<i>XMM-Newton</i>X-ray study of early type stars in the Carina OB1 association

Antokhin, I. I.; Rauw, Grégor; Vreux, Jean-Marie; Hucht, K. A. van der; Brown, J. C.

doi:10.1051/0004-6361:20065711

Cited by 47 publications

(74 citation statements)

References 89 publications

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“….7, much like many of the O single stars, confirming a finding of the XMM survey of the Carina region by Antokhin et al (2008). All of these stars have soft X-ray spectra and show no strong time variability, consistent with the x-ray emission expected from wind shocks embedded in an O-star wind (Owocki & Cohen 1999).…”

Section: Carina Ob Starssupporting

confidence: 81%

The Chandra survey of Carina OB stars

et al. 2010

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Abstract. We have combined 22 deep Chandra ACIS-I pointings to map over one square degree of the Carina complex. Our x-ray survey detects 69 of 70 known O-type stars and 61 of 130 known early B stars. The majority of single O stars display soft X-ray spectra and have a mean log LX /L b ol ≈ −7.5 suggesting shocks embedded in the O-star winds. Over OB stars show unusually high X-ray luminosities, high shock temperatures or time variability, not predicted for embedded wind shocks.Keywords. X-rays: stars, X-rays: binaries, stars: early-type, stars: pre-main-sequenceThe Chandra Carina Complex Project (CCCP) survey area contains over 200 known massive stars: the LBV η Car, the Wolf Rayet stars WR 22, WR 24 and WR 25, 70 known O stars, and 130 B0-B3 stars with known spectral types. We have constructed a searchable electronic database of x-ray and optical properties for the 200 Carina OB stars. We divide the massive star population in Carina into four main groups based on spectral type and luminosity class: LBV/WR stars (4), O-type binaries (15), O-type single stars (55), and B0-B3 stars (130). We note that none of the B stars are typed as spectroscopic binaries. The goal of this study is to characterize L X , L X /L bol , the x-ray temperatures kT , and the temporal variability of single and binary OB stars, to look for new candidate colliding wind systems (e.g., Stevens et al. 1992) and magnetically confined wind shock sources (e.g., ud-Doula & Owocki 2002).The Chandra CCD spectra of the 78 OB stars with more than 50 ACIS counts were fit in XSPEC using a one-or two-temperature APEC emission model, and a two-component absorption model: a fixed TBABS column density to represent cold, neutral ISM absorption (assuming A V /N H = 1.6×10 21 cm −2 per mag), and free column density to represent absorption from the overlying stellar wind. L X was calculated correcting only for the ISM column. For single O stars, log L X /L bol = −7.59 ± 0.23, with no such trend for B stars. Table 1 highlights three notable single O stars: HD 93250, O4 III(fc), MJ 496, O8.5 V, and MJ 449, O8.5 V((f)), all of which have kT > 1.7 keV, log L X /L bol > −7

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Section: Carina Ob Starssupporting

confidence: 81%

The Chandra survey of Carina OB stars

et al. 2010

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“…(11) and (12) (filled and empty circles) for individual stars. This is compared with the mean observational relations (corrected for the interstellar absorption) derived by Antokhin et al (2008) and Sana et al (2006, with uncertainty). Empty circles denote values for stars showing the "weak wind problem".…”

Section: X-ray Luminositymentioning

confidence: 94%

“…By doing this, our list may be considered as representative of a diverse population of O stars found in real star clusters. This allows us to compare the trend in Xray luminosity of our synthetic O star population with the real clusters recently observed by Sana et al (2006) and Antokhin et al (2008).…”

Section: Test Starsmentioning

confidence: 94%

“…The fact that a substantial fraction of the wind is too hot to give a significant signature in the ultraviolet spectrum of the star could be an explanation for the weak-wind problem (Krtička & Kubát 2009). Sana et al (2006) and Antokhin et al (2008) divide the X-rays into three energy bands, soft (0.5−1.0 keV), medium (1.0−2.5 keV), and hard (2.5−10.0 keV). The observations show that the slope of the L X − L relation is roughly the same in the soft and medium band as in the total X-ray emission, whereas the observations in the hard band show a large dispersion.…”

Section: X-ray Luminositymentioning

confidence: 99%

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X-ray emission from hydrodynamical simulations in non-LTE wind models

Krtička

Feldmeier

Oskinova

et al. 2009

A&A

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Hot stars are sources of X-ray emission originating in their winds. Although hydrodynamical simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on simplifying approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability (seeded by the base perturbation) to derive the analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from observations. Furthermore, the slope of the L X − L relation is in better agreement with observations, however the X-ray luminosity is underestimated by a factor of three. We propose a possible solution for this discrepancy.

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“…In recent years, new studies investigating this so-called "canonical" relation have been performed, using detailed observations of rich open clusters and associations, notably NGC 6231 (XMM-Newton, Sana et al 2006), Carina OB1 (XMM-Newton, Antokhin et al 2008), Westerlund 2 (Chandra, Nazé et al 2008a), and Cyg OB2 (Chandra, Albacete Colombo et al 2007). For the clusters with the most well constrained stellar content (NGC 6231 and Carina OB1), the derived L X − L bol relations are far tighter (dispersions of only 40%) than in the RASS analysis.…”

Section: Introductionmentioning

confidence: 99%

Hot stars observed by XMM-Newton

Nazé¹

2009

A&A

144

164

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Aims. Following the advent of increasingly sensitive X-ray observatories, deep observations of early-type stars became possible. However, the results for only a few objects or clusters have until now been reported and there has been no large survey comparable to that based upon the ROSAT All-Sky Survey (RASS). Methods. A limited survey of X-ray sources, consisting of all public XMM-Newton observations (2XMMi) and slew survey data (XMMSL1), is now available. The X-ray counterparts to hot, massive stars have been searched for in these catalogs. Results. About 300 OB stars were detected with XMM-Newton. Half of them were bright enough for a spectral analysis to be possible, and we make available the detailed spectral properties that were derived. The X-ray spectra of O stars are represented well by low (<1 keV) temperature components and seem to indicate that an absorption column is present in addition to the interstellar contribution. The X-ray fluxes are well correlated with the bolometric fluxes, with a scatter comparable to that of the RASS studies and thus larger than found previously with XMM-Newton for some individual clusters. These results contrast with those of B stars that exhibit a large scatter in the L X − L BOL relation, no additional absorption being found, and the fits indicate a plasma at higher temperatures. Variability (either within one exposure or between multiple exposures) was also investigated whenever possible: short-term variations are far more rare than long-term ones (the former affects a few percent of the sample, while the latter concerns between one third and two thirds of the sources).Conclusions. This paper presents the results of the first high-sensitivity investigation of the overall high-energy properties of a sizable sample of hot stars.

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XMM-NewtonX-ray study of early type stars in the Carina OB1 association

Cited by 47 publications

References 89 publications

The Chandra survey of Carina OB stars

The Chandra survey of Carina OB stars

X-ray emission from hydrodynamical simulations in non-LTE wind models

Hot stars observed by XMM-Newton

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