The X-ray spectral-timing contribution of the stellar wind in the hard state of Cyg X-1
Lai E, De Marco B, Zdziarski AA, Belloni TM, Mondal S, Uttley P, Grinberg , Wilms J, Rozanska A (2022)
Publication Type: Journal article
Publication year: 2022
Journal
Book Volume: 512
Pages Range: 2671-2685
Journal Issue: 2
Abstract
The clumpy stellar wind from the companion star in high-mass X-ray binaries causes variable, partial absorption of the emission from the X-ray source. We studied XMM-Newton observations from a 7.22 d long monitoring campaign, in order to constrain the effects of the stellar wind on the short-time-scale X-ray spectral-timing properties of Cygnus X-1. We find these properties to change significantly in the presence of the wind. In particular, the longest sampled time-scales (corresponding to temporal frequencies of ν ∼0.1-1 Hz) reveal an enhancement of the fractional variability power, while on the shortest sampled time-scales (ν ∼1-10 Hz), the variability is suppressed. In addition, we observe a reduction (by up to a factor of ∼1.8) of the otherwise high coherence between soft and hard band light curves, as well as of the amplitude of the hard X-ray lags intrinsic to the X-ray continuum. The observed increase of low-frequency variability power can be explained in terms of variations of the wind column density as a consequence of motions of the intervening clumps. In this scenario (and assuming a terminal velocity of v∞ = 2400 km s-1), we obtain an estimate of l ∼0.5-1.5 × 10-4R∗ for the average radial size of a clump. On the other hand, we suggest the behaviour at high frequencies to be due to scattering in an optically thicker medium, possibly formed by collision of the stellar wind with the edge of the disc.
Authors with CRIS profile
Involved external institutions
Polska Akademia Nauk (PAN) / Polish Academy of Sciences
Poland (PL)
National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF)
Italy (IT)
University of Amsterdam
Netherlands (NL)
European Space Astronomy Centre (ESAC)
Spain (ES)
Poland (PL)
National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF)
Italy (IT)
University of Amsterdam
Netherlands (NL)
European Space Astronomy Centre (ESAC)
Spain (ES)
How to cite
APA:
Lai, E., De Marco, B., Zdziarski, A.A., Belloni, T.M., Mondal, S., Uttley, P.,... Rozanska, A. (2022). The X-ray spectral-timing contribution of the stellar wind in the hard state of Cyg X-1. Monthly Notices of the Royal Astronomical Society, 512(2), 2671-2685. https://dx.doi.org/10.1093/mnras/stac688
MLA:
Lai, E., et al. "The X-ray spectral-timing contribution of the stellar wind in the hard state of Cyg X-1." Monthly Notices of the Royal Astronomical Society 512.2 (2022): 2671-2685.
BibTeX: Download