The X‐Ray Outburst of H1743−322 in 2003: High‐Frequency QPOs with a 3 : 2 Frequency Ratio

Abstract

The 2003 X-ray outburst of the candidate black hole binary, H1743-322, was investigated in frequent pointed observations (2-250 keV) with the Rossi X-Ray Timing Explorer (RXTE). One particular program of 130 observations is organized into 111 time intervals and searched for the presence of high-frequency quasi-periodic oscillations (HFQPOs) in the range 50-2000 Hz. Only a single observation (2003 June 13) yields a detection above 4 σ. The central frequency of 239 ± 4 Hz is consistent with the 240 Hz QPO reported for this source on 2003 May 28 (Homan and coworkers). We group the observations in several different ways and compute average power-density spectra (PDS) in a search for further evidence of HFQPOs. Significant results are found for two groups defined by the presence of low-frequency QPOs (0.1-20 Hz) and an absence of "band-limited" power continua. (1) The nine time intervals with the highest X-ray flux yield a QPO at 166 ± 5 Hz. (4.1 σ; 3-35 keV). (2) The group with lower X-ray flux (24 time intervals) produces a QPO at 242 ± 3 Hz (6.0 σ; 7-35 keV). The ratio of these two frequencies is 1.46 ± 0.05. This finding is consistent with results obtained for three other black hole systems that exhibit commensurate HFQPOs in a 3 : 2 ratio. Furthermore, the occurrence of H1743-322's slower HFQPO at times of higher X-ray luminosity closely resembles the behavior of XTE J1550-564 and GRO J1655-40. We discuss our results in terms of resonance models that invoke frequencies set by general relativity.