Type II supernovae from the Carnegie Supernova Project-I

Abstract

Type II supernovae (SNe II) show great photometric and spectroscopic diversity which is attributed to the varied physical characteristics of their progenitor and explosion properties. In this study, the third of a series of papers where we analyse a large sample of SNe II observed by the Carnegie Supernova Project-I, we present correlations between their observed and physical properties. Our analysis shows that explosion energy is the physical property that correlates with the highest number of parameters. We recover previously suggested relationships between the hydrogen-rich envelope mass and the plateau duration, and find that more luminous SNe II with higher expansion velocities, faster declining light curves, and higher 56 Ni masses are consistent with higher energy explosions. In addition, faster declining SNe II (usually called SNe IIL) are also compatible with more concentrated 56 Ni in the inner regions of the ejecta. Positive trends are found between the initial mass, explosion energy, and 56 Ni mass. While the explosion energy spans the full range explored with our models, the initial mass generally arises from a relatively narrow range. Observable properties were measured from our grid of bolometric LC and photospheric velocity models to determine the effect of each physical parameter on the observed SN II diversity. We argue that explosion energy is the physical parameter causing the greatest impact on SN II diversity, that is, assuming the non-rotating solar-metallicity single-star evolution as in the models used in this study. The inclusion of pre-SN models assuming higher mass loss produces a significant increase in the strength of some correlations, particularly those between the progenitor hydrogen-rich envelope mass and the plateau and optically thick phase durations. These differences clearly show the impact of having different treatments of stellar evolution, implying that changes in the assumption of standard single-star evolution are necessary for a complete understanding of SN II diversity.

Comparison of the Core-collapse Evolution of Two Nearly Equal-mass Progenitors

“…Observationally, this also implies that the explosion of a star similar to the progenitor of F15.78 would appear much dimmer than a star similar to F15.79. The higher 56 Ni yield and 2.5 times higher explosion energy in F15.79 follows the strong correlation between the explosion energy and the production of 56 Ni seen in observations (see, e.g., Martinez et al 2022). As discussed in Section 2, the 15.79 M ☉ preSN model has higher compactness than the 15.78 M ☉ preSN model, correlating with the higher 56 Ni yields inF15.79, agreement with the finding of Ebinger et al (2019), for neutrino-driven, spherically symmetric explosions, that higher compactness correlates with higher 56 Ni yields.…”

Weak Mass Loss from the Red Supergiant Progenitor of the Type II SN 2021yja

“…See Appendix A for details of the photometry reduction. We also include publicly available photometry from the ATLAS forced photometry server (Tonry et al 2018a;Smith et al 2020) and the Supernova Observations and Simulations group (Martinez et al 2021). Figure 1 shows the light curve of SN 2021yja; the data are available in machinereadable format in the online journal.…”

The Properties of Fast Yellow Pulsating Supergiants: FYPS Point the Way to Missing Red Supergiants

“…One proposed solution to the RSG problem is that the RSGs with initial masses M i M h lose enough of their envelopes through mass loss or interactions with a binary companion to evolve blueward in the HR diagram before exploding (e.g., Ekström et al 2012;Neugent et al 2020), possibly as SESNe. Indeed, such enhanced mass-loss rates are observed in massive RSGs (Humphreys et al 2020), and may also be necessary to explain the observed diversity of SNe II (Martinez et al 2022).…”