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ATEL # 2738; M. Armas Padilla, N. Degenaar, R. Kaur, R. Wijnands, Y. Yang (University of Amsterdam)
on 15 Jul 2010; 10:39 UT
Password Certification: Rudy Wijnands (email@example.com)
Subjects: X-ray, Binaries, Black Holes, Neutron Stars, Transients
Referred to by ATEL #: 2807
After the re-brightening of the new very faint X-ray source XMMSL1 J171900.4-353217 [ATel #2607, #2722], an additional observation has been carried out using the XRT aboard Swift on July 13th 2010.
In this last pointing ~960 seconds only two counts were present in the source extraction region demonstrating that we did not detect the source in our observation.
We have calculated the upper limit on the flux with HEARSAC tool WebPIMMs (v4.1a) assuming an absorbed powerlaw model with an hydrogen column of 3.4E22 cm-2 (see ATel #2627) and a photon index of 2.11 (see ATel #2722). The count rate upper limit has been determined using the prescription for small numbers of counts given by Gehrels (1986). The resulting upper limit for the absorbed and unabsorbed 2-10 keV fluxes are 5.1E-13 ergs cm-2 s-1 and 6.8E-13 ergs cm-2 s-1, respectively. Adopting a source distance of 8kpc, a corresponding X-ray luminosity of 5.2E+33 ergs s-1 is inferred.
This low upper limit indicates that the source is a transient system that has returned to the quiescence state after an outburst of at least four months.
We thank the Swift team for approving and scheduling our Too observation.