Mass loss in main-sequence B stars

Krtička, Jiřı́

doi:10.1051/0004-6361/201321980

Cited by 118 publications

(142 citation statements)

References 76 publications

(125 reference statements)

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“…or even smaller (10 −7 M yr −1 ) for B stars (Krticka 2014). The corresponding stellar mass should be >20 M .…”

Section: Origin Of the Absorption Gasmentioning

confidence: 90%

UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

Zhou

Jiang

et al. 2015

ApJ

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We report the identification of an unusual absorption-line system in the quasar SDSS J080248.18 + 551328.9 and present a detailed study of the system, incorporating follow-up optical and near-IR spectroscopy. A few tens of absorption lines are detected, including He i*, Fe ii*, and Ni ii*, which arise from metastable or excited levels, as well as resonant lines in Mg i, Mg ii, Fe ii, Mn ii, and Ca ii. All of the isolated absorption lines show the same profile of width Δv ∼ 1500 km s −1 centered at a common redshift as that of the quasar emission lines, such as [O ii], [S ii], and hydrogen Paschen and Balmer series. With narrow Balmer lines, strong optical Fe ii multiplets, and weak [O iii] doublets, its emission-line spectrum is typical for that of a narrow-line Seyfert 1 galaxy (NLS1). We have derived reliable measurements of the gas-phase column densities of the absorbing ions/levels. Photoionization modeling indicates that the absorber has a density of n H ∼ (1.0-2.5) × 10 5 cm −3 and a column density of N H ∼ (1.0-3.2) × 10 21 cm −2 and is located at R ∼ 100-250 pc from the central supermassive black hole. The location of the absorber, the symmetric profile of the absorption lines, and the coincidence of the absorptionand emission-line centroid jointly suggest that the absorption gas originates from the host galaxy and is plausibly accelerated by stellar processes, such as stellar winds and/or supernova explosions. The implications for the detection of such a peculiar absorption-line system in an NLS1 are discussed in the context of coevolution between supermassive black hole growth and host galaxy buildup.

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“…or even smaller (10 −7 M yr −1 ) for B stars (Krticka 2014). The corresponding stellar mass should be >20 M .…”

Section: Origin Of the Absorption Gasmentioning

confidence: 90%

UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

Zhou

Jiang

et al. 2015

ApJ

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“…The values ofṀ act , listed in Table 4, are in good agreement with those obtained from the UV spectral analyses of HR 7355 (see Sec. 2) and other B-type stars with similar spectral types (Prinja 1989;Oskinova et al 2011;Krticka 2014) The indirect evaluation of the linear extension of the radio emitting region is also useful for estimating the brightness temperature of HR 7355. The average flux densities for HR 7355 are ≈ 15.5 mJy, in the frequency range 6-44 GHz.…”

Section: The Magnetosphere Of Hr 7355mentioning

confidence: 99%

The detection of variable radio emission from the fast rotating magnetic hot B-star HR 7355 and evidence for its X-ray aurorae

Leto

Trigilio

Oskinova

et al. 2017

Monthly Notices of the Royal Astronomical Society

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In this paper we investigate the multiwavelengths properties of the magnetic early B-type star HR 7355. We present its radio light curves at several frequencies, taken with the Jansky Very Large Array, and X-ray spectra, taken with the XMM-Newton X-ray telescope. Modeling of the radio light curves for the Stokes I and V provides a quantitative analysis of the HR 7355 magnetosphere. A comparison between HR 7355 and a similar analysis for the Ap star CU Vir, allows us to study how the different physical parameters of the two stars affect the structure of the respective magnetospheres where the non-thermal electrons originate. Our model includes a cold thermal plasma component that accumulates at high magnetic latitudes that influences the radio regime, but does not give rise to X-ray emission. Instead, the thermal X-ray emission arises from shocks generated by wind stream collisions close to the magnetic equatorial plane. The analysis of the X-ray spectrum of HR 7355 also suggests the presence of a non-thermal radiation. Comparison between the spectral index of the power-law X-ray energy distribution with the non-thermal electron energy distribution indicates that the non-thermal X-ray component could be the auroral signature of the non-thermal electrons that impact the stellar surface, the same non-thermal electrons that are responsible for the observed radio emission. On the basis of our analysis, we suggest a novel model that simultaneously explains the X-ray and the radio features of HR 7355 and is likely relevant for magnetospheres of other magnetic early type stars.

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“…The failed convergence of the models indicates that the radiative force is too weak to drive a wind. To test this, we calculated additional models with a fixed hydrodynamical structure, where we compared the radiative force with the gravity for four different fixed mass-loss rates equal to 10 −12 M ⊙ yr −1 , 10 −13 M ⊙ yr −1 , and 10 −14 M ⊙ yr −1 (for details see Krtička 2014). In all these models, the radiative force was lower than the gravity force.…”

Section: Calculated Wind Modelsmentioning

confidence: 99%

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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Mass loss in main-sequence B stars

Cited by 118 publications

References 76 publications

UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

The detection of variable radio emission from the fast rotating magnetic hot B-star HR 7355 and evidence for its X-ray aurorae

Stellar wind models of subluminous hot stars

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