Wolf-Rayet stars

Hucht, K. A. van der

doi:10.1007/bf00874055

Cited by 47 publications

(18 citation statements)

References 235 publications

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“…Also its ROSAT X-ray flux is among the larger ones for WR stars. Its X-ray luminosity excess is suggestive of a colliding-wind binary with a very long period (P ∼ > 10 yr), like WR 140 (Pollock 1989;Williams et al 1990;van der Hucht et al 1992;Corcoran et al 1995). Seward & Chlebowski (1982) derived from the Einstein (0.2-4.0 keV) data of WR 25, assuming a thermal model and d = 2.6 kpc, that L x 73.8 × 10 32 erg s −1 .…”

Section: Introductionmentioning

confidence: 97%

“…Drissen et al (1992) found optical polarization variability in WR 25 and suggested that this could be binary-induced in case of a longperiod (years) orbit. Van der Hucht et al (1992) emphasized the correlation between excess X-ray luminosities and nonthermal radio emission for a number of long-period WR binaries. At radio wavelengths, WR 25 has been detected to date only at 3 cm (Leitherer et al 1995;Chapman et al 1999).…”

Section: Introductionmentioning

confidence: 99%

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

Raassen¹,

Hucht²,

Mewe³

et al. 2003

A&A

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Abstract.We report the analysis of the first high-resolution X-ray spectra of the Wolf-Rayet (WR) object WR 25 (HD 93162, WN6ha+O4f) obtained with the eflection rating pectrometers () and the uropean hoton maging ameras (- and )  spectrometers on board the XMM-Newton satellite. The spectrum exhibits bright emission lines of the H-and Helike ions of Ne, Mg, Si and S, as well as Fe  to Fe  and Fe  lines. Line fluxes have been measured. The  and  spectra have been simultaneously fitted to obtain self-consistent temperatures, emission measures, and elemental abundances. Strong absorption by the dense WR stellar wind and the interstellar medium (ISM) is observed equivalent to N H = 7×10 21 cm −2 . Multi-temperature () fitting yields two dominant components around temperatures of 7.0 and 32 MK, respectively. The XMM intrinsic (i.e. unabsorbed, corrected for the stellar wind absorption and the absorption of ISM) X-ray luminosity of WR 25 is L x (0.5-10 keV) = 1.3 × 10 34 erg s −1 , and L x (0.5-10 keV) = 0.85 × 10 34 erg s −1 , (when correcting for the ISM only) assuming d = 3.24 kpc. The obtained chemical abundances are subsolar, except for S. This may be real, but could equally well be due to a weak coupling to the continuum, which is strongly influenced by the absorption column density and the subtracted background. The expected high N-abundance, as observed in the optical wavelength region, could not be confirmed due to the strong wind absorption, blocking out its spectral signature. The presence of the Fe  emission-line complex at ∼ 6.7 keV is argued as being indicative for colliding winds inside a WR+O binary system.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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

Raassen¹,

Hucht²,

Mewe³

et al. 2003

A&A

Self Cite

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“…W-R stars have dense yr~1) (M 0 \ 0.7È8 ] 10~5 M _ stellar winds with high terminal velocities (1000È3000 km s~1 ; Abbott & Conti 1987 ;Van der Hucht 1992). Therefore these have a signiÐcant impact on the surrounding medium ; the interaction of such stellar winds with ambient material gives rise to spectacular W-R ring nebulae.…”

Section: T He Origin Of the Hot Expanding Shellsmentioning

confidence: 99%

“…For this, we use the dimensionless parameters introduced by Tre †ers & Chu (1982), v and n, deÐned, respectively, as the ratio of the observed kinetic energy in the shell to the total kinetic energy injected by the wind and the ratio of the observed momentum in the shell to the total injected wind momentum. For the typical wind parameters of the W-R stars in the Galaxy yr~1 and a terminal veloc-(M 0 D 3 ] 10~5 M _ ity of 1000 km s~1 ; Abbott & Conti 1987 ;Van der Hucht 1992), the total momentum and kinetic energy injected by the wind over the lifetime of the shells are D2 ] 103 M _ km s~1 and D106…”

Section: T He Origin Of the Hot Expanding Shellsmentioning

confidence: 99%

Hot Expanding Shells in the Envelope of the Sagittarius B2 Molecular Cloud

Martı́n-Pintado

Gaume

Rodriguez‐fernandez

et al. 1999

ApJ

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We present high-resolution (3A) maps of the (3, 3) and (4, 4) lines of toward the southern part of NH 3 the molecular envelope of the Sagittarius B2 star-forming region. These maps reveal, for the Ðrst time, that the morphology of the hot gas in the Sgr B2 envelope is dominated by at least six rings, two arcs, and a Ðlament. The sizes of the rings are between 1 and 2.6 pc and their thicknesses between 0.2 and 0.4 pc. Most of the gas in the rings is warm, with kinetic temperatures, of 40È70 K, although some parts T k , of the low-velocity rings reach temperatures larger than 100 K. These hot rings and arcs represent regions of enhanced density and/or enhanced abundance in the Sgr B2 envelope. Some of the H 2 NH 3 hot rings show radial velocity gradients, which suggests that the rings and arcs correspond to threedimensional shells expanding at velocities of D6È10 km s~1. The walls of the hot shells are highly clumped and contain unresolved condensations in the line maps. There are two kinds of unre-([1A) solved condensations : those appearing in the (3, 3) line maps with only weak emission in the (4, 4) line and those with rather strong emission in the (4, 4) line compared with that of the (3, 3) line. For the Ðrst kind, we identify six condensations in the (3, 3) line maps that have brightness temperatures larger NH 3 than the kinetic temperatures. It is likely that these are newly found masers. We also Ðnd that NH 3 other masers in the region such as class II and masers are very well correlated in veloc-CH 3 OH H 2 CO ity and position with the hot shells. The large number of masers observed in the hot shells can be explained as a result of the combination of high abundance of volatile molecules like and NH 3, CH 3 OH, (produced by hot temperature and/or shock chemistry) and sufficient velocity coherence at the H 2 CO edges of the expanding shells. For the second kind of condensations, we have identiÐed three compact sources in the walls of the shells that are hot K) and have high densities cm~3). (T k Z 300 H 2 (Z106È107 These exhibit characteristics similar to those of the hot cores associated with newly formed massive stars. The inferred dust luminosity for the hot cores is at least 105 similar to the Orion A hot core. The L _ , high luminosity of the hot cores and the lack of associated radio continuum emission indicates that these are internally heated and very likely associated with the dense circumstellar material surrounding newly formed stars. The detection of hot cores suggests that massive star formation is not restricted to only Sgr B2N and Sgr B2M but is also taking place in the envelope of Sgr B2. Very likely, this star formation has been triggered by the expanding bubbles that produce the shells seen in the inversion lines. We NH 3 discuss the possible origin of these hot shells. We Ðnd that a wind-blown bubble driven by typical Galactic Wolf-Rayet stars could account for the kinetic energies and the momenta observed in the hot shells. A cluster containing massive evolved stars such as the ...

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“…There are some uncertainties about the distances of ζ Pup and γ 2 Velorum. The estimated Hipparcos distance to the Wolf–Rayet WC8+O spectroscopic binary γ 2 Velorum is 258 −31 +41 pc and to the O4I(n)f star ζ Pup it is 429 −77 +120 pc (van der Hucht et al 1997). However, Pozzo et al (2000) argued that the distance to the γ 2 Velorum may be the same as that for the Vela OB2 association.…”

Section: Introductionmentioning

confidence: 98%

Kinematics of the young stellar objects associated with the cometary globules in the Gum Nebula

Choudhury

Bhatt

2009

Monthly Notices of the Royal Astronomical Society

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An analysis of the proper motion measurements of the young stellar objects (YSOs) associated with the cometary globules (CGs) in the Gum Nebula is presented. While earlier studies based on the radial‐velocity measurements of the CGs suggested expansion of the system of the CGs, the observed proper motion of the YSOs shows no evidence for expansion. In particular, the kinematics of two YSOs embedded in CGs are inconsistent with the supernova explosion of the companion of ζ Pup, about 1.5 Myr ago being the cause of the expansion of the system of the CGs. YSOs associated with the CGs share the average proper motion of the member stars of the Vela OB2 association. A few YSOs that have relatively large proper motions are found to show relatively low infrared excesses.

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Wolf-Rayet stars

Cited by 47 publications

References 235 publications

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

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

Hot Expanding Shells in the Envelope of the Sagittarius B2 Molecular Cloud

Kinematics of the young stellar objects associated with the cometary globules in the Gum Nebula

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