X-ray irradiation of the winds in binaries with massive components

Krtička, Jiřı́; Kubát, Jiřı́; Krtičková, Iva

doi:10.1051/0004-6361/201525637

Cited by 34 publications

(54 citation statements)

References 150 publications

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“…However, for stronger X-ray irradiation, the ions with a lower charge disappear, which leads to the decrease of the radiative force. This may even lead to wind inhibition in the direction towards the compact companion (Krtička et al 2015). This explains the trends given in Fig.…”

Section: Compact Companions: the Effect Of X-ray Irradiationmentioning

confidence: 63%

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Stellar wind models of subluminous hot stars

Krtička

Kubát

Krtičková

2016

A&A

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1Ú stav teoretické fyziky a astrofyziky, Masarykova univerzita, Kotlářská 2, CZ-611 37 Brno, Czech Republic 2 Astronomickýústav, Akademie vědČeské republiky, Fričova 298, CZ-251 65 Ondřejov, Czech Republic Received ABSTRACTContext. Mass-loss rate is one of the most important stellar parameters. Mass loss via stellar winds may influence stellar evolution and modifies stellar spectrum. Stellar winds of subluminous hot stars, especially subdwarfs, have not been studied thoroughly. Aims. We aim to provide mass-loss rates as a function of subdwarf parameters and to apply the formula for individual subdwarfs, to predict the wind terminal velocities, to estimate the influence of the magnetic field and X-ray ionization on the stellar wind, and to study the interaction of subdwarf wind with mass loss from Be and cool companions. Methods. We used our kinetic equilibrium (NLTE) wind models with the radiative force determined from the radiative transfer equation in the comoving frame (CMF) to predict the wind structure of subluminous hot stars. Our models solve stationary hydrodynamical equations, that is the equation of continuity, equation of motion, and energy equation and predict basic wind parameters. Results. We predicted the wind mass-loss rate as a function of stellar parameters, namely the stellar luminosity, effective temperature, and metallicity. The derived wind parameters (mass-loss rates and terminal velocities) agree with the values derived from the observations. The radiative force is not able to accelerate the homogeneous wind for stars with low effective temperatures and high surface gravities. We discussed the properties of winds of individual subdwarfs. The X-ray irradiation may inhibit the flow in binaries with compact components. In binaries with Be components, the winds interact with the disk of the Be star. Conclusions. Stellar winds exist in subluminous stars with low gravities or high effective temperatures. Despite their low mass-loss rates, they are detectable in the ultraviolet spectrum and cause X-ray emission. Subdwarf stars may lose a significant part of their mass during the evolution. The angular momentum loss in magnetic subdwarfs with wind may explain their low rotational velocities. Stellar winds are especially important in binaries, where they may be accreted on a compact or cool companion.

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Section: Compact Companions: the Effect Of X-ray Irradiationmentioning

confidence: 63%

“…We studied the effect of X-ray irradiation on the subdwarf wind in a similar way to our earlier wind-irradiation studies (Krtička et al 2015), i.e., in the direction to the compact companion (see Fig. 7).…”

Section: Compact Companions: the Effect Of X-ray Irradiationmentioning

confidence: 99%

Stellar wind models of subluminous hot stars

Krtička

Kubát

Krtičková

2016

A&A

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“…To make the problem tractable, the modelling either simplifies the radiative driving enabling us to unveil the large-scale three-dimensional (3D) flow structure (Blondin et al 1990), or it solves the wind equations in spherical symmetry (1D) and provides detailed calculation of the radiative force. The latter approach (Krtička et al 2012(Krtička et al , 2015Sander et al 2018) is able to estimate binary parameters for which the influence of X-rays becomes important. Wind models with detailed radiative force also show the decrease of the wind velocity due to X-ray irradiation, which was detected observationally (van Loon et al 2001;Watanabe et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Wind inhibition by X-ray irradiation in HMXBs: the influence of clumping and the final X-ray luminosity

Krtička

Kubát

Krtičková

2018

A&A

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1 Ústav teoretické fyziky a astrofyziky, Masarykova univerzita, Kotlářská 2, CZ-611 37 Brno, Czech Republic 2 Astronomický ústav, Akademie vědČeské republiky, Fričova 298, CZ-251 65 Ondřejov, Czech Republic Received ABSTRACTContext. In wind-powered X-ray binaries, the radiatively driven stellar wind from the primary may be inhibited by the X-ray irradiation. This creates the feedback that limits the X-ray luminosity of the compact secondary. Wind inhibition might be weakened by the effect of small-scale wind inhomogeneities (clumping) possibly affecting the limiting X-ray luminosity. Aims. We study the influence of X-ray irradiation on the stellar wind for different radial distributions of clumping. Methods. We calculate hot star wind models with external irradiation and clumping using our global wind code. The models are calculated for different parameters of the binary. We determine the parameters for which the X-ray wind ionization is so strong that it leads to a decrease of the radiative force. This causes a decrease of the wind velocity and even of the mass-loss rate in the case of extreme X-ray irradiation. Results. Clumping weakens the effect of X-ray irradiation because it favours recombination and leads to an increase of the wind massloss rate. The best match between the models and observed properties of high-mass X-ray binaries (HMXBs) is derived with radially variable clumping. We describe the influence of X-ray irradiation on the terminal velocity and on the mass-loss rate in a parametric way. The X-ray luminosities predicted within the Bondi-Hoyle-Lyttleton theory agree nicely with observations when accounting for X-ray irradiation. Conclusions. The ionizing feedback regulates the accretion onto the compact companion resulting in a relatively stable X-ray source. The wind-powered accretion model can account for large luminosities in HMXBs only when introducing the ionizing feedback. There are two possible states following from the dependence of X-ray luminosity on the wind terminal velocity and mass-loss rate. One state has low X-ray luminosity and a nearly undisturbed wind, and the second state has high X-ray luminosity and exhibits a strong influence of X-rays on the flow.

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“…Clumping factors are f cl = 5.0 (red), f cl = 6.0 (blue) and f cl = 7.0 (green). Resulting FASTWIND spectra for HD 164794 with T eff = 43.8 kK, log g = 3.92, R * /R = 13.1 (stellar parameters taken fromKrtička et al 2015)Ṁ = 2.3 × 10 −6 M yr −1 . Clumping factors are f cl = 5.0 (red), f cl = 2.0 (blue) and f cl = 1.0 (homogeneous, green).…”

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Self-consistent Solutions for Line-driven Winds of Hot Massive Stars: The m-CAK Procedure

Gormaz-Matamala

Curé

Cidale

et al. 2019

ApJ

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Massive stars present strong stellar that which are described by the radiation driven wind theory. Accurate mass-loss rates are necessary to properly describe the stellar evolution across the Hertzsprung-Russel Diagram. We present a self-consistent procedure that coupled the hydrodynamics with calculations of the line-force, giving as results the line-force parameters, the velocity field, and the mass-loss rate. Our calculations contemplate the contribution to the line-force multiplier from more than ∼ 900, 000 atomic transitions, an NLTE radiation flux from the photosphere and a quasi-LTE approximation for the occupational numbers. A full set of line-force parameters for T eff ≥ 32, 000 K, surface gravities higher than 3.4 dex for two different metallicities are presented, with their corresponding wind parameters (terminal velocities and mass-loss rates). The already known dependence of line-force parameters on effective temperature is enhanced by the dependence on log g. The terminal velocities present a stepper scaling relation with respect to the escape velocity, this might explain the scatter values observed in the hot side of the bistability jump. Moreover, a comparison of selfconsistent mass-loss rates with empirical values shows a good agreement. Self-consistent wind solutions are used as input in FASTWIND to calculate synthetic spectra. We show, comparing with the observed spectra for three stars, that varying the clumping factor, the synthetic spectra rapidly converge into the neighbourhood region of the solution. It is important to stress that our self-consistent procedure significantly reduces the number of free parameters needed to obtain a synthetic spectrum.

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X-ray irradiation of the winds in binaries with massive components

Cited by 34 publications

References 150 publications

Stellar wind models of subluminous hot stars

Stellar wind models of subluminous hot stars

Wind inhibition by X-ray irradiation in HMXBs: the influence of clumping and the final X-ray luminosity

Self-consistent Solutions for Line-driven Winds of Hot Massive Stars: The m-CAK Procedure

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