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Swift localisation of SAX J1750.8-2900

ATel #1431; D. Steeghs (Warwick/CfA), J. Kennea (PSU), M. A.P. Torres (CfA), G. Roelofs (CfA), P. Jonker (SRON/CfA), J. Homan (MIT) and J. M. Miller (Michigan)
on 17 Mar 2008; 19:09 UT
Credential Certification: Danny Steeghs (dsteeghs@cfa.harvard.edu)

Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar

Referred to by ATel #: 1434, 1446, 1472

Following the report of renewed activity of the neutron star transient SAX J1750.8-2900 (Markwardt & Swank, ATel #1425; see also #1426, #1428), we obtained a target of opportunity observation with the Swift satellite in order to improve its X-ray position.

The XRT observations were acquired in Photon counting mode on Mar 17th 2008 at 12:27 UT for 1ks. We detect a bright, piled-up point source in the field of view that unfortunately falls near a detector hot column. This affected our ability to determine the source position. We have compared source centroid estimates using a variety of methods and report a preliminary position of:

RA(J2000) = 17h 50m 24.6s,
Dec(J2000) = -29d 02m 12s,

with an estimated uncertainty of 5-7 arc-seconds based on the scatter between our individual centroid estimates. This position lies 11 arcseconds away from the SAX position of this source, which has an 1 arc-minute error circle and is thus consistent with SAX J1750.8-2900.

No counterpart is detected in the V-band UVOT image, and we note that this sight-line suffers from considerable extinction. Near-infrared imaging of the field is planned to search for a counterpart within the Swift error circle.