Bibcode
Bianchi, Luciana; Lamers, Henry J. G. L. M.; Hutchings, J. B.; Massey, Philip; Kudritzki, Rolf; Herrero, Artemio; Lennon, Danny J.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 292, no. 1, p. 213-220
Fecha de publicación:
12
1994
Número de citas
21
Número de citas referidas
20
Descripción
We present and discuss the UV spectrum of the supergiant star in
NGC206-277 in M 31, obtained with the Faint Object Spectrograph (FOS) on
Hubble Space Telescope (HST). An optical blue spectrum taken at Kitt
Peak National Observatory (KPNO) is also shown. From the optical and UV
line spectra we classify the star B1.5Ia. We fit the continuum far-UV
flux distribution, deriving Teff = 20,000 K, and with this
temperature we find log g = 2.5 by comparing the Hgamma line
and He I lines with predictions from Non-Local Thermodynamic Equilibrium
(NLTE) models. We analyze the stellar UV wind line profiles with the SEI
method and derive a terminal velocity of upsiloninfinity
approximately equal to 700 km/s. We fit the Halpha emission
line obtained at the WHT with a newly developed (by H.J.G.L.M.L.) code
similar to the SEI method for UV lines, and derive dm/dt = 1.3 +/- 0.5
10-6 solar mass/yr. We find that the P Cygni profiles of the
M 31 star have slightly weaker and narrower absorptions, and no emission
component. We correct our previously published mass-loss estimate for an
O star (NGC206-231) in the same association. The correct value is dm/dt
approximately equals 10-6 solar mass/yr, assuming solar
abundances.