The Open UniversitySkip to content

The Remarkable rapid X-ray, ultraviolet, optical and infrared variability in the black hole XTE J1118+480

Hynes, R.I.; Haswell, C.A.; Cui, W.; Shrader, C.R.; O'Brien, K.; Chaty, S.; Skillman, D.R.; Patterson, J. and Horne, K. (2003). The Remarkable rapid X-ray, ultraviolet, optical and infrared variability in the black hole XTE J1118+480. Monthly Notices of the Royal Astronomical Society, 345(1) pp. 292–310.

DOI (Digital Object Identifier) Link:
Google Scholar: Look up in Google Scholar


The transient black-hole binary XTE J1118+480 exhibited dramatic rapid variability at all wavelengths which were suitably observed during its 2000 April–July outburst. We examine time-resolved X-ray, ultraviolet, optical and infrared data spanning the plateau phase of the outburst. We find that both X-ray and infrared bands show large amplitude variability. The ultraviolet and optical variability is more subdued, but clearly correlated with that seen in the X-rays. The ultraviolet, at least, appears to be dominated by the continuum, although the lines are also variable. Using the X-ray variations as a reference point, we find that the ultraviolet (UV) variability at long wavelengths occurs later than that at short wavelengths. Uncertainty in the Hubble Space Telescope timing prohibits a determination of the absolute lag with respect to the X-rays, however. The transfer function is clearly not a delta-function, exhibiting significant repeatable structure. For the main signal we can rule out an origin in reprocessing on the companion star – the lack of variation in the lags is not consistent with this, given a relatively high orbital inclination. Weak reprocessing from the disc and/or companion star may be present, but is not required, and another component must dominate the variability. This could be variable synchrotron emission correlated with X-ray variability, consistent with our earlier interpretation of the infrared (IR) flux as due to synchrotron emission rather than thermal disc emission. In fact, the broad-band energy distribution of the variability from IR to X-rays is consistent with expectations of optically thin synchrotron emission. We also follow the evolution of the low-frequency quasi-periodic oscillation in X-rays, UV, and optical. Its properties at all wavelengths are similar, indicating a common origin.

Item Type: Journal Item
ISSN: 1365-2966
Keywords: accretion; accretion discs; binaries: close; stars; XTE J1118+480; ultraviolet; X-rays
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 4876
Depositing User: Users 6041 not found.
Date Deposited: 12 Jul 2006
Last Modified: 07 Dec 2018 08:57
Share this page:


Altmetrics from Altmetric

Citations from Dimensions

Actions (login may be required)

Policies | Disclaimer

© The Open University   contact the OU