The soft gamma-ray repeater in the supernova remnant N49

by David Marsden, Rick Rothschild, and Richard Lingenfelter,
to be published in Proceedings of the 1995 Gamma-Ray Burst Workshop, San Diego.


The supernova remnant N49 in the Large Magellanic Cloud was observed in soft X-rays using the High Resolution Imager aboard the ROSAT satellite. An image of the entire nebula in the 0.1-2.4 keV bandpass was obtained, with a mean counting rate of 0.777+/-0.004 count/s in a total livetime of ~50000 s. Image analysis determined the position of the X-ray hotspot (RX 0525-6604), coincident with the error box of the soft gamma-ray repeater 0525-66, to be R.A.= 5h26m0.55s and Dec=-66 4'35.56'' (J2000.0) with an uncertainty of 5 arcsec in radius, due almost entirely to the ROSAT pointing uncertainty. We have searched for periodicity in the signal from RX0525-6604 in the period range 7.5-8.5 s, the approximate period observed from this source during the March 5, 1979 gamma-ray burst. No evidence for ~8 s periodicity from RX0525-6604 was found, and the upper limit on the pulsed fraction was determined to be 66%, for pulse profiles typical of X-ray pulsars.

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