2009A&A...498..837M


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.25CET06:45:37

2009A&A...498..837M - Astronomy and Astrophysics, volume 498, 837-852 (2009/5-2)

Analysis of Galactic late-type O dwarfs: more constraints on the weak wind problem.

MARCOLINO W.L.F., BOURET J.-C., MARTINS F., HILLIER D.J., LANZ T. and ESCOLANO C.

Abstract (from CDS):

We investigate the stellar and wind properties of a sample of late-type O dwarfs. Previous analyses of such stars have found very low mass-loss rates; rates much lower than predicted by theory (the weak wind problem). Far-UV to optical spectra of five Galactic O stars were analyzed: HD 216898 (O9IV/O8.5V), HD 326329 (O9V), HD 66788 (O8V/O9V), ζ Oph (O9.5Vnn), and HD 216532 (O8.5V((n))). We used a grid of TLUSTY models to obtain effective temperatures, gravities, rotational velocities, and to identify wind lines. Wind parameters for each object were obtained using expanding atmosphere models calculated with the CMFGEN code. The spectra of our sample have primarily a photospheric origin. A weak wind signature is seen in CIV λλ1548, 1551, from which mass-loss rates consistent with previous CMFGEN results for O8-O9V stars were derived (∼10–10-10–9M/yr). A discrepancy of roughly two orders of magnitude is found between these mass-loss rates and the values predicted by theory ({dot}(M)Vink), confirming a breakdown or a steepening of the modified wind momentum-luminosity relation at log L*/L≲5.2. We have estimated the carbon abundance for the stars of our sample and concluded that its value cannot be reduced to sufficiently small values to solve the weak wind problem. Upper limits on {dot}(M) were established for all objects using lines of different ions: P v λλ1118, 1128, CIII λ1176, NV λλ1239, 1243, SiIV λλ1394, 1403, and NIV λ1718. All the values obtained are in disagreement with theoretical predictions, bringing support to the reality of weak winds. Together with CIV λλ1548, 1551, the use of NV λλ1239, 1243 results in the lowest mass-loss rates: the upper limits indicate that {dot}(M) must be less than about -1.0dex {dot}(M)Vink. Upper mass-loss rate limits obtained for other transitions are also low: they indicate that {dot}(M) must be less than about (-0.5±0.2)dex {dot}(M)Vink. We studied the behavior of the Hα line with different mass-loss rates. For two stars, only models with very low {dot}(M)'s provide the best fit to the UV and optical spectra. We also explored ways to fit the observed spectra with the theoretical mass-loss rates. By using large amounts of X-rays, we could reduce the predicted wind emission to the observed levels. However, unrealistic X-ray luminosities had to be used (logLX/LBol>-3.5). The validity of the models used in our analyses is discussed.

Abstract Copyright:

Journal keyword(s): stars: atmospheres - stars: mass-loss - stars: fundamental parameters - stars: early-type

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 - 2021
#notes
1 AzV 83 s*b 00 50 52.0009104477 -72 42 14.942933567 12.233 13.244 13.366   13.67 O7Iaf+ 43 0
2 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9600 1
3 NGC 346 Cl* 00 59 05.090 -72 10 33.24           ~ 451 0
4 HD 7113 Em* 01 09 13.066 -73 11 38.92     11.7     ~ 117 0
5 V* AE Aur Or* 05 16 18.1489437436 +34 18 44.347016027 5.48 6.18 5.96     O9.5V 529 1
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 15050 1
7 * tet01 Ori C ** 05 35 16.46375 -05 23 22.8486 4.20 5.15 5.13 4.91 4.73 O7Vp 1285 1
8 * mu. Col V* 05 45 59.8953630749 -32 18 23.164726112 3.84 4.90 5.18 5.30 5.57 O9.5V 462 0
9 HD 42088 * 06 09 39.5726383124 +20 29 15.455220620 6.73 7.58 7.57 8.45   O6V((f))z 233 0
10 HD 46202 ** 06 32 10.4728 +04 57 59.818 7.60 8.36 8.19 7.98 7.86 O9.2V 258 0
11 HD 66788 * 08 04 08.5402852477 -27 29 08.858514821 8.44 9.92 9.83 9.85   O8/9(Ib) 52 0
12 HD 93028 SB* 10 43 15.3392956864 -60 12 04.229601354 7.29 8.24 8.30 9.26   O9IV 151 0
13 HD 93146A * 10 44 00.1578 -60 05 09.863 7.57 8.48 8.45     O7V((f))z 80 0
14 HD 93146 ** 10 44 00.159 -60 05 09.88   8.25 8.24 9.28   O6V+O9.5V 81 0
15 * tau Sco * 16 35 52.9528530 -28 12 57.661515 1.55 2.56 2.81 2.93 3.18 B0.2V 861 0
16 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1739 2
17 NAME Sco OB 1 As* 16 53.5 -41 57           ~ 195 0
18 NGC 6231 OpC 16 54 08.51 -41 49 36.0   2.83 2.6     ~ 487 0
19 HD 326329 ** 16 54 14.01 -41 50 08.7   8.8   8.97   O9.7V 13 0
20 V* V1297 Sco Al* 16 56 05.2156792717 -40 20 57.576409562 7.87 9.11 9.29 9.29   O7.5Vz 123 0
21 Schulte 2 V* 20 31 22.0268723645 +41 31 28.363066323 12.01 11.82 10.64     B1Ib: 55 0
22 * 10 Lac ** 22 39 15.6786372 +39 03 00.971152 3.650 4.670 4.880 4.98 5.19 O9V 720 0
23 HD 216532 V* 22 52 30.5564449825 +62 26 25.946675282 8.06 8.46 8.0     O8.5V(n) 131 0
24 HD 216898 * 22 55 42.4581895079 +62 18 22.820044865 8.10 8.58 8.04     O9V 141 0
25 HD 217086 Y*O 22 56 47.1887219290 +62 43 37.654789076 7.88 8.30 7.66 8.35   O7Vnn((f))z 244 0
26 NAME III CEP ASSOC As* 23 04.2 +63 24           ~ 296 0

    Equat.    Gal    SGal    Ecl

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2020.11.25-06:45:37

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