Characteristics and classification of A-type supergiants in the Small Magellanic Cloud

Abstract

We address the relationship between spectral type and physical properties for A-type supergiants in the SMC. We first construct a self-consistent classification scheme for A supergiants, employing the calcium K to H epsilon line ratio as a temperature-sequence discriminant. Following the precepts of the `MK process', the same morphological criteria are applied to Galactic and SMC spectra with the understanding there may not be a correspondence in physical properties between spectral counterparts in different environments. We then discuss the temperature scale, concluding that A supergiants in the SMC are systematically cooler than their Galactic counterparts at the same spectral type, by up to ~10%. Considering the relative line strengths of H gamma and the CH G-band we extend our study to F and early G-type supergiants, for which similar effects are found. We note the implications for analyses of extragalactic luminous supergiants, for the flux-weighted gravity-luminosity relationship and for population synthesis studies in unresolved stellar systems.

arXiv comment14 pages, 14 figures, accepted by MNRAS; minor section removed prior to final publication

References in corpus (7)

• The Anglo-Australian Observatory's 2dF Facility
• A-type Supergiant Abundances in the SMC: Probes of Evolution
• A new extragalactic distance determination method using the flux-weighted gravity of late B and early A supergiants
• A Spectacular Post-Starburst Quasar
• Analysis of Four A-F Supergiants in M31 from Keck HIRES Spectroscopy
• Stellar spectroscopy far beyond the Local Group
• 3C 295, a cluster and its cooling flow at z=0.46

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