Spectroscopy of massive stars in NGC 6822 and M33

Citation
L. Bianchi et al., Spectroscopy of massive stars in NGC 6822 and M33, PUB AST S P, 113(784), 2001, pp. 697-702
Citations number
27
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC
ISSN journal
0004-6280 → ACNP
Volume
113
Issue
784
Year of publication
2001
Pages
697 - 702
Database
ISI
SICI code
0004-6280(200106)113:784<697:SOMSIN>2.0.ZU;2-P
Abstract
We present blue spectra of massive stars in the Local Group galaxies NGC 68 22 and M33. For all the targets, selected from our previous Hubble Space Te lescope WFPC2 photometry, no previous spectroscopic studies exist, to our k nowledge, except for a bright Wolf-Rayet star in NGC 6822. Photospheric par ameters T-eff and gravity are derived by a model fit of the Balmer lines an d multiband (UV to optical) photometry combined and are compared with evolu tionary models. Inferred masses range from approximate to7 to approximate t o 40 M-. in the sample. From M the spectroscopy, we classify the Wolf-Rayet star in NGC 6822 as WN3(-4), with no hydrogen. We estimate its progenitor mass of approximate to 40 +/- 10 M-.. For two stars in the NGC 6822 sample, our data are not sufficient to establish whether they are foreground stars toward NGC 6822 or they belong to the galaxy.