LUMINOUS AND VARIABLE STARS IN M31 AND M33. I. THE WARM HYPERGIANTS AND POST-RED SUPERGIANT EVOLUTION

Journal Article · Sat Aug 10 04:00:00 EDT 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/773/1/46· OSTI ID:22140260

Humphreys, Roberta M.; Davidson, Kris; Grammer, Skyler; Kneeland, Nathan ^[1]; Martin, John C. ^[2]; Weis, Kerstin; Burggraf, Birgitta ^[3]

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1. Minnesota Institute for Astrophysics, 116 Church Street SE, University of Minnesota, Minneapolis, MN 55455 (United States)
2. University of Illinois, Springfield, IL (United States)
3. Astronomical Institute, Ruhr-Universitaet Bochum (Germany)

The progenitors of Type IIP supernovae (SNe) have an apparent upper limit to their initial masses of about 20 M{sub Sun }, suggesting that the most massive red supergiants evolve to warmer temperatures before their terminal explosion. But very few post-red supergiants are known. We have identified a small group of luminous stars in M31 and M33 that are candidates for post-red supergiant evolution. These stars have A-F-type supergiant absorption line spectra and strong hydrogen emission. Their spectra are also distinguished by the Ca II triplet and [Ca II] doublet in emission formed in a low-density circumstellar environment. They all have significant near- and mid-infrared excess radiation due to free-free emission and thermal emission from dust. We estimate the amount of mass they have shed and discuss their wind parameters and mass loss rates, which range from a few Multiplication-Sign 10{sup -6} to 10{sup -4} M{sub Sun} yr{sup -1}. On an H-R diagram, these stars will overlap the region of the luminous blue variables (LBVs) at maximum light; however, the warm hypergiants are not LBVs. Their non-spherical winds are not optically thick, and they have not exhibited any significant variability. We suggest, however, that the warm hypergiants may be the progenitors of the ''less luminous'' LBVs such as R71 and even SN1987A.

• OSTI ID: 22140260
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 773; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
DENSITY
EMISSION
EXPLOSIONS
GALAXIES
MASS TRANSFER
SPECTRA
SPHERICAL CONFIGURATION
STELLAR WINDS
SUPERNOVAE
VISIBLE RADIATION