Peculiar nature of hard X-ray eclipse in SS433 fromINTEGRALobservations

Abstract

The analysis of hard X-ray INTEGRAL observations (2003X-ray INTEGRAL observations ( -2008 of superaccreting Galactic microquasar SS433 at precessional phases of the source with the maximum disc opening angle is carried out. It is found that the shape and width of the primary X-ray eclipse are strongly variable, suggesting additional absorption in dense stellar wind and gas outflows from the optical A7I component and the wind-wind collision region. The independence of the observed hard X-ray spectrum on the accretion disc precessional phase suggests that hard X-ray emission (20-100 keV) is formed in an extended, hot, quasi-isothermal corona, probably heated by interaction of relativistic jet with inhomogeneous wind outflow from the precessing supercritical accretion disc. A joint modelling of X-ray eclipsing and precessional hard X-ray variability of SS433 revealed by INTEGRAL by a geometrical model suggests the binary mass ratio q = m x /m v 0.25-0.5. The absolute minimum of joint orbital and precessional χ 2 residuals is reached at q 0.3. The found binary mass ratio range allows us to explain the substantial precessional variability of the minimum brightness at the middle of the primary optical eclipse. For the mass function of the optical star f v = 0.268 M as derived from Hillwig & Gies data, the obtained value of q 0.3 yields the masses of the components m x 5.3 M , m v 17.7 M , confirming the black hole nature of the compact object in SS433.

INTEGRAL observations of SS433: system's parameters and nutation of supercritical accretion disc

“…The precession light curves were separately constructed for uneclipsed (0.2 < φ orb < 0.8) and middle-eclipse (0.95 < φ orb <1.05) observations. Light curves in both bands show precessional variability and were used to constrain binary system parameters (seeCherepashchuk et al (2009) and Section 5 below).…”

Searching for Exoplanets around X-Ray Binaries with Accreting White Dwarfs, Neutron Stars, and Black Holes

“…Our theoretical examples illustrate key features, but are not designed to capture the full complexity of real X-ray light curves, which may be affected by geometrical effects and time variability. Fortunately, there are many published examples of X-ray eclipses by stars, detected in spite of all of the complicating factors (e.g., van Teeseling 1997; Ramsay et al 2001;Porquet et al 2005;Cherepashchuk et al 2009;Nucita et al 2009;Kennedy et al 2017;Ponti et al 2017). In most cases, a dip in the X-ray light curve that is shorter in duration and/or more shallow than the stellar eclipse would also be detectable.…”

Peculiarities in the orbital and precessional variability of SS433 from INTEGRAL observations

“…The presence of absorption lines in the optical spectrum of the companion [10,12] suggests its spectral classification as ∼ A7Ib supergiant. Assuming these lines to be produced in the optical star photosphere, their observed orbital Doppler shifts would correspond to the mass ratio of compact (M Modeling of all INTEGRAL eclipses of the source available before 2010 [6] using a purely geometrical model yeilded independent constraints on the binary mass ratio q = 0.25 − 0.5 with the most probable value q = 0.3, suggesting the mass of the compact companion M x ≃ 5.3M ⊙ and the optical star M v ≃ 17.7M ⊙ for the observed optical star mass function f v = 0.268M ⊙ . This places SS433 among black-hole high-mass X-ray binaries.…”

“…Here we analyze hard X-ray eclipses of SS433 near the T3 moment in combination with the precessional variability as observed by INTEGRAL, and interpret them in terms of our multicomponent geometrical model (see [6] for more detail).…”