Deciphering the VHE gamma-rays spectra of Extreme High-Frequency peaked BL Lac Objects through a Photohadronic Model
Abstract
Extreme high-frequency peaked BL Lac objects (EHBLs) have their synchrotron peak above ∼ 1 keV and their inverse Compton peak extends up to several TeVs. Due to low luminosity of EHBLs, these objects are often undetected, and only a small number of them are thus known. As a result, they are poorly understood. Using a photohadronic model and including extragalactic background light correction we analyzed 22 very high-energy (VHE) gamma-ray spectra of 15 EHBL sources observed in different periods. We find that the photohadronic model used can adequately describe the observed VHE spectral energy distribution and furthermore, we classify them according to the value of the photon spectral index, δ. The redshift of the EHBL HESS J1943+213 is also tightly constrained using the same photohadronic model. Within the sample, a plurality of flaring epochs fall in the high-emission state which is followed by the low-emission state and the very-high-emission state respectively. These fractions of flaring epochs characterize only the present sample, not the EHBL population at large. Due to the anomalous behavior of the VHE gamma-ray spectra of the EHBL H 2356-309, we suggest it to be a new subclass of EHBL having hard and very soft intrinsic spectra during different flaring epochs.
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BibTeX
@misc{sahu2026deciphering,
title = {{Deciphering the VHE gamma-rays spectra of Extreme High-Frequency peaked BL Lac Objects through a Photohadronic Model}},
author = {Sarira Sahu and D. I. Páez-Sánchez and A. U. Puga Oliveros and M. E. Iglesias Martínez and Jose Guerra Carmenate and R. de J. Pacheco-Aké and G. Sánchez-Colón and Subhash Rajpoot and P. Fernández de Córdoba and Gaetano Lambiase},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.30641},
eprint = {2609.30641},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.30641},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Deciphering the VHE gamma-rays spectra of Extreme High-Frequency peaked BL Lac Objects through a Photohadronic Model
AU - Sarira Sahu
AU - D. I. Páez-Sánchez
AU - A. U. Puga Oliveros
AU - M. E. Iglesias Martínez
AU - Jose Guerra Carmenate
AU - R. de J. Pacheco-Aké
AU - G. Sánchez-Colón
AU - Subhash Rajpoot
AU - P. Fernández de Córdoba
AU - Gaetano Lambiase
PY - 2026
DA - 2026/09/25
PB - arXiv
DO - 10.48550/arxiv.2609.30641
UR - https://arxiv.org/abs/2609.30641
AB - Extreme high-frequency peaked BL Lac objects (EHBLs) have their synchrotron peak above ∼ 1 keV and their inverse Compton peak extends up to several TeVs. Due to low luminosity of EHBLs, these objects are often undetected, and only a small number of them are thus known. As a result, they are poorly understood. Using a photohadronic model and including extragalactic background light correction we analyzed 22 very high-energy (VHE) gamma-ray spectra of 15 EHBL sources observed in different periods. We find that the photohadronic model used can adequately describe the observed VHE spectral energy distribution and furthermore, we classify them according to the value of the photon spectral index, δ. The redshift of the EHBL HESS J1943+213 is also tightly constrained using the same photohadronic model. Within the sample, a plurality of flaring epochs fall in the high-emission state which is followed by the low-emission state and the very-high-emission state respectively. These fractions of flaring epochs characterize only the present sample, not the EHBL population at large. Due to the anomalous behavior of the VHE gamma-ray spectra of the EHBL H 2356-309, we suggest it to be a new subclass of EHBL having hard and very soft intrinsic spectra during different flaring epochs.
ER -