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Autores principales: de Menezes, Raniere, Massaro, Francesco, Visentin, Elisa, Di Pierro, Federico, Zhang, Haocheng
Formato: Preprint
Publicado: 2025
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Acceso en línea:https://arxiv.org/abs/2512.13785
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author de Menezes, Raniere
Massaro, Francesco
Visentin, Elisa
Di Pierro, Federico
Zhang, Haocheng
author_facet de Menezes, Raniere
Massaro, Francesco
Visentin, Elisa
Di Pierro, Federico
Zhang, Haocheng
contents The eponymous BL Lac object BL Lacertae is one of the most well-monitored active galactic nuclei, frequently observed from radio to gamma rays. Its relatively soft $γ$-ray spectrum peaks near 500~MeV, and since 2020 it has undergone an exceptional series of flaring episodes. The observed emission is well described by synchrotron self-Compton (SSC) models, with negligible contribution from external seed photons. We investigate the physical origin of BL~Lacertae's $γ$-ray temporal and spectral variability using data from the Large Area Telescope (LAT) on board the \textit{Fermi} Gamma-ray Space Telescope, and show that this variability can be explained by a single varying parameter, namely the electrons' peak energy, $γ_p$, under a single-zone SSC scenario with a log-parabolic electron distribution. We use a Markov chain Monte Carlo to estimate the spectral parameters of BL Lacertae over time, selected from an adaptive-binned gamma-ray light curve. We then study the correlation between the inverse Compton peak luminosity, $L_{IC}$, and the position of this peak on the SED energy axis, $E_p$, and compare it with what is expected for a single-zone SSC scenario when only one parameter is free to vary. We find a correlation $L_{IC} = 10^{42.33\pm0.15\pm0.18_{sys}}E_p^{0.98\pm0.05\pm0.06_{sys}}$, consistent, within the errors, with the linear relation $L_{\mathrm{IC}} \propto E_p$, expected when $γ_p$ is the only free parameter in the assumed SSC model. This result supports a minimalist SSC scenario in which changes in $γ_p$ dominate the observed temporal and spectral variability of BL~Lacertae.
format Preprint
id arxiv_https___arxiv_org_abs_2512_13785
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A minimalist approach to BL Lacertae: explaining gamma-ray spectral and temporal variability with a single physical parameter
de Menezes, Raniere
Massaro, Francesco
Visentin, Elisa
Di Pierro, Federico
Zhang, Haocheng
High Energy Astrophysical Phenomena
The eponymous BL Lac object BL Lacertae is one of the most well-monitored active galactic nuclei, frequently observed from radio to gamma rays. Its relatively soft $γ$-ray spectrum peaks near 500~MeV, and since 2020 it has undergone an exceptional series of flaring episodes. The observed emission is well described by synchrotron self-Compton (SSC) models, with negligible contribution from external seed photons. We investigate the physical origin of BL~Lacertae's $γ$-ray temporal and spectral variability using data from the Large Area Telescope (LAT) on board the \textit{Fermi} Gamma-ray Space Telescope, and show that this variability can be explained by a single varying parameter, namely the electrons' peak energy, $γ_p$, under a single-zone SSC scenario with a log-parabolic electron distribution. We use a Markov chain Monte Carlo to estimate the spectral parameters of BL Lacertae over time, selected from an adaptive-binned gamma-ray light curve. We then study the correlation between the inverse Compton peak luminosity, $L_{IC}$, and the position of this peak on the SED energy axis, $E_p$, and compare it with what is expected for a single-zone SSC scenario when only one parameter is free to vary. We find a correlation $L_{IC} = 10^{42.33\pm0.15\pm0.18_{sys}}E_p^{0.98\pm0.05\pm0.06_{sys}}$, consistent, within the errors, with the linear relation $L_{\mathrm{IC}} \propto E_p$, expected when $γ_p$ is the only free parameter in the assumed SSC model. This result supports a minimalist SSC scenario in which changes in $γ_p$ dominate the observed temporal and spectral variability of BL~Lacertae.
title A minimalist approach to BL Lacertae: explaining gamma-ray spectral and temporal variability with a single physical parameter
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2512.13785