Luminous and Variable Stars in M31 and M33. V. the Upper HR Diagram

Roberta M Humphreys, Kris Davidson, David Hahn, John C. Martin, Kerstin Weis

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12 Scopus citations


We present HR diagrams for the massive star populations in M31 and M33, including several different types of emission-line stars: the confirmed luminous blue variables (LBVs), candidate LBVs, B[e] supergiants, and the warm hypergiants. We estimate their apparent temperatures and luminosities for comparison with their respective massive star populations and evaluate the possible relationships of these different classes of evolved, massive stars, and their evolutionary state. Several of the LBV candidates lie near the LBV/S Dor instability strip that supports their classification. Most of the B[e] supergiants, however, are less luminous than the LBVs. Many are very dusty with the infrared flux contributing one-third or more to their total flux. They are also relatively isolated from other luminous OB stars. Overall, their spatial distribution suggests a more evolved state. Some may be post-RSGs (red supergiants) like the warm hypergiants, and there may be more than one path to becoming a B[e] star. There are sufficient differences in the spectra, luminosities, spatial distribution, and the presence or lack of dust between the LBVs and B[e] supergiants to conclude that one group does not evolve into the other.

Original languageEnglish (US)
Article number40
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 2017

Bibliographical note

Funding Information:
Research by R.H. and K.D. on massive stars is supported by the National Science Foundation AST-1109394. J.C.M.'s collaborative work is supported by NSF grant AST-1108890.


  • galaxies: individual(M31, M33)
  • stars: massive
  • supergiants

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