Understanding the properties of Pop III stars is prerequisite to elucidating the nature of primeval galaxies, the chemical enrichment and reionization of the early IGM, and the origin of supermassive black holes. While the primordial IMF remains unknown, recent evidence from numerical simulations and stellar archaeology suggests that some Pop III stars may have had lower masses than previously thought, 15 - 50 Ms in addition to 50 - 500 Ms. The detection of Pop III supernovae by JWST, WFIRST or the TMT could directly probe the primordial IMF for the first time. We present numerical simulations of 15 - 40 Ms Pop III core-collapse SNe done with the Los Alamos radiation hydrodynamics code RAGE. We find that they will be visible in the earliest galaxies out to z ~ 10 - 15, tracing their star formation rates and in some cases revealing their positions on the sky. Since the central engines of Pop III and solar-metallicity core-collapse SNe are quite similar, future detection of any Type II supernovae by next-generation NIR instruments will in general be limited to this epoch.
The merger of two white dwarfs (a.k.a. double degenerate merger) has often been cited as a potential progenitor of type Ia supernovae. Here we combine population synthesis, merger and explosion models with radiation-hydrodynamics light-curve models to study the implications of such a progenitor scenario on the observed type Ia supernova population. Our standard model, assuming double degenerate mergers do produce thermonuclear explosions, produces supernova light-curves that are broader than the observed type Ia sample. In addition, we discuss how the shock breakout and spectral features of these double degenerate progenitors will differ from the canonical bare Chandrasekhar-massed explosion models. We conclude with a discussion of how one might reconcile these differences with current observations.
Astronomers have proposed a number of mechanisms to produce supernova explosions. Although many of these mechanisms are now not considered primary engines behind supernovae, they do produce transients that will be observed by upcoming ground-based surveys and NASA satellites. Here we present the first radiation-hydrodynamics calculations of the spectra and light curves from three of these failed supernovae: supernovae with considerable fallback, accretion induced collapse of white dwarfs, and energetic helium flashes (also known as type .Ia supernovae).
We investigate the effect of including a significant ``binary twin population (binaries with almost equal mass stars, q = M2/M1 > 0.95) for the production of double compact objects and some resulting consequences, including LIGO inspiral rate and some properties of short-hard gamma-ray bursts. We employ very optimistic assumptions on the twin fraction (50%) among all binaries, and therefore our calculations place an upper limits on the influence of twins on double compact object populations. We show that for LIGO the effect of including twins is relatively minor: although the merger rates does indeed increase when twins are considered, the rate increase is fairly small (1.5). Also, chirp mass distribution for double compact objects formed with or without twins are almost indistinguishable. If double compact object are short-hard GRB progenitors, including twins in population synthesis calculations does not alter significantly the earlier rate predictions for the event rate. However, for one channel of binary evolution, introducing twins more than doubles the rate of ``very prompt NS-NS mergers (time to merger less than 1 Myr) compared to models with the ``flat q distribution. In that case, 70% of all NS-NS binaries merge within 100 Myr after their formation, indicating a possibility of a very significant population of ``prompt short-hard gamma-ray bursts, associated with star forming galaxies. We also point out that, independent of assumptions, fraction of such prompt neutron star mergers is always high, 35--70%. We note that recent observations (e.g., Berger et al.) indicate that fraction of short-hard GRBs found in young hosts is at least 40% and possibly even 80%.
