The hard TeV spectrum of 1ES 0229+200: new clues from Swift

TL;DR

This paper presents new Swift observations of 1ES 0229+200 that support a synchrotron-self Compton model explaining its extremely hard TeV spectrum through a high minimum energy electron distribution.

Contribution

It provides observational evidence from Swift data that supports a specific SSC model with a high minimum electron energy for the hard TeV spectrum of 1ES 0229+200.

Findings

Detection of a spectral break between UV and X-ray bands.

Confirmation of a very hard synchrotron continuum.

Support for the high minimum energy electron distribution model.

Abstract

The BL Lac object 1ES 0229+200 (z=0.14) has been detected by HESS during observations taking place in 2005-2006. The TeV spectrum, when corrected for the absorption of gamma-ray photons through the interaction with the extragalactic background light, is extremely hard, even if the most conservative level for the background is considered. The case of 1ES 0229+200 is very similar to that of 1ES 1101-232, for which a possible explanation, in the framework of the standard one-zone synchrotron-self Compton model, is that the high-energy emission is synchrotron-self Compton radiation of electrons distributed as a power law with a large value of the minimum energy. In this scenario the hard TeV spectrum is accompanied by a very hard synchrotron continuum below the soft X-ray band. We will show that recent Swift observations of 1ES 0229+200 in the critical UV-X-ray band strongly support this model, showing the presence of the expected spectral break and hard continuum between the UV and the X-ray bands.