2001A&A...366..623H


C.D.S. - SIMBAD4 rel 1.7 - 2020.08.09CEST05:07:32

2001A&A...366..623H - Astronomy and Astrophysics, volume 366, 623-635 (2001/2-1)

An analysis of HST UV spectra of Cyg OB2 stars.

HERRERO A., PULS J., CORRAL L.J., KUDRITZKI R.P. and VILLAMARIZ M.R.

Abstract (from CDS):

As a first step of a vigorous program to investigate the Wind Momentum - Luminosity Relationship (WLR) of Galactic O-stars by analyzing stars belonging to the same cluster we present UV HST observations of six supergiants and one giant in the Cyg OB2 association. Terminal and turbulent wind velocities, velocity laws and metal ion column densities are derived and mean ionization fractions are estimated. Turbulent velocities are mostly in the range 10-14% of v. The terminal velocities agree well with the average v vs. spectral class relationship compiled by Kudritzki & Puls (2000). We compare the observed v vs. escape velocity (depending on the diagnostics of the stellar mass) correlation with the predictions of the radiatively driven wind theory and find better agreement with the spectroscopic masses rather than with the evolutionary ones. The β velocity field exponents are in the range 0.7-0.8, without any trend towards larger values. We show that for a single luminosity class there is a tight relationship between Teff and <ρ> (the mean density at the point in the stellar wind, where half the wind terminal velocity is reached). In consequence, the ionization fractions show the same trend with both, Teff and <ρ>: we find that NV increases with Teff, SiIV decreases and CIV does not clearly correlate. As a byproduct, we also derive interestellar HI column densities towards Cyg OB2, which turn out to be quite large. For one object (Cyg OB2#2) we find inconsistencies making the association membership questionable.

Abstract Copyright:

Journal keyword(s): stars: atmospheres - stars: early-types - stars: supergiants - stars: fundamental parameters - stars: winds, outflows - Galaxy: open clusters and associations: individual: Cyg OB2

Simbad objects: 19

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Number of rows : 19

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 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10949 1
2 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5148 1
3 HD 14947 s*b 02 26 46.9895793276 +58 52 33.116841083 7.83 8.44 7.98     O4.5If 237 0
4 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 5698 1
5 * zet Per V* 03 54 07.9224751 +31 53 01.081262 2.19 2.97 2.85 2.71 2.62 B1Ib 814 0
6 NAME LMC G 05 23 34.6 -69 45 22     0.4     ~ 14874 1
7 HD 39777 * 05 54 34.6960054175 -04 03 52.963431157 5.58 6.381 6.551     B2III/IV 85 0
8 BD+75 325 HS* 08 10 49.4901623070 +74 57 57.936226530 8.002 9.23 9.50 9.698 9.884 sdO5 232 0
9 * sig Sco bC* 16 21 11.3157134 -25 35 34.051476 2.32 3.02 2.89 1.69 1.58 O9.5(V)+B7(V) 825 0
10 HD 227634 * 20 06 01.3608572564 +35 45 55.907129543 7.03 8.17 7.92     B0.2II 70 0
11 Schulte 2 V* 20 31 22.0268723645 +41 31 28.363066323 12.01 11.82 10.64     B1Ib: 55 0
12 BD+40 4219 * 20 32 13.8220814591 +41 27 12.005606749 11.50 11.40 10.22     O7III((f)) 103 0
13 Schulte 12 s*b 20 32 40.9574572449 +41 14 29.276333992 16.1 14.45 11.702     B3-4Ia+ 359 0
14 Ass Cyg OB 2 As* 20 33.2 +41 19           ~ 794 0
15 Schulte 7 * 20 33 14.1095790591 +41 20 21.903381641 12.24 12.00 10.55     O3If* 129 0
16 BD+40 4227A SB* 20 33 15.0780900764 +41 18 50.478859468 10.42 10.27 8.98 8.03 6.83 O6Ib(fc)+O4.5:III:(fc) 216 0
17 Schulte 8C * 20 33 17.9821559015 +41 18 31.192311433 12.2 11.43 10.19     O4.5III(fc) 74 0
18 BD+41 3804 s*b 20 33 46.1097446575 +41 33 00.958715569 11.82 11.41 9.88     O9.7Iab 91 0
19 BD+41 3807 SB* 20 34 08.5147839926 +41 36 59.407506888 11.74 11.52 10.03     O5.5Ifc 112 0

    Equat.    Gal    SGal    Ecl

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2020.08.09-05:07:32

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