Description
Over time, core-collapse supernova (CCSN) spectra become redder due to dust formation and cooling of the SN ejecta. A UV detection of a CCSN at late times is thus atypical. Additionally, a late time UV detection of a peculiar transient can therefore provide diagnostics as to their nature. An example of this is AT2018cow, a peculiar transient that was still UV-bright four years after it was discovered.
A late time UV detection may be a sign of interaction between the SN ejecta and the circumstellar material (CSM) that was expelled from the progenitor star before the SN explosion. The UV luminosities and light-curves provide information about how and when the CSM was formed and can help constrain progenitor models.
We investigate what fraction of CCSNe are detected in the UV between 2--5 years after the explosion. We use a sample of 51 nearby CCSNe observed with the Hubble Space Telescope (HST) within 2-5 years of discovery. We find two point sources, with a low chance alignment probability, within the uncertainty region of the SN position,which are therefore likely related to the SNe, both of which are known to be an interacting SN. We compare these detections to models of UV emission of interacting CCSNe and the limited amount of late-time UV observations available for interacting CCSNe in the literature.
We conclude that late-time UV observations of CCSNe and peculiar transients are a valuable asset for investigating the local environments of CCSNe and uncovering the nature of peculiar transients.
