Yi Cao

Fast and Furious: Young Supernovae and Their Progenitors

Observations of supernovae within a few days of explosion provide unique constraints to the nature of their progenitors. Since 2013, as a part of my thesis, I used the intermediate Palomar Transient Factory (iPTF) to systematically study extraordinarily young supernovae. I will first provide an overview of iPTF survey design, summarize the fast turnaround discovery pipeline and then outline the rapid response follow-up. The highlights of my work are as follows: 1) We observed a strong declining UV pulse from a low-velocity Type Ia supernova which is consistent with the expected radiation from a supernova slamming into a companion star. This UV pulse strongly suggests the so-called "single degenerate" channel for Type Ia supernovae. 2) We found a peculiar Type Ia supernova which follows the empirical relation between peak magnitude, lightcurve shape and maximum color for cosmological measurement. It also shares observational features with super-Chandrasekhar events, indicating an ejecta mass exceeding the Chandrasekhar limit. Thus this object probably arises from the so-called "double-degenerate" channel. Our observations together support multiple origin channels of Type Ia supernovae. Additionally, we identified the first progenitor candidate of a Type Ib supernova in the pre-explosion HST images. Our multi-wavelength observations of this young Type Ib supernova constrain its progenitor to be smaller than several solar radii and with strong mass loss. I will end my talk with prospects for this field with the upcoming Zwicky Transient Facility.