X-Ray Observations of Old Nearby Supernovae—Constraints on Compact Object Populations and Late Interaction

Abstract The properties of the population of compact objects created in core-collapse supernovae (SNe) are uncertain. X-ray observations years to decades after the explosions offer a way to gain insight into this, as hard X-ray emission from the central regions will emerge as the ejecta absorption decreases. Here, we analyze and place upper limits on late-time X-ray emission in 242 nearby SNe, using 607 observations from Chandra, XMM-Newton, Swift, and NuSTAR. We use absorption models based on 3D simulations of neutrino-driven explosions to account for absorption of emission from the compact objects by the asymmetric ejecta. We detect X-ray emission from 12 SNe, including 4 for the first time (SN 1982R, SN 1984J, SN 1992bu, and SN 2003gk), and several of the others at later epochs than before. The X-ray spectra of these SNe are consistent with interaction with the circumstellar medium (CSM), with the possible exception of SN 1979C, which shows an additional hard component, as also noted in previous studies at earlier epochs. This emission may be due to a pulsar wind nebula. Using the upper limits in the full sample, we also perform a population synthesis to constrain the fraction of SNe that produce pulsars and the properties of the pulsars themselves. We find that pulsar populations with mean initial spin periods ≳100 ms are favored. Finally, we note that the high luminosities of several of the SNe with CSM interaction imply interactions with dense shells.