G290.1–0.8 ( MSH 11–6 1 A ) is a supernova remnant ( SNR ) whose X-ray morphology is centrally bright .
However , unlike the class of X-ray composite SNRs whose centers are dominated by nonthermal emission , presumably driven by a central pulsar , we show that the X-ray emission from G290.1–0.8 is thermal in nature , placing the remnant in an emerging class which includes such remnants as W44 , W28 , 3C391 , and others .
The evolutionary sequence which leads to such X-ray properties is not well understood .
Here we investigate two scenarios for such emission : evolution in a cloudy interstellar medium , and early-stage evolution of a remnant into the radiative phase , including the effects of thermal conduction .
We construct models for these scenarios in an attempt to reproduce the observed center-filled X-ray properties of G290.1–0.8 , and we derive the associated age , energy , and ambient density conditions implied by the models .
We find that for reasonable values of the explosion energy , the remnant age is of order ( 1 - 2 ) \times 10 ^ { 4 } yr .
This places a fairly strong constraint on any association between G290.1–0.8 and PSR J1105-610 , which would require an anomalously large velocity for the pulsar .