A spectral hardening in the Fermi-LAT Data of 1ES 0502+675

TL;DR

This study analyzes Fermi-LAT data of the blazar 1ES 0502+675, revealing a significant spectral hardening around 1 GeV during a flaring state, interpreted as a transition between emission components.

Contribution

It identifies a spectral hardening feature in the gamma-ray spectrum of 1ES 0502+675 and interprets it within a one-zone SSC model, highlighting a transition between emission components.

Findings

Significant spectral hardening at ~1 GeV during flaring state.

Photon index changes from ~2.36 to ~1.33 across the break.

Spectral hardening explained as transition between synchrotron and SSC components.

Abstract

The $\gamma$-ray spectral feature of the blazar 1ES 0502+675 is investigated by using Fermi Large Area Telescope (Fermi-LAT) Pass 8 data (between 100 MeV and 300 GeV) covering from 2008 August to 2021 April. A significant ($\sim4\sigma$) hardening at $\sim$ 1 GeV is found in the $\gamma$-ray spectrum during a moderately flaring state (MJD 55050-55350). The photon index below and above the break energy is $\Gamma_1=2.36\pm0.31$ and $\Gamma_2=1.33\pm0.11$, respectively. In the rest of the observations, the $\gamma$-ray spectrum can be described by a power-law form with the photon index of $\approx1.6$. In the frame of a one-zone synchrotron self-Compton (SSC) model, the spectral hardening is interpreted as the transition between the synchrotron component and the SSC component. This could be the result of a slight increase of the break/maximum Lorentz factor of the electrons.