Testing magnetically confined wind shock models for β Cephei using XMM-Newton and 
Chandra phase-resolved X-ray observations

Favata, F.; Neiner, C.; Testa, Paola; Hussain, G. A. J.; Sanz-Forcada, J.

doi:10.1051/0004-6361:20078529

Cited by 35 publications

(66 citation statements)

References 42 publications

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“…The Chandra spectra show emission lines that are broader than for coronal sources, but surprisingly narrow for a stellar wind shock scenario; together with the presence of hard emission and X-ray plasma locations at several stellar radii also make τ Sco a candidate for MCWS generated X-ray emission. Another example is the pulsating, hot magnetic giant star β Cep, where Favata et al (2009) again find a good agreement between the predictions from the dynamic MCWS model and X-ray observations. It does again exhibit no flares, and with temperatures well below 10 MK the X-ray emission is remarkably soft, despite its X-ray brightness of log L X = 4 × 10 30 erg s −1 .…”

Section: What About Hotter Magnetic Stars?supporting

confidence: 54%

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: What About Hotter Magnetic Stars?supporting

confidence: 54%

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

Robrade

Schmitt

2011

A&A

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“…The X-ray lines thus generally appear quite narrow, confirming the results found for other B stars (e.g. Waldron & Cassinelli 2007;Cohen et al 2008;Favata et al 2009). …”

Section: Line Fitssupporting

confidence: 86%

“…In any case, not many comparisons between X-ray and optical abundances can be found in the literature. For HD 205021, Favata et al (2009) derived O, Si, and Fe abundances that are depleted compared to photospheric abundances. Nazé & Rauw (2008) confirmed the depletion in C and O of HD 93030 as well as its enrichment in N reported in the optical domain by Hubrig et al (2008).…”

Section: Global Fitsmentioning

confidence: 98%

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B stars seen at high resolution by XMM-Newton

Cazorla

Nazé

2017

A&A

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We report on the properties of 11 early B stars observed with gratings on board XMM-Newton and Chandra, thereby doubling the number of B stars analysed at high resolution. The spectra typically appear soft, with temperatures of 0.2-0.6 keV, and moderately bright (log[L X /L BOL ] ∼ −7) with lower values for later type stars. In line with previous studies, we also find an absence of circumstellar absorption, negligible line broadening, no line shift, and formation radii in the range 2 -7 R ⋆ . From the X-ray brightnesses, we derived the hot mass-loss rate for each of our targets and compared these values to predictions or values derived in the optical domain: in some cases, the hot fraction of the wind can be non-negligible. The derived X-ray abundances were compared to values obtained from the optical data, with a fair agreement found between them. Finally, half of the sample presents temporal variations, either in the long-term, short-term, or both. In particular, HD 44743 is found to be the second example of an X-ray pulsator, and we detect a flare-like activity in the binary HD 79351, which also displays a high-energy tail and one of the brightest X-ray emissions in the sample.

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“…No -the mass-loss rate is too low for any accumulation to occur; no Hα emission is expected (example: β Cep; see Favata et al 2009). …”

Section: The Magnetosphere Zoomentioning

confidence: 99%

Modeling the winds and magnetospheres of active OB stars

Townsend

2010

Proc. IAU

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Abstract. After briefly reviewing the theory behind the radiative line-driven winds of OB stars, I examine the processes that can generate structure in them; these include both intrinsic instabilities, and surface perturbations such as pulsation and rotation. I then delve into wind channeling and confinement by magnetic fields as a mechanism for forming longer-lived circumstellar structures. With a narrative that largely follows the historical progression of the field, I introduce the key insights and results that link the first detection of a magnetosphere, over three decades ago, to the recent direct measurement of magnetic braking in a number of active OB stars.

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Testing magnetically confined wind shock models for β Cephei using XMM-Newton and Chandra phase-resolved X-ray observations

Cited by 35 publications

References 42 publications

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

B stars seen at high resolution by XMM-Newton

Modeling the winds and magnetospheres of active OB stars

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Testing magnetically confined wind shock models for β Cephei using XMM-Newton and Chandra phase-resolved X-ray observations

Cited by 35 publications

References 42 publications

New X-ray observations of IQ Aurigae andα2 Canum Venaticorum

New X-ray observations of IQ Aurigae andα2 Canum Venaticorum

B stars seen at high resolution by XMM-Newton

Modeling the winds and magnetospheres of active OB stars

Contact Info

Product

Resources

About

New X-ray observations of IQ Aurigae andα² Canum Venaticorum

New X-ray observations of IQ Aurigae andα² Canum Venaticorum