Wind suppression by X-rays in Cygnus X-3

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http://hdl.handle.net/10138/332341

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Vilhu , O , Kallman , T R , Koljonen , K I I & Hannikainen , D C 2021 , ' Wind suppression by X-rays in Cygnus X-3 ' , Astronomy & Astrophysics , vol. 649 , 176 . https://doi.org/10.1051/0004-6361/202140620

Title: Wind suppression by X-rays in Cygnus X-3
Author: Vilhu, Osmi; Kallman, T. R.; Koljonen, K. I. I.; Hannikainen, D. C
Contributor organization: Department of Physics
Date: 2021-06-01
Language: eng
Number of pages: 10
Belongs to series: Astronomy & Astrophysics
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202140620
URI: http://hdl.handle.net/10138/332341
Abstract: Context. The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star.Aims. We aim to estimate how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3.Methods. We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott & Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. We solved the wind equations at different orbital angles from the line joining the stars and took the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We compared them to those obtained from observations.Results. We found that the ionization potentials of the ions contributing the most to the line force fall in the extreme-UV region (100-230 angstrom). If the flux in this region is high, the line force is weak, and consequently, the wind velocity is low. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping, this correlation disappears. We compared the XSTAR method used here with the comoving frame method and found that they agree reasonably well with each other.Conclusions. We show that soft X-rays in the extreme-UV region from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2-3) solar masses.
Subject: 114 Physical sciences
115 Astronomy, Space science
binaries: general
stars: winds
outflows
stars: black holes
accretion
accretion disks
radiative transfer
MASS-LOSS RATES
STELLAR WINDS
CYG X-3
RADIATIVE-TRANSFER
SPECTRAL-ANALYSES
STARS
MODELS
ACCRETION
I.
Peer reviewed: Yes
Rights: unspecified
Usage restriction: openAccess
Self-archived version: publishedVersion


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