ASCA solid state imaging spectrometer observations of O stars

Corcoran, M. F.; Waldron, W. L.; Macfarlane, J. J.; Chen, W.; Pollock, A. M. T.; Torii, K.; Kitamoto, S.; Miura, Noriaki; Egoshi, M.; Ohno, Yasuhide

doi:10.1086/187641

Cited by 37 publications

(38 citation statements)

References 3 publications

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“…Their uncertainties are supposed to have the same relative values as those for the emission measures because the luminosity is mostly determined by the emission measures in this temperature range, and therefore L X ∝ EM. The total luminosities (summed over the three temperature components) in other energy bands (0.5-4 keV, 0.1-2.4 keV, and 0.4-4 keV) for Einstein, ROSAT, ASCA given in the papers by Cassinelli & Swank (1983), Haberl &White (1993), andCorcoran et al (1994), respectively, do agree with our values when taking differences in interstellar absorption or distance into account. The abundances are relative to solar photospheric values (Lodders et al 2009).…”

Section: A 3-t Modelsupporting

confidence: 88%

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The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

Raassen

Pollock

2013

A&A

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Aims. We analyze the high-resolution X-ray spectrum of the supergiant O-star δ Orionis (O9.5II) with line ratios of He-like ions and a thermal plasma model, and we examine its variability. Methods. The O-supergiant δ Ori was observed in the wavelength range 5-175 Å by the X-ray detector HRC-S in combination with the grating LETG aboard Chandra. We studied the He-like ions in combination with the UV-radiation field to determine local plasma temperatures and to establish the distance of the X-ray emitting ions to the stellar surface. We measured individual lines by means of Gaussian profiles, folded through the response matrix, to obtain wavelengths, line fluxes, half widths at half maximum (HWHM) and line shifts to characterize the plasma. We consider multitemperature models in collisional ionization equilibrium (CIE) to determine temperatures, emission measures, and abundances.Results. Analysis of the He-like triplets extended to N vi and C v implies ionization stratification with the hottest plasma to be found within a few stellar radii 3 R * (Mg xi) and the coolest farther out, far beyond the acceleration zone, up to 49 R * (N vi) and 75 R * (C v).The observed temperatures cover a range from about 0.1 to 0.7 keV, i.e., 1-8 MK. The X-ray luminosity (L x ) is ∼1.5 × 10 32 erg/s in the range from 0.07 to 3 keV covered by LETGS. Velocity widths of about 1040 km s −1 have been determined.

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Section: A 3-t Modelsupporting

confidence: 88%

“…The spectrum of δ Ori was studied in X-rays with earlier satellites by Cassinelli & Swank (1983), Haberl & White (1993), and Corcoran et al (1994) and most recently at high resolution A&A 550, A55 (2013) References. (a) Van Leeuwen (2007).…”

Section: Introductionmentioning

confidence: 99%

The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

Raassen

Pollock

2013

A&A

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“…The ROSAT All-Sky Survey detected several X-ray sources identified with new T Tauri stars Neuhäuser et al 1995Neuhäuser et al , 1997Alcalá et al 1996;Magazzu et al 1997). The central hot star was observed with ASCA by Corcoran et al (1994) who found a hard spectrum with temperatures of 0.3 and 2.3 keV. Recently, Barrado et al (2011) has performed an XMM-Newton observation of two fields to the east and west of the cluster centre, partially overlapping our observation.…”

Section: Introductionsupporting

confidence: 68%

XMM-Newtonobservations of the young open cluster aroundλ Orionis

Franciosini

Sacco

2011

A&A

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Aims. We studied the X-ray properties of the young (∼1−8 Myr) open cluster around the hot (O8 III) star λ Ori and compared them with those of the similarly-aged σ Ori cluster to investigate possible effects of the different ambient environment. Methods. We analysed an XMM-Newton observation of the cluster using EPIC imaging and low-resolution spectral data. We studied the variability of detected sources, and performed a spectral analysis of the brightest sources in the field using multi-temperature models.Results. We detected 167 X-ray sources, of which 58 are identified with known cluster members and candidates, from massive stars down to low-mass stars with spectral types ∼M5.5. Another 23 sources were identified with new possible photometric candidates. Late-type stars have a median log L X /L bol ∼ −3.3, close to the saturation limit. Variability was observed in ∼35% of late-type members or candidates, including six flaring sources. The emission from the central hot star λ Ori is dominated by plasma at 0.2−0.3 keV, with a weaker component at 0.7 keV, consistently with a wind origin. The coronae of late-type stars can be described by two plasma components with temperatures T 1 ∼ 0.3−0.8 keV and T 2 ∼ 0.8−3 keV, and subsolar abundances Z ∼ 0.1−0.3 Z , similar to what is found in other star-forming regions and associations. No significant difference was observed between stars with and without circumstellar discs, although the smallness of the sample of stars with discs and accretion does not allow us to draw definitive conclusions. Conclusions. The X-ray properties of λ Ori late-type stars are comparable to those of the coeval σ Ori cluster, suggesting that stellar activity in λ Ori has not been significantly affected by the different ambient environment.

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“…Unacceptable fits of HD 104237 and HD 200775 seem to be caused by small structures in the spectra, which might be unknown emission lines or absorptions. The best-fit temperature ranges between kT $ 1 5 keV, which is significantly higher than the X-ray temperature of MS OB stars (kT < 1 keV; e.g., Corcoran et al 1994). …”

Section: Spectramentioning

confidence: 87%

X‐Ray Study of Herbig Ae/Be Stars

Hamaguchi

Yamauchi

Koyama

2005

ApJ

132

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We present ASCA results of intermediate-mass pre-main-sequence ( PMS) stars, or Herbig Ae/Be (HAeBe) stars. Among the 35 ASCA pointed sources, we detect 11 plausible X-ray counterparts. X-ray luminosities of the detected sources in the 0.5-10 keV band are in the range of log L X $ 30 32 ergs s À1 , which is systematically higher than those of low-mass PMS stars. This fact suggests that the contribution of a possible low-mass companion is not large. Most of the bright sources show significant time variation; in particular, two HAeBe stars-MWC 297 and TY CrA-exhibit flarelike events with long decay timescales (e-folding time $10À60 ks). These flare shapes are similar to those of low-mass PMS stars. The X-ray spectra are successfully reproduced by an absorbed one-or two-temperature thin-thermal plasma model. The temperatures are in the range of kT $ 1 5 keV, significantly higher than those of main-sequence OB stars (kT < 1 keV). These X-ray properties are not explained by wind-driven shocks, but are more likely due to magnetic activity. On the other hand, the plasma temperature rises as absorption column density increases or as HAeBe stars ascend to earlier phases. The X-ray luminosity reduces after stellar age of a few times 10 6 yr. X-ray activity may be related to stellar evolution. The age of the activity decay is apparently near the termination of jet or outflow activity. We thus hypothesize that magnetic activity originates from the interaction of the large-scale magnetic fields coupled to the circumstellar disk. We also discuss differences in X-ray properties between HAeBe stars and main-sequence OB stars.

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ASCA solid state imaging spectrometer observations of O stars

Cited by 37 publications

References 3 publications

The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

XMM-Newtonobservations of the young open cluster aroundλ Orionis

X‐Ray Study of Herbig Ae/Be Stars

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