Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way

Journal Article · Fri Dec 01 04:00:00 EST 1978 · Astrophys. J., Suppl. Ser.; (United States)

DOI:https://doi.org/10.1086/190559· OSTI ID:6418546

Humphreys, R M

In this paper the fundamental properties of the brightest known stars in our Galaxy are determined for future comparison with results for the most luminous stars in other galaxies. The H-R diagrams (M/sub v/ versus spectral type and M/sub bol/ versus log T/sub e/), the luminosities of the brightest stars, and the ratios of blue to red supergiants are all discussed, and a catalog of over 1000 supergiants and O stars in associations and clusters is included at the end of the paper.The ''theoretical'' H-R diagram (M/sub bol/ versus log T/sub e/) reveals a group of superluminous O stars with M/sub bol/ between -12 mag, a lack of evolved supergiants at these very high luminosities, and an apparent upper limit to the luminosities of the later-type supergiants (>B5) near M/sub bol/=-9.5 mag.The most luminous red supergiants have a maximum visual luminosity near M/sub v/approx. =-8 mag, supporting the suggestion by Sandage and Tammann that they are good distance indicators. Excluding the superluminous star Cyg OB 2 No. 12 (M/sub v/approx. =-9.9 mag), the brightest blue stars are found at M/sub v/approx. =-8.5 mag.The variation of the ratio of blue to red supergiants with luminosity is discussed. There is also evidence for a gradient in this ratio with distance from the galactic center, although the results are limited by the incompleteness of the data.

• Research Organization: University of Minnesota, Minneapolis
• OSTI ID: 6418546
• Journal Information: Astrophys. J., Suppl. Ser.; (United States), Journal Name: Astrophys. J., Suppl. Ser.; (United States) Vol. 38:4; ISSN APJSA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
640105 -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DIAGRAMS
GALAXIES
GIANT STARS
HERTZSPRUNG-RUSSELL DIAGRAM
LUMINOSITY
MAIN SEQUENCE STARS
MILKY WAY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RED GIANT STARS
STAR CLUSTERS
STARS
SUPERGIANT STARS