Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants-neutron stars and black holes-are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood.

The plateau in the duration distribution of long Gamma-Ray Bursts (LGRBs) provides a direct observational evidence for the Collapsar model. The plateau reflects the fact that the observed duration satisfies: T 90 = t e − t b where t e is the time that the central engine operates and t b is a threshold time, interpreted within the Collapsar model as the time it takes for the relativistic jet to penetrate the stellar envelope. Numerical simulation and macronova observations suggest that compact binary mergers involve mass ejection. If short-Gamma Ray Bursts (sGRBs) arise from such mergers, their jets should cross this surrounding ejecta before producing the prompt emission. Like in LGRBs, this should result in a distinct short plateau in the GRBs' duration distribution. We present a new analysis of the duration distribution for the three GRB satellites: BATSE, Swift and Fermi. We find a clear evidence for a short (∼ 0.4 sec) plateau in the duration distribution. This plateau is consistent with the expected jet crossing time, provided that the ejecta is of order of a few percent of solar masses.

GRB 170817A is a weak short gamma-ray burst (GRB) accompanied by the gravitational wave (GW) event GW170817. It is believed, that an off beaming relativistic jet, produces this weak GRB. Here we use the E p,i − E iso and Γ − E iso relations to determine the Lorentz factor Γ and the viewing angle from the edge of the jet θ • . This corresponds to the on-axis E p,i = 415 +361 −167 keV and E iso = (2.447 ergs of the GRB, which is an intrinsically weak short GRB. Interestingly, the Doppler factor and the luminosity follow a universal relation from GRBs and blazars, which indicates they may share similar radiation mechanism.

Abstract. Cosmic neutrino events detected by the IceCube Neutrino Observatory with energy30 TeV have poor angular resolutions to reveal their origin. Ultrahigh-energy cosmic rays (UHECRs), with better angular resolutions at > 60 EeV energies, can be used to check if the same astrophysical sources are responsible for producing both neutrinos and UHECRs. We test this hypothesis, with statistical methods which emphasize invariant quantities, by using data from the Pierre Auger Observatory, Telescope Array and past cosmic-ray experiments. We find that the arrival directions of the cosmic neutrinos are correlated with ≥ 100 EeV UHECR arrival directions at confidence level ≈ 90%. The strength of the correlation decreases with decreasing UHECR energy and no correlation exists at energy ∼ 60 EeV. A search in astrophysical databases within 3 • of the arrival directions of UHECRs with energy ≥ 100 EeV, that are correlated with the IceCube cosmic neutrinos, resulted in 18 sources from the Swift-BAT X-ray catalog with redshift z ≤ 0.06. We also found 3 objects in the Kühr catalog of radio sources using the same criteria. The sources are dominantly Seyfert galaxies with Cygnus A being the most prominent member. We calculate the required neutrino and UHECR fluxes to produce the observed correlated events, and estimate the corresponding neutrino luminosity (25 TeV-2.2 PeV) and cosmic-ray luminosity (500 TeV-180 EeV), assuming the sources are the ones we found in the Swift-BAT and Kühr catalogs. We compare these luminosities with the X-ray luminosity of the corresponding sources and discuss possibilities of accelerating protons to 100 EeV and produce neutrinos in these sources.arXiv:1501.05158v2 [astro-ph.HE] 8 Jul 2015

High-energy neutrino (HEN) and gravitational wave (GW) can probe astrophysical sources in addition to electromagnetic observations. Multimessenger studies can reveal nature of the sources which may not be discerned from one type of signal alone. We discuss HEN emission in connection with the Advanced Laser Interferometer Gravitational-wave Observatory (ALIGO) event GW150914 which could be associated with a short gamma-ray burst (GRB) detected by the Fermi Gamma-ray Burst Monitor (GBM) 0.4 s after the GW event and within localization uncertainty of the GW event. We calculate HEN flux from this short GRB, GW150914-GBM, and show that non-detection of a high-energy starting event (HESE) by the IceCube Neutrino Observatory can constrain the total isotropic-equivalent jet energy of this short burst to be less than 3 × 10 52 erg.