2003ApJ...586..996M


C.D.S. - SIMBAD4 rel 1.7 - 2021.04.16CEST09:46:59

2003ApJ...586..996M - Astrophys. J., 586, 996-1018 (2003/April-1)

Constraints the ionization balance of hot-star winds from FUSE observations of O stars in the Large Magellanic Cloud.

MASSA D., FULLERTON A.W., SONNEBORN G. and HUTCHINGS J.B.

Abstract (from CDS):

We present Far Ultraviolet Spectroscopic Explorer (FUSE) spectra for 25 O stars in the Large Magellanic Cloud. We analyze wind profiles for the resonance lines from C III, N III, S IV, P V, S VI, and O VI in the FUSE range using a ``Sobolev with exact integration'' method. In addition, the available data from either IUE or the Hubble Space Telescope for the resonance lines of Si IV, C IV, and N V are also modeled. Because several of the FUSE wind lines are unsaturated, the analysis provides meaningful optical depths (or equivalently, mass-loss rate times ionization fractions, M{dot}q) as a function of normalized velocity, w=v/v. Ratios of M{dot}q (which are independent of M{dot}) determine the behavior of the relative ionization as a function of w. The results demonstrate that, with the exception of O VI in all stars and S VI in the later stars, the ionization in the winds shifts toward lower ionization stages at higher w (contrary to the expectations of the nebular approximation). This result implies that the dominant production mechanism for O VI and S VI in the late O stars differs from the other ions. Using the Vink et al. relationship between stellar parameters and mass-loss rate, we convert the measurements into mean ionization fractions for each ion, <qi>. Because the derived ion fractions never exceed unity, we conclude that the derived values of M{dot} are not too small. However, q(P V), which is expected to be the dominant stage of ionization in some of these winds, is never greater than 0.20. This implies that either the calculated values of M{dot} are too large, the assumed abundance of phosphorus is too large, or the winds are strongly clumped. The implications of each possibility are discussed. Correlations between the mean ion fractions and physical parameters such as Teff, v, and the mean wind density, <ρ>, are examined. Two clear relationships emerge. First, as expected, the mean ionization fraction of the lower ions (C III, N III, Si IV, S IV) decreases with increasing Teff. Second, the mean ion fraction of S VI in the latest stars and O VI in all stars increases with increasing v. This reaffirms the notion, first introduced by Cassinelli & Olson, that O VI is produced nonradiatively. Finally, we discuss specific characteristics of three stars, BI 272, BI 208, and Sk -67°166. For BI 272, the ionic species present in its wind suggest it is much hotter than its available (uncertain) spectral type of O7: II-III:. In the case of BI 208, our inability to fit its observed profiles suggests that its wind is not spherically symmetric. For Sk -67°166, quantitative measurements of its line strengths confirm the suggestion by Walborn et al. that it is a nitrogen-rich O star.

Abstract Copyright:

Journal keyword(s): Galaxies: Individual: Name: Large Magellanic Cloud - Galaxies: Individual: Name: Small Magellanic Cloud - Stars: Early-Type - Stars: Winds, Outflows - Ultraviolet: Stars

Simbad objects: 31

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Number of rows : 31

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9757 1
2 HD 268605 s*b 04 50 18.9253786780 -67 39 38.040164010 10.244 11.2 11.377   11.322 O9.5/B0Ia 80 0
3 SK -65 21 s*b 05 01 22.2743959588 -65 41 47.883234212 11.119 12.08 12.70   12.373 O9.7Iab 36 0
4 HD 270952 WR* 05 01 23.0763030544 -65 52 33.203698483 10.944 11.871 12.07   12.187 O6Iaf+ 51 0
5 SK -70 60 * 05 04 40.7778680984 -70 15 34.500345452 12.609 13.646 13.914   13.967 O4V 24 0
6 SK -70 69 * 05 05 18.6719268373 -70 25 49.876064190 12.586 13.616 13.854   14.074 O3V(f) 39 0
7 SK -67 69 * 05 14 20.0724897322 -67 08 03.171856399 11.950 13.012 13.040   13.330 O3III 24 0
8 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15288 1
9 SK -69 124 * 05 25 18.2523127241 -69 03 11.491757380 11.583 12.664 12.826   12.791 OB 24 0
10 SK -67 101 * 05 25 56.2418446809 -67 30 28.813100962   12.46 12.63     O8II((f)) 29 1
11 BI 170 * 05 26 47.6920860192 -69 06 12.020925555 11.823 12.914 13.116   12.975 O9.5Ib 25 0
12 SK -67 111 s*b 05 26 48.0782222412 -67 29 29.782065045   12.33 12.42     O6Iaf(n)pv 45 0
13 BI 173 * 05 27 09.9443110675 -69 07 56.453557872 11.85 12.86 13.00     O8III 24 0
14 SK -70 91 ** 05 27 33.5736776673 -70 36 47.954697209 11.369 12.55 12.78   12.937 O2III(f*)+OB 26 0
15 SK -66 100 * 05 27 45.4472881165 -66 55 15.296369854 12.227 12.976 13.204   13.501 O6II(f) 44 0
16 HD 269676 ** 05 31 15.654 -71 04 09.69 11.134 11.42 11.55 12.06 12.191 O6+O9: 74 0
17 HD 269698 s*b 05 31 44.2083142709 -67 38 01.378514813 9.520 12.00 12.22 12.47 11.167 O4Ia 109 0
18 SK -67 167 s*b 05 31 51.9126469266 -67 39 41.376030558 11.243 12.364 12.586   11.819 O4If+n 38 0
19 NGC 2014 As* 05 32 24 -67 41.3   9.17 8.97     ~ 75 0
20 SK -67 191 * 05 33 34.0159625782 -67 30 19.744843272 12.153 13.214 13.436   14.838 O8V 24 0
21 BI 208 * 05 33 57.3356464592 -67 24 20.182430788 12.742 13.716 13.921   14.141 O7V 18 0
22 HD 269810 Em* 05 35 13.8987303206 -67 33 27.540351680   12.08 12.22 12.53   O3III(f*) 99 0
23 BI 229 * 05 35 32.1627416112 -66 02 37.668305511 12.290 12.78 13.178   12.881 O7III 19 0
24 SK -66 169 s*b 05 36 54.6614257665 -66 38 22.426839132   12.43 12.56     O9.7Ia+ 32 0
25 SK -66 172 * 05 37 05.3866803996 -66 21 35.035689408   13.01 13.1     OB 37 0
26 HD 269896 s*b 05 37 49.1360518133 -68 55 01.642483154 11.338 9.493 11.449 11.49   ON9.7Ia+ 79 0
27 BI 272 * 05 44 23.1094405128 -67 14 29.219368741 12.163 13.127 13.201   13.524 O7III 23 0
28 HD 270145 s*b 05 48 49.6518988004 -70 03 57.836005522 10.903 12.110 12.166     O6.5Iaf 43 1
29 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1108 1
30 HD 93521 * 10 48 23.5116139485 +37 34 13.089937784 5.67 6.79 7.03     O9.5IIInn 406 1
31 * tau Sco * 16 35 52.9528530 -28 12 57.661515 1.55 2.56 2.81 2.93 3.18 B0.2V 867 0

    Equat.    Gal    SGal    Ecl

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2021.04.16-09:46:59

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