Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants

0574020 - ASÚ 2024 RIV CH eng J - Journal Article
Kraus, Michaela - Kourniotis, Michail - Arias, M.L. - Torres, A.F. - Nickeler, Dieter Horst
Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants.
Galaxies. Roč. 11, č. 3 (2023), č. článku 76. E-ISSN 2075-4434
R&D Projects: GA ČR(CZ) GA20-00150S
Institutional support: RVO:67985815
Keywords : stars * massive * supergiants
OECD category: Astronomy (including astrophysics,space science)
Impact factor: 2.5, year: 2022
Method of publishing: Open access

Massive stars expel large amounts of mass during their late evolutionary phases. We aim to unveil the physical conditions within the warm molecular environments of B[e] supergiants (B[e]SGs) and yellow hypergiants (YHGs), which are known to be embedded in circumstellar shells and disks. We present K-band spectra of two B[e]SGs from the Large Magellanic Cloud and four Galactic YHGs. The CO band emission detected from the B[e]SGs LHA 120-S 12 and LHA 120-S 134 suggests that these stars are surrounded by stable rotating molecular rings. The spectra of the YHGs display a rather diverse appearance. The objects 6 Cas and V509 Cas lack any molecular features. The star [FMR2006] 15 displays blue-shifted CO bands in emission, which might be explained by a possible close to pole-on oriented bipolar outflow. In contrast, HD 179821 shows blue-shifted CO bands in absorption. While the star itself is too hot to form molecules in its outer atmosphere, we propose that it might have experienced a recent outburst. We speculate that we currently can only see the approaching part of the expelled matter because the star itself might still block the receding parts of a (possibly) expanding gas shell.
Permanent Link: https://hdl.handle.net/11104/0344383