Pair-production supernovae: Theory and observation

Abstract

Nonrotating stars that end their lives with masses 140 M⊙ M⋆ 260 M⊙ should explode as pair-production supernovae (PPSNe). Here I review the physical properties of these objects as well as the prospects for them to be constrained observationally.In very massive stars, much of the pressure support comes from the radiation field, meaning that they are loosely bound, and that (d lg p/d lg ρ) adiabatic near the center is close to the minimum value necessary for stability. Near the end of C/O burning, the central temperature increases to the point that photons begin to be converted into electron-positron pairs, softening the equation of state below this critical value. The result is a runaway collapse, followed by explosive burning that completely obliterates the loosely-bound star. While these explosions can be up to 100 times more energetic that core collapse and Type Ia supernovae, their peak luminosities are only slightly greater. However, due both to copious Ni 56 production and hydrogen recombination, they are brighter much longer, and remain observable for ≈ 1 year.Since metal enrichment is a local process, PPSNe should occur in pockets of metal-free gas over a broad range of redshifts, greatly enhancing their detectability, and distributing their nucleosyntehtic products about the Milky Way. This means that measurements of the abundances of metal-free stars should be thought of as directly constraining these objects. It also means that ongoing supernova searches, which limit the contribution of very massive stars to < ∼ 1 % of the total star formation rate density out to z ≈ 2, already provide weak constraints for PPSN models. A survey with the NIRCam instrument on JWST, on the other hand, would be able to extend these limits to z ≈ 10. Observing a 0.3 deg 2 patch of sky for ≈ 1 week per year for three consecutive years, such a program would either detect or rule out the existence of these remarkable objects.

ARE SUPERLUMINOUS SUPERNOVAE AND LONG GRBs THE PRODUCTS OF DYNAMICAL PROCESSES IN YOUNG DENSE STAR CLUSTERS?

“…(According to Yungelson et al 2008, these limits are somewhat higher and occur between 250 and 800 M ⊙ .) These stars collapse in a luminous pairinstability supernova (Rakavy & Shaviv 1967;Langer et al 2007;Scannapieco 2009;Cooke et al 2012), giving rise to a SLSN-R, because these supernovae produce large amounts of 56 Ni, as was proposed for SN2007bi by Pan et al (2012). The Arches star cluster is located in the regime of forming a ∼ 170 M ⊙ collision runaway star, which is in the range for leading to a pair instability supernova.…”

“…3 the area to the right of the right-most solid blue curve and below the sold red curve). We speculate that these extremely massive stars produce SLSN-I/II by collapsing to a black hole of intermediate mass (Scannapieco 2009). The mass of the collision runaway can reach values of up to a few 10 3 M ⊙ (Portegies Zwart & McMillan 2002).…”