Extreme- and high-synchrotron-peaked blazars at the limit of Fermi-LAT detectability: the γ-ray spectrum of 1BIGB sources.

We present the 1–100 GeV spectral energy distribution (SED) for a population of 148 high-synchrotron-peaked (HSP) blazars recently detected with Fermi -LAT as part of the First Brazil-ICRANet Gamma-ray Blazar (1BIGB) catalogue. Most of the 1BIGB sources have their γ-ray spectral properties presented here for the first time, representing a significant new extension of the γ-ray blazar population. Since our sample was originally selected from an excess signal in the 0.3–500 GeV band, the sources stand out as promising TeV blazar candidates, potentially in reach of the forthcoming very high energy (VHE) γ-ray observatory, Cherenkov Telescope Array (CTA). The flux estimates presented here are derived considering PASS8 data, integrating over more than 9 yr of Fermi -LAT observations. We also review the full broad-band fit between 0.3 and 500 GeV presented in the original 1BIGB paper for all sources, updating the power-law parameters with currently available Fermi -LAT data set. The importance of these sources in the context of VHE population studies with both current instruments and the future CTA is evaluated. To do so, we select a subsample of 1BIGB sources and extrapolate their γ-ray SEDs to the highest energies, properly accounting for absorption due to the extragalactic background light. We compare those extrapolations to the published CTA sensitivity curves and estimate their detectability by CTA. Two notable sources from our sample, namely 1BIGB J224910.6 − 130002 and 1BIGB J194356.2+211821, are discussed in greater detail. All γ-ray SEDs are made publicly available via the Brazilian Science Data Center (BSDC) service, maintained at CBPF, in Rio de Janeiro. [ABSTRACT FROM AUTHOR]