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1. The GRAVITY Young Stellar Object survey -- IX. Spatially resolved kinematics of hot hydrogen gas in the star/disk interaction region of T Tauri stars

Author

GRAVITY Collaboration, Wojtczak, J. A., Labadie, L., Perraut, K., Tessore, B., Soulain, A., Ganci, V., Bouvier, J., Dougados, C., Alécian, E., Nowacki, H., Cozzo, G., Brandner, W., Garatti, A. Caratti o, Garcia, P., Lopez, R. Garcia, Sanchez-Bermudez, J., Amorim, A., Benisty, M., Berger, J. -P., Bourdarot, G., Caselli, P., Clénet, Y., de Zeeuw, P. T., Davies, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Föster-Schreiber, N. M., Gendron, E., Gillessen, S., Grant, S., Grellmann, R., Heißel, G., Henning, Th., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Kervella, P., Labour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., Ott, T., Paumard, T., Perrin, G., Scheithauer, S., Shangguan, J., Shimizu, T., Spezzano, S., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., and Widmann, F.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Aims: We aim to spatially and spectrally resolve the Br-gamma hydrogen emission line with the methods of interferometry in order to examine the kinematics of the hydrogen gas emission region in the inner accretion disk of a sample of solar-like young stellar objects. The goal is to identify trends and categories among the sources of our sample and to discuss whether or not they can be tied to different origin mechanisms associated with Br-gamma emission in T Tauri stars, chiefly and most prominently magnetospheric accretion. Methods: We observed a sample of seven T Tauri stars for the first time with VLTI GRAVITY, recording spectra and spectrally dispersed interferometric quantities across the Br-gamma line in the NIR K-band. We use them to extract the size of the Br-gamma emission region and the photocenter shifts. To assist in the interpretation, we also make use of radiative transfer models of magnetospheric accretion to establish a baseline of expected interferometric signatures if accretion is the primary driver of Br-gamma emission. Results: From among our sample, we find that five of the seven T~Tauri stars show an emission region with a half-flux radius in the range broadly expected for magnetospheric truncation. Two of the five objects also show Br-gamma emission primarily originating from within the corotation radius, while two other objects exhibit extended emission on a scale beyond 10 R$_*$, one of them even beyond the K~band continuum half-flux radius of 11.3 R$_*$. Conclusions: We find strong evidence to suggest that for the two weakest accretors in the sample, magnetospheric accretion is the primary driver of Br-gamma radiation. The results for the remaining sources imply either partial or strong contributions coming from spatially extended emission components in the form of outflows, such as stellar or disk winds., Comment: Version corresponds to the one in A&A production. The author list has been amended with "GRAVITY Collaboration" as first entry in keeping with the convention established for papers published by the GRAVITY consortium in recent years

Published
2022
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2. The GRAVITY Young Stellar Object survey. VII. The inner dusty disks of T Tauri stars

Author

The GRAVITY Collaboration, Perraut, K., Labadie, L., Bouvier, J., Ménard, F., Klarmann, L., Dougados, C., Benisty, M., Berger, J. -P., Bouarour, Y. -I., Brandner, W., Garatti, A. Caratti o, Caselli, P., de Zeeuw, P. T., Garcia-Lopez, R., Henning, T., Sanchez-Bermudez, J., Sousa, A., van Dishoeck, E., Alécian, E., Amorim, A., Clénet, Y., Davies, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Förster-Schreiber, N. M., Garciaınst, P., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Heissel, G., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Ott, T., Paumard, T., Perrin, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L., Vincent, F., von Fellenberg, S., and Widmann, F.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

These protoplanetary disks in T Tauri stars play a central role in star and planet formation. We spatially resolve at sub-au scales the innermost regions of a sample of T Tauri's disks to better understand their morphology and composition. We extended our homogeneous data set of 27 Herbig stars and collected near-IR K-band observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of ~4000-6000 K and ~0.4-10 Lsun. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometric data and search for trends between the properties of the disk and the central star. The best-fit models of the disk's inner rim correspond to wide rings. We extend the Radius-luminosity relation toward the smallest luminosities (0.4-10 Lsun) and find the R~L^(1/2) trend is no longer valid, since the K-band sizes measured with GRAVITY are larger than the predicted sizes from sublimation radius computation. No clear correlation between the K-band half-flux radius and the mass accretion rate is seen. Having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of the half-flux radius of the inner dusty disk. Our measurements agree with models that take into account the scattered light. The N-to-K band size ratio may be a proxy for disentangling disks with silicate features in emission from disks with weak and/or in absorption silicate features. When comparing inclinations and PA of the inner disks to those of the outer disks (ALMA) in nine objects of our sample, we detect misalignments for four objects., Comment: Accepted for publication in A&A; 20 pages, 15 figures, 9 tables

Published
2021
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3. The GRAVITY Young Stellar Object survey VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

Author

GRAVITY Collaboration, Ganci, V., Labadie, L., Klarmann, L., de Valon, A., Perraut, K., Benisty, M., Brandner, W., Garatti, A. Caratti o, Dougados, C., Eupen, F., Lopez, R. Garcia, Grellmann, R., Sanchez-Bermudez, J., Wojtczak, A., Garcia, P., Amorim, A., Bauböck, M., Berger, J. -P., Caselli, P., Clénet, Y., Foresto, V. Coudé du, de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, T., Hippler, S., Horrobin, M., Hubert, Z., Jiménez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Heißel, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., and Woillez, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

The formation and evolution of planetary systems impact the primordial accretion disk. HD141569 is the only known pre-main sequence star characterized by a hybrid disk. Observations probed the outer-disk structure showing a complex system of rings and interferometric observations attempted to characterize its inner 5 au region, but derived limited constraints. The goal of this work was to explore with new high-resolution interferometric observations the properties of the dust and gas in the internal regions of HD141569. We observed HD141569 on mas scales with GRAVITY/VLTI in the near-infrared at low and high spectral resolution. We interpreted the visibilities and spectral energy distribution with geometrical models and radiative transfer techniques to constrain the dust emission. We analyzed the high spectral resolution quantities to investigate the properties of the Br-Gamma line emitting region. Thanks to the combination of three different epochs, GRAVITY resolves the inner dusty disk in the K band. Data modeling shows that an IR excess of about 6% is spatially resolved and that the origin of this emission is confined in a ring of material located at a radius of 1 au from the star with a width smaller than 0.3 au. The MCMax modeling suggests that this emission could originate from a small amount of QHPs, while large silicate grain models cannot reproduce at the same time the observational constraints on the properties of near-IR and mid-IR fluxes. The differential phases in the Br-Gamma line clearly show an S-shape that can be best reproduced witha gas disk in Keplerian rotation, confined within 0.09 au. This is also hinted at by the double-peaked Br-Gamma emission line shape. The modeling of the continuum and gas emission shows that the inclination and position angle of these two components are consistent with a system showing relatively coplanar rings on all scales., Comment: Accepted for publication in A&A; 25 pages, 15 figures, 5 tables

Published
2021
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4. The GRAVITY Young Stellar Object Survey. VI. Mapping the variable inner disk of HD 163296 at sub-au scales

Author

Sanchez-Bermudez, J., Garatti, A. Caratti o, Lopez, R. Garcia, Perraut, K., Labadie, L., Benisty, M., Brandner, W., Dougados, C., Garcia, P. J. V., Henning, Th., Klarmann, L., Amorim, A., Bauböck, M., Berger, J. P., Bouquin, J. B. Le, Caselli, P., Clénet, Y., Foresto, V. Coudé du, de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Heissel, G., Horrobin, M., Hubert, Z., Jiménez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Léna, P., Ott, T., Paumard, T., Perrin, G., Pineda, J. E., Rodríguez-Coira, G., Rousset, G., Segura-Cox, D. M., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., and Woillez, J.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures, etc.) of stars and planets. Understanding such physical processes is one of the main astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. This study aims at characterizing the morphology of the inner disk in HD 163296 with multi-epoch near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer (VLTI). Our goal is to depict the K-band (lambda_0 ~ 2.2 um) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival PIONIER (H-band; lambda_0 ~ 1.65 um) data of the source. We performed a Gradient Descent parametric model fitting to recover the sub-au morphology of our source. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H- and K-bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and persistence of this asymmetric structure on timescales of several years, we argue that it is a dusty feature (e.g., a vortex or dust clouds), probably, made by a mixing of sillicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk., Comment: Accepted to be published in Astronomy and Astrophysics; main-body: 11 pages, 3 figures and 3 tables

Published
2021
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5. A measure of the size of the magnetospheric accretion region in TW Hydrae

Author

Lopez, R. Garcia, Natta, A., Garatti, A. Caratti o, Ray, T. P., Fedriani, R., Koutoulaki, M., Klarmann, L., Perraut, K., Sanchez-Bermudez, J., Benisty, M., Dougados, C., Labadie, L., Brandner, W., Garcia, P. J. V., Henning, Th., Caselli, P., Duvert, G., de Zeeuw, T., Grellmann, R., Abuter, R., Amorim, A., Bauboeck, M., Berger, J. P., Bonnet, H., Buron, A., Clénet, Y., Foresto, V. Coudé du, de Wit, W., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Dabo, C. E. Garcia, Gendron, E., Genzel, R., Gillessen, S., Habibi, M., Haubois, X., Haussmann, F., Hippler, S., Hubert, Z., Horrobin, M., Rosales, A. Jimenez, Jocou, L., Kervella, P., Kolb, J., Lacour, S., Bouquin, J. -B. Le, Léna, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramirez, A., 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., Woillez, J., Yazici, S., and Zins, G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the so-called corotation radius where the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that Hydrogen is mostly emitted in a region of a few milliarcseconds across, usually located within the dust sublimation radius. Its origin is still a matter of debate and it can be interpreted as coming from the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that the Br gamma emission is spatially resolved rules out that most of the emission comes from the magnetosphere. This is due to the weak magnetic fields (some tenths of G) detected in these sources, resulting in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. However, the small angular size of the magnetosphere (a few tenths of milliarcseconds), along with the presence of winds emitting in Hydrogen make the observations interpretation challenging. Here, we present direct evidence of magnetospheric accretion by spatially resolving the inner disk of the 60 pc T Tauri star TW Hydrae through optical long baseline interferometry. We find that the hydrogen near-infrared emission comes from a region approximately 3.5 stellar radii (R*) across. This region is within the continuum dusty disk emitting region (Rcont = 7 R*) and smaller than the corotation radius which is twice as big. This indicates that the hydrogen emission originates at the accretion columns, as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (>1au)., Comment: Publish in Nature

Published
2021
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6. The GRAVITY young stellar object survey V. The orbit of the T Tauri binary star WW Cha

Author

GRAVITY Collaboration, Eupen, F., Labadie, L., Grellmann, R., Perraut, K., Brandner, W., Duchêne, G., Köhler, R., Sanchez-Bermudez, J., Lopez, R. Garcia, Garatti, A. Caratti o, Benisty, M., Dougados, C., Garcia, P., Klarmann, L., Amorim, A., Bauböck, M., Berger, J. P., Caselli, P., Clénet, Y., Foresto, V. Coudé du, de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Ganci, V., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, Th., Hippler, S., Horrobin, M., Hubert, Z., Jiménez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Bouquin, J. B. Le, Léna, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rodríguez-Coira, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., and Wojtczak, A.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission. This makes WW Cha a very interesting source for studying the influence of dynamical effects on circumstellar as well as circumbinary material. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. We find the secondary star orbiting the primary with a period of T=206.55 days, a semimajor axis of a=1.01 au, and a relatively high eccentricity of e=0.45. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, the dynamical mass of Mtot=3.20 Msol can be explained by a mass ratio between ~0.5 and 1. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks' structures. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena., Comment: Accepted for publication in A&A; 24 pages, 14 figures, 3 tables; affiliations corrected

Published
2021
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7. 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., and Zins, G.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
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., Comment: Accepted in A&A

Published
2020
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8. The GRAVITY young stellar object survey III. The dusty disk of RY Lup

Author

GRAVITY Collaboration, Bouarour, Y. -I., Perraut, K., Ménard, F., Brandner, W., Garatti, A. Caratti o, Caselli, P., van Dishoeck, E., Dougados, C., Garcia-Lopez, R., Grellmann, R., Henning, T., Klarmann, L., Labadie, L., Natta, A., Sanchez-Bermudez, J., Thi, W. -F., de Zeeuw, P. T., Amorim, A., Bauböck, M., Benisty, M., Berger, J. -P., Clenet, Y., Foresto, V. Coudé du, Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Filho, M., Gao, F., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Jiménez-Rosales, A., Jocou, L., Hippler, S., Horrobin, M., Hubert, Z., Kervella, P., Lacour, S., Bouquin, J. -B. Le, Léna, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Vincent, F. H., von Fellenberg, S. D., Widmann, F., and Wiest, M.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the Spectral Energy Distribution and match the interferometric observations. To match the SED , our model requires a stellar luminosity of 2.5 Lsun, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 Rsun. These revised fundamental parameters, when combined with the mass estimates available , lead to an age of 0.5-2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12~au from the central star. This model corresponds to an inclination of the inner disk of 50deg, which is in mild tension with previous determinations of a more inclined outer disk from SPHERE (70 deg in NIR) and ALMA(67 $\pm$5 deg) images, but consistent with the inclination determination from the ALMA CO spectra (55$\pm$5deg). Increasing the inclination of the inner disk to 70 deg leads to a higher line-of-sight extinction and therefore requires a higher stellar luminosity of 4.65 Lsun to match the observed flux levels. This luminosity would translate to a stellar radius of 3.13~Rsun, leading to an age of 2-3~Ma, and a stellar mass of about 2 Msun, in disagreement with the observed dynamical mass estimate of 1.3-1.5 Msun. Critically, this high-inclination inner disk model also fails to reproduce the visibilities observed with GRAVITY., Comment: Accepted for publication in A&A; 11 pages, 5 figures, 3 tables

Published
2020
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9. The GRAVITY young stellar object survey. II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO

Author

GRAVITY Collaboration, Garatti, A. Caratti o, Fedriani, R., Lopez, R. Garcia, Koutoulaki, M., Perraut, K., Linz, H., Brandner, W., Garcia, P., Klarmann, L., Henning, T., Labadie, L., Sanchez-Bermudez, J., Lazareff, B., van Dishoeck, E. F., Caselli, P., de Zeeuw, P. T., Bik, A., Benisty, M., Dougados, C., Ray, T. P., Amorim, A., Berger, J. -P., Clénet, Y., Foresto, V. Coudé du, Duvert, G., Eckart, A., Eisenhauer, F., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gordo, P., Jocou, L., Horrobin, M., Kervella, P., Lacour, S., Bouquin, J. -B. Le, Léna, P., Grellmann, R., Ott, T., Paumard, T., Perrin, G., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Thi, W. F., Vincent, F. H., and Widmann, F.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved. We deploy near-infrared (NIR) spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 $\mu$m). We present the first GRAVITY/VLTI observations at high spectral (R=4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS2. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases ($\leq$8$^{\circ}$). Our best ellipsoid model provides a disc inclination of 34$^{\circ}$$\pm$1$^{\circ}$, a disc major axis position angle of 166$^{\circ}$$\pm$1$^{\circ}$, and a disc diameter of 3.99$\pm$0.09 mas (or 1.69$\pm$0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74$\pm^{0.08}_{0.07}$ mas (1.16$\pm$0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and $PA$ matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of $M_*\sim$14.7$^{+2}_{-3.6}$ M$_{\odot}$ by combining our interferometric and spectral modelling results., Comment: Accepted for publication in A&A letters

Published
2020
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10. The GRAVITY Young Stellar Object survey -- I. Probing the disks of Herbig Ae/Be stars in terrestrial orbits

Author

Perraut, K., Labadie, L., Lazareff, B., Klarmann, L., Segura-Cox, D., Benisty, M., Bouvier, J., Brandner, W., Garatti, A. Caratti o, Caselli, P., Dougados, C., Garcia, P., Garcia-Lopez, R., Kendrew, S., Koutoulaki, M., Kervella, P., Lin, C. -C., Pineda, J., Sanchez-Bermudez, J., van Dishoeck, E., Abuter, R., Amorim, A., Berger, J. -P., Bonnet, H., Buron, A., Cantalloube, F., Clénet, Y., Foresto, V. Coudé du, Dexter, J., de Zeeuw, P. T., Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gordo, P., Grellmann, R., Haubois, X., Haussmann, F., Henning, T., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Lacour, S., Bouquin, J. -B. Le, Léna, P., Mérand, A., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rabien, S., Ray, T., Rau, C., Rousset, G., Scheithauer, S., Straub, O., Straubmeier, C., Sturm, E., Vincent, F., Waisberg, I., Wank, I., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Woillez, J., and Yazici, S.

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. The processes of disk evolution and planet formation are intrinsically linked. We spatially resolve with GRAVITY/VLTI in the K-band the sub au-scale region of 27 stars to gain statistical understanding of their properties. We look for correlations with stellar parameters, such as luminosity, mass, temperature and age. Our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data. Our best models correspond to smooth and wide rings, implying that wedge-shaped rims at the dust sublimation edge are favored, as found in the H-band. The closure phases are generally non-null with a median value of ~10 deg, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20-25 deg but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to ~1e4 Lsun and confirm the significant spread around the mean relation observed in the H-band. Gapped sources exhibit a large N-to-K band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the 2 Ms mass range, we observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the N-to-K size ratio. However, the size of the current sample does not yet permit us to invoke a clear universal evolution mechanism across the HAeBe mass range. The measured locations of the K-band emission suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation., Comment: Accepted for publication in A&A; 23 pages, 16 figures, 7 tables

Published
2019
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11. NU Ori: a hierarchical triple system with a strongly magnetic B-type star

Author

Shultz, M., Bouquin, J. -B. Le, Rivinius, Th., Wade, G. A., Kochukhov, O., Alecian, E., Petit, V., Pfuhl, O., Karl, M., Gao, F., Grellmann, R., Lin, C. -C., Garcia, P., Lacour, S., MiMeS, the, and Collaborations, BinaMIcS

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with 4 components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer (VLTI) dataset. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution we show that the Zeeman Stokes $V$ signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding $M_{\rm Aa} = 14.9 \pm 0.5 M_\odot$, $M_{\rm Ab} = 3.9 \pm 0.7 M_\odot$, and $M_{\rm C} = 7.8 \pm 0.7 M_\odot$. The rotational period obtained from longitudinal magnetic field $\langle B_z \rangle$ measurements is $P_{\rm rot} = 1.09468(7)$ d, consistent with previous results. Modeling of $\langle B_z \rangle$ indicates a surface dipole magnetic field strength of $\sim 8$ kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric H$\alpha$ emission, and we find marginal evidence of emission at the expected level ($\sim$1% of the continuum)., Comment: 17 pages, 14 figures, 7 tables, accepted for publication in MNRAS

Published
2018
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12. VLTI-AMBER velocity-resolved aperture-synthesis imaging of Eta Carinae with a spectral resolution of 12000. Studies of the primary star wind and innermost wind-wind collision

Author

Weigelt, G., Hofmann, K. -H., Schertl, D., Clementel, N., Corcoran, M. F., Damineli, A., de Wit, W. -J., Grellmann, R., Groh, J., Guieu, S., Gull, T., Heininger, M., Hillier, D. J., Hummel, C. A., Kraus, S., Madura, T., Mehner, A., Mérand, A., Millour, F., Moffat, A. F. J., Ohnaka, K., Patru, F., Petrov, R. G., Rengaswamy, S., Richardson, N. D., Rivinius, T., Schöller, M., Teodoro, M., and Wittkowski, M.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Context. The mass loss from massive stars is not understood well. Eta Car is a unique object for studying the massive stellar wind during the LBV phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Methods. Observations of Eta Car were carried out with the ESO VLTI and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Br Gamma 2.166 micrometer emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately -140 to -376 km/s measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of -277 km/s, the position angle of the symmetry axis of the fan is ~ 126 degree. The fan-shaped structure extends approximately 8.0 mas (~ 18.8 au) to the southeast and 5.8 mas (~ 13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three-dimensional hydrodynamical, radiative transfer models of the massive interacting winds of Eta Car.

Published
2016
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13. Resolved astrometric orbits of ten O-type binaries

Author

Bouquin, J. -B. Le, Sana, H., Gosset, E., De Becker, M., Duvert, G., Absil, O., Anthonioz, F., Berger, J. -P., Ertel, S., Grellmann, R., Guieu, S., Kervella, P., Rabus, M., and Willson, M.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Our long term aim is to derive model-independent stellar masses and distances for long period massive binaries by combining apparent astrometric orbit with double-lined radial velocity amplitudes (SB2). We follow-up ten O+O binaries with AMBER, PIONIER and GRAVITY at the VLTI. Here, we report about 130 astrometric observations over the last 7 years. We combine this dataset with distance estimates to compute the total mass of the systems. We also compute preliminary individual component masses for the five systems with available SB2 radial velocities. Nine over the ten binaries have their three dimensional orbit well constrained. Four of them are known colliding wind, non-thermal radio emitters, and thus constitute valuable targets for future high angular resolution radio imaging. Two binaries break the correlation between period and eccentricity tentatively observed in previous studies. It suggests either that massive star formation produce a wide range of systems, or that several binary formation mechanisms are at play. Finally, we found that the use of existing SB2 radial velocity amplitudes can lead to unrealistic masses and distances. If not understood, the biases in radial velocity amplitudes will represent an intrinsic limitation for estimating dynamical masses from SB2+interferometry or SB2+Gaia. Nevertheless, our results can be combined with future Gaia astrometry to measure the dynamical masses and distances of the individual components with an accuracy of 5 to 15\%, completely independently of the radial velocities., Comment: Accepted in A&A; Astrometric positions available in CDS; revised version after language edition

Published
2016
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14. Masses of the components of SB2 binaries observed with Gaia. II. Masses derived from PIONIER interferometric observations for Gaia validation

Author

Halbwachs, J. -L., Boffin, H. M. J., Bouquin, J. -B. Le, Kiefer, F., Famaey, B., Salomon, J. -B., Arenou, F., Pourbaix, D., Anthonioz, F., Grellmann, R., Guieu, S., Sana, H., Guillout, P., Jorissen, A., Lebreton, Y., Mazeh, T., Tal-Or, L., and Gomez-Moran, A. Nebot

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

In anticipation of the Gaia astrometric mission, a sample of spectroscopic binaries is being observed since 2010 with the Sophie spectrograph at the Haute--Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 % when combined with Gaia astrometric measurements. In order to validate the masses derived from Gaia, interferometric observations are obtained for three SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186. The masses of the six stellar components are derived. Due to its edge-on orientation, HIP 14157 is probably an eclipsing binary. We note that almost all the derived masses are a few percent larger than the expectations from the standard spectral-type-mass calibration and mass-luminosity relation. Our calculation also leads to accurate parallaxes for the three binaries, and the Hipparcos parallaxes are confirmed., Comment: 10 pages, 3 figures, accepted by MNRAS

Published
2015
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15. Monitoring the Dusty S-Cluster Object (DSO/G2) on its Orbit towards the Galactic Center Black Hole

Author

Valencia-S., M., Eckart, A., Zajacek, M., Peissker, F., Parsa, M., Grosso, N., Mossoux, E., Porquet, D., Jalali, B., Karas, V., Yazici, S., Shahzamanian, B., Sabha, N., Saalfeld, R., Smajic, S., Grellmann, R., Moser, L., Horrobin, M., Borkar, A., Marin, M. Garcia, Dovciak, M., Kunneriath, D., Karssen, G. D., Bursa, M., Straubmeier, C., and Bushouse, H.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

We analyse and report in detail new near-infrared (1.45 - 2.45 microns) observations of the Dusty S-cluster Object (DSO/G2) during its approach to the black hole at the center of the Galaxy that were carried out with ESO VLT/SINFONI between February and September 2014. Before May 2014 we detect spatially compact Br-gamma and Pa-alpha line emission from the DSO at about 40mas east of SgrA*. The velocity of the source, measured from the red-shifted emission, is 2700+-60 km/s. No blue-shifted emission above the noise level is detected at the position of SgrA* or upstream the presumed orbit. After May we find spatially compact Br-gamma blue-shifted line emission from the DSO at about 30mas west of SgrA* at a velocity of -3320+-60 km/s and no indication for significant red-shifted emission. We do not detect any significant extension of velocity gradient across the source. We find a Br-gamma-line full width at half maximum of 50+-10 Angstroem before and 15+-10 Angstroem after the peribothron transit, i.e. no significant line broadening with respect to last year is observed. Br-gamma line maps show that the bulk of the line emission originates from a region of less than 20mas diameter. This is consistent with a very compact source on an elliptical orbit with a peribothron time passage in 2014.39+-0.14. For the moment, the flaring activity of the black hole in the near-infrared regime has not shown any statistically significant increment. Increased accretion activity of SgrA* may still be upcoming. We discuss details of a source model according to which the DSO is rather a young accreting star than a coreless gas and dust cloud., Comment: 32 pages - 3 tables - 17 figure - accepted by ApJ

Published
2014
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16. Mid-infrared interferometry of the massive young stellar object NGC 2264 IRS 1

Author

Grellmann, R., Ratzka, Th., Kraus, S., Linz, H., Preibisch, Th., and Weigelt, G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The optically invisible infrared-source NGC 2264 IRS 1 is thought to be a massive young stellar object (~10 Msun). Although strong infrared excess clearly shows that the central object is surrounded by large amounts of circumstellar material, no information about the spatial distribution of this circumstellar material has been available until now. We used the ESO Very Large Telescope Interferometer to perform long-baseline interferometric observations of NGC 2264 IRS 1 in the mid-infrared regime. Our observations resolve the circumstellar material around NGC 2264 IRS 1, provide the first direct measurement of the angular size of the mid-infrared emission, and yield direct constraints on the spatial distribution of the dust. We use different approaches (a geometrical model, a temperature-gradient model, and radiative transfer models) to jointly model the observed interferometric visibilities and the spectral energy distribution. The derived visibility values between ~0.02 and ~0.3 show that the mid-infrared emission is clearly resolved. The characteristic size of the MIR-emission region is ~30-60 AU; this value is typical for other YSOs with similar or somewhat lower luminosities. A comparison of the sizes for the two position angles shows a significant elongation of the dust distribution. Simple spherical envelope models are therefore inconsistent with the data. The radiative transfer modeling of our data suggests that we observe a geometrically thin and optically thick circumstellar disk with a mass of about 0.1 Msun. Our modeling indicates that NGC 2264 IRS 1 is surrounded by a flat circumstellar disk that has properties similar to disks typically found around lower-mass young stellar objects. This result supports the assumption that massive young stellar objects form via accretion from circumstellar disks., Comment: 11 pages, accepted for publication in A&A

Published
2011
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17. The GRAVITY Young Stellar Object survey -- IX. Spatially resolved kinematics of hot hydrogen gas in the star/disk interaction region of T Tauri stars

Author

Wojtczak, J. A., Labadie, L., Perraut, K., Tessore, B., Soulain, A., Ganci, V., Bouvier, J., Dougados, C., Alécian, E., Nowacki, H., Cozzo, G., Brandner, W., Garatti, A. Caratti O, Garcia, P., Lopez, R. Garcia, Sanchez-Bermudez, J., Amorim, A., Benisty, M., Berger, J. -P., Bourdarot, G., Caselli, P., Clénet, Y., de Zeeuw, P. T., Davies, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Föster-Schreiber, N. M., Gendron, E., Gillessen, S., Grant, S., Grellmann, R., Heißel, G., Henning, Th., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Kervella, P., Labour, S., Lapeyrère, V., Bouquin, J. -B. Le, Léna, P., Lutz, D., Mang, F., Ott, T., Paumard, T., Perrin, G., Scheithauer, S., Shangguan, J., Shimizu, T., Spezzano, S., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., Widmann, F., and Alecian, Evelyne

Subjects
[SDU.ASTR.SR] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

Aims: We aim to spatially and spectrally resolve the Br-gamma hydrogen emission line with the methods of interferometry in order to examine the kinematics of the hydrogen gas emission region in the inner accretion disk of a sample of solar-like young stellar objects. The goal is to identify trends and categories among the sources of our sample and to discuss whether or not they can be tied to different origin mechanisms associated with Br-gamma emission in T Tauri stars, chiefly and most prominently magnetospheric accretion. Methods: We observed a sample of seven T Tauri stars for the first time with VLTI GRAVITY, recording spectra and spectrally dispersed interferometric quantities across the Br-gamma line in the NIR K-band. We use them to extract the size of the Br-gamma emission region and the photocenter shifts. To assist in the interpretation, we also make use of radiative transfer models of magnetospheric accretion to establish a baseline of expected interferometric signatures if accretion is the primary driver of Br-gamma emission. Results: From among our sample, we find that five of the seven T~Tauri stars show an emission region with a half-flux radius in the range broadly expected for magnetospheric truncation. Two of the five objects also show Br-gamma emission primarily originating from within the corotation radius, while two other objects exhibit extended emission on a scale beyond 10 R$_*$, one of them even beyond the K~band continuum half-flux radius of 11.3 R$_*$. Conclusions: We find strong evidence to suggest that for the two weakest accretors in the sample, magnetospheric accretion is the primary driver of Br-gamma radiation. The results for the remaining sources imply either partial or strong contributions coming from spatially extended emission components in the form of outflows, such as stellar or disk winds.

Published
2022

18. VI. Mapping the variable inner disk of HD 163296 at sub-au scales

Author

Sanchez-Bermudez, J., Caratti O Garatti, A., Garcia Lopez, R., Perraut, K., Labadie, L., Benisty, M., Brandner, W., Dougados, C., Garcia, P., Henning, Th., Klarmann, L., Amorim, A., Bauböck, M., Berger, J., Le Bouquin, J., Caselli, P., Clénet, Y., Coudé Du Foresto, V., de Zeeuw, P., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Heissel, G., Horrobin, M., Hubert, Z., Jiménez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrère, V., Léna, P., Ott, T., Paumard, T., Perrin, G., Pineda, J., Rodríguez-Coira, G., Rousset, G., Segura-Cox, D., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Van Dishoeck, E., Vincent, F., Von fellenberg, S., Widmann, F., Woillez, J., 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, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

International audience; Context. Protoplanetary disks drive some of the formation process (e.g., accretion, gas dissipation, formation of structures) of stars and planets. Understanding such physical processes is one of the most significant astrophysical questions. HD 163296 is an interesting young stellar object for which infrared and sub-millimeter observations have shown a prominent circumstellar disk with gaps plausibly created by forming planets. Aims. This study aims to characterize the morphology of the inner disk in HD 163296 with multi-epoch, near-infrared interferometric observations performed with GRAVITY at the Very Large Telescope Interferometer. Our goal is to depict the K -band ( λ 0 ~ 2.2 μm) structure of the inner rim with milliarcsecond (sub-au) angular resolution. Our data is complemented with archival Precision Integrated-Optics Near-infrared Imaging ExpeRiment ( H -band; λ 0 ~ 1.65 μm) data of the source. Methods. We performed a gradient descent parametric model fitting to recover the sub-au morphology of our source. Results. Our analysis shows the existence of an asymmetry in the disk surrounding the central star of HD 163296. We confirm variability of the disk structure in the inner ~2 mas (0.2 au). While variability of the inner disk structure in this source has been suggested by previous interferometric studies, this is the first time that it is confirmed in the H - and K -bands by using a complete analysis of the closure phases and squared visibilities over several epochs. Because of the separation from the star, position changes, and the persistence of this asymmetric structure on timescales of several years, we argue that it is probably a dusty feature (e.g., a vortex or dust clouds) made by a mixing of silicate and carbon dust and/or refractory grains, inhomogeneously distributed above the mid-plane of the disk.

Published
2021

19. The GRAVITY young stellar object survey

Author

Koutoulaki, M., Garcia Lopez, R., Natta, A., Fedriani, R., Caratti o Garatti, A., 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., Coudé du Foresto, V., 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., Jimenez Rosales, A., Jocou, L., Kervella, P., Kolb, J., Lacour, S., Le Bouquin, J.-B., 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., Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)

Subjects
[SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

International audience; Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 μ m, most likely originating in the innermost regions of a circumstellar disc. Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc. Methods. We used the second-generation Very Large Telescope Interferometer instrument 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 local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements. Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of ~10.58 ± 2.65 R ⊙ . The K -band continuum emission from the disc is inclined by 63° ± 1°, with a position angle of 116° ± 1°, 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 ( N CO = (0.9–9) × 10 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. Conclusions. 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.

Published
2021

20. 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

21. The GRAVITY young stellar object survey VIII. Gas and dust faint inner rings in the hybrid disk of HD141569

Author

Ganci, V., Labadie, L., Klarmann, L., de Valon, A., Perraut, K., Benisty, M., Brandner, W., Garatti, A. Caratti O., Dougados, C., Eupen, F., Garcia Lopez, R., Grellmann, R., Sanchez-Bermudez, J., Wojtczak, A., Garcia, P., Amorim, A., Baubock, M., Berger, J. -P., Caselli, P., Clenet, Y., Coude du Foresto, V., de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, T., Hippler, S., Horrobin, M., Hubert, Z., Jimenez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V., Le Bouquin, J-B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., Ganci, V., Labadie, L., Klarmann, L., de Valon, A., Perraut, K., Benisty, M., Brandner, W., Garatti, A. Caratti O., Dougados, C., Eupen, F., Garcia Lopez, R., Grellmann, R., Sanchez-Bermudez, J., Wojtczak, A., Garcia, P., Amorim, A., Baubock, M., Berger, J. -P., Caselli, P., Clenet, Y., Coude du Foresto, V., de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, T., Hippler, S., Horrobin, M., Hubert, Z., Jimenez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V., Le Bouquin, J-B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., and Woillez, J.

Abstract

Context. The formation and evolution of planetary systems impact the evolution of the primordial accretion disk in its dust and gas content. HD 141569 is a peculiar object in this context as it is the only known pre-main sequence star characterized by a hybrid disk. Observations with 8 m class telescopes probed the outer-disk structure showing a complex system of multiple rings and outer spirals. Furthermore, interferometric observations attempted to characterize its inner 5 au region, but derived limited constraints. Aims. The goal of this work was to explore with new high-resolution interferometric observations the geometry, properties, and dynamics of the dust and gas in the internal regions of HD 141569. Methods. We observed HD 141569 on milliarcsecond scales with GRAVITY/VLTI in the near-infrared (IR) at low (R similar to 20) and high (R similar to 4000) spectral resolution. We interpreted the interferometric visibilities and spectral energy distribution with geometrical models and through radiative transfer techniques using the code MCMax to constrain the dust emission. We analyzed the high spectral resolution quantities (visibilities and differential phases) to investigate the properties of the Brackett-gamma (Br gamma) line emitting region. Results. Thanks to the combination of three different epochs, GRAVITY resolves the inner dusty disk in the K band with squared visibilities down to V-2 similar to 0.8. A differential phase signal is also detected in the region of the Br gamma line along most of the six baselines. Data modeling shows that an IR excess of about 6% is spatially resolved and that the origin of this emission is confined in a ring of material located at a radius of similar to 1 au from the star with a width less than or similar to 0.3 au. The MCMax modeling suggests that this emission could originate from a small amount (1.4 x 10(-8) M-circle plus) of quantum-heated particles, while large silicate grain models cannot reproduce at the same time

Published
2021

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

Author

Koutoulaki, M., Lopez, R. Garcia, Natta, A., Fedriani, R., Garatti, A. Caratti O., 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., Bauboeck, M., Benisty, M., Berger, J. P., Buron, A., Caselli, P., Clenet, Y., du Foresto, V. Coude, 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., Le Bouquin, J-B, Lena, P., Linz, H., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramirez-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., Koutoulaki, M., Lopez, R. Garcia, Natta, A., Fedriani, R., Garatti, A. Caratti O., 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., Bauboeck, M., Benisty, M., Berger, J. P., Buron, A., Caselli, P., Clenet, Y., du Foresto, V. Coude, 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., Le Bouquin, J-B, Lena, P., Linz, H., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramirez-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., and Zins, G.

Abstract

Context. 51 Oph is a Herbig Ae/Be star that exhibits strong near-infrared CO ro-vibrational emission at 2.3 mu m, most likely originating in the innermost regions of a circumstellar disc.Aims. We aim to obtain the physical and geometrical properties of the system by spatially resolving the circumstellar environment of the inner gaseous disc.Methods. We used the second-generation Very Large Telescope Interferometer instrument 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 local thermal equilibrium ring model of the CO emission to reproduce the spectrum and CO line displacements.Results. Our interferometric data show that the star is marginally resolved at our spatial resolution, with a radius of similar to 10.58 2.65R(circle dot). The K-band continuum emission from the disc is inclined by 63 degrees +/- 1 degrees, with a position angle of 116 degrees +/- 1 degrees, 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 (N-CO = (0.9-9) x 10(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.Conclusions. 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

Published
2021

23. The GRAVITY young stellar object survey VII. The inner dusty disks of T Tauri stars

Author

Perraut, K., Labadie, L., Bouvier, J., Menard, F., Klarmann, L., Dougados, C., Benisty, M., Berger, J-P, Bouarour, Y-, I, Brandner, W., Garatti, A. Caratti o, Caselli, P., de Zeeuw, P. T., Garcia-Lopez, R., Henning, T., Sanchez-Bermudez, J., Sousa, A., van Dishoeck, E., Alecian, E., Amorim, A., Clenet, Y., Davies, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Foerster-Schreiber, N. M., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Heissel, G., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V, Le Bouquin, J-B, Lena, P., Lutz, D., Ott, T., Paumard, T., Perrin, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L., Vincent, F., von Fellenberg, S., Widmann, F., Perraut, K., Labadie, L., Bouvier, J., Menard, F., Klarmann, L., Dougados, C., Benisty, M., Berger, J-P, Bouarour, Y-, I, Brandner, W., Garatti, A. Caratti o, Caselli, P., de Zeeuw, P. T., Garcia-Lopez, R., Henning, T., Sanchez-Bermudez, J., Sousa, A., van Dishoeck, E., Alecian, E., Amorim, A., Clenet, Y., Davies, R., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Foerster-Schreiber, N. M., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Grellmann, R., Heissel, G., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V, Le Bouquin, J-B, Lena, P., Lutz, D., Ott, T., Paumard, T., Perrin, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Tacconi, L., Vincent, F., von Fellenberg, S., and Widmann, F.

Abstract

Context. T Tauri stars are surrounded by dust and gas disks. As material reservoirs from which matter is accreted onto the central star and planets are built, these protoplanetary disks play a central role in star and planet formation. Aims. We aim at spatially resolving at sub-astronomical unit (sub-au) scales the innermost regions of the protoplanetary disks around a sample of T Tauri stars to better understand their morphology and composition. Methods. Thanks to the sensitivity and the better spatial frequency coverage of the GRAVITY instrument of the Very Large Telescope Interferometer, we extended our homogeneous data set of 27 Herbig stars and collected near-infrared K-band interferometric observations of 17 T Tauri stars, spanning effective temperatures and luminosities in the ranges of similar to 4000-6000 K and similar to 0.4-10 L-circle dot, respectively. We focus on the continuum emission and develop semi-physical geometrical models to fit the interferometric data and search for trends between the properties of the disk and the central star. Results. As for those of their more massive counterparts, the Herbig Ae/Be stars, the best-fit models of the inner rim of the T Tauri disks correspond to wide rings. The GRAVITY measurements extend the radius-luminosity relation toward the smallest luminosities (0.4-10 L-circle dot). As observed previously, in this range of luminosities, the R proportional to L-1/2 trend line is no longer valid, and the K-band sizes measured with GRAVITY appear to be larger than the predicted sizes derived from sublimation radius computation. We do not see a clear correlation between the K-band half-flux radius and the mass accretion rate onto the central star. Besides, having magnetic truncation radii in agreement with the K-band GRAVITY sizes would require magnetic fields as strong as a few kG, which should have been detected, suggesting that accretion is not the main process governing the location of the half-flux radius of the inn

Published
2021

24. The GRAVITY young stellar object survey V. The orbit of the T Tauri binary star WWCha

Author

Eupen, F., Labadie, L., Grellmann, R., Perraut, K., Brandner, W., Duchene, G., Kohler, R., Sanchez-Bermudez, J., Lopez, R. Garcia, Garatti, A. Caratti O., Benisty, M., Dougados, C., Garcia, P., Klarmann, L., Amorim, A., Baubock, M., Berger, J. P., Caselli, P., Clenet, Y., Foresto, V. Coude du, Zeeuw, P. T. de, Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Ganci, V, Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, Th, Hippler, S., Horrobin, M., Hubert, Z., Jimenez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V, Bouquin, J. B. Le, Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rodriguez-Coira, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., Wojtczak, A., Eupen, F., Labadie, L., Grellmann, R., Perraut, K., Brandner, W., Duchene, G., Kohler, R., Sanchez-Bermudez, J., Lopez, R. Garcia, Garatti, A. Caratti O., Benisty, M., Dougados, C., Garcia, P., Klarmann, L., Amorim, A., Baubock, M., Berger, J. P., Caselli, P., Clenet, Y., Foresto, V. Coude du, Zeeuw, P. T. de, Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Ganci, V, Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, Th, Hippler, S., Horrobin, M., Hubert, Z., Jimenez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyrere, V, Bouquin, J. B. Le, Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rodriguez-Coira, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., and Wojtczak, A.

Abstract

Context. Close young binary stars are unique laboratories for the direct measurement of pre-main-sequence (PMS) stellar masses and their comparison to evolutionary theoretical models. At the same time, a precise knowledge of their orbital parameters when still in the PMS phase offers an excellent opportunity for understanding the influence of dynamical effects on the morphology and lifetime of the circumstellar as well as circumbinary material. Aims. The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission, which makes it dynamically a very interesting source in the above context. The goal of this work is to determine the astrometric orbit and the stellar properties of WW Cha using multi-epoch interferometric observations. Methods. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, we constrain the mass ratio. Results. We find the secondary star orbiting the primary with a period of T = 206.55 days, a semimajor axis of a = 1.01 au, and a relatively high eccentricity of e = 0.45. The dynamical mass of M-tot = 3.20 M-circle dot can be explained by a mass ratio between similar to 0.5 and 1, indicating an intermediate-mass T Tauri classification for both components. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE, resul

Published
2021

25. The GRAVITY young stellar object survey : II. First spatially resolved observations of the CO bandhead emission in a high-mass YSO

Author

Garatti, A. Caratti O., Fedriani, R., Lopez, R. Garcia, Koutoulaki, M., Perraut, K., Linz, H., Brandner, W., Garcia, P., Klarmann, L., Henning, T., Labadie, L., Sanchez-Bermudez, J., Lazareff, B., van Dishoeck, E. F., Caselli, P., de Zeeuw, P. T., Bik, Adrianus, Benisty, M., Dougados, C., Ray, T. P., Amorim, A., Berger, J-P, Clenet, Y., du Foresto, V. Coude, Duvert, G., Eckart, A., Eisenhauer, F., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gordo, P., Jocou, L., Horrobin, M., Kervella, P., Lacour, S., Le Bouquin, J-B, Lena, P., Grellmann, R., Ott, T., Paumard, T., Perrin, G., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Thi, W. F., Vincent, F. H., Widmann, F., Garatti, A. Caratti O., Fedriani, R., Lopez, R. Garcia, Koutoulaki, M., Perraut, K., Linz, H., Brandner, W., Garcia, P., Klarmann, L., Henning, T., Labadie, L., Sanchez-Bermudez, J., Lazareff, B., van Dishoeck, E. F., Caselli, P., de Zeeuw, P. T., Bik, Adrianus, Benisty, M., Dougados, C., Ray, T. P., Amorim, A., Berger, J-P, Clenet, Y., du Foresto, V. Coude, Duvert, G., Eckart, A., Eisenhauer, F., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gordo, P., Jocou, L., Horrobin, M., Kervella, P., Lacour, S., Le Bouquin, J-B, Lena, P., Grellmann, R., Ott, T., Paumard, T., Perrin, G., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Thi, W. F., Vincent, F. H., and Widmann, F.

Abstract

Context. The inner regions of the discs of high-mass young stellar objects (HMYSOs) are still poorly known due to the small angular scales and the high visual extinction involved.Aims. We deploy near-infrared spectro-interferometry to probe the inner gaseous disc in HMYSOs and investigate the origin and physical characteristics of the CO bandhead emission (2.3-2.4 mu m).Methods. We present the first GRAVITY/VLTI observations at high spectral (R=4000) and spatial (mas) resolution of the CO overtone transitions in NGC 2024 IRS 2.Results. The continuum emission is resolved in all baselines and is slightly asymmetric, displaying small closure phases (<= 8 degrees). Our best ellipsoid model provides a disc inclination of 34 degrees +/- 1 degrees, a disc major axis position angle (PA) of 166 degrees +/- 1 degrees, and a disc diameter of 3.99 +/- 0.09 mas (or 1.69 +/- 0.04 au, at a distance of 423 pc). The small closure phase signals in the continuum are modelled with a skewed rim, originating from a pure inclination effect. For the first time, our observations spatially and spectrally resolve the first four CO bandheads. Changes in visibility, as well as differential and closure phases across the bandheads are detected. Both the size and geometry of the CO-emitting region are determined by fitting a bidimensional Gaussian to the continuum-compensated CO bandhead visibilities. The CO-emitting region has a diameter of 2.74 +/-(0.08)(0.07) +/- 0.07 0.08 mas (1.16 +/- 0.03 au), and is located in the inner gaseous disc, well within the dusty rim, with inclination and PA matching the dusty disc geometry, which indicates that both dusty and gaseous discs are coplanar. Physical and dynamical gas conditions are inferred by modelling the CO spectrum. Finally, we derive a direct measurement of the stellar mass of M-* similar to 14.7(-3.6)(+2)M(circle dot) M * similar to 14 . 7 - 3.6 + 2 M circle dot by combining our interferometric and spectral modelling resu

Published
2020
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26. A measure of the size of the magnetospheric accretion region in TW Hydrae

Author

Lopez, R. Garcia, Natta, A., Caratti O Garatti, A., Ray, T. P., Fedriani, R., Koutoulaki, M., Klarmann, L., Perraut, K., Sanchez-Bermudez, J., Benisty, M., Dougados, C., Labadie, L., Brandner, W., Garcia, P. J. V., Henning, Th., Caselli, P., Duvert, G., de Zeeuw, T., Grellmann, R., Abuter, R., Amorim, A., Bauboeck, M., Berger, J. P., Bonnet, H., Buron, A., Clenet, Y., Coude du Foresto, V., de Wit, W., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Garcia Dabo, C. E., Gendron, E., Genzel, R., Gillessen, S., Habibi, M., Haubois, X., Haussmann, F., Hippler, S., Hubert, Z., Horrobin, M., Jimenez Rosales, A., Jocou, L., Kervella, P., Kolb, J., Lacour, S., Le Bouquin, J. -B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramirez, A., 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., Woillez, J., Yazici, S., Zins, G., Lopez, R. Garcia, Natta, A., Caratti O Garatti, A., Ray, T. P., Fedriani, R., Koutoulaki, M., Klarmann, L., Perraut, K., Sanchez-Bermudez, J., Benisty, M., Dougados, C., Labadie, L., Brandner, W., Garcia, P. J. V., Henning, Th., Caselli, P., Duvert, G., de Zeeuw, T., Grellmann, R., Abuter, R., Amorim, A., Bauboeck, M., Berger, J. P., Bonnet, H., Buron, A., Clenet, Y., Coude du Foresto, V., de Wit, W., Eckart, A., Eisenhauer, F., Filho, M., Gao, F., Garcia Dabo, C. E., Gendron, E., Genzel, R., Gillessen, S., Habibi, M., Haubois, X., Haussmann, F., Hippler, S., Hubert, Z., Horrobin, M., Jimenez Rosales, A., Jocou, L., Kervella, P., Kolb, J., Lacour, S., Le Bouquin, J. -B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Ramirez, A., 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., Woillez, J., Yazici, S., and Zins, G.

Abstract

Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius(1-3). The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett gamma (Br gamma) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere(4-6)because the weak magnetic fields (some tenths of a gauss) detected in these sources(7,8)result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds(9,10)make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit). The size of the inner disk of the T Tauri star T

Published
2020

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

Author

Bouarour, Y. -I., Perraut, K., Menard, F., Brandner, W., Caratti o Garatti, A., Caselli, P., van Dishoeck, E., Dougados, C., Garcia-Lopez, R., Grellmann, R., Henning, T., Klarmann, L., Labadie, L., Natta, A., Sanchez-Bermudez, J., Thi, W. -F., de Zeeuw, P. T., Amorim, A., Baubock, M., Benisty, M., Berger, J. -P., Clenet, Y., du Foresto, V. Coude, Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Filho, M., Gao, F., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Jimenez-Rosales, A., Jocou, L., Hippler, S., Horrobin, M., Hubert, Z., Kervella, P., Lacour, S., Le Bouquin, J. -B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Vincent, F. H., von Fellenberg, S. D., Widmann, F., Wiest, M., Bouarour, Y. -I., Perraut, K., Menard, F., Brandner, W., Caratti o Garatti, A., Caselli, P., van Dishoeck, E., Dougados, C., Garcia-Lopez, R., Grellmann, R., Henning, T., Klarmann, L., Labadie, L., Natta, A., Sanchez-Bermudez, J., Thi, W. -F., de Zeeuw, P. T., Amorim, A., Baubock, M., Benisty, M., Berger, J. -P., Clenet, Y., du Foresto, V. Coude, Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Filho, M., Gao, F., Garcia, P., Gendron, E., Genzel, R., Gillessen, S., Jimenez-Rosales, A., Jocou, L., Hippler, S., Horrobin, M., Hubert, Z., Kervella, P., Lacour, S., Le Bouquin, J. -B., Lena, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rousset, G., Scheithauer, S., Shangguan, J., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., Vincent, F. H., von Fellenberg, S. D., Widmann, F., and Wiest, M.

Abstract

Context. Studies of the dust distribution, composition, and evolution of protoplanetary disks provide clues for understanding planet formation. However, little is known about the innermost regions of disks where telluric planets are expected to form.Aims. We aim constrain the geometry of the inner disk of the T Tauri star RY Lup by combining spectro-photometric data and interferometric observations in the near-infrared (NIR) collected at the Very Large Telescope Interferometer. We use PIONIER data from the ESO archive and GRAVITY data that were obtained in June 2017 with the four 8m telescopes.Methods. We use a parametric disk model and the 3D radiative transfer code MCFOST to reproduce the spectral energy distribution (SED) and match the interferometric observations. MCFOST produces synthetic SEDs and intensity maps at different wavelengths from which we compute the modeled interferometric visibilities and closure phases through Fourier transform.Results. To match the SED from the blue to the millimetric range, our model requires a stellar luminosity of 2.5 L-circle dot, higher than any previously determined values. Such a high value is needed to accommodate the circumstellar extinction caused by the highly inclined disk, which has been neglected in previous studies. While using an effective temperature of 4800 K determined through high-resolution spectroscopy, we derive a stellar radius of 2.29 R-circle dot. These revised fundamental parameters, when combined with the mass estimates available (in the range 1.3-1.5 M-circle dot), lead to an age of 0.5-2.0 Ma for RY Lup, in better agreement with the age of the Lupus association than previous determinations. Our disk model (that has a transition disk geometry) nicely reproduces the interferometric GRAVITY data and is in good agreement with the PIONIER ones. We derive an inner rim location at 0.12 au from the central star. This model corresponds to an inclination of the inner disk of 50 degrees, which is in mild tensi

Published
2020

28. Hunting Exoplanets with Single-Mode Optical Interferometry

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., and European Southern Observatory (ESO)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The GRAVITY instrument was primarily conceived for imaging and astrometry of the Galactic centre. However, its sensitivity and astrometric capabilities have also enabled interferometry to reach a new domain of astrophysics: exoplanetology. In March 2019, the GRAVITY collaboration published the first spectrum and astrometry of an exoplanet obtained by optical interferometry. In this article, we show how this observation is paving the way to even more exciting discoveries — finding new planets, and characterising their atmospheres., Published in The Messenger vol. 178, pp. 47-49, December 2019.

Published
2019

29. The GRAVITY Young Stellar Object survey

Author

Collaboration, Gravity, Perraut, K., Labadie, L., Lazareff, B., Klarmann, L., Segura-Cox, D., Benisty, M., Bouvier, J., Brandner, W., Caratti O Garatti, A., Caselli, P., Dougados, C., Garcia, P., Garcia-Lopez, R., Kendrew, S., Koutoulaki, M., Kervella, P., Lin, C.-C., Pineda, J., Sanchez-Bermudez, J., Van Dishoeck, E., Abuter, R., Amorim, A., Berger, J.-P., BONNET, H., Buron, A., Cantalloube, F., Clénet, Y., Coudé Du Foresto, V., Dexter, J., De Zeeuw, P. T., Duvert, G., Eckart, A., Eisenhauer, F., Eupen, F., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Gordo, P., Grellmann, R., Haubois, X., Haussmann, F., Henning, T., Hippler, S., Horrobin, M., Hubert, Z., Jocou, L., Lacour, S., Le Bouquin, J.-B., Léna, P., Mérand, A., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rabien, S., Ray, T., Rau, C., Rousset, G., Scheithauer, S., Straub, O., Straubmeier, C., Sturm, E., Vincent, F., Waisberg, I., Wank, I., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Woillez, J., Yazici, S., Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Max-Planck-Institut für Extraterrestrische Physik (MPE), LIttoral ENvironnement et Sociétés - UMR 7266 (LIENSs), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), National Tsing Hua University [Hsinchu] (NTHU), Laboratoire de Radiopathologie (LRP), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), European Southern Observatory (ESO), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute Patology and Imunology Molecular, Fac Ciencias, Universidade do Porto [Porto], Département de Chimie Moléculaire (DCM), Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS)-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, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Extraterrestrial Physics (MPE), Physikalisches Institut [Köln], Universität zu Köln, Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Institut Européen des membranes (IEM), Université de Montpellier (UM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS), Diamond Light Source, Harwell, Berks, England, AUTRES, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology [2007-2019] (Grenoble INP [2007-2019])-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology [2007-2019] (Grenoble INP [2007-2019])-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), LIttoral ENvironnement et Sociétés - UMRi 7266 (LIENSs), 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), Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de la Santé et de la Recherche Médicale (INSERM), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-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), and Universidade do Porto

Subjects
infrared: ISM, stars: formation, techniques: interferometric, Astrophysics::Solar and Stellar Astrophysics, techniques: high angular resolution, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], circumstellar matter, Astrophysics::Galaxy Astrophysics
Abstract

International audience; Context. The formation and the evolution of protoplanetary disks are important stages in the lifetime of stars. Terrestrial planets form or migrate within the innermost regions of these protoplanetary disks and so, the processes of disk evolution and planet formation are intrinsically linked. Studies of the dust distribution, composition, and evolution of these regions are crucial to understanding planet formation. Aims: We built a homogeneous observational dataset of Herbig Ae/Be disks with the aim of spatially resolving the sub au-scale region to gain a statistical understanding of their morphological and compositional properties, in addition to looking for correlations with stellar parameters, such as luminosity, mass, and age. Methods: We observed 27 Herbig Ae/Be stars with the GRAVITY instrument installed at the combined focus of the Very Large Telescope Interferometer (VLTI) and operating in the near-infrared K-band, focused on the K-band thermal continuum, which corresponds to stellar flux reprocessed by the dust grains. Our sample covers a large range of effective temperatures, luminosities, masses, and ages for the intermediate-mass star population. The circumstellar disks in our sample also cover a range of various properties in terms of reprocessed flux, flared or flat morphology, and gaps. We developed semi-physical geometrical models to fit our interferometric data. Results: Our best-fit models correspond to smooth and wide rings that support previous findings in the H-band, implying that wedge-shaped rims at the dust sublimation edge are favored. The measured closure phases are generally non-null with a median value of 10°, indicating spatial asymmetries of the intensity distributions. Multi-size grain populations could explain the closure phase ranges below 20-25° but other scenarios should be invoked to explain the largest ones. Our measurements extend the Radius-Luminosity relation to 104 L⊙ luminosity values and confirm the significant spread around the mean relation observed by PIONIER in the H-band. Gapped sources exhibit a large N-to-K band size ratio and large values of this ratio are only observed for the members of our sample that would be older than 1 Ma, less massive, and with lower luminosity. In the mass range of 2 M⊙, we do observe a correlation in the increase of the relative age with the transition from group II to group I, and an increase of the N-to-K size ratio. However, the size of the current sample does not yet permit us to invoke a clear, universal evolution mechanism across the Herbig Ae/Be mass range. The measured locations of the K-band emission in our sample suggest that these disks might be structured by forming young planets, rather than by depletion due to EUV, FUV, and X-ray photo-evaporation. GTO programs with run ID: 0103.C-0347; 0102.C-0408; 0101.C-0311; 0100.C-0278; 099.C-0667.

Published
2019

30. Images at the Highest Angular Resolution with GRAVITY: The Case of η Carinae

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., and European Southern Observatory (ESO)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::High Energy Astrophysical Phenomena, 0103 physical sciences, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences
Abstract

The main goal of an interferometer is to probe the physics of astronomical objects at the highest possible angular resolution. The most intuitive way of doing this is by reconstructing images from the interferometric data. GRAVITY at the Very Large Telescope Interferometer (VLTI) has proven to be a fantastic instrument in this endeavour. In this article, we describe the reconstruction of the wind-wind collision cavity of the massive binary η Car with GRAVITY across two spectral lines: HeI and Brγ., Published in The Messenger vol. 178, pp. 31-33, December 2019.

Published
2019

31. Spatially Resolving the Quasar Broad Emission Line Region

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J.M., Beust, H., Blind, N., Bonnefoy, M., Bonnet, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L.H., Cantalloube, F., Caratti, O, Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, É., Clénet, Y., Collin, C., Coudé Du, Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., De Wit, W.-J., Dexter, J., Zeeuw, T. de, Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M.C., Finger, G., Förster Schreiber, N.M., Gao, F., García Dabó, C.E., Garcia Lopez, R., Garcia, P.J.V., Gendron, É., Genzel, R., Gerhard, O., Gil, J.P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S.F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C.~A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B.M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J.E., Plewa, P.M., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J.R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T.T., Spyromilio, J., Sternberg, A., Stock, M.R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L.J., Thi, W.-F., Tristram, K.R.W., Valenzuela, J.J., Boekel, R. van, Dishoeck, E.F. van, Vermot, P., Vincent, F., Von Fellenberg, S., Waisberg, I., Wang, J.J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., 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, and 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)

Subjects
General Relativity and Quantum Cosmology, [SDU]Sciences of the Universe [physics], Astrophysics::High Energy Astrophysical Phenomena, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences, Astrophysics::Galaxy Astrophysics
Abstract

The angular resolution of the Very Large Telescope Interferometer (VLTI) and the excellent sensitivity of GRAVITY have led to the first detection of spatially resolved kinematics of high velocity atomic gas near an accreting super- massive black hole, revealing rotation on sub-parsec scales in the quasar 3C 273 at a distance of 550 Mpc. The observations can be explained as the result of circular orbits in a thick disc configuration around a 300 million solar mass black hole. Within an ongoing Large Programme, this capability will be used to study the kinematics of atomic gas and its relation to hot dust in a sample of quasars and Seyfert galaxies. We will measure a new radius-luminosity relation from spatially resolved data and test the current methods used to measure black hole mass in large surveys., Published in The Messenger vol. 178, pp. 20-24, December 2019.

Published
2019

32. Multiple Star Systems in the Orion Nebula

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., and European Southern Observatory (ESO)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

GRAVITY observations reveal that most massive stars in the Orion Trapezium cluster live in multiple systems. Our deep, milliarcsecond-resolution interferometry fills the gap at 1–100 astronomical units (au), which is not accessible to traditional imaging and spectroscopy, but is crucial to uncovering the mystery of high-mass star formation.The new observations find a significantly higher companion fraction than earlier studies of mostly OB associations. The observed distribution of mass ratios declines steeply with mass and follows a Salpeter power-law initial mass function. The observations therefore exclude stellar mergers as the dominant formation mechanism for massive stars in Orion., Published in The Messenger vol. 178, pp. 36-38, December 2019.

Published
2019
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33. Spatially Resolving the Inner Gaseous Disc of the Herbig Star 51 Oph through its CO Ro-vibration Emission

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., and European Southern Observatory (ESO)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Near-infrared interferometry gives us the opportunity to spatially resolve the circumstellar environment of young stars at sub-astronomical-unit (au) scales, which a standalone telescope could not reach. In particular, the sensitivity of GRAVITY on the VLTI allows us to spatially resolve the CO overtone emission at 2.3 microns. In this article, we present a new method of using the model of the CO spectrum to reconstruct the differential phase signal and extract the geometry and size of the emitting region., Published in The Messenger vol. 178, pp. 40-42, December 2019.

Published
2019
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34. An Image of the Dust Sublimation Region in the Nucleus of NGC 1068

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., 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, and 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)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::High Energy Astrophysical Phenomena, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences, Astrophysics::Galaxy Astrophysics
Abstract

The superb resolution of the Very Large Telescope Interferometer (VLTI) and the unrivalled sensitivity of GRAVITY have allowed us to reconstruct the first detailed image of the dust sublimation region in an active galaxy. In the nearby archetypal Seyfert 2 galaxy NGC 1068, the 2 µm continuum emission traces a highly inclined thin ring-like structure with a radius of 0.24 pc. The observed morphology challenges the picture of a geometrically and optically thick torus., Published in The Messenger vol. 178, pp. 24-26, December 2019.

Published
2019

35. Probing the Discs of Herbig Ae/Be Stars at Terrestrial Orbits

Author

Abuter, R., Accardo, M., Adler, T., Amorim, A., Anugu, N., Ávila, G., Bauböck, M., Benisty, M., Berger, J.-P., Bestenlehner, J. M., Beust, H., Blind, N., Bonnefoy, M., BONNET, H., Bourget, P., Bouvier, J., Brandner, W., Brast, R., Buron, A., Burtscher, L., Cantalloube, F., Caratti O Garatti, A., Caselli, P., Cassaing, F., Chapron, F., Charnay, B., Choquet, E., Clénet, Y., Collin, C., Coudé Du Foresto, V., Davies, R., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., de Wit, W.-J., Dexter, J., De Zeeuw, T., Dougados, C., Dubus, G., Duvert, G., Ebert, M., Eckart, A., Eisenhauer, F., Esselborn, M., Eupen, F., Fédou, P., Ferreira, M. C., Finger, G., Förster Schreiber, N. M., Gao, F., García Dabó, C. E., Garcia Lopez, R., Garcia, P. J. V., Gendron, É., Genzel, R., Gerhard, O., Gil, J. P., Gillessen, S., Gonté, F., Gordo, P., Gratadour, D., Greenbaum, A., Grellmann, R., Grözinger, U., Guajardo, P., Guieu, S., Habibi, M., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Hönig, S. F., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Hummel, C. A., Jakob, G., Janssen, A., Jimenez Rosales, A., Jochum, L., Jocou, L., Kammerer, J., Karl, M., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Kishimoto, M., Klarmann, L., Klein, R., Köhler, R., Kok, Y., Kolb, J., Koutoulaki, M., Kulas, M., Labadie, L., Lacour, S., Lagrange, A.-M., Lapeyrère, V., Laun, W., Lazareff, B., Le Bouquin, J.-B., Léna, P., Lenzen, R., Lévêque, S., Lin, C.-C., Lippa, M., Lutz, D., Magnard, Y., Maire, A.-L., Mehrgan, L., Mérand, A., Millour, F., Mollière, P., Moulin, T., Müller, A., Müller, E., Müller, F., Netzer, H., Neumann, U., Nowak, M., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Peterson, B. M., Petrucci, P.-O., Pflüger, A., Pfuhl, O., Phan Duc, T., Pineda, J. E., Plewa, P. m., Popovic, D., Pott, J.-U., Prieto, A., Pueyo, L., Rabien, S., Ramírez, A., Ramos, J. R., Rau, C., Ray, T., Riquelme, M., Rodríguez-Coira, G., Rohloff, R.-R., Rouan, D., Rousset, G., Sanchez-Bermudez, J., Schartmann, M., Scheithauer, S., Schöller, M., Schuhler, N., Segura-Cox, D., Shangguan, J., Shimizu, T. T., Spyromilio, J., Sternberg, A., Stock, M. R., Straub, O., Straubmeier, C., Sturm, E., Suárez Valles, M., Tacconi, L. J., Thi, W.-F., Tristram, K. R. W., Valenzuela, J. J., Van Boekel, R., Van Dishoeck, E. F., Vermot, P., Vincent, F., Von fellenberg, S., Waisberg, I., Wang, J. J., Wank, I., Weber, J., Weigelt, G., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yang, P., Yazici, S., Ziegler, D., Zins, G., and European Southern Observatory (ESO)

Subjects
[SDU]Sciences of the Universe [physics], Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

More than 4000 exoplanets are known to date in systems that differ greatly from our Solar System. In particular, inner exoplanets tend to follow orbits around their parent star that are much more compact than that of Earth. These systems are also extremely diverse, covering a range of intrinsic properties. Studying the main physi- cal processes at play in the innermost regions of the protoplanetary discs is crucial to understanding how these planets form and migrate so close to their host. With GRAVITY, we focused on the study of near-infrared emission of a sample of young intermediate- mass stars, the Herbig Ae/Be stars., Published in The Messenger vol. 178, pp. 38-40, December 2019.

Published
2019
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36. The GRAVITY young stellar object survey

Author

GRAVITY Collaboration, Eupen, F., Labadie, L., Grellmann, R., Perraut, K., Brandner, W., Duch��ne, G., K��hler, R., Sanchez-Bermudez, J., Lopez, R. Garcia, Garatti, A. Caratti o, Benisty, M., Dougados, C., Garcia, P., Klarmann, L., Amorim, A., Baub��ck, M., Berger, J. P., Caselli, P., Cl��net, Y., Foresto, V. Coud�� du, de Zeeuw, P. T., Drescher, A., Duvert, G., Eckart, A., Eisenhauer, F., Filho, M., Ganci, V., Gao, F., Gendron, E., Genzel, R., Gillessen, S., Heissel, G., Henning, Th., Hippler, S., Horrobin, M., Hubert, Z., Jim��nez-Rosales, A., Jocou, L., Kervella, P., Lacour, S., Lapeyr��re, V., Bouquin, J. B. Le, L��na, P., Ott, T., Paumard, T., Perrin, G., Pfuhl, O., Rodr��guez-Coira, G., Rousset, G., Scheithauer, S., Shangguan, J., Shimizu, T., Stadler, J., Straub, O., Straubmeier, C., Sturm, E., van Dishoeck, E., Vincent, F., von Fellenberg, S. D., Widmann, F., Woillez, J., and Wojtczak, A.

Subjects
Techniques: Interferometric, Young stellar object, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, 010309 optics, Stars: Pre-Main Sequence, 0103 physical sciences, Binary star, Astrophysics::Solar and Stellar Astrophysics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), Techniques: High Angular Resolution, Orbital elements, Physics, Infrared excess, Herbig Ae/Be, Astronomy and Astrophysics, Mass ratio, Accretion (astrophysics), Binaries: Close, T Tauri star, Astrophysics - Solar and Stellar Astrophysics, 13. Climate action, Space and Planetary Science, Stars: Variables: T Tauri, Astrophysics::Earth and Planetary Astrophysics, Circumbinary planet, Stars: Individual: WW Cha
Abstract

The young T Tauri star WW Cha was recently proposed to be a close binary object with strong infrared and submillimeter excess associated with circum-system emission. This makes WW Cha a very interesting source for studying the influence of dynamical effects on circumstellar as well as circumbinary material. We derive the relative astrometric positions and flux ratios of the stellar companion in WW Cha from the interferometric model fitting of observations made with the VLTI instruments AMBER, PIONIER, and GRAVITY in the near-infrared from 2011 to 2020. For two epochs, the resulting uv-coverage in spatial frequencies permits us to perform the first image reconstruction of the system in the K band. The positions of nine epochs are used to determine the orbital elements and the total mass of the system. We find the secondary star orbiting the primary with a period of T=206.55 days, a semimajor axis of a=1.01 au, and a relatively high eccentricity of e=0.45. Combining the orbital solution with distance measurements from Gaia DR2 and the analysis of evolutionary tracks, the dynamical mass of Mtot=3.20 Msol can be explained by a mass ratio between ~0.5 and 1. The orbital angular momentum vector is in close alignment with the angular momentum vector of the outer disk as measured by ALMA and SPHERE. The analysis of the relative photometry suggests the presence of infrared excess surviving in the system and likely originating from truncated circumstellar disks. The flux ratio between the two components appears variable, in particular in the K band, and may hint at periods of triggered higher and lower accretion or changes in the disks' structures. The knowledge of the orbital parameters, combined with a relatively short period, makes WW Cha an ideal target for studying the interaction of a close young T Tauri binary with its surrounding material, such as time-dependent accretion phenomena., Comment: Accepted for publication in A&A; 24 pages, 14 figures, 3 tables; affiliations corrected

Published
2021

37. NU Ori : a hierarchical triple system with a strongly magnetic B-type star

Author

Shultz, Matthew, Le Bouquin, J. -B, Rivinius, Th., Wade, G. A., Kochukhov, Oleg, Alecian, E., Petit, V., Pfuhl, O., Karl, M., Gao, F., Grellmann, R., Lin, C. -C, Garcia, P., Lacour, S., Shultz, Matthew, Le Bouquin, J. -B, Rivinius, Th., Wade, G. A., Kochukhov, Oleg, Alecian, E., Petit, V., Pfuhl, O., Karl, M., Gao, F., Grellmann, R., Lin, C. -C, Garcia, P., and Lacour, S.

Abstract

NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with four components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer data set. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the Zeeman Stokes V signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding M-Aa = 14.9 +/- 0.5 M-circle dot, M-Ab = 3.9 +/- 0.7 M-circle dot, and M-C = 7.8 +/- 0.7 M-circle dot. The rotational period obtained from longitudinal magnetic field (B-z) measurements is P-rot = 1.09468(7)d, consistent with previous results. Modelling of (B-z) indicates a surface dipole magnetic field strength of similar to 8 kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric Ha emission, and we find marginal evidence of emission at the expected level (similar to 1 per cent of the continuum).

Published
2019
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38. NU Ori: a hierarchical triple system with a strongly magnetic B-type star

Author

Shultz, M., Le Bouquin, J. -B., Rivinius, Th., Wade, G. A., Kochukhov, O., Alecian, E., Petit, V., Pfuhl, O., Karl, M., Gao, F., Grellmann, R., Lin, C. -C., Garcia, P., Lacour, S., Shultz, M., Le Bouquin, J. -B., Rivinius, Th., Wade, G. A., Kochukhov, O., Alecian, E., Petit, V., Pfuhl, O., Karl, M., Gao, F., Grellmann, R., Lin, C. -C., Garcia, P., and Lacour, S.

Abstract

NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with four components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer data set. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the Zeeman Stokes V signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding M-Aa = 14.9 +/- 0.5 M-circle dot, M-Ab = 3.9 +/- 0.7 M-circle dot, and M-C = 7.8 +/- 0.7 M-circle dot. The rotational period obtained from longitudinal magnetic field (B-z) measurements is P-rot = 1.09468(7)d, consistent with previous results. Modelling of (B-z) indicates a surface dipole magnetic field strength of similar to 8 kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric Ha emission, and we find marginal evidence of emission at the expected level (similar to 1 per cent of the continuum).

Published
2019

39. Multiple star systems in the Orion nebula

Author

Collaboration, G., Karl, M., Pfuhl, O., Eisenhauer, F., Genzel, R., Grellmann, R., Habibi, M., Abuter, R., Accardo, M., Amorim, A., Anugu, N., Ávila, G., Benisty, M., Berger, J., Blind, N., Bonnet, H., Bourget, P., Brandner, W., Brast, R., Buron, A., Caratti O Garatti, A., Chapron, F., Clénet, Y., Collin, C., Coudé Du Foresto, V., de Wit, W., de Zeeuw, T., Deen, C., Delplancke-Ströbele, F., Dembet, R., Derie, F., Dexter, J., Duvert, G., Ebert, M., Eckart, A., Esselborn, M., Fédou, P., Finger, G., Garcia, P., Garcia Dabo, C., Garcia Lopez, R., Gao, F., Gendron, É., Gillessen, S., Gonté, F., Gordo, P., Grözinger, U., Guajardo, P., Guieu, S., Haguenauer, P., Hans, O., Haubois, X., Haug, M., Haußmann, F., Henning, T., Hippler, S., Horrobin, M., Huber, A., Hubert, Z., Hubin, N., Jakob, G., Jochum, L., Jocou, L., Kaufer, A., Kellner, S., Kendrew, S., Kern, L., Kervella, P., Kiekebusch, M., Klein, R., Köhler, R., Kolb, J., Kulas, M., Lacour, S., Lapeyrère, V., Lazareff, B., Le Bouquin, J., Léna, P., Lenzen, R., Lévêque, S., Lin, C., Lippa, M., Magnard, Y., Mehrgan, L., Mérand, A., Moulin, T., Müller, E., Müller, F., Neumann, U., Oberti, S., Ott, T., Pallanca, L., Panduro, J., Pasquini, L., Paumard, T., Percheron, I., Perraut, K., Perrin, G., Pflüger, A., Duc, T., Plewa, P., Popovic, D., Rabien, S., Ramírez, A., Ramos, J., Rau, C., Riquelme, M., Rodríguez-Coira, G., Rohloff, R., Rosales, A., Rousset, G., Sanchez-Bermudez, J., Scheithauer, S., Schöller, M., Schuhler, N., Spyromilio, J., Straub, O., Straubmeier, C., Sturm, E., Suarez, M., Tristram, K., Ventura, N., Vincent, F., Waisberg, I., Wank, I., Widmann, F., Wieprecht, E., Wiest, M., Wiezorrek, E., Wittkowski, M., Woillez, J., Wolff, B., Yazici, S., Ziegler, D., and Zins, G.

Abstract

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium cluster with the recently comissioned GRAVITY instrument. We observed a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for θ1 Ori B, θ2 Ori B, and θ2 Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary θ1 Ori C and we are able to derive a new orbit for θ1 Ori D. We find a system mass of 21.7 M☉ and a period of 53 days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about two, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints toward a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.

Published
2018

40. The spatial extent of polycyclic aromatic hydrocarbons emission in the Herbig star HD 179218

Author

Taha, A. S., Labadie, L., Pantin, E., Matter, A., Alvarez, C., Esquej, P., Grellmann, R., Rebolo, R., Telesco, C., Wolf, S., Taha, A. S., Labadie, L., Pantin, E., Matter, A., Alvarez, C., Esquej, P., Grellmann, R., Rebolo, R., Telesco, C., and Wolf, S.

Abstract

Aims. We investigate, in the mid-infrared, the spatial properties of the polycyclic aromatic hydrocarbons (PAHs) emission in the disk of HD 179218, an intermediate-mass Herbig star at similar to 300 pc. Methods. We obtained mid-infrared images in the PAH-1, PAH-2 and Si-6 filters centered at 8.6, 11.3, and 12.5 mu m, and N-band low-resolution spectra using CanariCam on the 10-m Gran Telescopio Canarias (GTC). We compared the point spread function (PSF) profiles measured in the PAH filters to the profile derived in the Si-6 filter, where the thermal continuum emission dominates. We performed radiative transfer modeling of the spectral energy distribution (SED) and produced synthetic images in the three filters to investigate different spatial scenarios. Results. Our data show that the disk emission is spatially resolved in the PAH-1 and PAH-2 filters, while unresolved in the Si-6 filter. Thanks to very good observing conditions, an average full width at half maximum (FWHM) of 0.232 '', 0.280 '' and 0.293 '' is measured in the three filters, respectively. Gaussian disk fitting and quadratic subtraction of the science and calibrator PSFs suggests a lower-limit characteristic angular diameter of the emission of similar to 100 mas, or similar to 30 au. The photometric and spectroscopic results are compatible with previous findings. Our radiative transfer (RT) modeling of the continuum suggests that the resolved emission should result from PAH molecules on the disk atmosphere being UV-excited by the central star. Simple geometrical models of the PAH component compared to the underlying continuum point to a PAH emission uniformly extended out to the physical limits of the disk model. Furthermore, our RT best model of the continuum requires a negative exponent of the surface density power-law, in contrast with earlier modeling pointing to a positive exponent. Conclusions. We have spatially resolved - for the first time to our knowledge - the PAHs emission in the disk of HD

Published
2018

41. A measure of the size of the magnetospheric accretion region in TW Hydrae.

Author

GRAVITY Collaboration, Garcia Lopez, R., Natta, A., Caratti o Garatti, A., Ray, T. P., Fedriani, R., Koutoulaki, M., Klarmann, L., Perraut, K., Sanchez-Bermudez, J., Benisty, M., Dougados, C., Labadie, L., Brandner, W., Garcia, P. J. V., Henning, Th., Caselli, P., Duvert, G., de Zeeuw, T., and Grellmann, R.

Abstract

Stars form by accreting material from their surrounding disks. There is a consensus that matter flowing through the disk is channelled onto the stellar surface by the stellar magnetic field. This is thought to be strong enough to truncate the disk close to the corotation radius, at which the disk rotates at the same rate as the star. Spectro-interferometric studies in young stellar objects show that hydrogen emission (a well known tracer of accretion activity) mostly comes from a region a few milliarcseconds across, usually located within the dust sublimation radius1–3. The origin of the hydrogen emission could be the stellar magnetosphere, a rotating wind or a disk. In the case of intermediate-mass Herbig AeBe stars, the fact that Brackett γ (Brγ) emission is spatially resolved rules out the possibility that most of the emission comes from the magnetosphere4–6 because the weak magnetic fields (some tenths of a gauss) detected in these sources7,8 result in very compact magnetospheres. In the case of T Tauri sources, their larger magnetospheres should make them easier to resolve. The small angular size of the magnetosphere (a few tenths of a milliarcsecond), however, along with the presence of winds9,10 make the interpretation of the observations challenging. Here we report optical long-baseline interferometric observations that spatially resolve the inner disk of the T Tauri star TW Hydrae. We find that the near-infrared hydrogen emission comes from a region approximately 3.5 stellar radii across. This region is within the continuum dusty disk emitting region (7 stellar radii across) and also within the corotation radius, which is twice as big. This indicates that the hydrogen emission originates in the accretion columns (funnel flows of matter accreting onto the star), as expected in magnetospheric accretion models, rather than in a wind emitted at much larger distance (more than one astronomical unit). The size of the inner disk of the T Tauri star TW Hydrae is determined using optical long-baseline interferometric observations, indicating that hydrogen emission comes from a region approximately 3.5 stellar radii across. [ABSTRACT FROM AUTHOR]

Published
2020
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43. The adventure of carbon stars : Observations and modeling of a set of C-rich AGB stars

Author

Rau, G., Hron, J., Paladini, C., Aringer, B., Eriksson, Kjell, Marigo, P., Nowotny, W., Grellmann, R., Rau, G., Hron, J., Paladini, C., Aringer, B., Eriksson, Kjell, Marigo, P., Nowotny, W., and Grellmann, R.

Abstract

Context. Modeling stellar atmospheres is a complex and intriguing task in modern astronomy. A systematic comparison of models with multi-technique observations is the only efficient way to constrain the models. Aims. We intend to perform self-consistent modeling of the atmospheres of six carbon-rich AGB stars (R Lep, R Vol, Y Pav, AQ Sgr, U Hya, and X TrA) with the aim of enlarging the knowledge of the dynamic processes occurring in their atmospheres. Methods. We used VLTI/MIDI interferometric observations, in combination with spectro-photometric data, and compared them with self-consistent, dynamic model atmospheres. Results. We found that the models can reproduce spectral energy distribution (SED) data well at wavelengths longer than 1 mu m, and the interferometric observations between 8 mu m and 10 mu m. Discrepancies observed at wavelengths shorter than 1 mu m in the SED, and longer than 10 mu m in the visibilities, could be due to a combination of data- and model-related effects. The models best fitting the Miras are significantly extended, and have a prominent shell-like structure. On the contrary, the models best fitting the non-Miras are more compact, showing lower average mass loss. The mass loss is of episodic or multi-periodic nature but causes the visual amplitudes to be notably larger than the observed ones. A number of stellar parameters were derived from the model fitting: T-Ross, L-Ross, M, C/O, and. M. Our findings agree well with literature values within the uncertainties. TRoss, and LRoss are also in good agreement with the temperature derived from the angular diameter T(theta((V-K))) and the bolometric luminosity from the SED fitting L-bol, except for AQ Sgr. The possible reasons are discussed in the text. Finally, theta(Ross) and theta((V-K)) agree with one another better for the Miras than for the non-Miras targets, which is probably connected to the episodic nature of the latter models. We also located the stars in the H-R diagram, comparing t

Published
2017
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44. Resolved astrometric orbits of ten O-type binaries

Author

Le Bouquin, J. -B., Sana, H., Gosset, E., De Becker, M., Duvert, G., Absil, O., Anthonioz, F., Berger, J. -P., Ertel, S., Grellmann, R., Guieu, S., Kervella, P., Rabus, M., Willson, M., Le Bouquin, J. -B., Sana, H., Gosset, E., De Becker, M., Duvert, G., Absil, O., Anthonioz, F., Berger, J. -P., Ertel, S., Grellmann, R., Guieu, S., Kervella, P., Rabus, M., and Willson, M.

Abstract

Aims. Our long-term aim is to derive model-independent stellar masses and distances for long period massive binaries by combining apparent astrometric orbit with double-lined radial velocity amplitudes (SB2). Methods. We followed-up ten O+O binaries with AMBER, PIONIER and GRAVITY at the VLTI. Here, we report on 130 astrometric observations over the last seven years. We combined this dataset with distance estimates to compute the total mass of the systems. We also computed preliminary individual component masses for the five systems with available SB2 radial velocities. Results. Nine of the ten binaries have their three-dimensional orbit well constrained. Four of them are known to be colliding wind, non-thermal radio emitters, and thus constitute valuable targets for future high angular resolution radio imaging. Two binaries break the correlation between period and eccentricity tentatively observed in previous studies. This suggests either that massive star formation produces a wide range of systems, or that several binary formation mechanisms are at play. Finally, we found that the use of existing SB2 radial velocity amplitudes can lead to unrealistic masses and distances. Conclusions. If not understood, the biases in radial velocity amplitudes will represent an intrinsic limitation for estimating dynamical masses from SB2+ interferometry or SB2+ Gaia. Nevertheless, our results can be combined with future Gaia astrometry to measure the dynamical masses and distances of the individual components with an accuracy of 5 to 15%, completely independently of the radial velocities.

Published
2017

45. Resolved astrometric orbits of ten O-type binaries

Author

Le Bouquin, J.-B., primary, Sana, H., additional, Gosset, E., additional, De Becker, M., additional, Duvert, G., additional, Absil, O., additional, Anthonioz, F., additional, Berger, J.-P., additional, Ertel, S., additional, Grellmann, R., additional, Guieu, S., additional, Kervella, P., additional, Rabus, M., additional, and Willson, M., additional

Published
2017
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46. The adventure of carbon stars

Author

Rau, G., primary, Hron, J., additional, Paladini, C., additional, Aringer, B., additional, Eriksson, K., additional, Marigo, P., additional, Nowotny, W., additional, and Grellmann, R., additional

Published
2017
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47. Accurate stellar masses for SB2 components: Interferometric observations for Gaia validation

Author

Halbwachs, J. -L, Boffin, H. M. J., Le Bouquin, J. -B, Famaey, B., Salomon, J. -B, Frédéric Arenou, Pourbaix, D., Anthonioz, F., Grellmann, R., Guieu, S., Guillout, P., Jorissen, A., Kiefer, F., Lebreton, Y., Mazeh, T., Nebot Gómez-Morán, A., Sana, H., Tal-Or, L., Observatoire astronomique de Strasbourg (ObAS), Université de Strasbourg (UNISTRA)-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), 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 Libre de Bruxelles [Bruxelles] (ULB), 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), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), University of Amsterdam [Amsterdam] (UvA), F. Martins, S. Boissier, V. Buat, L. Cambrésy, P. Petit, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG ), 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)-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)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université libre de Bruxelles (ULB), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Lebreton, Yveline, and F. Martins, S. Boissier, V. Buat, L. Cambrésy, P. Petit

Subjects
[SDU] Sciences of the Universe [physics], [PHYS]Physics [physics], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU]Sciences of the Universe [physics], [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], ComputingMilieux_MISCELLANEOUS, [PHYS] Physics [physics]
Abstract

National audience

Published
2015

48. NU Ori: a hierarchical triple system with a strongly magnetic B-type star.

Author

Shultz, M, Le Bouquin, J-B, Rivinius, Th, Wade, G A, Kochukhov, O, Alecian, E, Petit, V, Pfuhl, O, Karl, M, Gao, F, Grellmann, R, Lin, C-C, Garcia, P, Lacour, S, and the MiMeS and BinaMIcS Collaborations

Subjects
STEINER systems, STELLAR magnetic fields, BINARY systems (Astronomy), NEBULA spectra, DWARF galaxies
Abstract

NU Ori is a massive spectroscopic and visual binary in the Orion Nebula Cluster, with four components: Aa, Ab, B, and C. The B0.5 primary (Aa) is one of the most massive B-type stars reported to host a magnetic field. We report the detection of a spectroscopic contribution from the C component in high-resolution ESPaDOnS spectra, which is also detected in a Very Large Telescope Interferometer data set. Radial velocity (RV) measurements of the inner binary (designated Aab) yield an orbital period of 14.3027(7) d. The orbit of the third component (designated C) was constrained using both RVs and interferometry. We find C to be on a mildly eccentric 476(1) d orbit. Thanks to spectral disentangling of mean line profiles obtained via least-squares deconvolution, we show that the Zeeman Stokes V signature is clearly associated with C, rather than Aa as previously assumed. The physical parameters of the stars were constrained using both orbital and evolutionary models, yielding M Aa = 14.9 ± 0.5 M⊙, M Ab = 3.9 ± 0.7 M⊙, and M C = 7.8 ± 0.7 M⊙. The rotational period obtained from longitudinal magnetic field 〈 B |$z$| 〉 measurements is P rot = 1.09468(7) d, consistent with previous results. Modelling of 〈 B |$z$| 〉 indicates a surface dipole magnetic field strength of ∼8 kG. NU Ori C has a magnetic field strength, rotational velocity, and luminosity similar to many other stars exhibiting magnetospheric Hα emission, and we find marginal evidence of emission at the expected level (∼1 per cent of the continuum). [ABSTRACT FROM AUTHOR]

Published
2019
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49. Masses of the components of SB2s observed with Gaia - II. Masses derived from PIONIER interferometric observations for Gaia validation

Author

Halbwachs, J. -L., Boffin, H. M. J., Le Bouquin, J. -B., Kiefer, F., Famaey, B., Salomon, J. -B., Arenou, F., Pourbaix, D., Anthonioz, F., Grellmann, R., Guieu, S., Sana, H., Guillout, P., Jorissen, A., Lebreton, Y., Mazeh, T., Tal-Or, L., Gomez-Moran, A. Nebot, Halbwachs, J. -L., Boffin, H. M. J., Le Bouquin, J. -B., Kiefer, F., Famaey, B., Salomon, J. -B., Arenou, F., Pourbaix, D., Anthonioz, F., Grellmann, R., Guieu, S., Sana, H., Guillout, P., Jorissen, A., Lebreton, Y., Mazeh, T., Tal-Or, L., and Gomez-Moran, A. Nebot

Abstract

In anticipation of the Gaia astrometric mission, a sample of spectroscopic binaries is being observed since 2010 with the Spectrograph pour l'Observation des PHenomenes des Interieurs stellaires et des Exoplanetes (SOPHIE) spectrograph at the Haute-Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 per cent when combined with Gaia astrometric measurements. In order to validate the masses derived from Gaia, interferometric observations are obtained for three SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186. The masses of the six stellar components are derived. Due to its edge-on orientation, HIP 14157 is probably an eclipsing binary. We note that almost all the derived masses are a few per cent larger than the expectations from the standard spectral type-mass calibration and mass-luminosity relation. Our calculation also leads to accurate parallaxes for the three binaries, and the Hipparcos parallaxes are confirmed.

Published
2016

50. VLTI-AMBER velocity-resolved aperture-synthesis imaging of eta Carinae with a spectral resolution of 12 000 Studies of the primary star wind and innermost wind-wind collision zone

Author

Weigelt, G., Hofmann, K. -H., Schertl, D., Clementel, N., Corcoran, M. F., Damineli, A., de Wit, W. -J., Grellmann, R., Groh, J., Guieu, S., Gull, T., Heininger, M., Hillier, D. J., Hummel, C. A., Kraus, S., Madura, T., Mehner, A., Merand, A., Millour, F., Moffat, A. F. J., Ohnaka, K., Patru, F., Petrov, R. G., Rengaswamy, S., Richardson, N. D., Rivinius, T., Schoeller, M., Teodoro, M., Wittkowski, M., Weigelt, G., Hofmann, K. -H., Schertl, D., Clementel, N., Corcoran, M. F., Damineli, A., de Wit, W. -J., Grellmann, R., Groh, J., Guieu, S., Gull, T., Heininger, M., Hillier, D. J., Hummel, C. A., Kraus, S., Madura, T., Mehner, A., Merand, A., Millour, F., Moffat, A. F. J., Ohnaka, K., Patru, F., Petrov, R. G., Rengaswamy, S., Richardson, N. D., Rivinius, T., Schoeller, M., Teodoro, M., and Wittkowski, M.

Abstract

Context. The mass loss from massive stars is not understood well. eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of eta Car's primary star wind and wind-wind collision zone with a high spatial resolution of similar to 6 mas (similar to 14 au) and high spectral resolution of R = 12000. Methods. Observations of eta Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Br gamma 2.166 mu m emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately 140 to 376 km s(-1) measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of 277 km s(-1), the position angle of the symmetry axis of the fan is similar to 126 degrees. The fan-shaped structure extends approximately 8.0 mas (similar to 18.8 au) to the southeast and 5.8 mas (similar to 13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-depe

Published
2016

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