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Swift/XRT monitoring of the latest outburst from XMMUJ174716.1-281048: the source is still active

ATel #1496; L. Sidoli (INAF-IASF Milano), P. Romano (INAF-IASF Palermo), M. Del Santo (INAF-IASF Roma), R. Wijnands (UvA) and N. Degenaar (UvA)
on 29 Apr 2008; 15:04 UT
Credential Certification: Lara Sidoli (sidoli@mi.iasf.cnr.it)

Subjects: X-ray, Transient

Referred to by ATel #: 2050, 2624, 3471, 7293

The Very Faint X-ray Transient (VFXT) XMMUJ174716.1-281048 (ATel #147 and Sidoli et al., 2006, A&A 456, 287) is being observed with Swift/XRT since May 2007 (Degenaar et al. 2007, ATel #1136), in order to monitor the level of activity during the latest outburst, which started in 2003 (Del Santo et al., 2007, A&A 468, L17; ATel #1078, #1136). XMMUJ174716.1-281048 is indeed the first VFXT with a ``quasi persistent" behaviour.

The last previous Swift/XRT observation (Sidoli et al., 2007, ATel #1174) detected the source at a rate of (3.56+/-0.71)E-02 counts/s in July 2007 and at (1.50+/-0.35)E-02 counts/s in Aug 2007 (0.2-10 keV).

Swift/XRT observed XMMUJ174716.1-281048 on 28 Apr 2008. The source is still active, with a 0.2-10 keV count rate of (2.89+/-0.48)E-02 count/s, which translates into a 0.2-10 keV flux, corrected for the absorption, of ~3.3E-12 erg/cm2/s (assuming a power law model with a photon index of 2.25, absorbed by a column density of 9E22 cm-2). The source activity is not decreasing, with a duration of the latest outburst of probably more than five years, confirming what suggested by Del Santo et al. (2007, A&A 468, L17), that the source is a "quasi persistent" transient.

We will continue the monitoring of the source flux in the next months with Swift/XRT.

We would like to thank the Swift Team for making these observations possible, in particular N. Gehrels, the duty scientists as well as the science planners.