RXTE PCA and Swift BAT Detect A Small Outburst of the Burster SAX J1753.5-2349

ATel #1799; C. B. Markwardt (CRESST/U. Md./NASA/GSFC), H. A. Krimm (CRESST/USRA/NASA/GSFC), J. H. Swank (NASA/GSFC)
on 22 Oct 2008; 14:22 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Craig B. Markwardt (craigm@lheamail.gsfc.nasa.gov)

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RXTE PCA and Swift BAT monitoring observations have detected an outburst of the X-ray burster SAX J1753.5-2349. With the PCA, the source was first detected on 2008-10-11 in the 2-10 keV band. A dedicated PCA scan produced a position of (RA,Dec) = 268.52, -23.86 (J2000), with a 95% error radius of 5 arcmin. With the BAT, the source was first detected on 2008-10-16 (15-50 keV), at a position of (RA,Dec) = 268.40, -23.82 (J2000), with a 95% error radius of 3 arcmin. Both of these positions reasonably consistent with the cataloged position of SAX J1753.5-2349 (in 't Zand et al. 1998, astro-ph/9802304v1).

Since detection, the source flux rose to about 8 mCrab (PCA 2-10 keV), and 7 mCrab (BAT 15-150 keV). The most recent PCA measurement on 2008-10-22 02:55 suggests a decline to about 2 mCrab (2-10 keV). A dedicated PCA pointed observation does not show obvious evidence of pulsations or QPOs.

As first discovered by the BeppoSAX WFC instrument in 1996 and 1997, SAX J1753.5-2349 was known as an X-ray burster without detectable persistent emission (ibid). Now, PCA and BAT are detecting persistent emission with no bursts, but that is not a particular surprise, since the recent amount of exposure is low.

INTEGRAL reported a source in 2006, IGR J17536-2339, whose position is marginally consistent with the SAX source (Turler et al. ATEL #790).