The Faint End of the Main Sequence
New infrared observations of the two faintest known, late M dwarfs, Wolf 359 and +4°4048B (=VB 10) provide accurate luminosities and moderately well-determined temperatures (2500° and 2250° K, respectively). The photometric observations are fitted to a blackbody energy distribution on the assumption that line and band blocking affect most of the spectrum below 1 μ; the temperature structure is taken as that of a gray body. The resulting data, together with Johnson's observations for dM4 and dM5 stars, which have been reanalyzed, calibrate the faint end of the main sequence, with results given in a table and a figure. The bolometric corrections are very large and increase steeply to 6 mag, so that the faintest known stars are, in fact, not very faint; Wolf 359 has L = 13 X 10^(-4) L_☉, and VB 10 has L = 5 X 10^(-4) L_☉. A statistical discussion of Luyten's faint red stars of large proper motion gives L = 4 X 10^(-4) L_☉. With a conventional mass-luminosity relation, ℳ ≥ 0.09 ℳ_☉ , for stars of known luminosity. Stars of still lower mass, such as L726-8, are difficult to interpret.
© 1970 The University of Chicago. Received 1970 January 19; revised 1970 February 16. The experimental work was supported by a National Aeronautics and Space Administration grant NGL 05-022-007; the analysis was largely carried out by one of us (J. L. G.) while at the Institute for Advanced Study, and later under AFOSR grant 69-1401.
Published - 1970ApJ___161__519G.pdf