| Title | The luminosities of M supergiants and the distances to M 101, NGC 2403, and M 81. |
| Authors | Humphreys, R. M.; Aaronson, M.; Lebofsky, M.; McAlary, C. W.; Strom, S. E.; Capps, R. W. |
| Bibcode | 1986AJ.....91..808H Search ADS ↗ |
| Abstract | Near-infrared (JHK) photometry of candidate red supergiants in NOC 2403, M81, and M101 plus far-red spectroscopy of a few stars in M101 is used to separate the supergiants and foreground dwarfs. The visual, infrared, and bolometric luminosities, intrinsic infrared colors, and the extinction can be determined for the M supergiant members with the advantages of JHK photometry. The properties of the confirmed M supergiants in NGC 2403 and in M81 are very much as we would expect for the morphological types and chemical compositions of these galaxies. Their luminosities are in excellent agreement with the previous results for the brightest red supergiants in the spiral and irregular galaxies in the Local Group. There is strong evidence for high extinction in M81 very likely due to a combination of internal and external reddening. This high extinction for stars in M81 supports a true distance modulus comparable to that for NGC 2403. If we adopt the Sandage and Tammaun distance modulus of 29.2 mag, the nine confirmed M supergiants in M101 are overluminous by a magnitude or more, compared with the M supergiant populations in all other galaxies studied. Their bolometric luminosities ≃ - 10.5 mag) imply initial masses of 65-85 Msun for most of these stars, in conflict with our current understanding of the effects of mass loss on the evolutionary tracks for massive stars and the stability limit for evolved stars of such high initial mass and luminosity. If we adopt the upper luminosity boundary implied by the limits to stability for these stars' atmospheres and the physics of massive-star evolution, we can set a limit on the true distance modulus to M101 of (m - M)0 = 28.4 mag. |
| Objects | 4 Objects Search NED ↙ |
