Continued Chandra monitoring observations of the Galactic Center magnetar
ATel #5922; Nanda Rea (CSIC-IEEC; U. Amsterdam), Daryl Haggard (Northwestern/CIERA), Fred Baganoff (MIT), Craig Heinke (U. Alberta), Gian Luca Israel (INAF-OAR), Gabriele Ponti (MPE), on behalf of a larger collaboration
on 26 Feb 2014; 17:37 UT
Credential Certification: Nanda Rea (rea@ieec.uab.es)
Subjects: X-ray, Neutron Star, Soft Gamma-ray Repeater, Transient, Pulsar
We have observed SGR J1745-29 (Kennea et al. 2013, ApJ 770, L24; Mori et al. 2013, ApJ 770, L23; Rea et al. 2013, ApJ 775, L34) with the ACIS-S camera onboard Chandra for about 47ks starting on 2014-02-21 (ObsID 16508), as part of the on-going Chandra X-ray monitoring of the Galactic Center region (PIs: Haggard, Baganoff, Rea).
The magnetar is still bright, as suggested by the Swift/XRT Galactic Center monitoring (Degenaar et al. 2014; ATel #5861), with an ACIS-S count rate of 0.16(2) cts/s (errors are given at 1-sigma confidence level). The observed 1-10keV flux of the magnetar is 3.2(1)x10^-12 erg/s/cm^2, and we can significantly detect pulsations at its spin period. The energy spectrum is well modeled by an absorbed blackbody with a neutral Hydrogen column density of N_H=1.11(4)x10^23 cm^-2, suggesting that the X-ray emission is dominated by a hot spot of 1.2(1)km radius (at a distance of 8.3kpc) with a temperature of kT=0.84(2)keV (chi^2=1.08 with 245 dof).
Assuming a distance of 8.3kpc, the hot spot bolometric luminosity (derived de-absorbing and extrapolating the X-ray spectrum) has decayed in 303 days from about 2.6 to 1.1x10^35 erg/s, relatively slow for a magnetar outburst (see Rea & Esposito 2011, ASSP, Springer; Pons & Rea 2012, ApJ 750, L6). Note that the upper limit on the quiescent bolometric luminosity of SGR J1745-29 can be as high as 10^35 erg/s if in quiescence the entire magnetar surface has a temperature of kT~0.3keV (still consistent with the archival Chandra non-detections).
We thank Scott Wolk and the Science Operations and Flight Operations teams of the Chandra X-ray Observatory for their dedicated work scheduling these observations.
