Gamma-Ray bursts: accumulating afterglow implications, progenitor clues, and prospects

Nanosecond radio bursts from strong plasma turbulence in the Crab pulsar

The Crab pulsar was discovered by the occasional exceptionally bright radio pulses it emits, subsequently dubbed 'giant' pulses. Only two other pulsars are known to emit giant pulses. There is no satisfactory explanation for the occurrence of giant pulses, nor is there a complete theory of the pulsar emission mechanism in general. Competing models for the radio emission mechanism can be distinguished by the temporal structure of their coherent emission. Here we report the discovery of isolated, highly polarized, two-nanosecond subpulses within the giant radio pulses from the Crab pulsar. The plasma structures responsible for these emissions must be smaller than one metre in size, making them by far the smallest objects ever detected and resolved outside the Solar System, and the brightest transient radio sources in the sky. Only one of the current models--the collapse of plasma-turbulent wave packets in the pulsar magnetosphere--can account for the nanopulses we observe.

TeV neutrinos from successful and choked gamma-ray bursts

Core collapse of massive stars resulting in a relativistic fireball jet which breaks through the stellar envelope is a widely discussed scenario for gamma-ray burst production. For very extended or slow rotating stars, the jet may be unable to break through the envelope. Both penetrating and choked jets will produce, by photomeson interactions of accelerated protons, a burst of greater, greater than or similar to 5 TeV neutrinos while propagating in the envelope. The predicted flux, from both penetrating and choked jets, should be easily detectable by planned 1 km(3) neutrino telescopes.

Probing microquasars with TeV neutrinos

The jets associated with galactic microquasars are believed to be ejected by accreting stellar mass black holes or neutron stars. We show that if the energy content of the jets in the transient sources is dominated by electron-proton plasma, then a several hour outburst of 1-100 TeV neutrinos produced by photomeson interactions should precede the radio flares associated with major ejection events. Several neutrinos may be detected during a single outburst by a 1 km(2) detector, thereby providing a powerful probe of microquasar jet physics.