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Additional Observations of XTE J1752-223

ATel #2261; C. B. Markwardt (U. Maryland & NASA/GSFC), S. D. Barthelmy (NASA/GSFC), P. A. Evans (U. Leicester), J. H. Swank (NASA/GSFC)
on 26 Oct 2009; 00:19 UT
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient

Referred to by ATel #: 2263, 2265, 2268, 2269, 2278, 2280, 2387, 2424

We report on additional observations of XTE J1752-223, a new transient recently reported active (ATEL #2258).

Swift performed a dedicated follow-up observation at 2009-10-25 at 06:08 UT. A bright X-ray source was detected by the XRT instrument, heavily piled up. The best fit position from XRT is, R.A. = 268.06307 = 17:52:15.14 ; Dec. = -22.34274 = -22:20:33.8 (J2000) with estimated position error of about 5 arcsec. This position is consistent with the previously reported X-ray / gamma-ray positions (ATEL #2258).

Accounting for pile-up by removing the central region (56 arcsec radius), the best fit spectrum is consistent with an absorbed power law (N_H = 4.7 x 10^{21} cm^{-2}; photon index = 1.2), with an observed flux of 7.3 x 10^{-10} erg cm^{-2} s^{-1} in the 0.5-10 keV band. There are no obvious signatures of pulsations, although there is significant intrinsic variability of about 12% r.m.s.

We also note that Swift BAT triggered a second time today (2009-10-25 at 16:14 UT, trigger #373792), which suggests a rising 15-150 keV X-ray flux.

Given the lack of pulsations and the spectrum, we speculate that the source is a black hole candidate in the hard spectral state.