AXP 1E1547.0-5408: Swift-XRT analysis

ATel #1761; K. L. Page, A. P. Beardmore (U. Leicester) and H. A. Krimm (CRESST/GSFC/USRA)
on 4 Oct 2008; 14:21 UT
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Credential Certification: Kim Page (kpa@star.le.ac.uk)

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Swift-XRT started observing the field of the AXP 1E1547.0-5408 82 seconds after the first BAT trigger (Krimm et al., GCN Circ. 8311) and a clear X-ray source was found. Using 84 s of XRT Photon Counting mode data and 1 UVOT images, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) of RA, Dec = 237.72433, -54.30643 which is equivalent to:

RA (J2000): 15 50 53.84
Dec (J2000): -54 18 23.2

with an uncertainty of 1.4 arcsec (radius, 90% confidence). This position is 2.5 arcsec from CXOU J155054.1-541824 (Gelfand & Gaensler 2007), which they identify with 1E1547.0-5408.

The XRT detected an increased count rate at around 520 s, coincident with one of the BAT spikes mentioned in Krimm et al. (GCN Circ. 8318); similarly a brightening was seen at the time of the second trigger reported in GCN Circ. 8312. In both cases, the XRT registered a single, bright 2.5 s frame of data.

The spectrum from the first two orbits of PC data can be modelled by a highly-absorbed power-law, with Gamma = 2.33 +0.31/-0.29 and NH = (4.9 +0.8/-0.7) x 10^22 cm^-2.