| Name: Sushmita Agarwal |
| Affiliation: Tata Institute of Fundamental Research, Mumbai |
| Conference ID: ASI2026_439 |
| Title: Extending the VHE Horizon: Systematic Hunting for high-synchrotron peaked Blazars and Prospects for the Cherenkov Observatory |
| Abstract Type: Oral |
| Abstract Category: High Energy Phenomena, Fundamental Physics and Astronomy |
| Author(s) and Co-Author(s) with Affiliation: Sushmita Agarwal(TIFR, Mumbai), Vaidehi S. Paliya(IUCAA, Pune) |
| Abstract: The detection of very high-energy (VHE; E > 100 GeV) gamma rays from extragalactic sources is a major frontier in high-energy astrophysics. Current and upcoming ground-based Cherenkov facilities, including the Indian experiment Major Atmospheric Cherenkov Experiment (MACE), are well positioned to bridge the 20–100 GeV observational gap. These instruments will substantially improve sensitivity to faint and distant VHE sources, enabling a more complete census of the high-energy extragalactic sky.
High-synchrotron-peaked (HSP) blazars are the dominant extragalactic sources of VHE gamma-ray emission. Identifying these objects is essential for constraining particle acceleration in relativistic jets and for probing the Extragalactic Background Light (EBL). However, the current VHE source catalog remains sparse and is largely biased toward detections during high flaring episodes.
We conduct a systematic search for VHE-emitting HSP blazars in a sample of 1,045 sources using 16 years of Fermi-LAT data. We identify 92 new VHE candidates and confirm 52 previously known emitters. The VHE population is characterized by lower redshifts (⟨z⟩ ≈ 0.2), brighter synchrotron peaks, and significantly harder gamma-ray spectra (photon index < 2) compared to non-VHE sources. Possible redshift-related selection biases and their spectral implications will be discussed in detail in the talk.
We detect VHE photons during both quiescent and active states, suggesting that VHE emission arises from a persistent acceleration component in relativistic jets rather than being purely flare-driven. This enlarged population of VHE-emitting HSP blazars provides a robust target set for deep-exposure observations. The results are particularly timely for current and upcoming Cherenkov facilities, including the Indian experiment Major Atmospheric Cherenkov Experiment, and will inform source selection and long-term monitoring strategies for next-generation observatories such as the Cherenkov Telescope Array Observatory.
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