Seminars at FGG

Signatures of a jet cocoon in early spectra of a supernova associated with a gamma-ray burst

Speaker: Luca Izzo (Instituto Astrofisico de Andalucia)

Date and time: 2019-04-29 12:30

Long γ-ray bursts are associated with energetic, broad-lined, stripped-envelope supernovae that are characterised by an high-velocity ejecta, of the order of 30,000 km/s. In this talk, I will present and discuss the case of SN 2017iuk, associated with GRB 171205A, which displays features at extremely high expansion velocities (~100,000 km/s) within the first day after the burst. These features are characterized by chemical abundances that differ from those observed in the ejecta of SN 2017iuk at later times and in the ejecta of other SNe associated with GRBs. Thanks to a detailed observational monitoring and an accurate spectral synthesis analysis of the early phases of SN 2017iuk, we conclude that these features originate from the mildly relativistic hot cocoon that is generated by the GRB ultra-relativistic jet, while it is expanding and decelerating into the medium surrounding the progenitor star.