The supergiant fast X-ray transient IGR J18483-0311 in quiescence: XMM-Newton, Swift, and Chandra observations

IGR J18483-0311 was discovered with INTEGRAL in 2003 and later classified as a supergiant fast X-ray transient. It was observed in outburst many times, but its quiescent state is still poorly known. Here we present the results of XMM-Newton, Swift, and Chandra observations of IGR J18483-0311. These data improved the X-ray position of the source, and provided new information on the timing and spectral properties of IGR J18483-0311 in quiescence. We report the detection of pulsations in the quiescent X-ray emission of this source, and give for the first time a measurement of the spin-period derivative of this source. In IGR J18483-0311 the measured spin-period derivative of -(1.3±0.3)×10 s s likely results from light travel time effects in the binary. We compare the most recent observational results of IGR J184830311 and SAX J1818.6-1703, the two supergiant fast X-ray transients for which a similar orbital period has been measured.