Examining The Outflows of High Energy Stellar Explosions

We conduct a detailed study of high-energy stellar explosions, with a focus on the outflows of massive stars. We begin by examining the emission and cooling mechanisms of GRB afterglows. We present an implementation of a self-consistent way of modeling synchrotron self-Compton (SSC) effects in gamma-ray burst afterglows, with and without approximated Klein-Nishina suppressed scattering for the afterglow modeling code boxfit. We discuss the changes in spectral shape and evolution due to SSC effects, and comment on how these changes affect physical parameters derived from broadband modeling. We show that SSC effects can have a profound impact on the shape of the X-ray light curve. We then discuss the results of applying the modified boxfit to a sample of both long and short GRBs as a way to better understand them as a class of objects.

We then explore the more typical explosions of massive stars in the local Universe. We present results from modeling core-collapse supernovae evolved from pre-main sequence models with wind-driven mass-loss. We construct a software pipeline to follow cradle-to-grave massive star evolution beginning with progenitor modeling up to iron core collapse with MESA. We then use the Supernova Evolution Code (SNEC) to explode the star and follow the evolution of the ejecta with the cosmic ray hydro (ChN) code. ChN allows us to model a remnant’s dynamics and broadband spectrum as a function of age. We quantify the impact of progenitor evolution on the bulk observable characteristics of the remnant, including its dynamics and spectral properties, and quantitatively compare ChN output to observable quantities in SNR. For a broad range of progenitor masses, we find our results in good agreement with observation at all points in the pipeline.

Finally, we consider the effects of intra-remnant absorption on the observed emission from young supernova remnants. We show that structural information about the remnant can be gleaned by examining the asymmetric absorption of the Doppler-shifted X-ray emission. We discuss the importance of next-generation observatories such as XRISM and Athena in being able to resolve the doppler-shifted lines. Additionally, we model absorption along the line-of-sight to the central compact object to place limits on the detectability of the CCO in the first years after core-collapse.