Nebular Phase Supernovae
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Magellan Telescopes (Yuri Beletsky, left). Image taken on IMACS f/2 on the Baade Telescope containting a Nebular SN Ia (Abigail Polin, right).
The nebular phase occurs after the SN ejecta expands and cools until it reaches a point where it becomes diffuse enough that it is optically thin to radiation. At this phase, the ejecta cools through emission spectra that reveal the composition of the inner regions of the SN. I am currently the lead developer of SedoNeb, the NLTE nebular phase companion to Sedona. I use SedoNeb to model the nebular emission spectra of a variety of transients.
While modeling the nebular spectra of SNe Ia, I learned there is a dearth of Type Ia SNe observed during this epoch. I have leveraged my time as postdoc at Carnegie to help address this need. Since 2021, I have been the principal investigator of 14 nights on the Magellan 6.5 meter telescopes which I use to target SNe Ia for nebular phase spectroscopy. My goal is to perform coincident (same night) optical and infrared spectra, as there are two conflicting features at this epoch that point to the origin of the SN. In the optical an excess of [Ca II] points towards a double detonation, and in the infrared, the presence of stable Ni would indicated a Chandrasekhar mass explosion. So, the combination of these two wavelengths ranges should definitively place individual SNe Ia into a progenitor class.