We present motivations for and study feasibility of a small, rapid-optical/IR responsegamma-ray burst (GRB) space observatory. By analyzing existing GRB data, we give realisticdetection rates for X-ray and optical/IR instruments of modest size under actual flightconditions. Given new capabilities of fast optical/IR response (~1 s to target) andsimultaneous multi-band imaging, such an observatory can have a reasonable event rate,likely leading to new science. Requiring a Swift-like orbit, duty cycle,and observing constraints, a Swift-BAT scaled down to 190 cm2of detector area would still detect and locate about 25 GRB yr-1 for a triggerthreshold of 6.5σ. About 23% of X–ray located GRB would be detectedoptically for a 10 cm diameter instrument (~6 yr-1 for the6.5σ X-ray trigger).

The potential of GRB analyses (including highly redshifted objects) with ESA mission Gaiais briefly addressed.

The origin of ultra-high energy cosmic rays (UHECR) has been widely regarded as one ofthe major questions in the frontiers of particle astrophysics. Gamma ray bursts (GRB), themost violent explosions in the universe second only to the Big Bang, have been a popularcandidate site for UHECR productions. The recent IceCube report on the non-observation ofGRB induced neutrinos therefore attracts wide attention. This dilemma requires aresolution: either the assumption of GRB as UHECR accelerator is to be abandoned or theexpected GRB induced neutrino yield was wrong. It has been pointed out that IceCube hasoverestimated the neutrino flux at GRB site by a factor of ~5. In this paper we pointout that, in addition to the issue of neutrino production at source, the neutrinooscillation and the possible neutrino decay during their flight from GRB to Earth shouldfurther reduce the detectability of IceCube, which is most sensitive to the muon-neutrinoflavor as far as point-source identification is concerned. Specifically, neutrinooscillation will reduce the muon-neutrino flavor ratio from 2/3 per neutrino at GRB sourceto 1/3 on Earth, while neutrino decay, if exists and under the assumption of normalhierarchy of mass eigenstates, would result in a further reduction of muon-neutrino ratioto 1/8. With these in mind, we note that there have been efforts in recent years inpursuing other type of neutrino telescopes based on Askaryan effect, which can inprinciple observe and distinguish all three flavors with comparable sensitivities. Suchnew approach may therefore be complementary to IceCube in shedding more lights on thiscosmic accelerator question.

Owing to its wide sky coverage and broad energy range, the FermiGamma-ray Burst Monitor (GBM) is an excellent observer of the transient hardX-ray sky. GBM detects about 240 triggered Gamma-Ray Bursts (GRBs) per year, includingover 30 which also trigger the Swift Burst Alert Telescope (BAT). Thenumber of GRBs seen in common with Swift is smaller than expected fromthe overlap in sky coverage because GBM is not as sensitive as the BAT and the GBM GRBpopulation is thus skewed to the brighter, closer bursts. This population includes about45 short GRBs per year, giving GBM an excellent opportunity to observe the electromagneticcounterpart to any gravitational wave candidate resulting from the merger of compactbinary members. The same characteristics make GBM an ideal partner for neutrino searchesfrom nearby GRBs, and for the elusive Very-High Energy (VHE) counterparts to GRBs. Withthe deployment of the next-generation gravitational-wave detectors (Advanced LIGO/VIRGO)and VHE experiments (CTA and HAWC) potentially within the lifetime of the FermiGamma-ray Space Telescope, the prospects for breakthrough observations aregood.

Cosmic-rays are subatomic particles of energies ranging between a few eV to hundreds ofTeV. These particles register a power-law spectrum, and it seems that most of themoriginate from astrophysical galactic and extragalactic sources. The shock acceleration insuperalfvenic astrophysical plasmas, is believed to be the main mechanism responsible forthe production of the non-thermal cosmic-rays. Especially, the importance of the very highenergy cosmic-ray acceleration, with its consequent gamma-ray radiation and neutrinoproduction in the shocks of the relativistic jets of Gamma Ray Bursts, is a favourabletheme of study. I will discuss the cosmic-ray shock acceleration mechanism particularlyfocusing on simulation studies of cosmic-ray acceleration occurring in the relativisticshocks of GRB jets.