Optical and Infrared Observations of SN 2006X in M100 and a
Possible Hint for the Presence of Circumstellar Dust

Xiaofeng Wang
University of California at Berkeley


In this report I will present our observations of the type Ia supernova 2006X in the nearby galaxy in M100. SN 2006X is highly reddened [E$(B - V)_{host}$ = 1.41$\pm$0.04] by abnormal dust with $R_V$ = 1.48$\pm$0.06 and is characteristic of strong, high-velocity features of both intermediate-mass and iron-group elements in the early-epoch spectra. More than the anomalous extinction and the rapid expansion behavior, SN 2006X also shows noticeably small late-time decline rate in the $B$ band [e.g., $\beta$ = 0.92$\pm$0.05 (100 d)$^{-1}$] and relatively blue continuum than normal SNe Ia at nebular phase. This may invoke additional energy process beyond the radioactive decay. The presence of a light echo around the SN is confirmed by the Keck spectrum and the $HST$ images taken around 300 days after the maximum light. Moreover the echo may imply the distribution of the dust around SN 2006X on both interstellar and circumstellar scales. I will also discuss the impact of our observations of 06X-like events to the understanding of SN Ia progenitor system.