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R. I. Hynes (University of Southampton), C. A. Haswell, S. Chaty (The Open University), W. Cui (MIT), C. R. Shrader (NASA/GSFC)
The black hole candidate XTE\,J1118+480 has been in an unusual low-state outburst since January 2000. It has exhibited large amplitude rapid variability on timescales of tens of seconds and less at all wavelengths with a sufficient count rate to detect such variability. We will compare X-ray data with simultaneous (UV) and contemporaneous (UV--IR) data. Very similar power density spectra are seen at X-ray and UV wavelengths, with a prominent low-frequency QPO at ~.1\,Hz, evolving with time. Simultaneous X-ray and UV lightcurves are well correlated down to timescales of seconds. The correlated variability could arise either from reprocessing of X-ray variations by the disc or companion star, or from a component of emission originating in the X-ray production region, likely close to the compact object. Possible lags between the wavebands will constrain explanations. This presentation is funded by the Leverhulme Trust.
The author(s) of this abstract have provided an email address for comments about the abstract: rih@astro.soton.ac.uk