In this paper I briefly review recent progress in the field of groundbased gamma ray astrophysics.

The Gamma-Ray Optical Counterpart Search Experiment (GROCSE) presents new experimental upper limits on the optical flux from gamma-ray bursts (GRBs). Our experiment consisted of a fully-automated very wide-field opto-electronic detection system that imaged locations of GRBs within a few seconds of receiving trigger signals provided by BATSE’s real-time burst coordinate distribution network (BAC...

Gamma-band (25-90 Hz) peaks in local field potential (LFP) power spectra are present throughout the cerebral cortex and have been related to perception, attention, memory, and disorders (e.g., schizophrenia and autism). It has been theorized that gamma oscillations provide a "clock" for precise temporal encoding and "binding" of signals about stimulus features across brain regions. For gamma to...

The Gamma-Ray Large Area Space Telescope (GLAST), scheduled to be launched in fall 2007, is the next generation satellite for high-energy gamma-ray astronomy. The Large Area Telescope (LAT), GLAST main instrument, with a wide field of view (> 2 sr), a large effective area (> 8000 cm at 1 GeV) and 20 MeV 300 GeV energy range, will provide excellent high energy gamma-ray observations for Dark Mat...

In models for gamma ray burst afterglows, it is normally assumed that the external shock strongly amplifies the magnetic field and that this field maintains a steady value throughout the shocked region. We discuss the effects of modifying this (probably simplistic) assumption. The observations are incompatible with a post-shock field that decays too rapidly. However if the field pervaded only a...

We point out that already existing literature on relativistic collisionless MHD shocks show that the parameter σ ≡ upstream proper magnetic energy density/upstream rest mass energy density, plays an important role in determining the structure and accelerating properties of such shocks. By adopting the value of σ ≈ 0.002 which corresponds to the relativistic shock associated with the Crab nebula...

Gamma-Ray Burst (GRB) prompt emission can, for specific conditions, be so powerful and short-pulsed to strongly influence any surrounding plasma. In this paper, we briefly discuss the possibility that a very intense initial burst of radiation produced by GRBs satisfy the intensity and temporal conditions to cause stochastic wake-field particle acceleration in a surrounding plasma of moderate de...

We study the internal structural properties of 37 long duration gamma-ray burst (GRB) host galaxies imaged with the Hubble Space Telescope. Our goal is to gain insights in the type of galaxies that gives rise to GRBs, and the relationship of GRB hosts to high-redshift galaxies selected through more traditional photometric methods. We measure structural properties of our sample from Hubble Space...

Two gamma-radiation distribution field measurement experiments are described in the paper. Because of principally dangerous nature of gamma-radiation, the idea was to extensively use robotic systems and automation to minimize human exposure to radiation. The experiment setup as well as Orpheus robotic system are described. Algorithm to autonomously navigate the robot based on RTK GNSS in predef...