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Towards a unified scheme of blazar evolution
E. Oukacha & Y. Becherini (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France)
e-Print: https://arxiv.org/abs/2507.03088 [astro-ph.HE]
DOI: https://doi.org/10.1051/0004-6361/202555303
A&A, Forthcoming article, Accepted: 02 July 2025
We apply modern machine-learning models (XGBoost and the TabPFN foundation model) to Fermi 4LAC-DR3 data to classify blazars, especially the “blazar candidates of uncertain type” (BCUs), and to map their properties in a reduced 2D latent space. This visualization uncovers a smooth continuum from Flat Spectrum Radio Quasars to BL Lac objects, with Changing-Look Blazars occupying the middle ground, supporting a gradual shift from radiatively efficient to inefficient accretion regimes. A single probability score, together with the latent-space map, emerges as a compact, physics-motivated way to capture blazar diversity beyond rigid class labels.
Sensitivity to point-like sources of the ALTO atmospheric particle detector array designed for 200 GeV–50 TeV γ-ray astronomy
M. Punch (APC, Paris), M. Senniappan (Linnaeus U.), Y. Becherini (APC, Paris), G. Kukec Mezek (Linnaeus U.), S. Thoudam (Khalifa U., Abu Dhabi) et al.
e-Print: https://arxiv.org/pdf/2303.15248 [astro-ph.IM]
DOI: 10.1016/j.jheap.2023.03.003 (publication)
Published in: JHEAp 39 (2023), 1-13
In the context of atmospheric shower arrays designed for γ-ray astronomy and in the context of the ALTO project, we present: a
study of the impact of heavier nuclei in the cosmic-ray background on the estimated γ-ray detection performance based on
dedicated Monte Carlo simulations, a method to calculate the sensitivity to a point-like source, and finally, the required observation times to reach a firm detection on a list of known point-like sources
Signal extraction in atmospheric shower arrays designed for 200 GeV–50 TeV γ-ray astronomy
M. Senniappan (Linnaeus U.), Y. Becherini (Linnaeus U.), M. Punch (APC, Paris and Linnaeus U.), S. Thoudam (Khalifa U., Abu Dhabi), T. Bylund (Linnaeus U.) et al.
e-Print: https://arxiv.org/abs/2105.06728 [astro-ph.IM]
DOI: 10.1088/1748-0221/16/07/P07050 (publication)
Published in: JINST 16 (2021) 07, P07050
The paper presents SEMLA, a machine-learning–based method for γ-ray signal extraction in the ALTO atmospheric shower array (200 GeV–50 TeV). SEMLA cleans events, filters poor reconstructions, separates γ-rays from protons, and reconstructs energies—optimizing sensitivity for soft-spectrum sources like AGN and GRBs.
Very high energy γ-ray emission from two blazars of unknown redshift and upper limits on their distance
H.E.S.S. Collaboration, ..., T. Bylund (Linnaeus U.), Y. Becherini (Linnaeus U.) et al.
e-Print: https://arxiv.org/abs/2004.03306 [astro-ph.HE]
DOI: https://doi.org/10.1093/mnras/staa999
Published in: Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 4, June 2020, Pages 5590–5602
H.E.S.S. detected very-high-energy (E > 100 GeV) γ-ray emission from the BL Lac objects KUV 00311-1938 and PKS 1440-389, accompanied by multi-wavelength observations with Fermi/LAT, Swift (XRT, UVOT), and ATOM. Extrapolation of the Fermi/LAT spectra provides redshift upper limits of z < 0.98 for KUV 00311-1938 and z < 0.53 for PKS 1440-389.
The γ-ray spectrum of the core of Centaurus A as observed with H.E.S.S. and Fermi-LAT
H.E.S.S. Collaboration, ..., Y. Becherini (Linnaeus U.), D. Prokhorov (Linnaeus U.) et al.
e-Print: https://arxiv.org/abs/1807.07375 [astro-ph.HE]
DOI: https://doi.org/10.1051/0004-6361/201832640
Published in: A&A, 619 (2018) A71
H.E.S.S. and Fermi-LAT observations of Centaurus A’s core reveal a γ-ray spectrum spanning five energy decades, with VHE emission detected at 12σ significance (250 GeV–6 TeV, Γ ≈ 2.5). The spectrum shows hardening above ~3 GeV, inconsistent with a simple single-zone SSC model and pointing to an additional γ-ray component, likely jet-related. No significant variability is observed.
A new analysis strategy for detection of faint gamma-ray sources with Imaging Atmospheric Cherenkov Telescopes
Y. Becherini (Université Paris Cité, CNRS, Astroparticule et Cosmologie, 75013 Paris, France) et al.
e-Print: https://arxiv.org/pdf/1104.5359 [astro-ph.HE]
DOI: https://doi.org/10.1016/j.astropartphys.2011.03.005
Published in: Astroparticle Physics, Volume 34, Issue 12, July 2011, Pages 858-870
A new multivariate background rejection method for IACTs, tested with H.E.S.S. data, improves sensitivity by 1.2–1.8 over standard analysis, cutting observation time by up to a factor of 3.2 while remaining robust to background variations.
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