Suggestions regarding the effective temperatures and bolometric corrections for B-type stars

Abstract

Bolometric corrections and effective temperatures are presented for fourteen model atmospheres which are believed to represent main-sequence B-type stars. The models are in radiative and mechanical equilibrium, and the opacity is due to absorption from hydrogen, helium, and H and from electron scattering. 1~o account is taken of line blanketing. An estimate is made of the maximum changes that might occur as a result of line blanketing, and of where each spectral type should be written on the theoretical curve which relates bolometric corrections, BC, to effective temperature, T e. For the purpose of estimating stellar radfi from observed visual absolute magnitudes, it is necessary to know the quanti ty BC + 10 log T e as a function of spectral type. I t is shown that this quanti ty is sensitive neither to the details of the model construction nor to spectral type. Consequently, the present theoretical results are adequate for finding radii. I t is shown that the present estimates of absolute visual magnitude, M~, and mass for B-type stars are consistent with the estimates of Te, BC, and log g (the acceleration of gravity) that may be made from model atmosphere studies. The problem of identifying a model atmosphere with a real star is considered and it is shown that the strengths of some of the spectral lines which are used for the classification of early B-type and O-type stars are sensitive to such parameters as the extent of the atmosphere and turbulence. Thus at types about B1 and earlier it is not possible to define a unique relationship between spectral type and effective temperature. The net radiation field is not necessarily the dominant factor controlling the strengths of the lines which are used for classification purposes.