X-ray diagnostics of massive star winds

Oskinova, L. M.

doi:10.1016/j.asr.2016.06.030

Cited by 20 publications

(18 citation statements)

References 201 publications

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“…Microclumping affects also the wind ionization equilibrium and therefore the strength of ultraviolet wind line profiles (Crowther et al 2002;Evans et al 2004). The inhomogeneities may be optically thick in continuum, possibly affecting the shape of X-ray line profiles (Feldmeier et al 2003;Oskinova 2016), and optically thick in lines, affecting the ultraviolet wind line profiles (Oskinova et al 2007). To proceed toward more realistic mass-loss rates on the observational side, it is necessary to understand the influence of optically thin and optically thick inhomogeneities on the observational tracers (Sundqvist et al 2010(Sundqvist et al , 2011Šurlan et al 2012Shenar et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Comoving frame models of hot star winds

Krtička

Kubát

2017

A&A

101

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We calculate global (unified) wind models of main-sequence, giant, and supergiant O stars from our Galaxy. The models are calculated by solving hydrodynamic, kinetic equilibrium (also known as NLTE) and comoving frame (CMF) radiative transfer equations from the (nearly) hydrostatic photosphere to the supersonic wind. For given stellar parameters, our models predict the photosphere and wind structure and in particular the wind mass-loss rates without any free parameters. Our predicted mass-loss rates are by a factor of 2-5 lower than the commonly used predictions. A possible cause of the difference is abandoning of the Sobolev approximation for the calculation of the radiative force, because our models agree with predictions of CMF NLTE radiative transfer codes. Our predicted mass-loss rates agree nicely with the mass-loss rates derived from observed near-infrared and X-ray line profiles and are slightly lower than mass-loss rates derived from combined UV and Hα diagnostics. The empirical mass-loss rate estimates corrected for clumping may therefore be reconciled with theoretical predictions in such a way that the average ratio between individual massloss rate estimates is not higher than about 1.6. On the other hand, our predictions are by factor of 4.7 lower than pure Hα mass-loss rate estimates and can be reconciled with these values only assuming a microclumping factor of at least eight.

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Section: Introductionmentioning

confidence: 99%

Comoving frame models of hot star winds

Krtička

Kubát

2017

A&A

101

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“…X-ray emission is a common feature among massive stars of spectral types O through early B (Oskinova 2016). In single Ostars, a soft X-ray emission is thought to be generated by intrinsic shocks in the stellar winds (Owocki et al 1988;Feldmeier et al 1997a,b).…”

Section: Introductionmentioning

confidence: 99%

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

Pillitteri¹,

Fossati²,

Castro³

et al. 2018

A&A

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Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them (∼ 10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star ρ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyzed FORS2 ESO VLT spectra of ρ Oph A taken at two epochs and detected a longitudinal component of the magnetic field of order of ∼ 500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of ρ Oph A and further constrained its age. We conclude that ρ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars.

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“…This opens up the possibility to estimate the optical depth of the winds, and hence to infer the mass loss rates (e.g., Cohen et al ). Yet, the complex interplay between contributions from plasma at different temperatures and with different locations inside the wind, on the one hand, and absorption by a clumpy cool wind, on the other, leads to quite complex situations (e.g., Oskinova ). Therefore, it is necessary to analyze the high‐resolution X‐ray spectra along with high‐resolution optical and UV spectra to achieve a consistent picture.…”

Section: What We Have Learned So Farmentioning

confidence: 99%

Perspectives for observing hot massive stars with XMM‐Newton in the years 2017–2027

Rauw

2017

Astron Nachr

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XMM-Newton has deeply changed our picture of X-ray emission of hot, massive stars. High-resolution X-ray spectroscopy as well as monitoring of these objects helped us gain a deeper insight into the physics of single massive stars with or without magnetic fields, as well as of massive binary systems, where the stellar winds of both stars interact. These observations also revealed a number of previously unexpected features that challenge our understanding of the dynamics of the stellar winds of massive stars. I briefly summarize the results obtained over the past 15 years and highlight the perspectives for the next decade. It is anticipated that coordinated (X-ray and optical or UV) monitoring and time-critical observations of either single or binary massive stars will become the most important topics in this field over the coming years. Synergies with existing or forthcoming X-ray observatories (NuStar, Swift, eROSITA) will also play a major role and will further enhance the importance of XMM-Newton in our quest for understanding the physics of hot, massive stars.

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X-ray diagnostics of massive star winds

Cited by 20 publications

References 201 publications

Comoving frame models of hot star winds

Comoving frame models of hot star winds

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

Perspectives for observing hot massive stars with XMM‐Newton in the years 2017–2027

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