Search for TeV $\gamma$--ray emission from blazar 1ES1218+304 with TACTIC telescope during March-April 2013

TL;DR

This study reports on TeV gamma-ray observations of blazar 1ES 1218+304 using the TACTIC telescope, finding no significant activity but setting upper limits and analyzing multi-wavelength data from radio to gamma rays.

Contribution

First simultaneous multi-wavelength analysis of 1ES 1218+304 during TACTIC observations, providing upper limits on TeV emission and multi-band activity without detection.

Findings

No TeV gamma-ray activity detected during observation period.

Established upper limits on TeV flux consistent with previous measurements.

No significant variability observed across radio, optical, UV, X-ray, and gamma-ray bands.

Abstract

In this paper, we present results of TeV $\gamma$--ray observations of the high synchrotron peaked BL Lac object 1ES 1218+304 (z=0.182) with the $TACTIC$ (TeV Atmospheric Cherenkov Telescope with Imaging Camera). The observations are primarily motivated by the unusually hard GeV-TeV spectrum of the source despite its relatively large redshift. The source is observed in the TeV energy range with the $TACTIC$ from March 1, 2013 to April 15, 2013 (MJD 56352--56397) for a total observation time of 39.62 h and no evidence of TeV $\gamma$--ray activity is found from the source. The corresponding 99$\%$ confidence level upper limit on the integral flux above a threshold energy of 1.1 TeV is estimated to be 3.41 $\times10^{-12}$ photons cm$^{-2}$ s$^{-1}$ (i.e $<23\%$ Crab Nebula flux) assuming a power law differential energy spectrum with photon index 3.0, as previously observed by the $MAGIC$ and $VERITAS$ telescopes. For the study of multi-wavelength emission from the source, we use nearly simultaneous optical, UV and and X--ray data collected by the UVOT and XRT instruments on board the \emph{Swift} satellite and high energy $\gamma$--ray data collected by the Large Area Telescope on board the \emph{Fermi} satellite. We also use radio data at 15 GHz from OVRO 40 m telescope in the same period. No significant increase of activity is detected from radio to TeV $\gamma$--rays from 1ES1218+304 during the period from March 1, 2013 to April 15, 2013.