Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.

Humphreys, R. M.

doi:10.1086/190559

Cited by 700 publications

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“…These settings are as follows: i) From 4110 to 4310 Å (covering Si II λλ4128, 4131 , Si IV λ4116 and He II λ4200). Humphreys (1978); b Garmany & Stencel (1992); c Barlow & Cohen (1977); d Denizman & Hack (1988); * from calibrations (Humphreys & McElroy 1984).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

“…In particular, for stars which are members of OB associations, we drew mainly from Humphreys (1978) but also consulted the lists published by Garmany & Stencel (1992) and by Barlow & Cohen (1977). In most cases, good agreement between the three datasets was found, and only for Cyg OB3 did the distance modulus provided by Humphreys turned out to be significantly larger than that provided by Garmany & Stencel. In this latter case two entries for d are given in Table 1.…”

Section: Sample Starsmentioning

confidence: 99%

“…Interestingly, the surface gravity of "our" B5 star, HD 191243 (log g = 2.6), appears also to be larger than what is typical for a supergiant of B5 subtype. With a distance modulus of 2.2 kps (Humphreys 1978), the absolute magnitude of HD 191243 would be more consistent with a supergiant classification, but with d = 1.75 kpc (Garmany & Stencel 1992) a luminosity class II is more appropriate. Thus, this star also seems to be misclassified 13 .…”

Section: Line-blanketed Analysesmentioning

confidence: 99%

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Bright OB stars in the Galaxy

Маркова¹,

Puls²

2007

A&A

189

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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Section: Observations and Data Reductionmentioning

confidence: 99%

Section: Sample Starsmentioning

confidence: 99%

Section: Line-blanketed Analysesmentioning

confidence: 99%

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Bright OB stars in the Galaxy

Маркова¹,

Puls²

2007

A&A

189

264

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“…Hutchings (1981) assumed an absolute distance modulus (m − M) = 10.7, converting to d = 1.38 kpc. Humphreys (1978) adopted d = 1.82 kpc, while Torres-Dodgen et al (1991) and Massey & Thompson (1991) Knödlseder (2000) assumed a distance d = 1.7 kpc. The possibility of clusters related to Cyg OB2 in the present study may help constrain the distance.…”

Section: Introductionmentioning

confidence: 99%

Does Cyg OB2 harbour any open cluster?

Bica

Bonatto

Dutra

2003

A&A

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Abstract.We report the detection of three new open cluster candidates located in Cygnus. Two of them are projected near the center of the rich compact association Cyg OB2. These two objects have been found during an optical inspection of that region with Digitized Sky Survey images. Using 2MASS photometry we determined their fundamental parameters. We assumed an age of 1-4 Myr and obtained a distance from the Sun d = 1.8 ± 0.2 kpc for both objects. Reddening values for Objects 1 and 2 are E(B− V) = 2.12± 0.06 and E(B− V) = 1.82± 0.06, respectively. A normal luminosity function is observed down to A0 stars, similar to that of NGC 6910. The two open cluster candidates may form a physical pair in Cyg OB2, similar to Tr 14/Tr 16 in Car OB1. Subsequently, we carried out a systematic search with 2MASS in a region 3 • × 3 • encompassing Cyg OB2. A third uncatalogued object resulted from this search which is projected just outside Cyg OB2.

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“…Crawford, Barnes & Warren (1974) used three methods (UBV photometry, the H-R diagram fitting and the equivalent width of the H β line) and obtained the distance to the association of about 2 kpc. Humphreys (1978) estimated the photometric distance to Cyg OB3 to be about 2.3 kpc. Janes & Adler (1982) quote in their catalogue the distance to NGC 6871 as only 1.8 kpc.…”

Section: Introductionmentioning

confidence: 99%

Evolutionary Constraints on the Masses of the Components of HDE 226868/Cyg X-1 Binary System

Ziółkowski

2005

Chin. J. Astron. Astrophys.

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Calculations carried out to model the evolution of HDE 226868, under different assumptions about the stellar wind mass loss rate, provide robust limits on the present mass of the star. It has to be in the range 40 ± 5 M ⊙ if the distance to the system is in the range 1.95 to 2.35 kpc and the effective temperature of HDE 226868 in the range 30000 to 31000 K. Extending the possible intervals of these parameters to 1.8 to 2.35 kpc and 28000 to 32000 K, one gets for the mass of the star the range 40 ± 10 M ⊙ . Including into the analysis observational properties such as the profiles of the emission lines, rotational broadening of the absorption lines and the ellipsoidal light variations, one can estimate also the mass of the compact component. It has to be in the ranges 20 ± 5 M ⊙ and 13.5 ÷ 29 M ⊙ for the cases described above. The same analysis (using the evolutionary models and the observational properties listed above) yields lower limit to the distance to the system of ∼ 2.0 kpc, if the effective temperature of HDE 226868 is higher than 30000 K. This limit to the distance does not depend on any photometric or astrometric considerations.

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Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.

Cited by 700 publications

References 0 publications

Bright OB stars in the Galaxy

Bright OB stars in the Galaxy

Does Cyg OB2 harbour any open cluster?

Evolutionary Constraints on the Masses of the Components of HDE 226868/Cyg X-1 Binary System

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