The K-band highest-resolution images of the Mira star R Car with GRAVITY-VLTI
| Autor: | Rosales-Guzman, A., Sanchez-Bermudez, J., Paladini, C., Alberdi, A., Brandner, W., Cannon, E., González-Torà, G., Haubois, X., Henning, Th., Kervella, P., Montarges, M., Perrin, G., Schödel, R., Wittkowski, M. |
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| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | A&A 674, A62 (2023) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1051/0004-6361/202245370 |
| Popis: | The mass-loss mechanisms in M-type AGB stars are not well understood, in particular, the formation of dust-driven winds from the innermost gaseous layers around these stars. One way to understand the gas-dust interaction in these regions and its impact on the mass-loss mechanisms is through the analysis of high-resolution observations of the stellar surface and its closest environment. We aim at characterizing the inner circumstellar environment (~3 R*) of the M-type Mira star R Car in the near-infrared at different phases of a pulsation period. We used GRAVITY interferometric observations in the K-band obtained at two different epochs over 2018. Those data were analyzed using parametric models and image reconstruction of both the pseudo-continuum and the CO band-heads observed. The reported data are the highest angular resolution observations on the source in the K-band. We determine sizes of R Car's stellar disk of 16.67 +- 0.05 mas (3.03 au) in January 2018 and 14.84+-0.06 mas (2.70 au) in February 2018, respectively. From our physical model, we determined temperatures and size ranges for the innermost CO layer detected around R Car. We find that magnesium composites, Mg2SiO4 and MgSiO3, have temperatures and condensation distances consistent with the ones obtained for the CO layer model and pure-line reconstructed images, being them the most plausible dust types responsible of wind formation. Our reconstructed images show evidence of asymmetrical and inhomogeneous structures, which might trace a complex and perhaps clumpy structure of the CO molecule distribution. Our work demonstrates that the conditions for dust nucleation and thus for initialising dust-driven winds in M-type AGB stars are met in R Car and we identify Magnesium composites as the most probable candidates. This observational evidence is crucial to constrain the role of convection and pulsation in M-type stars. Comment: Accepted to be published by A&A, 20 pages, 21 figures |
| Databáze: | arXiv |
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