Search for TeV $\gamma$ -rays from H1426+428 during 2004-07 with the TACTIC telescope

TL;DR

This study observed the BL Lac object H1426+428 with the TACTIC telescope over multiple years but did not detect significant TeV gamma-ray emission, setting an upper flux limit to inform future astrophysical models.

Contribution

First detailed multi-year TeV gamma-ray observations of H1426+428 with the TACTIC telescope resulting in flux upper limits rather than detection.

Findings

No statistically significant TeV gamma-ray signal detected.

Established an upper limit on gamma-ray flux at 3σ significance.

Results have implications for understanding EBL and AGN jet mechanisms.

Abstract

The BL Lac object H1426+428 ($z\equiv 0.129$) is an established source of TeV $\gamma$-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 $\gamma$-ray production mechanisms in the AGN jets. We have observed this source for about 244h in 2004, 2006 and 2007 with the TACTIC $\gamma$-ray telescope located at Mt. Abu, India. Detailed analysis of these data do not indicate the presence of any statistically significant TeV $\gamma$-ray signal from the source direction. Accordingly, we have placed an upper limit of $\leq1.18\times10^{-12}$ $photons$ $cm^{-2}$ $s^{-1}$ on the integrated $\gamma$-ray flux at 3$\sigma$ significance level.