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

TL;DR

This study tackles how late-time X-ray data can constrain the population of compact objects formed in core-collapse SNe. It assembles a large archival dataset of 607 X-ray observations from Chandra, XMM-Newton, Swift, and NuSTAR for 242 nearby SNe and analyzes them with absorption models grounded in 3D neutrino-driven SN explosions to account for ejecta geometry. Detected X-ray emission from 12 SNe (including four new cases) largely traces circumstellar material interaction, with SN 1979C potentially revealing a hard component from a pulsar wind nebula. Population synthesis of the non-detections and detections indicates pulsar birth properties with mean initial spin periods $\gtrsim 100\,\mathrm{ms}$ are favored, and several luminous events point to interactions with dense shells, refining our understanding of compact-object formation in SNe.

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 four 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 $\gtrsim100\rm~ ms$ are favored. Finally, we note that the high luminosities of several of the SNe with CSM interaction imply interactions with dense shells.