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Continuous X-ray monitoring of the third outburst of the magnetar CXOU J164710.2-455216

ATel #10878; Alice Borghese (U. Amsterdam), Francesco Coti Zelati (IEEC-CSIC), Nanda Rea (IEEC-CSIC, U. Amsterdam), Paolo Esposito (U. Amsterdam), on behalf of a larger collaboration
on 20 Oct 2017; 19:43 UT
Credential Certification: Nanda Rea (rea@ice.csic.es)

Subjects: X-ray, Transient, Pulsar, Magnetar

We are currently tracking the X-ray activity of the magnetar CXOU J164710.2-455216 since the onset of its third outburst on 2017 May 16, when Swift BAT triggered on an SGR-like burst from a direction consistent with the position of the magnetar (trigger=753085; D'Ai et al. 2017, GCN 21095). The XRT began observing the field about 60s after this trigger, and the source at that time was found at a 0.5-10 keV absorbed X-ray flux of 8.05(+1.68)(-3.97)e-12 erg/s/cm2, a factor of about 10 larger than the quiescent value.

Since then we are following the decay of this outburst with Swift, Chandra and NuSTAR observations. In particular, a part from the continuous Swift monitoring, three observations have been carried out simultaneously by Chandra and NuSTAR on 2017 May 25, June 16, and July 10.

Our last Swift observation was performed starting on 2017 October 12 at 00:55:33 (UT), with exposure time of 4.4 ks, and caught the source at an absorbed flux level of 2.78(+0.63)(-0.35)e-12 erg/s/cm2 in the energy band 0.5-10 keV, and with a count rate of about 0.05 cts/s. The spectrum could be well described by an absorbed black body with a column density of 2.4(2)e22 cm-2 and a temperature of kT=0.69(6) keV.

During the recovery of this third outburst, the source experienced another SGR-like burst, detected by Swift BAT on 2017 October 19 (trigger=780203; Beardmore et al. 2017, GCN 22024); see also Younes et al. 2017, ATel #10877).

We will continue to monitor the source: the Swift monitoring is already planned till 2017 October 27 (then the source will be not visible anymore). Further Swift observations, and a new simultaneous Chandra and NuSTAR observation will be performed in early 2018.