LUMINOUS AND VARIABLE STARS IN M31 AND M33. III. THE YELLOW AND RED SUPERGIANTS AND POST-RED SUPERGIANT EVOLUTION

Journal Article · Fri Jul 01 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/825/1/50· OSTI ID:22666137

Gordon, Michael S.; Humphreys, Roberta M.

Recent supernova (SN) and transient surveys have revealed an increasing number of non-terminal stellar eruptions. Though the progenitor class of these eruptions includes the most luminous stars, little is known of the pre-SN mechanics of massive stars in their most evolved state, thus motivating a census of possible progenitors. From surveys of evolved and unstable luminous star populations in nearby galaxies, we select a sample of yellow and red supergiant (RSG) candidates in M31 and M33 for review of their spectral characteristics and spectral energy distributions (SEDs). Since the position of intermediate- and late-type supergiants on the color–magnitude diagram can be heavily contaminated by foreground dwarfs, we employ spectral classification and multi-band photometry from optical and near-infrared surveys to confirm membership. Based on spectroscopic evidence for mass loss and the presence of circumstellar (CS) dust in their SEDs, we find that 30%–40% of the yellow supergiants are likely in a post-RSG state. Comparison with evolutionary tracks shows that these mass-losing, post-RSGs have initial masses between 20 and 40 M {sub ⊙}. More than half of the observed RSGs in M31 and M33 are producing dusty CS ejecta. We also identify two new warm hypergiants in M31, J004621.05+421308.06 and J004051.59+403303.00, both of which are likely in a post-RSG state.

• OSTI ID: 22666137
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 825; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CLASSIFICATION
COMPARATIVE EVALUATIONS
COSMIC DUST
ENERGY SPECTRA
EVOLUTION
GALAXIES
MASS TRANSFER
PHOTOMETRY
RED GIANT STARS
REVIEWS
STAR EVOLUTION
SUPERGIANT STARS
SUPERNOVAE
VARIABLE STARS