Early excess light in Type Ia supernovae

TYPEAstrophysics Seminar
Speaker:Naveh Levanon
Time:14:30 - 15:30
Location:Lidow 620
Remark:Ph.D seminar

Type Ia supernovae (SNe Ia) are the thermonuclear explosions of white dwarfs (WDs). The nature of SNe Ia progenitor systems is a subject of active debate. The ever-increasing rate and quality of SNe Ia observations in the last decade reveals more variety in SNe Ia events than any existing model can explain, and also offers more opportunity to constrain models using newly discovered phenomena. I will present one such case -- the case of early excess light, observed recently in a handful of SNe Ia. In these SNe a "bump" is seen in the light curve immediately after first light. While originally predicted to be the signature of an interaction with a non-degenerate companion star, we show a similar interaction can come about after the merger of two WDs. In such a merger the secondary WD is tidally disrupted and forms an accretion disk around the primary WD. Due to angular momentum conservation some of the disk material is ejected as the disk is accreted. If this accretion leads to a detonation in the primary WD, the explosion ejecta will hit the matter previously ejected from the disk, shocking it and generating a bump in the light curve. I will explain the merits of this alternative model and compare it and the other models for early excess light to observations.