1974/11/01 by A. H. Joy, Helmut A. Abt · 3 citations
Engineering · Physics and Astronomy · #Absolute magnitude #Apparent magnitude #Astronomical Observations and Instrumentation #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Photometry (optics) #Physics #Stars #Stellar classification #Stellar, planetary, and galactic studies
paper · doi:10.1086/190307
openalex publication_date 1974/11/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/14
Spectral types on a uniform system based on primarily TiO band strengths are given for 426 M dwarf stars. It is found that the frequency of emission-line stars increases steadily from 5 percent among the early M's through 50 percent at M4.5 to 100 percent for M5.5 and later. The absolute magnitudes of emission-line (dMe) and normal (dM) dwarfs average the same within 0.07 mag at a given spectral type. A new calibration of absolute magnitudes, based on trigonometric parallaxes, is given. The measured width of the main-sequence band can be accounted for mostly in terms of the errors in classification, parallaxes, and photometry and to some duplicity; the cosmic dispersion is less than 0.3 mag. The R - 1 colors of dMe stars are larger by 0.08 1 0.02(p.e.) mag than for dM stars, although the B - V colors do not show this effect. Subject headings: late-type stars - luminosities - spectral classification