We investigate if the gamma ray halo, for which recent evidence has been found in EGRET data, can be explained by neutralino annihilations in a clumpy halo. We find that the measured excess gamma ray flux can be explained through a moderate amount of clumping in the halo. Moreover, the required amount of clumping implies also a measureable excess of antiprotons at low energies, for which there ...

At the present time there are fewer then 10 confirmed sources of TeV gamma rays. While this lack of sources is partially due to the sensitivity of current instruments, it may also be due to the small field-of-view of current instruments coupled with the transient nature of astrophysical sources of TeV gamma rays. Milagro is a new type of extensive air shower array that uses water as the detecti...

EGRET can now study six pulsars since the recent detection of PSR B1951+32. Careful analysis of the three brightest pulsars shows that gamma rays are emitted through essentially the entire rotation. This calls into question the previous interpretation of the Crab’s lowlevel emission as due entirely to its nebula. The pulse light curves have either well-separated double peaks or very broad peaks...

The interest in the development of edible and biodegradable films has increased because it is every day more evident that non-degradable materials are doing much damage to the environment. Blends based on different ratios of plasticized poly(vinyl alcohol) (PVA), carboxymethyl cellulose (CMC) and Tannin compound were prepared by solution casting in the form of thin films. Then the blend films w...

We show that if the intrinsic break energy of Gamma-Ray Bursts (GRBs) is determined by the product of more than three random variables the observed break energy distribution becomes almost lognormal including the redshift effect because of the central limit theorem. The excess from the lognormal distribution at the low break energy is possibly due to the high redshift GRBs. The same argument ma...

We study the distribution of the durations of gamma-ray bursts (GRBs) in the unified model of short and long GRBs recently proposed by Yamazaki, Ioka, and Nakamura. Monte Carlo simulations show clear bimodal distributions, with lognormal-like shapes for both short and long GRBs, in a power-law as well as a Gaussian angular distribution of the subjets. We find that the bimodality comes from the ...

We show that the collapsar model of gamma-ray bursts results in a series of successive shocks and rarefaction waves propagating in the ‘‘ cork ’’ of stellar material being pushed ahead of the jet, as it emerges from the massive stellar progenitor. Our results are derived from analytical calculations assuming a hot, ultrarelativistic one-dimensional flowwith an initial Lorentz factor j 100. The ...

It is important to measure the bulk-etching rate for any solid state nuclear track detectors, because they have an application in different fields of sciences. The effect of gamma rays emitted from 60 Co source with different doses on LR-115 detector was studied. The bulk etching rate of the detectors was measured before and after irradiation using gamma source. From the results the values of t...

Most X-ray afterglows of gamma-ray bursts (GRBs) observed by the Swift satellite have a shallow decay phase ∝ t in the first thousands of seconds. We discuss that the shallow decay requires an unreasonably high gamma-ray efficiency, & 75–90%, within current models, which is difficult to be produced by internal shocks. Such a crisis may be avoided if a weak relativistic explosion occurs ∼ 10–10 ...