Progenitor and close-in circumstellar medium of type II supernova 2020fqv from high-cadence photometry and ultra-rapid UV spectroscopy

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 days post-explosion; ground-based spectroscopic observations starting 1.1 days 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 (<4 days 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 days 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 MZAMS ≈ 13.5–15 M⊙, 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.

Shock Breakout in Three-dimensional Red Supergiant Envelopes

“…This prolonged duration is often attributed to interaction with a dense wind beyond a traditional 1D photosphere (e.g., Gezari et al 2008;Haynie & Piro 2021) or by assuming an outer density that is orders of magnitude lower than traditional 1D models (Schawinski et al 2008). This prolonged SBO is further corroborated by differences between SNe-IIP seen by Kepler (Garnavich et al 2016) and TESS (Tinyanont et al 2021;Vallely et al 2021) compared to spherically symmetric SBO models. In upcoming years, the data are expected to improve dramatically, as future satellites such as the ULTRA-SAT instrument (Sagiv et al 2014;Asif et al 2021) are poised to capture hundreds of SN SBOs at high cadences, a number that will grow when combined with data from wide-field X-ray satellites (Bayless et al 2022).…”

The Renovated Thacher Observatory and First Science Results

“…Photometry is performed by one of two different general methods depending on the specifics of the field in question and the scientific requirements. While our pipeline is evolving and is subject to change, we outline the basic features of each method as our data has been used in published scientific works including the monitoring of Boyajian's Star (Boyajian et al 2018;Wilcox et al 2019) and Boyajian Star analogs (Arculli et al 2020;Browning et al 2021), eclipsing binaries (Healy et al 2019), transiting exoplanets (Jin-Ngo et al 2021), and transient studies (Tinyanont et al 2021;Sand et al 2021;Kilpatrick et al 2021;Gagliano et al 2021;Barna et al 2021;Jacobson-Galán et al 2020;Swift et al 2019Swift et al , 2018 5.1. Preliminary Data Handling and Calibrations 10 https://www.timesynctool.com/ Each observation is stored as a file according to the Flexible Image Transport System (FITS) format in a staging area within our institution's Drop Box.…”

Science with the Ultraviolet Explorer (UVEX)

“…ble UV spectral sequence has been acquired because of the slow response time of HST. The earliest HST UV spectrum of a SN yet obtained was 3.3 days after explosion (Tinyanont et al 2021). The Swift/UVOT slitless grism has rapid-response NUV capability, but has limited sensitivity and low resolution, with spectra that do not extend to the feature-rich FUV (Roming et al 2005;Bufano et al 2009).…”

“…The presence of CSM directly manifests as a more luminous UV display and different spectrum (Figure34). Grey vertical arrows: epochs of acquired UV spectra of SNe, including the International Ultraviolet Explorer (IUE) observations of SN 1987A which started 1.5 days after the neutrino burst(Pun et al 1995) and the earliest Hubble Space Telescope (HST) spectra, which were acquired ∼ 3.3 days after the estimated time of first light of SN 2020fqv(Tinyanont et al 2021). UVEX will thus explore a completely pristine part of the parameter space and will provide the characterization of stellar explosions of all types (from ordinary to rare explosions) in their earliest hottest phases.…”