Preliminary results of the Cerenkov EAS flashes the Crimean Astrophysical Observatory

The facility designed for the study of angular resolution of light in the extensive air showers EAS flashes is described. The threshold energy of the facility is about 3 x 10 to the 12h power eV. The data on the angular distribution of light in a flash and the ratio of the flux in the UV and visual region as a function of the distance to the axis of a shower are given. Obtained results are compared to the published computations

A High-Energy Study of the Geminga Pulsar

We present the results of deep X-ray and gamma-ray observations of the Geminga pulsar obtained in the final years of the ASCA and CGRO missions, and an upper limit from RXTE. A phase-connected ephemeris from the gamma-rays is derived that spans the years 1973-2000, after allowing for a minor glitch in frequency of Delta f/f = 6.2 x 10^-10 in late 1996. ASCA observations of the hard X-ray pulse profile in 1994 and 1999 confirm this glitch. An improved characterization of the hard X-ray pulse profile and spectrum from the long ASCA observation of 1999 confirms that there is a non-thermal X-ray component that is distinct from the gamma-ray spectrum as measured by EGRET. It can be parameterized as a power-law of photon index Gamma = 1.72 +/- 0.10 with a flux of 2.62 x 10^-13 ergs/cm^2/s in the 0.7-5 keV band and pulsed fraction 0.54 +/- 0.05, similar to, but more precise than values measured previously. An extrapolation of this spectrum into the energy band observed by the RXTE PCA is consistent with the non-detection of pulsed emission from Geminga with that instrument. These results are interpreted in the context of outer-gap models, and motivations for future X-ray observations of Geminga are given.Comment: 22 pages including 7 figure