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Title: Results of a southern-hemisphere search for gamma-ray sources at E/sub gamma/greater than or equal to3times10$sup 11$ eV

Abstract

The optical intensity interferometer operated by Sydney University at Narrabri, NSW, Australia, was converted in 1972 April to a sensitive detector of atmospheric Cerenkov light from extensive air showers (EAS) with E$sub 0$>2times10$sup 11$ eV. Its two 7-m aperture optical reflectors were separated by 120 m and pointed by computer at the mean altitude for the maximum development of EAS from the direction of an object to be studied. Off-axis photomultipliers on the reflectors viewed the atmospheric Cerenkov light from EAS muon cores, thus enabling rejection of greater than or equal to50 percent of EAS detected as being cosmic-ray-initiated. Possible (greater than or equal to3 sigma) sources were found in 1972 in the directions of Cen A (NGC 5128), the Vela Pulsar, and MP 1451, out of 11 candidate objects studied. The objects included pulsars, unusual X-ray sources, active galaxies, a supernova, and lower energy (approx.100 MeV) $gamma$-ray sources such as the galactic center. (Confirmation of the 1972 results was attempted in an improved series of observations in 1973 April-June and 1974 March-April. The Cen A result was confirmed and is reported elsewhere. Upper limits are given here for the other objects, together with evidence for a variable for amore » variable pulsed flux from the Vela Pulsar. Implications of the results are discussed. (AIP)« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Center for Astrophysics, Harvard College Observatory and Smithsonian Astrophysical Observatory
OSTI Identifier:
4113411
NSA Number:
NSA-33-018087
Resource Type:
Journal Article
Journal Name:
Astrophys. J., v. 201, no. 1, pp. 82-89
Additional Journal Information:
Other Information: Orig. Receipt Date: 30-JUN-76
Country of Publication:
United States
Language:
English
Subject:
N56300* -Physics (Astrophysics & Cosmology)-Quasi-stellar, Radio & X-Ray Sources; N56200 -Physics (Astrophysics & Cosmology)-Stars; N56500 -Physics (Astrophysics & Cosmology)-Galaxies; 640103* -Physics Research-Astrophysics & Cosmology-Quasi- Stellar, Radio & X-Ray Sources; *COSMIC GAMMA SOURCES- GAMMA RADIATION; CHERENKOV RADIATION; COSMIC X-RAY SOURCES; GALAXIES; MUONS; PULSARS; SUPERNOVAE

Citation Formats

Grindlay, J E, Helmken, H F, Brown, R H, Davis, J, and Allen, L R. Results of a southern-hemisphere search for gamma-ray sources at E/sub gamma/greater than or equal to3times10$sup 11$ eV. United States: N. p., 1975. Web.
Grindlay, J E, Helmken, H F, Brown, R H, Davis, J, & Allen, L R. Results of a southern-hemisphere search for gamma-ray sources at E/sub gamma/greater than or equal to3times10$sup 11$ eV. United States.
Grindlay, J E, Helmken, H F, Brown, R H, Davis, J, and Allen, L R. Wed . "Results of a southern-hemisphere search for gamma-ray sources at E/sub gamma/greater than or equal to3times10$sup 11$ eV". United States.
@article{osti_4113411,
title = {Results of a southern-hemisphere search for gamma-ray sources at E/sub gamma/greater than or equal to3times10$sup 11$ eV},
author = {Grindlay, J E and Helmken, H F and Brown, R H and Davis, J and Allen, L R},
abstractNote = {The optical intensity interferometer operated by Sydney University at Narrabri, NSW, Australia, was converted in 1972 April to a sensitive detector of atmospheric Cerenkov light from extensive air showers (EAS) with E$sub 0$>2times10$sup 11$ eV. Its two 7-m aperture optical reflectors were separated by 120 m and pointed by computer at the mean altitude for the maximum development of EAS from the direction of an object to be studied. Off-axis photomultipliers on the reflectors viewed the atmospheric Cerenkov light from EAS muon cores, thus enabling rejection of greater than or equal to50 percent of EAS detected as being cosmic-ray-initiated. Possible (greater than or equal to3 sigma) sources were found in 1972 in the directions of Cen A (NGC 5128), the Vela Pulsar, and MP 1451, out of 11 candidate objects studied. The objects included pulsars, unusual X-ray sources, active galaxies, a supernova, and lower energy (approx.100 MeV) $gamma$-ray sources such as the galactic center. (Confirmation of the 1972 results was attempted in an improved series of observations in 1973 April-June and 1974 March-April. The Cen A result was confirmed and is reported elsewhere. Upper limits are given here for the other objects, together with evidence for a variable for a variable pulsed flux from the Vela Pulsar. Implications of the results are discussed. (AIP)},
doi = {},
journal = {Astrophys. J., v. 201, no. 1, pp. 82-89},
number = ,
volume = ,
place = {United States},
year = {1975},
month = {10}
}