Copy the page URI to the clipboard
Cui, Wei; Shrader, Chris R.; Haswell, Carole. A. and Hynes, Robert I.
(2000).
DOI: https://doi.org/10.1086/312712
Abstract
We report the discovery of quasi-periodic oscillations (QPOs) at roughly 187 and 150 Hz in the X-ray intensity of X-ray nova XTE J1859+226. The source was observed during a recent outburst with the Rossi X-Ray Timing Explorer. Besides these high-frequency QPOs, we have also detected QPOs (and sometimes their harmonics) at 6–7 Hz and significant broadband variability at low frequencies. These properties, as well as the observed hard X-ray spectrum, make XTE J1859+226 a black hole candidate (BHC). The detection of QPOs at two distinct frequencies 100 Hz in two observations separated by about 4 hr provide additional insights into the high-frequency QPO phenomenon in BHCs. The importance lies in the proposed interpretations, which invariably involve the effects of strong gravity near a black hole. We compare our results to those of other BHCs and discuss the impact of the observational data on the models in a global context.