Evolution of the Light Echo of SN?1991T

摘要: Schmidt et al. presented strong evidence (photometry and spectroscopy) that the late time optical emission of SN 1991T in Virgo spiral NGC 4527 is caused by a light echo. Here, we present photometry with Wide Field Planetary Camera 2 high-resolution imaging polarimetry Faint Object on board Hubble Space Telescope, which demonstrates feature indeed echo original supernova. We show spatially resolved, complex, both growing size changing morphology. The slowly fading. Our primary interest to use for estimating distance host galaxy geometrically (see 1994 work Sparks). Given elapsed since supernova exploded small relatively distant, expected region maximally polarized cannot be fully resolved as yet. However, do find at center echo, simple models may used yield estimate. favor smaller distances, ≈15 Mpc being upper allowable distance, subject caveats described text. consistent dust cloud uniform density n ~ 0.9 cm-3 extending ≈50 pc front It encouraging even case very far from ideal, can this type observation derive distance.