RXTE pointed observations of H 1743-322

ATel #2788; T. M. Belloni, T. Muñoz-Darias, S. Motta, H. Stiele, D. Carbone (INAF - Osservatorio Astronomico di Brera)
on 12 Aug 2010; 20:22 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Tomaso Belloni (belloni@merate.mi.astro.it)

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The black hole transient H1743-322, currently in outburst (see ATel #2774, ATel #2781) was observed by RXTE four times on 2010 August 9 8:36UT August 10 9:40 UT, August 11 1:45 UT and August 12 5:38 UT). All four observations confirm that the systems is in the low-hard state. A spectral fit to the PCA data of the latest observation with an absorbed pexrav model and a Gaussian emission line at 6.4 keV yields a photon index of 1.74 +/- 0.02 and a reflection coverage factor of 0.86 +/- 0.28. The interstellar absorption was fixed to 1.6e22 cm^-2 (see Motta et al. 2010, arXiv:1006.4773). The 2-10 keV unabsorbed flux was 2.0e-9 erg cm^-2 s^-1, a factor of three higher than in the Swift observation on August 7th (ATel #2781). The power density spectrum of all observations is characterized by strong (29% fractional rms between 0.1 and 64 Hz) band-limited noise, with a marked type-C QPO around 1 Hz (increasing slightly in centroid frequency between the two observations) with its first overtone. A comparison with the 2008 and 2009 outbursts (see Motta et al.) shows that this flux level is comparable to that of the previous two transitions to the hard intermediate state. Additional observations at other wavelengths are needed to follow the system evolution. In addition, the first observation is characterized by a strong highly-coherent oscillation at a period around 100 seconds.

Light curve and hardness-intensity diagram for the current outburst of H 1743-322