<i>XMM-Newton</i>high-resolution X-ray spectroscopy of the Wolf-Rayet object WR 25 in the Carina OB1 association

Raassen, A. J. J.; Hucht, K. A. van der; Mewe, R.; Antokhin, I. I.; Rauw, Grégor; Vreux, Jean-Marie; Schmutz, W.; Güdel, M.

doi:10.1051/0004-6361:20030119

Cited by 46 publications

(60 citation statements)

References 84 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The photometric and polarization variability is small and stochastic (Drissen et al 1992). Raassen et al (2003) found no X-ray variations over the history of X-ray astronomy. Only very recently, the detection of radial velocity variations with a period of about 200 days has been reported (Gamen & Gosset, private communication).…”

Section: Comments On Individual Starsmentioning

confidence: 90%

The Galactic WN stars

Hamann¹,

Gräfener²,

Liermann³

2006

A&A

352

578

View full text Add to dashboard Cite

Context. Very massive stars pass through the Wolf-Rayet (WR) stage before they finally explode. Details of their evolution have not yet been safely established, and their physics are not well understood. Their spectral analysis requires adequate model atmospheres, which have been developed step by step during the past decades and account in their recent version for line blanketing by the millions of lines from iron and iron-group elements. However, only very few WN stars have been re-analyzed by means of line-blanketed models yet. Aims. The quantitative spectral analysis of a large sample of Galactic WN stars with the most advanced generation of model atmospheres should provide an empirical basis for various studies about the origin, evolution, and physics of the Wolf-Rayet stars and their powerful winds. Methods. We analyze a large sample of Galactic WN stars by means of the Potsdam Wolf-Rayet (PoWR) model atmospheres, which account for iron line blanketing and clumping. The results are compared with a synthetic population, generated from the Geneva tracks for massive star evolution. Results. We obtain a homogeneous set of stellar and atmospheric parameters for the Galactic WN stars, partly revising earlier results. Conclusions. Comparing the results of our spectral analyses of the Galactic WN stars with the predictions of the Geneva evolutionary calculations, we conclude that there is rough qualitative agreement. However, the quantitative discrepancies are still severe, and there is no preference for the tracks that account for the effects of rotation. It seems that the evolution of massive stars is still not satisfactorily understood.

show abstract

Section: Comments On Individual Starsmentioning

confidence: 90%

The Galactic WN stars

Hamann¹,

Gräfener²,

Liermann³

2006

A&A

352

578

View full text Add to dashboard Cite

show abstract

“…6.2. This feature is not unusual for Wolf-Rayet stars: extra X-ray absorption is produced by the material in the stellar wind and is observed for instance in the case of the WN6ha star WR 25 (Raassen et al 2003). Even worse, in the case of the WN8 star WR 40, the wind absorption is probably so large that no X-ray emission is actually escaping (Gosset et al 2005).…”

Section: X-ray Emission From Wr 20amentioning

confidence: 94%

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

Rauw¹,

Crowther

Becker³

et al. 2005

A&A

Self Cite

137

View full text Add to dashboard Cite

Abstract. We analyse the optical spectrum of the very massive binary system WR 20a (WN6ha + WN6ha). The most prominent emission lines, Hα and He  λ 4686, display strong phase-locked profile variability. From the variations of their equivalent widths and from a tomographic analysis, we find that part of the line emission probably arises in a wind interaction region between the stars. Our analysis of the optical spectrum of WR 20a indicates a reddening of A V 6.0 mag and a distance of ∼7.9 kpc, suggesting that the star actually belongs to the open cluster Westerlund 2. The location of the system at ∼1.1 pc from the cluster core could indicate that WR 20a was gently ejected from the core via dynamical interactions. Using a non-LTE model atmosphere code, we derive the fundamental parameters of each component: T eff = 43 000 ± 2000 K, log L bol /L 6.0,Ṁ = 8.5 × 10 −6 M yr −1 (assuming a clumped wind with a volume filling factor f = 0.1). Nitrogen is enhanced in the atmospheres of the components of WR 20a, while carbon is definitely depleted. Finally, the position of the binary components in the Hertzsprung-Russell diagram suggests that they are core hydrogen burning stars in a pre-LBV stage and their current atmospheric chemical composition probably results from rotational mixing that might be enhanced in a close binary compared to a single star of same age.

show abstract

“…Crowther et al (2010) have recently claimed to have observed such massive objects. However, WR 25 (or HD 93162), the most luminous star, is a binary star with a spectroscopically determined orbital period of 207.8 d (Raassen et al 2003). The second-most luminous star, WR 22, is an eclipsing binary.…”

Section: Positions In the Hr Diagrammentioning

confidence: 99%

Grids of stellar models with rotation

Georgy

Ekström

Meynet

et al. 2012

A&A

301

364

View full text Add to dashboard Cite

Context. In recent years, many very interesting observations have appeared concerning the positions of Wolf-Rayet (WR) stars in the Hertzsprung-Russell diagram (HRD), the number ratios of WR stars, the nature of Type Ibc supernova (SN) progenitors, long and soft gamma ray bursts (LGRB), and the frequency of these various types of explosive events. These observations represent key constraints on massive star evolution. Aims. We study, in the framework of the single-star evolutionary scenario, how rotation modifies the evolution of a given initial mass star towards the WR phase and how it impacts the rates of Type Ibc SNe. We also discuss the initial conditions required to obtain collapsars and LGRB. Methods. We used a recent grid of stellar models computed with and without rotation to make predictions concerning the WR populations and the frequency of different types of core-collapse SNe. Current rotating models were checked to provide good fits to the following features: solar luminosity and radius at the solar age, main-sequence width, red-giant and red-supergiant (RSG) positions in the HRD, surface abundances, and rotational velocities. Results. Rotating stellar models predict that about half of the observed WR stars and at least half of the Type Ibc SNe may be produced through the single-star evolution channel. Rotation increases the duration of the WNL and WNC phases, while reducing those of the WNE and WC phases, as was already shown in previous works. Rotation increases the frequency of Type Ic SNe. The upper mass limit for Type II-P SNe is ∼19.0 M for the non rotating models and ∼16.8 M for the rotating ones. Both values agree with observations. Moreover, present rotating models provide a very good fit to the progenitor of SN 2008ax. We discuss future directions of research for further improving the agreement between the models and the observations. We conclude that the mass-loss rates in the WNL and RSG phases are probably underestimated at present. We show that up to an initial mass of 40 M , a surface magnetic field inferior to about 200 G may be sufficient to produce some braking. Much lower values are needed at the red supergiant stage. We suggest that the presence/absence of any magnetic braking effect may play a key role in questions regarding rotation rates of young pulsars and the evolution leading to LGRBs.

show abstract

XMM-Newtonhigh-resolution X-ray spectroscopy of the Wolf-Rayet object WR 25 in the Carina OB1 association

Cited by 46 publications

References 84 publications

The Galactic WN stars

The Galactic WN stars

The spectrum of the very massive binary system WR 20a (WN6ha + WN6ha): Fundamental parameters and wind interactions

Grids of stellar models with rotation

Contact Info

Product

Resources

About