TITLE: GCN CIRCULAR NUMBER: 8149 SUBJECT: SGR 0501+4516: Proximity to supernova remnant HB9 DATE: 08/08/27 21:04:34 GMT FROM: Bryan Gaensler at U of Sydney B. M. Gaensler (U. Sydney) and S. Chatterjee (U. Sydney) report: We note that the newly identified magnetar SGR 0501+4516 (GCN 8113) is in close proximity to the Galactic supernova remnant (SNR) HB9 = G160.9+2.6. Specifically, the location of the SGR as determined by Swift XRT (GCN 8112; GCN 8148) is just outside the south-eastern rim of HB9. A 1.4 GHz radio image of the SNR taken from the Canadian Galactic Plane Survey, and showing the position of the SGR, is available at: http://www.physics.usyd.edu.au/~bmg/fig_sgr_snr.gif The angular separation from the SNR's centre is approximately 80 arcmin, corresponding to a projected space velocity of 1700-4300 km/s for a distance to the SNR of 1.5 kpc and an age of 8000-20000 years (Leahy & Aschenbach, 1995, A&A, 293, 853). The SGR's location outside the rim of a SNR and its high inferred space velocity are similar properties to those inferred for other SGRs. While there is as yet insufficient information to judge the validity of a physical association between SGR 0501+4516 and SNR HB9, we note that this anti-centre region is relatively devoid of SNRs and other evidence for massive star formation: there are only two other catalogued SNRs within 15 degrees of this position. A search for other neutron stars associated with HB9 (Kaplan et al., 2006, ApJS, 163, 344) did not detect any candidates.