A CHANDRA ACIS OBSERVATION OF THE X-RAY-LUMINOUS SN 1988Z

摘要

SN 1988Z is the most luminous X-ray-emitting supernova, initially detected in 1995 using the ROSATHRI with a luminosity of ～8 x 10~(40) ergs s~(-1) (Fabian &Terlevich 1996). Its high luminosity was ascribed to expansion of the blast wave into an especially dense circumstellar medium. In this paper, we describe a recent observation of SN 1988Z using the ACIS detector on Chandra. We readily detect SN 1988Z, obtaining ～30 net counts, which corresponds to a 0.2-2.0 keV luminosity of ～3.2 x 10~(39) ergs s~(-1). The calculated quantiles for the extracted counts allow a broad range of temperatures but require a temperature hotter than 5 keV if there is no intrinsic absorption. The long-term light curve (1995-2005) declines as t~(-2.6±0.6). This is one of the steepest X-ray light curves. The X-ray luminosity indicates that the emitting region has a high density ( > 10~5 cm~(-3)) and that the density profile is not consistent with a constant mass-loss stellar wind during the ～5000 yr before the explosion. If the circumstellar medium is due to progenitor mass loss, then the mass-loss rate is extremely high (～10~(-3) solar mass yr~(-1) [υ_w/10 km s~(-1)]). The X-ray results are compared with the predictions of models of SN 1988Z.