Study of the Composite Supernova Remnant MSH 11−62

We present the analysis of the X-ray data collected during an observation ofthe supernova remnant (SNR) MSH 11-62 by the Advanced Satellite for Cosmologyand Astrophysics (ASCA). We show that MSH 11-62 is a composite remnant whoseX-ray emission comes from two distinct contributions. Nonthermal, synchrotronemission, localized to a region of radius (~~)3' (consistent with a pointsource) dominates the total flux above 2 keV. A second contribution comes froma thermal component, extended up to a radius of (~~)6' and detected only atenergies below 2keV. The spatial and spectral analysis imply the presence of aneutron star losing energy at a rate of about (10**36 - 10**37) ergs/s. Nopulsed emission is detected and we set a limit on the pulsed fraction of 10%.This is consistent with the lack of a radio pulsar in the remnant, which mayindicate that the pulsed emission from the rapidly rotating compact object thatshould be powering the synchrotron nebula is beamed and our viewing directionis unfavorable. In either event, the central neutron star deposits much of itsspin-down energy into the surrounding synchrotron nebula where, through directimaging with broadband satellites such as ASCA, it is possible to study theenergetics and evolution of the compact remnant.Comment: 30 pages, including 5 figures, Latex. To appear in ApJ (May 20, 1998 issue, Vol. 499.