iPTF13bvn and PTF12os -- Two stripped-envelope supernovae discovered by the intermediate Palomar Transient Factory
Tuesday 08 November 2016
to 15:00 at
Christoffer Fremling (Stockholm University)
This thesis is based on research made by the intermediate Palomar Transient Factory [(i)PTF], and it is particularly closely tied to the still ongoing research on the stripped-envelope (SE) supernova (SN), iPTF13bvn (Type Ib), that occurred in the nearby galaxy NGC 5806. This SN was initially thought to have been the explosion of a very massive Wolf-Rayet (WR) star, but I have shown that this is very likely not the case. I suggest instead that the most likely scenario is that iPTF13bvn originated from a binary system where the envelope was stripped off from the SN progenitor by tidal forces from a companion star, in a similar way as for the very well studied Type IIb SN 2011dh. I have also investigated another SE SN, PTF12os (Type IIb), that occurred in the same galaxy as iPTF13bvn, with the conclusion that PTF12os and iPTF13bvn are very similar amongst themselves, and that both of them are also remarkably similar to SN 2011dh, in terms of all of the available observations (light-curves, spectra). Hydrodynamical models have been used to constrain the explosion parameters of iPTF13bvn, PTF12os and SN 2011dh; finding 56Ni masses in the range 0.063 − 0.075 M⊙, ejecta masses in the range 1.85 − 1.91 M⊙. Using the 56Ni-masses derived from our hydrodynamical modeling in combination with nebular models and late-time spectroscopy we were able to constrain the Zero-Age Main Sequence (ZAMS) mass to ∼ 12 M⊙ for iPTF13bvn and ≲ 15 M⊙ for PTF12os. In current stellar evolution models, stars with these masses on the ZAMS cannot lose their hydrogen envelopes and become SE SNe without binary interactions.