A survey of H alf emission in early-type high-luminosity stars.

Abstract

view Abstract Citations (120) References (83) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A survey of H-alpha emission in early-type high-luminosity stars. Rosendhal, J. D. Abstract High-dispersion Ha spectrograms have been obtained of 62 early-type high-luminosity stars in order to search for evidence for mass loss in stars in the upper left portion of the H-R diagram. in addition to a study of the strength and shape of Ha, detailed radial-velocity measurements have been made to look for possible velocity differences among the strong lines in the red region of the spectrum. The results of this investigation indicate that the lower limits to the absolute visual magnitudes at which Ha begins to show conspicuous emission are Mv -5.8 in the B( stars and Mv -6.8 in the B8-A3 stars. There is evidence from the radial-velocity studies for differential expansion and hence mass loss for stars approximately 0.5 mag less luminous than these limiting luminosities. Among the early B stars it appears that there is a critical luminosity of Mbol -8.2 at which strongly accelerated large-scale flows may develop. The apparent existence of an abrupt change in the velocity-gradient-luminosity relationship between the early and late B stars suggests that the mechanism driving the flows changes at about 13,000 K. Study of the line strengths indicates that the net strength of Ha is correlated with both luminosity and temperature, with there being no discontinuity in the relationship as the line goes from a net absorption to a net emission feature. Evidence is presented to support the hypothesis that all early-type supergiants which show emission are intrinsic spectrum variables. it is also argued that the presence of reversals near the center of the Ha absorption cores in several 0 stars and lower-luminosity early B supergiants may provide evidence for the existence of chromospheres in these stars. Subject headings: early-type stars - emission-line stars - luminous stars - mass loss Publication: The Astrophysical Journal Pub Date: December 1973 DOI: 10.1086/152555 Bibcode: 1973ApJ...186..909R full text sources ADS | data products SIMBAD (61)