Student Author: Adrien Thormann, (Class of 2010)

Faculty Author: Dr. Ben Sugerman

Scattered-light echoes are very rare, and have only been unambiguously resolved around a handful of sources.  They offer one of the most effective means to study the structure and make-up of circumstellar and interstellar dust and gas.  Light echoes profide exact three- dimensional positions of scattering dust, and also can be used to constrain that dust’s composition, size and number density.  Here, we present new data and analyses of echoes previously discovered around SN 1991T. These echoes appear to trace out a shell around the progenitor, either hourglass shaped or ellipsoidal, and with a size  scale of 20-30 lt-yr.   Also, the supernova may be significantly  offset from the center of this shell.  SN 1991T was a type-Ia supernova, thus it is unclear yet whether we are tracing the fossil remnant of the progenitor’s outflows, or those of its binary companion.

This research was conducted during the 2008 Goucher summer-research program and also for academic credit during the 2008-9 school year.  This project was supported with funding from Hubble Space Telescope Grant HST-GO-10607, and was presented at the Winter 2009 meeting of  the American Astronomical Society in San Diego, CA.   Click here for a PDF copy of the poster presented at that meeting.