ChandraHETGS Multiphase Spectroscopy of the Young Magnetic O Starθ1Orionis C

Gagné, Marc; Oksala, M. E.; Cohen, David H.; Tonnesen, Stephanie; ud‐Doula, Asif; Owocki, S. P.; Townsend, R. H. D.; Macfarlane, J. J.

doi:10.1086/430873

Cited by 215 publications

(306 citation statements)

References 49 publications

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“…Significant roughly sinusoidal shaped rotational modulation would be present if the star partially occults X-ray emitting material depending on rotational phase or when a disk around the star is viewed from different angles. An example are the X-ray brightness variations of the massive magnetic star θ 1 Ori C (Gagné et al 2005). This model assumes cylindrical symmetry for the system as is likely appropriate for a star with a disk and as is commonly observed when, e.g.…”

Section: Source Detections Light Curves and A Flarementioning

confidence: 99%

“…A well studied example is the magnetic O5 star θ 1 Ori C, where Gagné et al (2005) find that the dynamic MCWS model describes the X-ray properties of the star very well. It has an average X-ray luminosity of L X = 1×10 33 erg s −1 and using among other diagnostics f /i-line ratios, they conclude that the X-ray emitting plasma is located at distances of only 0.2 .…”

Section: What About Hotter Magnetic Stars?mentioning

confidence: 99%

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New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Robrade

Schmitt

2011

A&A

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Aims. We re-examine the scenario of X-ray emission from magnetically confined/channeled wind shocks (MCWS) for Ap/Bp stars, a model originally developed to explain the ROSAT detection of the A0p star IQ Aur. Methods. We present new X-ray observations of the A0p stars α 2 CVn (Chandra) and IQ Aur (XMM-Newton) and discuss our findings in the context of X-ray generating mechanisms of magnetic, chemically peculiar intermediate mass stars. Results. The X-ray luminosities of IQ Aur with log L X = 29.6 erg s −1 and α 2 CVn with log L X 26.0 erg s −1 differ by at least three orders of magnitude, although both are A0p stars. By studying a sample of comparison stars, we find that X-ray emission is preferably generated by more massive objects such as IQ Aur. Besides a strong, cool plasma component, significant amounts of hot (>10 MK) plasma are present during the quasi-quiescent phase of IQ Aur; moreover, diagnostics of the UV sensitive f /i line ratio in He-like O vii triplet point to X-ray emitting regions well above the stellar surface of IQ Aur. In addition we detect a large flare from IQ Aur with temperatures up to ∼100 MK and a peak X-ray luminosity of log L X ≈ 31.5 erg s −1 . The flare, showing a fast rise and e-folding decay time of less than half an hour, originates in a fairly compact structure and is accompanied by a significant metallicity increase. The X-ray properties of IQ Aur cannot be described by wind shocks only and require the presence of magnetic reconnection. This is most evident in the, to our knowledge, first X-ray flare reported from an A0p star. Conclusions. Our study indicates that the occurrence the of X-ray emission in A0p stars generated by magnetically channeled wind shocks depends on stellar properties such as luminosity, which promote a high mass loss rate, whereas magnetic field configuration and transient phenomena refine their appearance. While we cannot rule out unknown close companions, the X-ray emission from IQ Aur can be described consistently in the MCWS scenario, in which the very strong magnetic confinement of the stellar wind has led to the build-up of a rigidly rotating disk around the star, where magnetic reconnection and centrifugal breakout events occur.

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Section: Source Detections Light Curves and A Flarementioning

confidence: 99%

Section: What About Hotter Magnetic Stars?mentioning

confidence: 99%

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Robrade

Schmitt

2011

A&A

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“…Low-mass young stellar objects (YSOs) have been known as strong hard X-ray emitters due to flares caused by magnetic reconnection ( Feigelson & Montmerle 1999). It has recently been proposed that magnetic activity may be responsible for the hard emission seen in some young O stars (Schulz et al 2003;Gagné et al 2005;Stelzer et al 2005). There is also a possibility that the hard extended emission may be a special case of the wind-blown bubble employed to explain the soft diffuse emission.…”

Section: Introductionmentioning

confidence: 99%

Hard X‐Rays from Ultracompact HiiRegions in W49A

Tsujimoto

Hosokawa

Feigelson

et al. 2006

ApJ

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We report the Chandra detection of hard X-ray emission from the Welch ring in W49A, an organized structure of ultracompact (UC ) H ii regions containing a dozen nascent early-type stars. Two UC H ii regions are associated with hard X-ray emission in a deep Advanced CCD Imaging Spectrometer (ACIS) image exposed for $96.7 ks. One of the two X-ray sources has no near-infrared counterpart and is extended by $5 00 , or $0.3 pc, at a distance of $11.4 kpc, which is spatially aligned with the cometary radio continuum emission associated with the UC H ii region. The X-ray spectrum of the emission, when fit with a thermal model, indicates a heavily absorbed plasma with extinction of $5 ; 10 23 cm À2 , temperature $7 keV, and X-ray luminosity in the 3.0Y8.0 keV band of $3;10 33 ergs s À1 . Both the luminosity and the size of the emission resemble the extended hard emission found in UC H ii regions in Sagittarius B2, yet they are smaller by an order of magnitude than the emission found in massive star clusters such as NGC 3603. Three possibilities are discussed for the cause of the hard extended emission in the Welch ring: an ensemble of unresolved point sources, shocked interacting winds of the young O stars, and a wind-blown bubble interacting with ambient cold matter. Subject headingg s: H ii regions -ISM: individual ( W49A) -radio continuum: ISM -stars: early-type -X-rays: ISM

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“…These three stars do not have massive, spectroscopic companions, and their L X is too high to be produced by unseen, lower-mass pre-mainsequence (PMS) companions. For these three we consider two hypotheses: a more distant massive companion (as is the case for HD 93129A), or magnetically confined wind shocks (as in θ 1 Ori C, Gagné et al 2005). …”

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confidence: 99%

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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ChandraHETGS Multiphase Spectroscopy of the Young Magnetic O Starθ¹Orionis C

Cited by 215 publications

References 49 publications

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Hard X‐Rays from Ultracompact HiiRegions in W49A

The Chandra survey of Carina OB stars

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ChandraHETGS Multiphase Spectroscopy of the Young Magnetic O Starθ1Orionis C

Cited by 215 publications

References 49 publications

New X-ray observations of IQ Aurigae andα2 Canum Venaticorum

New X-ray observations of IQ Aurigae andα2 Canum Venaticorum

Hard X‐Rays from Ultracompact HiiRegions in W49A

The Chandra survey of Carina OB stars

Contact Info

Product

Resources

About

ChandraHETGS Multiphase Spectroscopy of the Young Magnetic O Starθ¹Orionis C

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

New X-ray observations of IQ Aurigae andα² Canum Venaticorum