Pair Instability Supernovae: Light Curves, Spectra, and Shock Breakout

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• Woosley, S. E.
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• Heger, Alexander

Abstract

For the initial mass range (140 M _sun < M < 260 M _sun) stars die in a thermonuclear runaway triggered by the pair-production instability. The supernovae they make can be remarkably energetic (up to ~10⁵³ erg) and synthesize considerable amounts of radioactive isotopes. Here we model the evolution, explosion, and observational signatures of representative pair instability supernovae (PI SNe) spanning a range of initial masses and envelope structures. The predicted light curves last for hundreds of days and range in luminosity from very dim to extremely bright (L ~ 10⁴⁴ erg s^-1). The most massive events are bright enough to be seen at high redshift, but the extended light curve duration (~1 yr)—prolonged by cosmological time-dilation—may make it difficult to detect them as transients. A more promising approach may be to search for the brief and luminous outbreak occurring when the explosion shock wave first reaches the stellar surface. Using a multi-wavelength radiation-hydrodynamics code we calculate that, in the rest frame, the shock breakout transients of PI SNe reach luminosities of 10⁴⁵-10⁴⁶ erg s^-1, peak at wavelengths ~30-170 Å, and last for several hours. We discuss how observations of the light curves, spectra, and breakout emission can be used to constrain the mass, radius, and metallicity of the progenitor.