Astronomy & Astrophysics Seminar: Stellar Explosions in dense CSM, with application to AT2018cow

Zoom: https://tau-ac-il.zoom.us/j/81239615480?pwd=qynx9sGBcqWlo2fNUEbZrq1VibGgwM.1

Abstract:

Massive stars shed mass through winds across their entire lives, and binary interactions can further sculpt circumstellar environments. When these stars die in a stellar explosion, the resulting ejecta interacts with the surrounding circumstellar medium (CSM), powering bright transients that encode the star's mass-loss history and illuminate the final stages of stellar evolution of massive stars. Deciphering the mass loss history, requires a theoretical understanding, and the ability to correctly identify the signs of CSM interaction.

In this talk, I will present the physics of stellar explosions interacting with dense CSM, with a focus on moderately optically thick environments, which are not as well understood. I will survey the key processes shaping the observed emission and introduce our model for X-ray transmission through photoionized medium, establishing the conditions under which X-rays produced at the interaction front can escape to the observer unabsorbed.

I will then turn to AT2018cow, the emblematic member of the newly emerging class of luminous fast blue optical transients (LFBOTs). I will present our model, in which a shock in aspherical CSM quantitatively reproduces nearly all observed features of AT2018cow with only four parameters, which are overconstrained. I will close by discussing the broader implications for our understanding of transients powered by CSM interaction, and their expected signatures.

Seminar Organizer: Dr. Jonathan Stern