Journal
ASTROPHYSICAL JOURNAL
Volume 773, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/773/1/46
Keywords
galaxies: individual (M31, M33); stars: massive; supergiants
Categories
Funding
- National Science Foundation [AST-1019394, AST-1108890, AST-9987045]
- NSF Telescope System Instrumentation Program (TSIP)
- Ohio Board of Regents
- Ohio State University Office of Research
- National Aeronautics and Space Administration
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1109394] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1108890] Funding Source: National Science Foundation
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The progenitors of Type IIP supernovae (SNe) have an apparent upper limit to their initial masses of about 20 M-circle dot, 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 Pi triplet and [Ca Pi] 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 x 10(-6) to 10(-4) M-circle dot yr(-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.
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