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Recent observations support the suggestion that short-duration gamma-ray bursts are produced by compact star mergers. The x-ray flares discovered in two short gamma-ray bursts last much longer than the previously proposed postmerger energy-release time scales. Here, we show that they can be produced by differentially rotating, millisecond pulsars after the mergers of binary neutron stars. The differential rotation leads to windup of interior poloidal magnetic fields and the resulting toroidal fields are strong enough to float up and break through the stellar surface. Magnetic reconnection-driven explosive events then occur, leading to multiple x-ray flares minutes after the original gamma-ray burst.

Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

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Gamma-ray bursts (GRBs) serve as powerful probes of the early Universe, with their luminous afterglows revealing the locations and physical properties of star forming galaxies at the highest redshifts, and potentially locating first generation (Population III) stars. Since GRB afterglows have intrinsically very simple spectra, they allow robust redshifts from low signal to noise spectroscopy, or photometry. Here we present a photometric redshift of z ∼ 9.4 for the Swift detected GRB 090429B based on -3deep observations with Gemini-North, the Very Large Telescope, and the GRB Optical and Near-infrared Detector. Assuming an Small Magellanic Cloud dust law (which has been found in a majority of GRB sight-lines), the 90% likelihood range for the redshift is 9.06 < z < 9.52, although there is a low-probability tail to somewhat lower redshifts. Adopting Milky Way or Large Magellanic Cloud dust laws leads to very similar conclusions, while a Maiolino law does allow somewhat lower redshift solutions, but in all cases the most likely redshift is found to be z > 7. The non-detection of the host galaxy to deep limits (Y (AB) ∼ 28, which would correspond roughly to 0.001L * at z = 1) in our late time optical and infrared observations with the Hubble Space Telescope, strongly supports the extreme redshift origin of GRB 090429B, since we would expect to have detected any low-z galaxy, even if it were highly dusty. Finally, the energetics of GRB 090429B are comparable to those of other GRBs, and suggest that its progenitor is not greatly different to those of lower redshift bursts.

In this review article we present an up-to-date progress report of the connection between long-duration (and their various sub-classes) gamma-ray bursts (GRBs) and their accompanying supernovae (SNe). The analysis presented here is from the point of view of an observer, with much of the emphasis placed on how observations, and the modelling of observations, have constrained what we known about GRB-SNe. We discuss their photometric and spectroscopic properties, their role as cosmological probes, including their measured luminosity−decline relationships, and how they can be used to measure the Hubble constant. We present a statistical analysis of their bolometric properties, and use this to determine the properties of the "average" GRB-SN: which has a kinetic energy of E K ≈ 2.5 × 10 52 erg (σ E K = 1.8 × 10 52 erg), an ejecta mass of M ej ≈ 6 M (σ M ej = 4 M ), a nickel mass of M Ni ≈ 0.4 M (σ M Ni = 0.2 M ), an ejecta velocity at peak light of v ≈ 20, 000 km s −1 (σ v ph = 8, 000 km s −1 ), a peak bolometric luminosity of L p ≈ 1×10 43 erg s −1 (σ Lp = 0.4×10 43 erg s −1 ), and it reaches peak bolometric light in t p ≈ 13 days (σ tp = 2.7 days). We discuss their geometry, as constrained from observations, and consider the various physical processes that are thought to power the luminosity of GRB-SNe, and whether differences exist between GRB-SNe and the SNe associated with ultra-long duration GRBs such as GRB 111209A/SN 2011kl. We discuss how observations of the environments of GRB-SNe further constrain the physical properties of their pre-explosion progenitor stars, and give a brief overview of the current theoretical paradigms of the central engines that produce the various types of GRB-SNe. Furthermore, we present an overview of the r-process, radioactively powered transients that have been photometrically associated with short-duration GRBs, and we conclude the review by discussing what additional research is needed to further our understanding of GRB-SNe, in particular the role of binary-formation channels and the connection of GRB-SNe with superluminous SNe. arXiv:1604.03549v2 [astro-ph.HE] 18 Jul 2016 1 A: Strong spectroscopic evidence. B: A clear light curve bump as well as some spectroscopic evidence resembling a GRB-SN. C: A clear bump consistent with other GRB-SNe at the spectroscopic redshift of the GRB. D: A bump, but the inferred SN properties are not fully consistent with other GRB-SNe or the bump was not well sampled or there is no spectroscopic redshift of the GRB. E: A bump, either of low significance or inconsistent with other GRB-SNe. * Denotes exact, K-corrected rest-frame filter observable. ‡ Values fixed during fit.k ands denote the filter-averaged luminosity (k) and stretch (s) factors relative to SN 1998bw.

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