Recent studies have shown that many massive stars lose part or all of their outer layers in their final years. For example, we have discovered a new class of supernovae, called Type Icn supernovae, which come from massive stars that lost all of their hydrogen and helium layers. I studied the first sample of supernovae belonging to this rare class. Using their photometric and spectroscopic datasets, combined with information about their host galaxies, we found that multiple types of progenitor stars and mass-loss mechanisms are likely needed to explain their observed diversity. Read more about this research here.

As we discover more supernovae, we've also discovered some transients that rise and fade in brightness much faster than other known classes. I am interested in finding these fast-evolving supernovae as quickly as possible in order to study their progenitor stars and powering mechanisms. In particular, I have published a comparison of some photometrically-identified fast-evolving supernovae to models and observations of supernovae powered by circumstellar interaction, in which the supernova ejecta collides with pre-existing material lost by the progenitor star. This comparison suggests that some fast-evolving supernovae are the explosions of massive stars that lost a significant fraction of their mass in their final years.

Much of my research involves comparing theoretical models to supernova observations within hours to days of their explosion in order to estimate properties of their progenitors, including their masses and radii, which are otherwise much harder to infer. For example, I used both analytical and numerical models to study the progenitor of a Type IIb supernova, SN 2020bio, which lost part of its outer hydrogen-rich envelope. Surprisingly, this study revealed that its progenitor was likely a lower-mass star than the progenitors of other Type IIb supernovae that lost a greater fraction of its hydrogen layer, suggesting previously-unknown diversity in the progenitors of this class of supernovae.

The advent of gravitational wave detectors such as LIGO has revolutionized multi-messenger astronomy, culminating in the discovery of the first electromagnetic counterpart to a binary neutron star merger, called a kilonova. I am involved in projects during LIGO O4 and beyond to search for and observe future kilonovae associated with binary neutron star mergers detected by LIGO. Much of my work involves writing software to automate the process of searching for these elusive transients and coordinating the electromagnetic follow-up observations across different facilities.