ROSAT OBSERVATIONS OF THE SOFT GAMMA-RAY BURST ERROR BOX COINCIDENT WITH THE SUPERNOVA REMNANT N49

摘要

The supernova remnant N49 in the Large Magellanic Cloud was observed in soft X-rays using the High Resolution Imager aboard the ROSAT satellite. A total 0.1-2.4 keV image of the nebula was obtained by the use of a pixon-based image deconvolution algorithm. Image analysis determined the position of the X-ray hot spot (RX J05260.3-660433) coincident with the error box of the soft gamma-ray repeater SGR 0525-66. The position is R.A. (J2000) = 5h26m0.31s and decl. (J2000) = - 66°4′33.20″ with an uncertainty of 5″ in radius, due almost entirely to the ROSAT pointing uncertainty. This positional uncertainty is a factor of 2 smaller than that obtained from previous data. Examinations of optical images of N49 show no stellar sources coincident with the X-ray position of RX J05260.3-660433, with an upper limit of m_v～21 mag. We have searched for periodicity in the signal from RX J05260.3-660433 in the period range 7.5-8.5 s, the approximate period observed from this source during the 1979 March 5 gamma-ray burst. No evidence for ～8 s periodicity was found, and the upper limit on the pulsed fraction was determined to be 66%, for pulse profiles typical of X-ray pulsars. The overall counting rate from the hot spot was consistent with a constant signal over the ～2 yr duration of the ROSAT observations.