2006ApJ...638..409H


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.20CET03:37:04

2006ApJ...638..409H - Astrophys. J., 638, 409-432 (2006/February-2)

Fundamental properties of O-type stars.

HEAP S.R., LANZ T. and HUBENY I.

Abstract (from CDS):

We present a comprehensive analysis of high-resolution, far-ultraviolet HST STIS, FUSE, and optical spectra of 18 O stars in the Small Magellanic Cloud. Our analysis is based on the OSTAR2002 grid of NLTE metal-line-blanketed model atmospheres calculated with our code TLUSTY. We systematically explore and present the sensitivity of various UV and optical lines to different stellar parameters. We have obtained consistent fits of the UV and the optical spectrum to derive the effective temperature, surface gravity, surface composition, and microturbulent velocity of each star. Stellar radii, masses, and luminosities follow directly. For stars of the same spectral subtype, we find a general good agreement between effective temperature determinations obtained with TLUSTY, CMFGEN, and FASTWIND models, which are all lower than the standard Teffcalibration of O stars. We propose a new calibration between the spectral type and effective temperature based on our results from UV metal lines, as well as optical hydrogen and helium lines. The lower effective temperatures translate into ionizing luminosities that are smaller by a factor of 3 compared to luminosities inferred from previous standard calibrations. The chemical composition analysis reveals that the surface of about 80% of the program stars is moderately to strongly enriched in nitrogen, while showing the original helium, carbon, and oxygen abundances. Our results support the new stellar evolution models that predict that the surface of fast rotating stars becomes nitrogen-rich during the main-sequence phase because of rotationally induced mixing. Enrichment factors are, however, larger than predicted by stellar evolution models. Most stars exhibit the ``mass discrepancy'' problem, which we interpret as a result of fast rotation that lowers the measured effective gravity. Nitrogen enrichment and low spectroscopic masses are therefore two manifestations of fast rotation. Our study thus emphasizes the importance of rotation in our understanding of the properties of massive stars and provides a framework for investigating populations of low-metallicity massive stars at low and high redshifts.

Abstract Copyright:

Journal keyword(s): Galaxies: Magellanic Clouds - Stars: Abundances - Stars: Atmospheres - Stars: Early-Type - Stars: Fundamental Parameters

Simbad objects: 26

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Number of rows : 26

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 LIN 78 Em* 00 46 32.63 -73 06 05.7 12.53 13.59 13.7   13.85 O3/4V 41 1
2 SK 10 s*b 00 46 42.1589052355 -73 24 55.493791820 11.903 12.984 13.176   13.35 O6.5I(f) 39 0
3 AzV 47 * 00 48 51.4904959784 -73 25 58.502738783 12.263 13.314 13.496   14.00 O8III 30 0
4 BBB SMC 1 * 00 50 17.2062292889 -72 53 30.261075405 12.093 13.144 13.326 13.39 13.47 OC7.5III((f)) 40 0
5 LIN 156 s*b 00 50 32.4054204297 -72 52 36.444460019 11.553 12.604 12.756   12.89 O5.5I(f) 46 0
6 AzV 80 * 00 50 43.80 -72 47 41.5 12.22 13.24 13.376   13.59 O4-6n(f)p 27 0
7 AzV 83 s*b 00 50 52.0009104477 -72 42 14.942933567 12.233 13.244 13.366   13.67 O7Iaf+ 42 0
8 AzV 95 * 00 51 21.5997393360 -72 44 14.875524423 12.67 13.64 13.83   13.95 O7III((f)) 34 0
9 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9228 1
10 AzV 170 s*b 00 55 42.4296940734 -73 17 30.524041493 12.86 13.82 14.11   14.25 O9.7I 24 0
11 Cl* NGC 346 MPG 12 * 00 58 14.24 -72 10 45.0   19.15 17.98   16.72 B0IV(Nstr) 28 0
12 Cl* NGC 346 ELS 28 * 00 58 31.7535036663 -72 10 57.966053276 13.58 14.73 14.94   15.23 OC6Vz 25 0
13 Cl* NGC 346 ELS 7 * 00 58 57.3952116864 -72 10 33.661396129 12.68 13.82 14.13   14.28 O4V((f+)) 48 0
14 Cl* NGC 346 W 3 * 00 59 00.7582411392 -72 10 28.171999499 11.46 12.61 12.80   13.63 O2III(f) 57 0
15 Cl* NGC 346 NMC 34 * 00 59 00.9620930111 -72 11 09.279979666 14.11 15.20 15.46   15.57 O6.5V 9 0
16 Cl* NGC 346 NMC 28 * 00 59 01.799 -72 10 31.23   13.95 14.18     O5.5V((f+)) 27 0
17 NGC 346 Cl* 00 59 05.090 -72 10 33.24           ~ 443 0
18 Cl* NGC 346 NMC 17 * 00 59 06.7476389850 -72 10 41.262026867 13.05 14.19 14.33   14.60 O8V 18 0
19 AzV 220 Em* 00 59 09.9684677094 -72 05 48.278343943 13.13 14.24 14.51   14.73 O7If 32 0
20 Cl* NGC 346 ELS 22 * 00 59 18.6174080795 -72 11 09.889202050   14.65 14.91     O9V 18 0
21 SK 80 s*b 00 59 31.9755771921 -72 10 46.109784216   12.12 12.31     O7Iaf+ 104 0
22 RMC 28 s*b 01 03 10.5476947249 -72 02 14.334409660 11.833 12.924 13.086   13.60 O9.7I 35 0
23 AzV 377 * 01 05 07.3822349267 -72 48 18.713796298 13.18 14.34 14.59   14.83 O5V((f)) 16 0
24 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14543 1
25 HD 93129 ** 10 43 57.486 -59 32 51.44 6.26 7.06 6.90     O2If*+O3.5V((f)) 188 1
26 HD 93843 Er* 10 48 37.7714362588 -60 13 25.516378731 6.37 7.29 7.33 8.23   O5III(fc) 153 0

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2020.02.20-03:37:05

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