Insights Into Stellar Explosions From Infrared Light

Abstract

Massive stars are the workhorse of the Universe. While accounting for a minute fraction of baryonic mass, their influence on the cosmos is profound. Their lives and deaths lead to nucleosynthesis of all elements heavier than helium, including those essential to life. They produce some of the most energetic eruptions and explosions, core-collapse (CC) supernovae (SNe) at the end of their life. These explosions are common, about once per century per galaxy, and are one of the primary drivers of the gas dynamics of their host galaxies. Despite their importance, many facets of the massive stars' evolution and their eventual death in CCSNe are still uncertain. In this thesis, I use a variety of observations in the infrared (IR) part of the electromagnetic spectrum to probe aspects of these stellar explosions elusive to visible light. IR observations of SNe remain sparse compared to the optical, even for the most nearby events. I present the first systematic study of CCSNe light curves from the Spitzer Space Telescope showing trends in IR properties of CCSNe and identifying outliers that exhibit signs of interactions between the SN shock and the circumstellar medium (CSM) ejected from the star. I also present in-depth explorations of nearby SN 2017eaw, a typical and common hydrogen-rich explosion; and SN 2014C, a hydrogen-poor explosion whose shock wave crashes into the CSM containing material lost from the star. IR observations provide insights into the chemical evolution and circumstellar environment in these SNe. In the second part of this thesis, I present the development and commissioning of a near-IR spectropolarimeter WIRC+Pol at Palomar Observatory. WIRC+Pol utilizes a novel, highly efficient polarization grating as its polarimetric beam splitter and spectral disperser. The resulting high sensitivity allows WIRC+Pol to observe sources as faint as J = 14.5 to 0.1% polarimetric accuracy in 2 hours. I also present the first scientific results from the instrument: the spectropolarimetric measurements of four nearby SNe, which are the first such observations in the IR. We detected polarization from SN 2018hna, which allowed us to constrain that its explosion geometry looks similar to the very well-studied SN 1987A observed from a different angle, suggesting the same underlying geometry.