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arXiv · 2306.10911

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

Michaela Kraus·Michalis Kourniotis·Maria Laura Arias·Andrea F. Torres·Dieter H. Nickeler
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Abstract

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.

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Michaela Kraus, Michalis Kourniotis, Maria Laura Arias, Andrea F. Torres, Dieter H. Nickeler. 2023-06-19. Dense Molecular Environments of B[e] Supergiants and Yellow Hypergiants. https://doi.org/10.3390/galaxies11030076

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