Open AccessCharacteristics and classification of A‐type supergiants in the Small Magellanic Cloud
Author(s) -
Evans Christopher J.,
Howarth Ian D.
Publication year - 2003
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-2966.2003.07038.x
Subject(s) - physics , supergiant , large magellanic cloud , astronomy , small magellanic cloud , astrophysics , blue supergiant , stellar classification , type (biology) , stars , red supergiant , ecology , biology
We address the relationship between spectral type and physical properties for A‐type supergiants in the Small Magellanic Cloud (SMC). First, we construct a self‐consistent classification scheme for A supergiants, employing the calcium K to Hε 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 that there may not be a correspondence in physical properties between spectral counterparts in different environments. Then we 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 per cent. Considering the relative line strengths of Hγ 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 luminous extragalactic supergiants, for the flux‐weighted gravity–luminosity relationship and for population synthesis studies in unresolved stellar systems.