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

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 ($\sim 4\sigma$) 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 ${\Gamma }_1=2.36\pm 0.31$ and ${\Gamma }_2=1.33\pm 0.11$, respectively. In the rest of the observations, the $\gamma$-ray spectrum can be described by a power-law form with the photon index of $\approx 1.6$. 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.

arXiv commentAccepted by MNRAS

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