A Tentative Line-like GeV Excess in Fermi Blazar 4FGL J1754.2+3212: Implications for Jet Physics and Beyond
Abstract
We report the detection of a tentative, narrow spectral feature in the GeV gamma-ray spectrum of the blazar 4FGL J1754.2+3212, using approximately 16.5 years of observations from the Fermi Large Area Telescope. A detailed likelihood analysis of the time-averaged spectrum reveals a localized, line-like excess at an energy of ∼31 GeV, with a local statistical significance of ∼3σ (3 degrees of freedom), without corrections for multiple trials and the look-elsewhere effect. This feature is not well described by standard smooth continuum models such as a single log-parabola. The addition of a Gaussian component significantly improves the spectral fit. If confirmed by future observations with higher sensitivity, this feature would represent a novel phenomenon in blazar astrophysics. We explore its potential physical origins, which could involve exotic processes such as dark matter annihilation or photon-axion-like-particle oscillations, or extreme astrophysical mechanisms within a structured jet. Regardless of its ultimate nature, this finding highlights the potential of deep spectral studies of blazars to reveal non-standard physics and challenges conventional one-zone emission models. Definitive verification awaits observations by next-generation instruments, particularly the Very Large Area γ-ray Space Telescope (VLAST).
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BibTeX
@misc{kang2026tentative,
title = {{A Tentative Line-like GeV Excess in Fermi Blazar 4FGL J1754.2+3212: Implications for Jet Physics and Beyond}},
author = {Shi-Ju Kang and Yue Yin and Yong-Gang Zheng and Qingwen Wu},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.28303},
eprint = {2609.28303},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.28303},
}
RIS
TY - UNPB
TI - A Tentative Line-like GeV Excess in Fermi Blazar 4FGL J1754.2+3212: Implications for Jet Physics and Beyond
AU - Shi-Ju Kang
AU - Yue Yin
AU - Yong-Gang Zheng
AU - Qingwen Wu
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.28303
UR - https://arxiv.org/abs/2609.28303
AB - We report the detection of a tentative, narrow spectral feature in the GeV gamma-ray spectrum of the blazar 4FGL J1754.2+3212, using approximately 16.5 years of observations from the Fermi Large Area Telescope. A detailed likelihood analysis of the time-averaged spectrum reveals a localized, line-like excess at an energy of ∼31 GeV, with a local statistical significance of ∼3σ (3 degrees of freedom), without corrections for multiple trials and the look-elsewhere effect. This feature is not well described by standard smooth continuum models such as a single log-parabola. The addition of a Gaussian component significantly improves the spectral fit. If confirmed by future observations with higher sensitivity, this feature would represent a novel phenomenon in blazar astrophysics. We explore its potential physical origins, which could involve exotic processes such as dark matter annihilation or photon-axion-like-particle oscillations, or extreme astrophysical mechanisms within a structured jet. Regardless of its ultimate nature, this finding highlights the potential of deep spectral studies of blazars to reveal non-standard physics and challenges conventional one-zone emission models. Definitive verification awaits observations by next-generation instruments, particularly the Very Large Area γ-ray Space Telescope (VLAST).
ER -