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XTE J1746-322 = IGR J17464-3213 = H1743-322

ATel #133; C. B. Markwardt (U. Maryland & GSFC) and J. H. Swank (GSFC)
on 29 Mar 2003; 03:15 UT
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

Subjects: X-ray, Gamma Ray, Binary, Black Hole, Transient

Referred to by ATel #: 136, 137, 138, 139, 141, 142, 180, 301

C. B. Markwardt (U. Maryland & GSFC) and J. H. Swank (GSFC) report the detection of a new source in RXTE PCA galactic bulge scans on MJD 52723.84, designated XTE J1746-322. The best fit position is R.A. = 17h46m30s, Decl. = -32o10' (equinox 2000.0), with approximate errors of 10', due to nearby confusing sources. This position is consistent with that of the newly reported INTEGRAL source IGR J17464-3213 (ATEL #132).

A pointed RXTE observation occurred on MJD 52726.83 with total good exposure time of 3.4 ks. The mean fluxes in the 2-10, 15-40, and 40-100 keV bands were approximately 50, 200 and 220 mCrab respectively. Compared to the reported INTEGRAL fluxes, the intensity appears to have increased. A strong quasiperiodic oscillation with period ~20 sec, and r.m.s. amplitude ~25%, is clearly seen in the X-ray light curve. No coherent pulsations were detected.

The X-ray spectrum is consistent with an absorbed power law with photon index 1.49 +/- 0.01 and an absorption column of 2.4 x 10**22 cm**-2. Signatures of compton reflection are apparent in the continuum spectrum, but there is no evidence for a line at 6.4 keV, with upper limit on the equivalent width of 45 eV (90 % confidence).

The INTEGRAL source position is consistent, to within the cited 2' error bar, with the HEAO source H1743-322 (also known as H1741-322). The spectrum and timing properties suggest that it is indeed a black hole candidate.