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Discovery of XTE J1747-274

ATel #498; C. B. Markwardt (U. Maryland & NASA/GSFC), J. H. Swank (NASA/GSFC)
on 23 May 2005; 16:25 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

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

Referred to by ATel #: 500, 521, 634, 838, 1459, 1461, 1468

A new source has appeared in scans of the galactic center by the RXTE Proportional Counter Array (PCA). The flux increase first became noticeable in PCA scans on May 11, 15 and 18. Unfortunately, because this region of the sky is relatively crowded, the flux increase was attributed to the nearby source GCRT J1746-2757.

On May 20, 14h UT, the flux had become bright enough to be distinct from other nearby sources. We fitted for the position in the bulge scan data, and found R.A. = 17h47m38s, Decl. = -27o26m (J2000), and thus designate the source XTE J1747-274.

Because there are a number of bright sources nearby, the position error is dominated by systematic uncertainties. Based on two trial fits, we estimate the error to be < 8 arcmin. There are no catalogged galactic X-ray sources within 15 arcmin of this position.

After re-processing the PCA scan data of the past few months with the new source included, no flux increase in GCRT J1746-2757 is needed. The fluxes of XTE J1747-274 on May 11.4, 15.6, 18.3 and 20.6 were 12 +/- 3, 17 +/- 4, 10 +/- 2 and 48 +/- 4 mCrab (2-10 keV), respectively. Thus the source appears to be brightening irregularly.

No pulsations or QPOs are detectable in the brief (10-20 second) PCA scan passes over the source.