XMM-Newton observations of the nitrogen-rich Wolf-Rayet star WR 1

Ignace, Richard; Oskinova, L. M.; Brown, J. C.

doi:10.1051/0004-6361:20031024

Cited by 32 publications

(34 citation statements)

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“…However, observations show the contrary-the handful of single WR stars with available spectral measurements all show X-ray emission harder than typically found in O stars (Skinner et al 2002a(Skinner et al , 2002bIgnace et al 2003). This trend is confirmed by our new data on WR 142.…”

Section: X-ray Emission From a Wo-type Star L47supporting

confidence: 82%

“…Observations with the XMM-Newton and Chandra X-ray telescopes established that some bona fide single WN stars are X-ray active (Skinner et al 2002a(Skinner et al , 2002bIgnace et al 2003;Oskinova 2005), while others are apparently not (Oskinova 2005;Gosset et al 2005). Oskinova et al (2003) found that no single WC star had been conclusively detected at X-ray energies, a result that continues to hold.…”

Section: Introductionmentioning

confidence: 99%

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Discovery of X-Ray Emission From the Wolf-Rayet Star Wr 142 of Oxygen Subtype

Oskinova

Hamann

Feldmeier

et al. 2009

ApJ

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We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or γ -ray burst. This is the first detection of X-ray emission from a WO-type star. We rule out any serendipitous X-ray sources within ≈ 1 of WR 142. WR 142 has an X-ray luminosity of L X ≈ 7 × 10 30 erg s −1 , which constitutes only 10 −8 of its bolometric luminosity. The hard X-ray spectrum suggests a plasma temperature of about 100 MK. Commonly, X-ray emission from stellar winds is attributed to embedded shocks due to the intrinsic instability of the radiation driving. From qualitative considerations we conclude that this mechanism cannot account for the hardness of the observed radiation. There are no hints for a binary companion. Therefore the only remaining, albeit speculative explanation must refer to magnetic activity. Possibly related, WR 142 seems to rotate extremely fast, as indicated by the unusually round profiles of its optical emission lines. Our detection implies that the wind of WR 142 must be relatively transparent to X-rays, which can be due to strong wind ionization, wind clumping, or nonspherical geometry from rapid rotation.

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Section: X-ray Emission From a Wo-type Star L47supporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Discovery of X-Ray Emission From the Wolf-Rayet Star Wr 142 of Oxygen Subtype

Oskinova

Hamann

Feldmeier

et al. 2009

ApJ

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“…Although the star is detected, the hot component seems to be absent or at least comparatively much cooler. Ignace et al (2003) also tentatively reported the detection in the X-ray spectrum of absorption features, interpreted as being due to K-shell absorption edges of N and Si. They argued that WR 1 is probably single contrary to WR 6 and WR 110.…”

Section: Send Offprint Requests To: E Gossetmentioning

confidence: 79%

“…Markedly puzzling in this respect is the observation of WR 1 (WN4) by Ignace et al (2003) who suspect that the Model B (1.2 keV) Model C (WR 25) hot component is absent in WR 1; they further argue that it could be the first example of an X-ray emission generated by a single WR star: a soft intrinsic emission due to shocks resulting from hydrodynamical instabilities in the wind. However, the observed count rates for WR 1 are still a factor 100 larger than our secure limit on WR 40.…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

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AnXMM-Newtonlook at the Wolf-Rayet star WR 40

Gosset¹,

Nazé²,

Claeskens³

et al. 2004

A&A

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Abstract. We present the results of an XMM-Newton observation of the field of the Wolf-Rayet star WR 40. Despite a nominal exposure of 20 ks and the high sensitivity of the satellite, the star itself is not detected: we thus derive an upper limit on its X-ray flux and luminosity. Joining this result to recent reports of a non-detection of some WC stars, we suggest that the X-ray emission from single normal Wolf-Rayet stars could often be insignificant despite remarkable instabilities in the wind. On the basis of a simple modelling of the opacity of the Wolf-Rayet wind of WR 40, we show that any X-ray emission generated in the particular zone where the shocks are supposed to be numerous will indeed have little chance to emerge from the dense wind of the Wolf-Rayet star. We also report the non-detection of the ejecta nebula RCW 58 surrounding WR 40. Concerning the field around these objects, we detected 33 X-ray sources, most of them previously unknown: we establish a catalog of these sources and cross-correlate it with catalogs of optical/infrared sources.

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X-ray spectroscopy of stars

Güdel

Nazé

2009

Astron Astrophys Rev

278

274

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Non-degenerate stars of essentially all spectral classes are soft X-ray sources. Their X-ray spectra have been important in constraining physical processes that heat plasma in stellar environments to temperatures exceeding one million degree. Low-mass stars on the cooler part of the main sequence and their pre-main sequence predecessors define the dominant stellar population in the galaxy by number. Their X-ray spectra are reminiscent, in the broadest sense, of X-ray spectra from the solar corona. The Sun itself as a typical example of a main-sequence cool star has been a pivotal testbed for physical models to be applied to cool stars. X-ray emission from cool stars is indeed ascribed to magnetically trapped hot gas analogous to the solar coronal plasma, although plasma parameters such as temperature, density, and element abundances vary widely. Coronal structure, its thermal stratification and geometric extent can also be interpreted based on various spectral diagnostics. New features have been identified in pre-main sequence stars; some of these may be related to accretion shocks on the stellar surface, fluorescence on circumstellar disks due to X-ray irradiation, or shock heating in stellar outflows. Massive, hot stars clearly dominate the interaction with the galactic interstellar medium: they are the main sources of ionizing radiation, mechanical energy and chemical enrichment in galaxies. High-energy emission permits to probe some of the most important processes at work in these stars, and put constraints on their most peculiar feature: the stellar wind. Medium and high-resolution spectroscopy have shed new light on these objects as well. Here, we review recent advances in our understanding of cool and hot stars through the study of X-ray spectra, in particular high-resolution spectra now available from XMM-Newton and CHANDRA. We address issues related to coronal

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XMM-Newton observations of the nitrogen-rich Wolf-Rayet star WR 1

Cited by 32 publications

References 37 publications

Discovery of X-Ray Emission From the Wolf-Rayet Star Wr 142 of Oxygen Subtype

Discovery of X-Ray Emission From the Wolf-Rayet Star Wr 142 of Oxygen Subtype

AnXMM-Newtonlook at the Wolf-Rayet star WR 40

X-ray spectroscopy of stars

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