Astrophys. J., 825, 50-50 (2016/July-1)
Luminous and variable stars in M31 and M33. III. The yellow and red supergiants and post-red supergiant evolution.
GORDON M.S., HUMPHREYS R.M. and JONES T.J.
Abstract (from CDS):
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☉. 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.
© 2016. The American Astronomical Society. All rights reserved.
galaxies: individual: (M31, M33) - stars: massive - supergiants
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<Available at CDS (J/ApJ/825/50): table2.dat table3.dat table4.dat table5.dat table6.dat table7.dat table8.dat table9.dat>
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