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Swift/XRT determines a precise location for IGR J17379-3747

ATel #1714; H. A. Krimm (CRESST/USRA/NASA GSFC), J. A. Kennea (PSU), P. A. Evans (U. Leicester), C. B. Markwardt (CRESST/UMD/NASA GSFC) on behalf of the Swift and RXTE teams
on 11 Sep 2008; 20:19 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)

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

Observations with the Swift X-Ray Telescope (XRT) of the hard X-ray source IGR J17379-3747 (XTE J1737-376) (Markwardt et al, ATel #1709) were carried out beginning at 2:42:26 UT on 2008-Sep-11 (MJD 543720) and lasting 2043 seconds over four consecutive spacecraft orbits.

The observation revealed a single bright point source at the location:
RA (J2000): 17h 37m 58.81s (264.49504)
Dec (J2000): -37d 46m 19.6s (-37.77211)
Err: 1.4" (90% confidence)

This is within the error circles of the positions found by Swift Burst Alert Telescope (BAT; Markwardt et al, ATel #1709) and INTEGRAL (Shaw et al, ATel #1711).

The XRT spectrum can be fit by an absorbed power law spectrum: N_H = (8.1 ± 0.7) x 1021 cm-2, Photon Index = 1.78 ± 0.08, Flux (0.3-10 keV) = (1.996 ±0.079) x 10-10 erg cm-2 s-1, Reduced chi2 = 1.72 (210 dof). The XRT light curve shows some variability, with a rate (0.3-10 keV) of 2.2 ± 0.5 cts/sec in the first three orbits, rising to 4.0 ± 0.8 cts/sec in the fourth orbit. The time averaged rate in the BAT remains steady at 0.003 ± 0.0008 cts/sec/cm2 (13 mcrab).

The RXTE PCA spectrum on 2008-09-09 was consistent with a power law, with photon index 1.98. The fluxes in the 2-10, 10-20 and 20-40 keV bands were, 16.4, 7.8 and 7.9 in units of erg/s/cm2, respectively. In PCA monitoring scans the source 2-10 keV flux has faded, with recent values of 12.3, 12.1, 7.1 and 5.4 mCrab, on Sep 5.1, 6.2, 9.0 and 10.2 respectively.

Swift/BAT Transient Monitor light curves for IGR J17379-3747