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RXTE observes hard state activity from GX 339-4

ATel #2384; John A. Tomsick (SSL/UC Berkeley)
on 13 Jan 2010; 07:07 UT
Credential Certification: John A. Tomsick (jtomsick@ssl.berkeley.edu)

Subjects: X-ray, Request for Observations, Black Hole, Transient

Referred to by ATel #: 2455, 2459, 2523, 2525, 3117, 3191, 3383

RXTE obtained a brief (<1 ks) observation of the black hole transient GX 339-4 after the announcement of new activity from this source by MAXI (Yamaoka et al., ATEL#2380). The observation, which started at 2010 Jan. 12, 11.7 h UT, showed that the source is in the hard state. The PCA energy spectrum can be described as an absorbed power-law with a photon index of 1.50 +/- 0.03, and the absorbed 3-25 keV flux is 1.2e-9 ergs/cm2/s. On Jan. 8, MAXI reported a 4-10 keV flux of 26 mCrab, and the RXTE measurement on Jan. 12 is only slightly higher, 28 mCrab (4-10 keV). The 0.01-64 Hz power spectrum is dominated by a zero-centered Lorentzian with a fractional rms amplitude of 50% +/- 9% (0.01-10 Hz). There is also evidence for a second component in the power spectrum below 0.1 Hz, and PCA light curves with 16 second time resolution show the flares that are the cause of this component. The hard state is usually associated with radio emission from a compact jet, and multi-wavelength observations are encouraged.