Unity and Diversity of Yellow Hypergiants Family

Abstract

We summarize the results of long-term spectral monitoring of yellow hypergiants (YHGs) of northern hemisphere with a R$\ge$60000 resolution. The spectra of these F-G stars of extremely high luminosity, compactly located at the top of the Hertzsprung-Russell diagram revealed a variety of spectral features: various types of H$\alpha$ profile, the presence (or absence) of forbidden and permitted emissions, as well as circumstellar components. Variability of spectral details of various nature is studied. Absolute luminosity, circumstellar envelope expansion rate and amplitude of pulsations are determined. The reliability of the YHG status for V1427 Aql is reliably confirmed; manifestations of a significant dynamic instability of the upper layers of the atmosphere of $\rho$ Cas after the 2017 ejection and stratification of its gas envelope are registered; the lack of companion in the system of the V509 Cas hypergiant is proven; a conclusion is made that the V1302 Aql hypergiant is approaching to the low-temperature boundary of the Yellow Void.

24 pages, 10 figures

References in corpus (5)

• Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry
• On the CO Near-IR Band and the Line Splitting Phenomenon in the Yellow Hypergiant Rho Cassiopeiae
• Luminous and Variable Stars in M31 and M33 V. The Upper HR Diagram
• HD 179821 (V1427 Aql, IRAS 19114+0002) -- A Massive Post-Red Supergiant Star?
• The structure and chemistry of the massive shell around AFGL 2343: 29SiO and HCN as tracers of high-excitation regions

Cited by in corpus (3)

• Detailed spectroscopy of post-AGB supergiant GSC 04050$-$02366 in IRAS Z02229+6208 IR source system
• Instability in the system of the distant post-AGB star LS III+52 24 (IRAS 22023+5249)
• Painting a Family Portrait of the Yellow Super- and Hypergiants in the Milky Way I. Constraining the Distances and Luminosities