Low-luminosity type IIP supernovae: SN 2005cs and SN 2020cxd as very low-energy iron core-collapse explosions

Abstract

SN 2020cxd is a representative of the family of low-energy, underluminous Type IIP supernovae (SNe), whose observations and analysis were recently reported by Yang et al. (2021). Here we re-evaluate the observational data for the diagnostic SN properties by employing the hydrodynamic explosion model of a 9 M ⊙ red supergiant progenitor with an iron core and a precollapse mass of 8.75 M ⊙ . The explosion of the star was obtained by the neutrino-driven mechanism in a fully self-consistent simulation in three dimensions (3D). Multi-band light curves and photospheric velocities for the plateau phase are computed with the one-dimensional radiation-hydrodynamics code STELLA, applied to the spherically averaged 3D explosion model as well as spherisized radial profiles in different directions of the 3D model. We find that the overall evolution of the bolometric light curve, duration of the plateau phase, and basic properties of the multi-band emission can be well reproduced by our SN model with its explosion energy of only 0.7 × 10 50 erg and an ejecta mass of 7.4 M ⊙ . These values are considerably lower than the previously reported numbers, but they are compatible with those needed to explain the fundamental observational properties of the prototype low-luminosity SN 2005cs. Because of the good compatibility of our photospheric velocities with line velocities determined for SN 2005cs, we conclude that the line velocities of SN 2020cxd are probably overestimated by up to a factor of about 3. The evolution of the line velocities of SN 2005cs compared to photospheric velocities in different explosion directions might point to intrinsic asymmetries in the SN ejecta.

Low luminosity Type II supernovae -- IV. SN 2020cxd and SN 2021aai, at the edges of the sub-luminous supernovae class

“…Considering these corrections, the MS mass of the progenitor of SN 2020cxd is estimated to be 8.9 -10.4 M . We note that, despite the different methodology applied, our results are consistent with those obtained by Kozyreva et al (2022): M 𝑒 𝑗 = 7.4 M , E = 0.07 foe and R = 408 R .…”

“…Here we provide additional photometric and spectroscopic coverage of this target. Just before our submission,Kozyreva et al (2022) presented an additional paper on the modelling of 2020cxd.MNRAS 000,1-17 (2022)…”