Long Plateau Doth So: How Internal Heating Sources Affect Hydrogen-Rich Supernova Light Curves

TL;DR

This paper introduces a semi-analytic model for hydrogen-rich supernova light curves that incorporates various internal heating sources, revealing how such sources influence the brightness and duration of the plateau phase.

Contribution

The study develops a versatile model accounting for different internal heating mechanisms, providing insights into supernova light curve features and implications for progenitor properties.

Findings

Internal heating can increase plateau brightness proportionally.

Maximum plateau duration increases by a factor of 2-3 with sustained heating.

Implications for minimum ejecta mass in long-lasting supernovae.

Abstract

Some hydrogen-rich core-collapse supernovae (type IIP SNe) exhibit evidence for a sustained energy source powering their light curves, resulting in a brighter and/or longer-lasting hydrogen-recombination plateau phase. We present a semi-analytic SNIIP light curve model that accounts for the effects of an arbitrary internal heating source, considering as special cases $^{56}$Ni/$^{56}$Co decay, a central engine (millisecond magnetar or accreting compact object), and shock interaction with a dense circumstellar disk. While a sustained internal power source can boost the plateau luminosity commensurate with the magnitude of the power, the duration of the recombination plateau can typically be increased by at most a factor $\sim 2-3$ compared to the zero-heating case. For a given ejecta mass and initial kinetic energy, the longest plateau duration is achieved for a constant heating rate at the highest magnitude that does not appreciably accelerate the ejecta. This finding has implications for the minimum ejecta mass required to explain particularly long-lasting supernovae such as iPTF14hls, and for confidently identifying rare explosions of the most-massive hydrogen-rich (e.g. population III) stars. We present a number of analytic estimates which elucidate the key features of the detailed model.