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Bright New Black Hole Transient XTE J1817-330

ATel #714; R. Remillard, A. M. Levine, E. H. Morgan (MIT), C. B. Markwardt (U. Maryland & NASA/GSFC), & J. H. Swank (NASA/GSFC)
on 28 Jan 2006; 21:32 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Jean Swank (swank@milkyway.gsfc.nasa.gov)

Subjects: X-ray, Black Hole, Transient

Referred to by ATel #: 717, 721, 724, 731, 733, 734, 738, 740, 742, 749, 933

We report a new source discovered by the RXTE ASM and follow-up observations with the RXTE PCA.

Observations with the RXTE All-Sky Monitor on 2006 Jan. 26 suggested the sudden appearance of a very bright X-ray source near ra=274.56, dec=-32.92 (degrees, J2000). The angular proximity to the sun limited the number of dwells and the position accuracy. The (2-12 keV) flux was 0.93 (0.03) Crab, compared to an upper limit (3 sigma) of 0.05 mCrab on Jan. 25. The spectrum appeared very soft, as frequently exhibited by black hole candidates.

The RXTE PCA pointed at the ASM position Jan 27 at 21 UT and confirmed the presence of a bright soft source. On Jan 28 at 14 UT the PCA scanned over the position and determined a position of ra=274.425, dec=-33.018, for which the systematic errors should be less than 30" (Jahoda et al. 2006). The spectrum exhibits little absorption (< 10^ 21 cm^-2). For both observations it can be described by black body contributions at about 0.8 and 0.4 keV and a powerlaw with photon index of 2-3. The fluxes were 1.2 and 1.35 Crab(2-10 keV), respectively, and 15 and 22 mCrab (10-30 keV). Source rms variability was only 1.3% during 900 seconds of observation.