RXTE Observes H1743-322 in Outburst

ATel #3277; T. E. Strohmayer
on 13 Apr 2011; 04:31 UT
Credential Certification: Tod Strohmayer (tod.strohmayer@nasa.gov)

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RXTE began observations of the recent outburst (ATels #3263, #3267) of the black hole candidate H1743-322 at 16:05:01 (UTC) on April 12, 2011. In a 2.4 ksec observation the source is detected at a count rate of 200 cts/s/PCU. Strong variability is evident in the form of harmonically spaced quasiperiodic oscillations (QPO) at a fundamental frequency of 0.43 Hz, and flat-topped, band limited noise below the QPO. The fundamental QPO has a fractional rms variability of 11% (3 - 30 keV), and the broad-band noise is strong with greater than 20% variability (rms). This behavior appears consistent with evolution into the hard intermediate state, and is similar to previously reported behavior of the source (ATel #1780). Interestingly, significant pulsations with a period of approximately 91 s are also evident in the power spectrum. Indeed, the pulsations can be seen by "eye" in a light curve binned at 16 s. The half-amplitude of the pulsation is approximately 16 cts/sec/PCU (3 - 30 keV). A likely possibility is that the pulsations are due to a second active source in the PCA field of view. Imaging observations could confirm or refute this hypothesis. Additional RXTE observations are planned.