Publication
Progenitor and close-in circumstellar medium of type II supernova 2020fqv from high-cadence photometry and ultra-rapid UV spectroscopy
Publisher:
Oxford University Press (OUP)
Date:
26-10-2021
DOI:
10.1093/MNRAS/STAB2887
Abstract: We present observations of SN 2020fqv, a Virgo-cluster type II core-collapse supernova (CCSN) with a high temporal resolution light curve from the Transiting Exoplanet Survey Satellite (TESS) covering the time of explosion ultraviolet (UV) spectroscopy from the Hubble Space Telescope (HST) starting 3.3 d post-explosion ground-based spectroscopic observations starting 1.1 d post-explosion along with extensive photometric observations. Massive stars have complicated mass-loss histories leading up to their death as CCSNe, creating circumstellar medium (CSM) with which the SNe interact. Observations during the first few days post-explosion can provide important information about the mass-loss rate during the late stages of stellar evolution. Model fits to the quasi-bolometric light curve of SN 2020fqv reveal 0.23 M⊙ of CSM confined within 1450 R⊙ (1014 cm) from its progenitor star. Early spectra (& d post-explosion), both from HST and ground-based observatories, show emission features from high-ionization metal species from the outer, optically thin part of this CSM. We find that the CSM is consistent with an eruption caused by the injection of ∼5 × 1046 erg into the stellar envelope ∼300 d pre-explosion, potentially from a nuclear burning instability at the onset of oxygen burning. Light-curve fitting, nebular spectroscopy, and pre-explosion HST imaging consistently point to a red supergiant (RSG) progenitor with $M_{\\rm ZAMS}\\approx 13.5\\!-\\!15 \\, \\mathrm{M}_{\\odot }$, typical for SN II progenitor stars. This finding demonstrates that a typical RSG, like the progenitor of SN 2020fqv, has a complicated mass-loss history immediately before core collapse.