X-Ray Luminosity and Size Relationship of Supernova Remnants in the LMC
Abstract
The Large Magellanic Cloud (LMC) has 60 confirmed supernova remnants (SNRs). Because of the known distance, 50 kpc, the SNRs' angular sizes can be converted to linear sizes, and their X-ray observations can be used to assess X-ray luminosities (LX). We have critically examined the LMC SNRs' sizes reported in the literature to determine the most plausible sizes. These sizes and the LX determined from XMM-Newton observations are used to investigate their relationship in order to explore the environmental and evolutionary effects on the X-ray properties of SNRs. We find: (1) Small LMC SNRs, a few to 10 pc in size, are all of Type Ia with LX>1036 ergs s-1. The scarcity of small core-collapse (CC) SNRs is a result of CCSNe exploding in the low-density interiors of interstellar bubbles blown by their massive progenitors during their main sequence phase. (2) Medium-sized (10-30 pc) CC SNRs show bifurcation in LX, with the X-ray-bright SNRs either in an environment associated with molecular clouds or containing pulsars and pulsar wind nebulae and the X-ray-faint SNRs being located in low-density interstellar environments. (3) Large (size>30 pc) SNRs show a trend of LX fading with size, although the scatter is large. The observed relationship between LX and sizes can help constrain models of SNR evolution.