Hunting extreme BL Lacertae blazars with Fermi-LAT

TL;DR

This study re-analyzed 10 years of Fermi-LAT gamma-ray data for 22 blazar candidates, identifying 17 new extreme high-synchrotron-peaked sources and assessing their potential for detection by current and future Cherenkov telescopes.

Contribution

It presents a comprehensive re-analysis of gamma-ray data and multi-wavelength modeling to identify new extreme blazar candidates and evaluate their VHE detectability.

Findings

Identified 17 new EHSP blazar candidates.

Found two VHE candidates detectable by current and future telescopes.

Compared physical parameters with prototypical EHSP blazars.

Abstract

The emission of very-high-energy photons (VHE, E>100 GeV$) in blazars is closely connected to the production of ultra-relativistic particles and the role of these gamma-ray sources as cosmic particle accelerators. This work focuses on a selection of 22 gamma-ray objects from the 2BIGB catalog of high-synchrotron-peaked sources, which are classified as blazar candidates of uncertain type in the 4FGL-DR2 catalog. We study these sources by means of a re-analysis of the first 10 years of gamma-ray data taken with the Fermi Large Area Telescope, including the attenuation by the extragalactic background light. Their broadband spectral energy distributions are also evaluated, using multi-wavelength archival data in the radio, optical, and X-ray bands, in terms of one-zone synchrotron-self-Compton models, adding an external Compton component when needed. Out of this analysis, we identify 17 new extreme high-synchrotron-peaked (EHSP) candidates and compare their physical parameters with those of prototypical EHSP blazars. Finally, the resulting models are used to assess their detectability by the present and future generation of ground-based imaging atmospheric Cherenkov telescopes. We find two VHE candidates within the reach of the current and next generation of Cherenkov telescopes: J0847.0-2336 and J1714.0-2029.