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Chandra Location of SGR 0501+4516

ATEL # 1824; Peter Woods (Dynetics), Ersin Gogus (Sabanci Univ), and Chryssa Kouveliotou (MSFC) report on behalf of a larger collaboration
on 30 Oct 2008; 22:36 UT
Password Certification: Peter Woods (

Subjects: Infra-Red, X-ray, Neutron Stars, Pulsars, Soft Gamma-ray Repeaters

The recently discovered Soft Gamma Repeater SGR 0501+4516 (Barthelmy et al. GCN 8113) was observed with the Chandra HRC-I on 2008 September 25 for an exposure of 10ks. The resulting image revealed two X-ray point sources - SGR 0501+4516 and a previously uncatalogued X-ray source (CXOU J050111.3+451525) displaced by 1.4 arcmin from the SGR location. The locations of these two sources are the following:

A search through the 2MASS catalogue revealed only one object (2MASS 05011132+4515252) within 10 arcsec of CXOU J050111.3+451525.

The location for this 2MASS star has a quoted uncertainty of 0.06 arcsec. The statistical uncertainty of the X-ray location of CXOU J050111.3+451525 is 0.09 arcsec (22 source counts). The X-ray and IR locations are well within the uncertainties, thus CXOU J050111.3+451525 is very likely the X-ray counterpart to 2MASS 05011132+4515252. Given the excellent alignment between these two localizations of presumably the same object, we estimate the absolute positional uncertainty of SGR 0501+4516 to be 0.11 arcsec (1 sigma). This position is consistent with the variable IR source discovered by Tanvir et al. (GCN 8126), thus confirming this object as the IR counterpart to SGR 0501+4516.

We thank Allyn Tennant for useful discussions and Harvey Tananbaum and the Chandra team for carrying out this ToO observation.

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