Search for TeV ${\hat{I}}^3$ -rays from H1426+428 during 2004-07 with the TACTIC telescope

Abstract

The BL Lac object H1426+428 ($z\equiv 0.129$) is an established source of TeV ${\hat{I}}^3$-rays and detections of these photons from this object also have important implications for estimating the Extragalactic Background Light (EBL) in addition to the understanding of the particle acceleration and ${\hat{I}}^3$-ray production mechanisms in the AGN jets. We have observed this source for about 244h in 2004, 2006 and 2007 with the TACTIC ${\hat{I}}^3$-ray telescope located at Mt. Abu, India. Detailed analysis of these data do not indicate the presence of any statistically significant TeV ${\hat{I}}^3$-ray signal from the source direction. Accordingly, we have placed an upper limit of $\le 1.18\times 10^{-12}$ $photons$ $c{m}^{-2}$ $s^{-1}$ on the integrated ${\hat{I}}^3$-ray flux at 3$\ddot{I}ƒ$ significance level.

11 pages, 5 figures accepted for publication in Journal of Physics G: Nuclear and Particle Physics