Fundamental parameters of massive stars

Crowther, P. A.

doi:10.1051/eas:2004048

Cited by 5 publications

(4 citation statements)

References 61 publications

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“…The standard deviation on the absolute magnitude of Galactic O supergiants given a spectral type is 0.45 mag (Martins et al 2005). Also, Crowther (2004) reported a scatter of 0.5 mag for OB stars. Thus, a typical uncertainty of 0.5 mag on the normalization was adopted for various spectral types, which was translated into uncertainties of the inferred distances.…”

Section: Stellar Modelsmentioning

confidence: 93%

The Nature of the Uv/Optical Emission of the Ultraluminous X-Ray Source in Holmberg Ii

Tao

Kaaret

Feng

et al. 2012

ApJ

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We report on UV and X-ray spectroscopy and broad-band optical observations of the ultraluminous X-ray source in Holmberg II. Fitting various stellar spectral models to the combined, non-simultaneous data set, we find that normal metallicity stellar spectra are ruled out by the data, while low metallicity, Z = 0.1Z ⊙ , late O-star spectra provide marginally acceptable fits, if we allow for the fact that X-ray ionization from the compact object may reduce or eliminate UV absorption/emission lines from the stellar wind. By contrast, an irradiated disk model fits both UV and optical data with χ 2 /dof = 175.9/178, and matches the nebular extinction with a reddening of E(B −V ) = 0.05 +0.05 −0.04 . These results suggest that the UV/optical flux of Holmberg II X-1 may be dominated by X-ray irradiated disk emission.

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Section: Stellar Modelsmentioning

confidence: 93%

The Nature of the Uv/Optical Emission of the Ultraluminous X-Ray Source in Holmberg Ii

Tao

Kaaret

Feng

et al. 2012

ApJ

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“…For other stars with known membership, a somewhat larger error of ±0.4 mag was adopted to account for a possible spread in distance within the host association. Finally, for HD 190603 and those two stars with calibrated M V , we assumed a typical uncertainty of ∆M V = ±0.5 mag, representative for the spread in M V of OB stars within a given spectral type (Crowther 2004) 3 .…”

Section: Sample Starsmentioning

confidence: 99%

Bright OB stars in the Galaxy

Маркова¹,

Puls²

2007

A&A

185

264

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Context. B-type supergiants represent an important phase in the evolution of massive stars. Reliable estimates of their stellar and wind parameters, however, are scarce, especially at mid and late spectral subtypes. Aims. We apply the NLTE atmosphere code FASTWIND to perform a spectroscopic study of a small sample of Galactic B-supergiants from B0 to B9. By means of the resulting data and incorporating additional datasets from alternative studies, we investigate the properties of OB-supergiants and compare our findings with theoretical predictions. Methods. Stellar and wind parameters of our sample stars are determined by line profile fitting, based on synthetic profiles, a Fourier technique to investigate the individual contributions of stellar rotation and "macro-turbulence" and an adequate approach to determine the Si abundances in parallel with micro-turbulent velocities. Results. Due to the combined effects of line-and wind-blanketing, the temperature scale of Galactic B-supergiants needs to be revised downward, by 10 to 20%, the latter value being appropriate for stronger winds. Compared to theoretical predictions, the wind properties of OB-supergiants indicate a number of discrepancies. In fair accordance with recent results, our sample indicates a gradual decrease in v ∞ over the bi-stability region, where the limits of this region are located at lower T eff than those predicted. Introducing a distance-independent quantity Q related to wind-strength, we show that this quantity is a well defined, monotonically increasing function of T eff outside this region. Inside and from hot to cool,Ṁ changes by a factor (in between 0.4 and 2.5) which is much smaller than the predicted factor of 5. Conclusions. The decrease in v ∞ over the bi-stability region is not over-compensated by an increase ofṀ , as frequently argued, provided that wind-clumping properties on both sides of this region do not differ substantially.

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“…For the clusters, we use UBV photometry and stellar classification of members to calculate effective temperature (log T eff ), bolometric correction (BC) and V ‐band extinction ( A V ) of each star (Massey et al 1995), using these values to then calculate the absolute magnitude ( M V ), bolometric magnitude ( M bol ) and hence luminosity (log L /L ⊙ ) (Crowther 2004). Masses are estimated using this resulting luminosity via the mass–luminosity relationship (Eddington 1924), with awareness that this relation is generally valid only for main‐sequence stars.…”

Section: Evolution Of Gsh 006−15+7mentioning

confidence: 99%

GSH 006−15+7: a local Galactic supershell featuring transition from H i emission to absorption

Moss

McClure-Griffiths

Braun

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We report on the discovery of a new Galactic supershell, GSH 006−15+7, from the Galactic All‐Sky Survey data. Observed and derived properties are presented, and we find that GSH 006−15+7 is one of the nearest physically large supershells known, with dimensions of ∼780 × 520 pc at a distance of ∼ 1.5 kpc. The shell wall appears in Hi emission at b≲−65 and in Hi self‐absorption (HiSA) at b≳−65. We use this feature along with HiSA diagnostics to estimate an optical depth of τ∼ 3, a spin temperature of ∼40 K and a swept‐up mass of M∼ 3 × 106 M⊙. We also investigate the origin of GSH 006−15+7, assessing the energy contribution of candidate powering sources and finding evidence in favour of a formation energy of ∼1052 erg. We find that this structure provides evidence for the transfer of mass and energy from the Galactic disc into the halo.

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Fundamental parameters of massive stars

Cited by 5 publications

References 61 publications

The Nature of the Uv/Optical Emission of the Ultraluminous X-Ray Source in Holmberg Ii

The Nature of the Uv/Optical Emission of the Ultraluminous X-Ray Source in Holmberg Ii

Bright OB stars in the Galaxy

GSH 006−15+7: a local Galactic supershell featuring transition from H i emission to absorption

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