young intermediate-mass star HD 163296, from VLTI/MATISSE observations. Methods. We use geometric models to fit the data. Our models include a smoothed ring, a flat disk with inner cavity, and a 2D Gaussian. The models can account for disk inclination and for azimuthal asymmetries as well. We also perform numerical hydro-dynamical simulations of the inner edge of the disk. Results. Our modeling reveals a significant brightness asymmetry in the L-band disk emission. The brightness maximum of the asymmetry is located at the NW part of the disk image, nearly at the position angle of the semimajor axis. The surface brightness ratio in the azimuthal variation is $3.5 \pm 0.2$. Comparing our result on the location of the asymmetry with other interferometric measurements, we confirm that the morphology of the $r, accepted for publication in A&A

Published
2021
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7. Mid-infrared circumstellar emission of the long-period Cepheid l Carinae resolved with VLTI/MATISSE

Author

M. Schuil, G. Zins, Y. Fantei, Udo Beckmann, Péter Ábrahám, Anthony Meilland, K. Shabun, Philippe Stee, Farrokh Vakili, Ronald Roelfsema, A. Böhm, Andrea Chiavassa, G. Niccolini, L. Labadie, L. Mosoni, M. Riquelme, Alexandre Gallenne, P. Antonelli, R. Frahm, J.-L. Lizon, Markus Schöller, Ralf-Rainer Rohloff, Florentin Millour, Jean-Michel Clausse, Udo Neumann, F. Wrhel, M. de Haan, J. Meisner, Leonard Burtscher, R. Huerta, F. Allouche, Luca Pasquini, E. Garces, Pierre Cruzalèbes, Nicolas Nardetto, S. Morel, Behnam Javanmardi, P. Bourget, L. Jochum, A. Ridinger, R. S. Le Poole, Th. Rivinius, Bruno Lopez, V. Hocdé, Marco Delbo, I. Percheron, P. Girard, J. C. González Herrera, M. Accardo, G. Bazin, Karl Heinz Hofmann, Laszlo Szabados, J. W. Isbell, Eric Pantin, Jaime Alonso, Josef Hron, D. Schertl, Eszter Pozna, L. Klarmann, Th. Henning, S. Rousseau, C. Connot, E. Nußbaum, Eddy Elswijk, Louise Breuval, Antoine Mérand, R. van Boekel, E. Kokoulina, Leander Mehrgan, József Varga, Roberto Abuter, Markus Wittkowski, T. Adler, E. Lagadec, Claudia Paladini, M. Heininger, F. Guitton, Nicolas Schuhler, W. Laun, Romain Petrov, A. Jaskó, S. Abadie, R. ter Horst, Stephane Lagarde, R. Brast, F. Y. J. Gonté, Norbert Hubin, William C. Danchi, V. Gámez Rosas, A. Soulain, Walter Jaffe, Pierre Kervella, W. Boland, Ramón Navarro, Michiel R. Hogerheijde, Julien Woillez, K. Meixner, Felix Bettonvil, S. Borgniet, J. Beltran, Uwe Graser, Ph. Berio, Ralf Klein, J. Idserda, M. Lopez, Klaus Meisenheimer, Andreas Glindemann, J.-U. Pott, H. Hanenburg, Lars Venema, Sylvie Robbe-Dubois, Alexis Matter, Tibor Agócs, R. Buter, M. Ebert, Carsten Dominik, P. Guajardo, Laurent Pallanca, A. Marcotto, R. Waters, A. Gabasch, R. Castillo, M. Lehmitz, Jean-Charles Augereau, Derek Ives, Yves Bresson, S. Kuindersma, A. Glazenborg, Claudia Cid, C. Stephan, Sebastian Wolf, L. Mohr, J. Kragt, Christoph Leinert, F. Rigal, N. Tromp, Xavier Haubois, N. Mauclert, Gerd Jakob, Gerd Weigelt, J. Vinther, A. Chelli, C. Bailet, Paul Bristow, A. Domiciano de Souza, T. Maurer, A. van Duin, Ralf Conzelmann, M. Mellein, G. Kroes, G. Yoffe, T. Phan Duc, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS., European Southern Observatory (ESO), COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Astronomy (MPIA), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and Low Energy Astrophysics (API, FNWI)

Subjects
Infrared, Cepheid variable, Astronomy, Astrophysics - astrophysics of galaxies, Flux, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - solar and stellar astrophysics, 010309 optics, Spitzer Space Telescope, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Spectroscopy, 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Research Programm of Institute for Mathematics, Astrophysics and Particle Physics, Stars: variables: Cepheids, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Circumstellar matter, Infrared: stars, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Stars, Wavelength, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Instrumentation: interferometers, Astrophysics of Galaxies (astro-ph.GA), Stars: atmospheres, Astrophysics::Earth and Planetary Astrophysics
Abstract

The nature of circumstellar envelopes (CSE) around Cepheids is still a matter of debate. The physical origin of their infrared (IR) excess could be either a shell of ionized gas, or a dust envelope, or both. This study aims at constraining the geometry and the IR excess of the environment of the long-period Cepheid $\ell$ Car (P=35.5 days) at mid-IR wavelengths to understand its physical nature. We first use photometric observations in various bands and Spitzer Space Telescope spectroscopy to constrain the IR excess of $\ell$ Car. Then, we analyze the VLTI/MATISSE measurements at a specific phase of observation, in order to determine the flux contribution, the size and shape of the environment of the star in the L band. We finally test the hypothesis of a shell of ionized gas in order to model the IR excess. We report the first detection in the L band of a centro-symmetric extended emission around l Car, of about 1.7$R_\star$ in FWHM, producing an excess of about 7.0\% in this band. In the N band, there is no clear evidence for dust emission from VLTI/MATISSE correlated flux and Spitzer data. On the other side, the modeled shell of ionized gas implies a more compact CSE ($1.13\pm0.02\,R_\star$) and fainter (IR excess of 1\% in the L band). We provide new evidences for a compact CSE of $\ell$ Car and we demonstrate the capabilities of VLTI/MATISSE for determining common properties of CSEs. While the compact CSE of $\ell$ Car is probably of gaseous nature, the tested model of a shell of ionized gas is not able to simultaneously reproduce the IR excess and the interferometric observations. Further Galactic Cepheids observations with VLTI/MATISSE are necessary for determining the properties of CSEs, which may also depend on both the pulsation period and the evolutionary state of the stars., Comment: 13 pages, 8 figures, accepted in Astronomy and Astrophysics

Published
2021
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8. VLTI-MATISSE L- and N-band aperture-synthesis imaging of the unclassified B[e] star FS Canis Majoris

Author

K.-H. Hofmann, A. Bensberg, D. Schertl, G. Weigelt, S. Wolf, A. Meilland, F. Millour, L. B. F. M. Waters, S. Kraus, K. Ohnaka, B. Lopez, R. G. Petrov, S. Lagarde, Ph. Berio, F. Allouche, S. Robbe-Dubois, W. Jaffe, Th. Henning, C. Paladini, M. Schöller, A. Mérand, A. Glindemann, U. Beckmann, M. Heininger, F. Bettonvil, G. Zins, J. Woillez, P. Bristow, P. Stee, F. Vakili, R. van Boekel, M. R. Hogerheijde, C. Dominik, J.-C. Augereau, A. Matter, J. Hron, E. Pantin, Th. Rivinius, W.-J. de Wit, J. Varga, L. Klarmann, K. Meisenheimer, V. Gámez Rosas, L. Burtscher, J. Leftley, J. W. Isbell, G. Yoffe, E. Kokoulina, W. C. Danchi, P. Cruzalèbes, A. Domiciano de Souza, J. Drevon, V. Hocdé, A. Kreplin, L. Labadie, C. Connot, E. Nußbaum, M. Lehmitz, P. Antonelli, U. Graser, C. Leinert, and Low Energy Astrophysics (API, FNWI)

Subjects
Stars: imaging, Aperture synthesis, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Stars: individual: FS CMa, Techniques: image processing, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Physics, B(e) star, biology, Stars: emission-line, Astronomy and Astrophysics, Be, Circumstellar matter, biology.organism_classification, Canis, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, Techniques: interferometric, Astrophysics::Earth and Planetary Astrophysics, Stars: individual: FS CMa, Astrophysics - Solar and Stellar Astrophysics
Abstract

Context: FS Canis Majoris (FS CMa, HD 45677) is an unclassified B[e] star surrounded by an inclined dust disk. The evolutionary stage of FS CMa is still debated. Perpendicular to the circumstellar disk, a bipolar outflow was detected. Infrared aperture-synthesis imaging provides us with a unique opportunity to study the disk structure. Aims: Our aim is to study the intensity distribution of the disk of FS CMa in the mid-infrared L and N bands. Methods: We performed aperture-synthesis imaging of FS CMa with the MATISSE instrument (Multi AperTure mid-Infrared SpectroScopic Experiment) in the low spectral resolution mode to obtain images in the L and N bands. We computed radiative transfer models that reproduce the L- and N-band intensity distributions of the resolved disks. Results: We present L- and N-band aperture-synthesis images of FS CMa reconstructed in the wavelength bands of 3.4-3.8 and 8.6-9.0 micrometer. In the L-band image, the inner rim region of an inclined circumstellar disk and the central object can be seen with a spatial resolution of 2.7 milliarcsec (mas). An inner disk cavity with an angular diameter of 6x12mas is resolved. The L-band disk consists of a bright northwestern (NW) disk region and a much fainter southeastern (SE) region. The images suggest that we are looking at the bright inner wall of the NW disk rim, which is on the far side of the disk. In the N band, only the bright NW disk region is seen. In addition to deriving the inclination and the inner disk radius, fitting the reconstructed brightness distributions via radiative transfer modeling allows one to constrain the innermost disk structure, in particular the shape of the inner disk rim., Comment: accepted for publication in A&A

Published
2021
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9. Why chromatic imaging matters

Author

Nuno Gomes, Thomas Henning, Roy van Boekel, Éric Thiébaut, J. Sanchez-Bermudez, J. W. Isbell, Laurent Bourgès, John S. Young, Bruno Lopez, Karl-Heinz Hofmann, Dieter Schertl, Fabien Baron, Paulo J. V. Garcia, Florentin Millour, Gilles Duvert, Alexis Matter, Gerd Weigelt, J.-U. Pott, Isbell, JW [0000-0002-1272-6322], Apollo - University of Cambridge Repository, Observatoire de la Côte d'Azur (OCA), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Computer science, FOS: Physical sciences, Iterative reconstruction, 01 natural sciences, 010309 optics, High angular resolution, Interferometric imaging, 0103 physical sciences, Computer vision, Chromatic scale, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Scientific instrument, Very Large Telescope, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, First generation, Interferometry, [SDU]Sciences of the Universe [physics], Optical interferometry, Space and Planetary Science, Image reconstruction, Artificial intelligence, Astrophysics - Instrumentation and Methods for Astrophysics, business
Abstract

During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u-v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction., Accepted for publication in Experimental Astronomy as part of the topical collection: Future of Optical-infrared Interferometry in Europe

Published
2018
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