The Type II supernova SN 2020jfo in M 61, implications for progenitor system, and explosion dynamics

Abstract

We present the discovery and extensive follow-up observations of SN 2020jfo, a Type IIP supernova (SN) in the nearby (14.5 Mpc) galaxy M 61. Optical light curves (LCs) and spectra from the Zwicky Transient Facility (ZTF), complemented with data from Swift/UVOT and near-infrared photometry is presented. These were used to model the 350-day duration bolometric light curve, which exhibits a relatively short (∼65 days) plateau. This implies a moderate ejecta mass (∼5 M⊙) at the time of explosion, whereas the deduced amount of ejected radioactive nickel is ∼0.025 M⊙. An extensive series of spectroscopy is presented, including spectropolarimetric observations. The nebular spectra are dominated by Hα, but also reveal emission lines from oxygen and calcium. Comparisons to synthetic nebular spectra indicate an initial progenitor mass of ∼12 M⊙. We also note the presence of stable nickel in the nebular spectrum, and SN 2020jfo joins a small group of SNe that have inferred super-solar Ni/Fe ratios. Several years of prediscovery data were examined, but no signs of precursor activity were found. Pre-explosion Hubble Space Telescope imaging reveals a probable progenitor star, detected only in the reddest band (MF814W ≈ −5.8) and it is fainter than expected for stars in the 10−15 M⊙ range. There is thus some tension between the LC analysis, the nebular spectral modeling, and the pre-explosion imaging. To compare and contrast, we present two additional core-collapse SNe monitored by the ZTF, which also have nebular Hα-dominated spectra. This illustrates how the absence or presence of an interaction with circumstellar material (CSM) affect both the LCs and in particular the nebular spectra. Type II SN 2020amv has a LC powered by CSM interaction, in particular after ∼40 days when the LC is bumpy and slowly evolving. The late-time spectra show strong Hα emission with a structure suggesting emission from a thin, dense shell. The evolution of the complex three-horn line profile is reminiscent of that observed for SN 1998S. Finally, SN 2020jfv has a poorly constrained early-time LC, but it is of interest because of the transition from a hydrogen-poor Type IIb to a Type IIn, where the nebular spectrum after the light-curve rebrightening is dominated by Hα, although with an intermediate line width.

A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf

“…We also show the collection of directly detected SN progenitors of Types II (light gray squares) and IIb (dark gray circles; see text in Section 4.1). O'Neill et al 2019;Rui et al 2019;Van Dyk et 2019;Sollerman et al 2021;Van Dyk et al 2023a). We emphasize though that many of these previous estimates were derived primarily using only a few (usually HST) optical bands and may systematically underestimate the luminosities of the stars without IR constraints on the SED.…”

SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova

“…With the exception of the blue supergiant progenitor of the peculiar SN II 1987A (Hillebrandt et al 1987;Arnett et al 1989), the yellow supergiant progenitor stars of hydrogen-poor SNe IIb (e.g., Aldering et al 1994), and the luminous blue variable (LBV) progenitor stars to SNe IIn (e.g., Gal-Yam & Leonard 2009), all of these systems are red supergiants (RSGs). These stars have massive, extended, hydrogen envelopes and make up the majority of directly identified progenitor stars to core-collapse SNe (SNe 2003gd, 2004A, 2004et, 2005cs, 2006my, 2008bk, 2009hd, 2009kr, 2009md, 2012A, 2012aw, 2012ec, 2016cok, 2017eaw, 2018aoq, 2020jfo, and 2022acko;Smartt et al 2004;Elias-Rosa et al 2010;Fraser et al 2010;Crockett et al 2011;Fraser et al 2011;Kochanek et al 2012;Maund et al 2013;Tomasella et al 2013;Fraser et al 2014;Maund et al 2014;Kochanek et al 2017;Kilpatrick & Foley 2018;O'Neill et al 2019;Rui et al 2019;Van Dyk et al 2019;Sollerman et al 2021;Van Dyk et al 2023a, 2023b. The lack of >20 M e RSG progenitor stars of SNe II despite the fact that they make up ≈15% of RSGs following a Salpeter initial mass function and RSGs with > L L log 5.2 ( )  are observed in the LMC, M31, and M33 (Drout et al 2012;Neugent et al 2020;Neugent 2021aNeugent , 2021b) has been noted as the "RSG problem" (Smartt et al 2009;Smartt 2009, although see also Davies & Beasor 2018).…”

SN 2018gj: A Short Plateau Type II Supernova with Persistent Blueshifted Ha Emission

“…However, there are reasons to believe otherwise, where it is possible to get a shorter plateau if the multiplicity (Eldridge et al 2018) or extensive mass loss in lower-mass RSG is considered (Teja et al 2022). In a study by Sollerman et al (2021), the progenitor of the short plateau object SN 2020jfo was solely detected in the F814W band of the Hubble Space Telescope (HST), estimating its mass to range from 10 to 15 M e . The lack of detection of the progenitor in the bluer bands indicated the progenitor as a cool and red star.…”