Long term lightcurve of the BL Lac object 1ES 0229+200 at TeV energies

TL;DR

This study analyzes over a decade of H.E.S.S. observations of the BL Lac object 1ES 0229+200, revealing flux variability at TeV energies that impacts constraints on intergalactic magnetic fields and compares multi-frequency data.

Contribution

It provides the first detailed long-term lightcurve of 1ES 0229+200 at TeV energies, demonstrating flux variability and its implications for astrophysical constraints.

Findings

Detected flux variability on yearly and monthly timescales.

Challenged previous assumptions of constant flux in the source.

Compared VHE variations with multi-frequency observations.

Abstract

The high-frequency peaked BL Lac object 1ES 0229+200 (z = 0.14) was first detected in very high energy (VHE, E > 100 GeV) $\gamma$-rays by the H.E.S.S. (High Energy Stereoscopic System) collaboration in 2006. No flux variability was reported in the initial study and its spectral characteristics have been used to derive constraints on the extragalactic background light (EBL) and on the intergalactic magnetic field (IGMF). 1ES 0229+200 has been observed with H.E.S.S. for $\sim$130 hours from 2004 to 2013: the full dataset analysed with a more sensitive method will be presented here. The results indicate that the source is not constant and displays flux variability on yearly and monthly timescales. The existence of flux variability affects the derivation of the constraints on the IGMF. The H.E.S.S. observations cover several simultaneous multi-frequency campaigns and the VHE variations are compared with those reported in different bands.