X-ray irradiation of the stellar wind in HMXBs with B supergiants: Implications for ULXs

Warning

This publication doesn't include Faculty of Arts. It includes Faculty of Science. Official publication website can be found on muni.cz.
Authors

KRTIČKA Jiří KUBÁT Jiří KRTIČKOVÁ Iva

Year of publication 2022
Type Article in Periodical
Magazine / Source Astronomy & Astrophysics
MU Faculty or unit

Faculty of Science

Citation
Web https://www.aanda.org/articles/aa/full_html/2022/03/aa42502-21/aa42502-21.html
Doi http://dx.doi.org/10.1051/0004-6361/202142502
Keywords X-rays: binaries; stars: winds; outflows; stars: mass-loss; stars: early-type; stars: massive; hydrodynamics
Description Wind-fed high-mass X-ray binaries are powered by accretion of the radiatively driven wind of the luminous component on the compact star. Accretion-generated X-rays alter the ionization state of the wind. Because higher ionization states drive the wind less effectively, X-ray ionization may brake acceleration of the wind. This causes a decrease in the wind terminal velocity and mass flux in the direction toward the X-ray source. Here we study the effect of X-ray ionization on the stellar wind of B supergiants. We determine the binary parameters for which the X-ray irradiation significantly influences the stellar wind. This can be conveniently studied in diagrams that plot the optical depth parameter versus the X-ray luminosity. For low optical depths or for high X-ray luminosities, X-ray ionization leads to a disruption in the wind aimed toward the X-ray source. Observational parameters of high-mass X-ray binaries with B-supergiant components appear outside the wind disruption zone. The X-ray feedback determines the resulting X-ray luminosity. We recognize two states with a different level of feedback. For low X-ray luminosities, ionization is weak, and the wind is not disrupted by X-rays and flows at large velocities, consequently the accretion rate is relatively low. On the other hand, for high X-ray luminosities, the X-ray ionization disrupts the flow braking the acceleration, the wind velocity is low, and the accretion rate becomes high. These effects determine the X-ray luminosity of individual binaries. Accounting for the X-ray feedback, estimated X-ray luminosities reasonably agree with observational values. We study the effect of small-scale wind inhomogeneities (clumping), showing that clumping weakens the effect of X-ray ionization by increasing recombination and the mass-loss rate. This effect is particularly important in the region of the so-called bistability jump. We show that ultraluminous X-ray binaries with LX less than or similar to 10(40) erg s(-1) may be powered by accretion of a B-supergiant wind on a massive black hole.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.