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Discovery of High-Frequency QPOs in Black Hole Candidate XTE J1859+226

Wei Cui·C. R. Shrader·C. A. Haswell·R. I. Hynes
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Abstract

We report the discovery of quasi-periodic oscillations (QPOs) at roughly 187 Hz and 150 Hz in the X-ray intensity of X-ray nova XTE J1859+226. The source was observed during a recent outburst with RXTE. Besides these high-frequency QPOs, we have also detected QPOs (and sometimes their harmonics) at 6--7 Hz, and significant broad-band 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 $\gtrsim 100$ Hz in two observations separated by about 4 hours 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.

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Wei Cui, C. R. Shrader, C. A. Haswell, R. I. Hynes. 2000-04-17. Discovery of High-Frequency QPOs in Black Hole Candidate XTE J1859+226. https://arxiv.org/abs/astro-ph/0004236

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