THE NATURE OF THE BRIGHTEST GALACTIC-CENTER HE-I EMISSION-LINE STAR

被引:0
作者
NAJARRO, F
HILLIER, DJ
KUDRITZKI, RP
KRABBE, A
GENZEL, R
LUTZ, D
DRAPATZ, S
GEBALLE, TR
机构
[1] MAX PLANCK INST ASTROPHYS, D-85740 GARCHING, GERMANY
[2] MAX PLANCK INST EXTRATERR PHYS, D-85740 GARCHING, GERMANY
[3] JOINT ASTRON CTR, HILO, HI 96720 USA
关键词
THE GALAXY; CENTER; INFRARED; STARS; EARLY-TYPE; EMISSION-LINE; SUPERGIANTS;
D O I
暂无
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present near-infrared spectroscopy and unified atmosphere/wind models of the brightest He I 2.058 mum emission line star (hereafter denoted AF) in the Galactic center. The near-infrared spectrum of this star exhibits broad emission lines of He I and H, with the strongest line at 2.058 mum showing shallow P-Cygni absorption, strengthening the stellar wind interpretation for the origin of the lines. None of the higher excitation lines typical of classical Wolf-Rayet stars are detected. From the atmosphere models we conclude that the star is undergoing extensive mass loss (M approximately 6 to 10 x 10(-5) M. yr-1), has a luminosity of 2 to 3 10(5)L., a moderate end velocity (V(infinity) approximately 700 km s-1) and a strongly enhanced helium abundance (N(He)/N(H)> .5). The AF star has an effective temperature of about 20,000 K and produces less-than-or-equal-to 10(48) Lyman continuum photons per second and < 10(38) helium continuum photons. These parameters are similar to those of evolved blue supergiants of type Ofpe/WN9 found in the Magellanic Clouds. Extrapolating from the AF star it is likely that the emission line stars so far detected (approximately 15) contribute a large fraction of the total luminosity (approximately 10(7)L.), and a significant fraction of the Lyman continuum luminosity (approximately 10(6)L.) of the central parsec. However, the He I stars make no contribution to the He ionizing photons. Less evolved, hotter O and/or Wolf-Rayet stars may provide the He I ionizing flux, and also contribute to the Lyman flux.
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页码:573 / 584
页数:12
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