2S 1553-54: Swift/XRT position

ATel #1371; P. T Boyd (NASA's GSFC), M. Still (UCL-MSSL), J. Kennea (Penn State) and H. A. Krimm (CRESST/GSFC/USRA)
on 26 Jan 2008; 17:02 UT
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)

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The transient accreting pulsar 2S 1553-54, discovered in outburst by Swift/BAT on 2007 Dec 31 (Krimm, ATel #1345) was observed by Swift XRT for 4081 seconds on 2008 January 24 to determine a refined position. The pulsar, which is still detected by BAT at a level of about 35 mCrab, is a bright, marginally piled-up XRT source with position:

RA (J2000) 15 57 47.75
Dec (J2000) -54 24 52.4

with a 3.5 arc-second error (90% containment). The XRT error circle lies within the SAS-3 35 arc-second aperture (Apparao, 1978, Nature, 271, 225.

No optical counterpart is detected in any UVOT filter down to the following 3-sigma limiting magnitudes.

Filter limiting Mag exposure time (s)
uvw2 19.8 460
uvm2 19.5 342
uvw1 19.3 230
u 19.0 115
b 19.4 115
v 18.4 115

This is the first detected outburst of this system since 1975 (SAS-3).