Shock cooling emission from explosions of massive stars: III. Blue Super Giants

TL;DR

This paper develops analytic models for the early light emission of supernovae from blue supergiant stars, extending previous work on red supergiants, and calibrates these models against detailed numerical simulations.

Contribution

It provides new analytic formulae for shock cooling emission from blue supergiants, calibrated with extensive numerical simulations including detailed opacities.

Findings

Analytic formulae accurately predict luminosity and temperature within 10-5%.

Models reproduce spectral energy distribution within 20-40%.

Extension of shock cooling emission models to blue supergiants.

Abstract

Light emission in the first hours and days following core-collapse supernovae is dominated by the escape of photons from the expanding shock-heated envelope. In preceding papers, we provided a simple analytic description of the time-dependent luminosity, $L$, and color temperature, $T_{\rm col}$, as well as of the small ($\simeq10\%$) deviations of the spectrum from blackbody at low frequencies, $h\nu< 3T_{\rm col}$, and of `line dampening' at $h\nu> 3T_{\rm col}$, for explosions of red supergiants (RSGs) with convective polytropic envelopes (without significant circum-stellar medium). Here, we extend our work to provide similar analytic formulae for explosions of blue supergiants with radiative polytropic envelopes. The analytic formulae are calibrated against a large set of spherically symmetric multi-group (frequency-dependent) calculations for a wide range of progenitor parameters (mass, radius, core/envelope mass ratios) and explosion energies. In these calculations we use the opacity tables we constructed (and made publicly available), that include the contributions of bound-bound and bound-free transitions. They reproduce the numeric $L$ and $T_{\rm col}$ to within 10\% and 5\% accuracy, and the spectral energy distribution to within $\sim20-40\%$. The accuracy is similar to that achieved for RSG explosions.