Detection of the BL Lac object 1ES1426+428 in the Very High Energy gamma-ray band by the CAT Telescope from 1998-2000 - IN2P3 - Institut national de physique nucléaire et de physique des particules Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2002

Detection of the BL Lac object 1ES1426+428 in the Very High Energy gamma-ray band by the CAT Telescope from 1998-2000

B. Khelifi
R. Bazer-Bachi
  • Function : Author
G. Debiais
  • Function : Author
Benoît Fabre
P. Goret
  • Function : Author
C. Gouiffes
  • Function : Author
F. Piron
M. Punch
L. Rob
  • Function : Author

Abstract

The BL Lac Object 1ES 1426+428, at a red-shift of z=0.129, has been monitored by the CAT telescope from February 1998 to June 2000. The accumulation of 26 hours of observations shows a gamma-ray signal of 321 events above 250 GeV at 5.2 standard deviations, determined using data analysis cuts adapted to a weak, steep-spectrum source. The source emission has an average flux of Phi_diff(400 GeV) = 6.73 +/- 1.27stat +/- 1.45syst x 10^-11 /cm^-2/s/TeV, and a very steep spectrum, with a differential spectral index of gamma = -3.60 +/- 0.57 which can be refined to gamma = -3.66 +/- 0.41 using a higher flux data subset. If, as expected from its broad-band properties, the Very High Energy emission is hard at the source, these observations support a strong absorption effect of gamma-rays by the Intergalactic Infrared field.

Dates and versions

in2p3-00013644 , version 1 (17-07-2006)

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Cite

A. Djannati-Atai, B. Khelifi, S. Vorobiov, R. Bazer-Bachi, G. Debiais, et al.. Detection of the BL Lac object 1ES1426+428 in the Very High Energy gamma-ray band by the CAT Telescope from 1998-2000. Astronomy and Astrophysics - A&A, 2002, 391, pp.L25-L28. ⟨in2p3-00013644⟩
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