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Search for Gamma-Ray events in ALBORZ observatory data

Khakian Ghomi, M ; Sharif University of Technology | 2009

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  1. Type of Document: Article
  2. Publisher: University of Lodz , 2009
  3. Abstract:
  4. At ALBORZ Observatory in Tehran (51° 200 , 35 ° 430' , 1200 m) we accumulated a complete year of data by a 4-fold square array of Water Cherenkov Detectors (WCDs) with the side 6.08 m. It is recorded about 800,000 fine EAS events from 2006/11/12 to 2007/11/20 by the approximate recording rate of 0.03. Time differences between each two, three, four, five and ... have a very good agreement with gammafunction, which shows the correct random nature of the events. Of course we expect that about less than 1% of the EAS events (≤9000 events) be electromagnetic and naturally not random, but the contribution is so small. Then by Farley/Storey procedure [1] we found a signature of real sidereal data. So we tried to find the data by Li/Ma method [2] around EGRET gamma sources, but we didn't find any acceptable signatures (statistical significance more than 2). Then by investigation of number of recorded events in 6 time intervals 10, 30, 100, 300, 1000 and 3000 seconds (time boxes) we found 12 non-random events. This procedure did by the investigation of deviation from Poisson distribution function in at least three of the six time boxes. By the angular resolution of our experiment we can attribute these events to a few EGRET sources, which this stage is under investigation now
  5. Keywords:
  6. EGRET sources ; Gamma-ray events ; Poisson distribution function ; Cosmic rays ; Observatories ; Poisson distribution ; Angular resolution ; Gamma source ; Square array ; Statistical significance ; Time interval ; Time-differences ; Water Cherenkov detectors ; Gamma rays
  7. Source: 31st International Cosmic Ray Conference, ICRC 2009, Lodz, 7 July 2009 through 15 July 2009 ; 2009
  8. URL: http://icrc2009.uni.lodz.pl/proc/pdf/icrc0575.pdf