Fundamental Parameters of B Supergiants

Abstract

To understand the chemical evolution of galaxies, we need a deep understanding of the evolution of massive stars and their role in processing and delivering chemical elements. B-type supergiants represent a substantial population in this context. We present here initial results from non-LTE, line-blanketed stellar atmosphere modelling [1] of a large sample of B0-B5 supergiants (see Fig.1). We focus in this report on revisions to the effective temperature scales, finding reasonable agreement with the temperatures of [2] for B1-B5 supergiants. For early type supergiants (B0-B1), the less luminous Ib’s are hotter than Ia’s as expected (excluding HD190603 (B1.5 Ia+) which is a hypergiant). The temperature discrepancy between B0 Ia’s & B0 Ib’s is up to 2500 K, decreasing to 1000 K for B0.5 and remains as 1000 K or less for later B type supergiants. Whilst some early B type supergiants are slightly cooler compared to the Humphreys et al. temperatures [2], a few B0.5 Ia & Ib stars appear to be slightly hotter. This discrepancy requires further investigation, since recent OB supergiant revised temperature scales have shown a trend for temperatures to be slightly cooler [3] than previously thought from [2].