Issue |
A&A
Volume 652, August 2021
|
|
---|---|---|
Article Number | A140 | |
Number of page(s) | 22 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361/202141240 | |
Published online | 25 August 2021 |
VLTI-MATISSE chromatic aperture-synthesis imaging of η Carinae’s stellar wind across the Brα line
Periastron passage observations in February 2020★
1
Max Planck Institute for Radio Astronomy,
Auf dem Hügel 69,
53121
Bonn,
Germany
e-mail: weigelt@mpifr-bonn.mpg.de
2
Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Boulevard de l’Observatoire, CS 34229,
06304
Nice Cedex 4, France
3
Leiden Observatory, Leiden University,
Niels Bohrweg 2,
2333 CA
Leiden, The Netherlands
4
Max Planck Institute for Astronomy,
Königstuhl 17,
69117
Heidelberg, Germany
5
Department of Physics and Astronomy & Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT PACC), University of Pittsburgh,
3941 O’Hara Street,
Pittsburgh,
PA 15260, USA
6
Institute for Astrophysics and Computational Sciences, The Catholic University of America,
620 Michigan Ave.,
N.E. Washington,
DC 20064, USA
7
Department of Physics and Astronomy, San José State University,
One Washington Square,
San Jose,
CA 95192-0106, USA
8
Astrophysics Science Division, NASA/GSFC,
Greenbelt,
MD 20771, USA
9
CRESST II and X-ray Astrophysics Laboratory, NASA/GSFC,
Greenbelt,
MD 20771, USA
10
Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Rua do Matão 1226, Cidade Universitária São Paulo-SP,
05508-090,
Brazil
11
Département de physique and Centre de Recherche en Astrophysique du Québec (CRAQ), Université de Montréal, CP 6128 Succ. A., Centre-Ville, Montréal,
Québec
H3C 3J7, Canada
12
California Institute of Technology, IPAC, M/C 100-22,
Pasadena,
CA 91125, USA
13
Department of Physics and Astronomy, Embry-Riddle Aeronautical University,
3700 Willow Creek Rd,
Prescott,
AZ,
86301, USA
14
European Southern Observatory,
Casilla 19001,
Santiago 19, Chile
15
European Southern Observatory,
Karl Schwarzschild Strasse 2,
85748
Garching, Germany
16
Instituto de Astronomía, Universidad Nacional Autónoma de México,
Apdo. Postal 70264,
Ciudad de México
04510, Mexico
17
Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello,
Fernández Concha 700,
Las Condes,
Santiago, Chile
18
School of Physics, Astrophysics Group, University of Exeter,
Stocker Road,
Exeter
EX4 4QL, UK
19
Department of Materials Science and Applied Mathematics, Malmö University,
20506
Malmö, Sweden
20
Department of Physics, University of Maryland, Baltimore County,
1000 Hilltop Circle,
Baltimore,
MD 21250, USA
21
School of Physics and Astronomy, University of Birmingham,
Edgbaston,
Birmingham,
B15 2TT, UK
22
University of Kiel, Institute of Theoretical Physics and Astrophysics,
Leibnizstrasse 15,
24118
Kiel, Germany
23
Anton Pannekoek Institute for Astronomy, University of Amsterdam,
Science Park 904,
1090 GE
Amsterdam, The Netherlands
24
Univ. Grenoble Alpes, CNRS, IPAG,
38000,
Grenoble, France
25
AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot,
Sorbonne Paris Cité,
91191
Gif-sur-Yvette, France
26
Institute for Mathematics, Astrophysics and Particle Physics, Radboud University,
PO Box 9010,
MC 62 6500 GL
Nijmegen, The Netherlands
27
SRON Netherlands Institute for Space Research,
Sorbonnelaan 2,
3584 CA
Utrecht, The Netherlands
28
Department of Astrophysics, University of Vienna,
Türkenschanzstrasse 17,
1180
Vienna, Austria
29
Trinity College Dublin, The University of Dublin,
Dublin, Ireland
30
Konkoly Observatory, Research Centre for Astronomy and Earth Sciences,
Konkoly Thege Miklósút 15-17,
1121
Budapest, Hungary
31
I. Physikalisches Institut, Universität zu Köln,
Zülpicher Str. 77,
50937 Köln, Germany
Received:
3
May
2021
Accepted:
30
June
2021
Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis ~15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, η Car A, is a luminous blue variable (LBV); the secondary, η Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV η Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution.
Aims. Our aim is to study the intensity distribution and kinematics of η Car’s WWC zone.
Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Brα imaging of η Car’s distorted wind.
Results. We present the first VLTI-MATISSE aperture-synthesis images of η Car A’s stellar windin several spectral channels distributed across the Brα 4.052 μm line (spectral resolving power R ~ 960). Our observations were performed close to periastron passage in February 2020 (orbital phase ~ 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (~14 au). The radius of the faintest outer wind regions is ~26 mas (~60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 ± 0.06 mas (6.54 ± 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.
Key words: stars: winds, outflows / stars: individual: η Carinae / stars: massive / stars: mass-loss / binaries: general / techniques: interferometric
© G. Weigelt et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.