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arXiv · 2402.13330

Curvature in the very-high energy gamma-ray spectrum of M87

H. E. S. S. Collaboration·F. Aharonian·F. Ait Benkhali·J. Aschersleben·H. Ashkar·M. Backes·V. Barbosa Martins·R. Batzofin·Y. Becherini·D. Berge·K. Bernlöhr·M. Böttcher·C. Boisson·J. Bolmont·M. de Bony de Lavergne·F. Bradascio·R. Brose·F. Brun·B. Bruno·T. Bulik C. Burger-Scheidlin·T. Bylund·S. Casanova·R. Cecil·J. Celic·M. Cerruti·T. Chand·S. Chandra·A. Chen·J. Chibueze·O. Chibueze·T. Collins·G. Cotter·J. Damascene Mbarubucyeye·A. Djannati-Ataï·J. Djuvsland·A. Dmytriiev·K. Egberts·S. Einecke·S. Fegan·G. Fontaine·S. Funk·S. Gabici·J. F. Glicenstein·J. Glombitza·G. Grolleron·L. Haerer·W. Hofmann·T. L. Holch·M. Holler·D. Horns·M. Jamrozy·F. Jankowsky·V. Joshi·I. Jung-Richardt·E. Kasai·K. Katarzyński·R. Khatoon·B. Khélifi·W. Kluźniak·Nu. Komin·K. Kosack·D. Kostunin·A. Kundu·R. G. Lang·S. Le Stum·F. Leitl·A. Lemière·M. Lemoine-Goumard·J. -P. Lenain·I. Lypova·A. Luashvili·J. Mackey·D. Malyshev·G. Martí-Devesa·R. Marx·A. Mehta·M. Meyer·A. Mitchell·R. Moderski·M. O. Moghadam·L. Mohrmann·A. Montanari·E. Moulin·T. Murach·M. de Naurois·J. Niemiec·S. Ohm·L. Olivera-Nieto·E. de Ona Wilhelmi·S. Panny·M. Panter·R. D. Parsons·U. Pensec·S. Pita·G. Pühlhofer·M. Punch·A. Quirrenbach·M. Regeard·A. Reimer·O. Reimer
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Abstract

The radio galaxy M87 is a variable very-high energy (VHE) gamma-ray source, exhibiting three major flares reported in 2005, 2008, and 2010. Despite extensive studies, the origin of the VHE gamma-ray emission is yet to be understood. In this study, we investigate the VHE gamma-ray spectrum of M87 during states of high gamma-ray activity, utilizing 20.2$\,$ hours the H.E.S.S. observations. Our findings indicate a preference for a curved spectrum, characterized by a log-parabola model with extra-galactic background light (EBL) model above 0.3$\,$TeV at the 4$\sigma$ level, compared to a power-law spectrum with EBL. We investigate the degeneracy between the absorption feature and the EBL normalization and derive upper limits on EBL models mainly sensitive in the wavelength range 12.4$\,$$\mu$m - 40$\,$$\mu$m.

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H. E. S. S. Collaboration, F. Aharonian, F. Ait Benkhali, J. Aschersleben, H. Ashkar, M. Backes, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, M. Böttcher, C. Boisson, J. Bolmont, M. de Bony de Lavergne, F. Bradascio, R. Brose, F. Brun, B. Bruno, T. Bulik C. Burger-Scheidlin, T. Bylund, S. Casanova, R. Cecil, J. Celic, M. Cerruti, T. Chand, S. Chandra, A. Chen, J. Chibueze, O. Chibueze, T. Collins, G. Cotter, J. Damascene Mbarubucyeye, A. Djannati-Ataï, J. Djuvsland, A. Dmytriiev, K. Egberts, S. Einecke, S. Fegan, G. Fontaine, S. Funk, S. Gabici, J. F. Glicenstein, J. Glombitza, G. Grolleron, L. Haerer, W. Hofmann, T. L. Holch, M. Holler, D. Horns, M. Jamrozy, F. Jankowsky, V. Joshi, I. Jung-Richardt, E. Kasai, K. Katarzyński, R. Khatoon, B. Khélifi, W. Kluźniak, Nu. Komin, K. Kosack, D. Kostunin, A. Kundu, R. G. Lang, S. Le Stum, F. Leitl, A. Lemière, M. Lemoine-Goumard, J. -P. Lenain, I. Lypova, A. Luashvili, J. Mackey, D. Malyshev, G. Martí-Devesa, R. Marx, A. Mehta, M. Meyer, A. Mitchell, R. Moderski, M. O. Moghadam, L. Mohrmann, A. Montanari, E. Moulin, T. Murach, M. de Naurois, J. Niemiec, S. Ohm, L. Olivera-Nieto, E. de Ona Wilhelmi, S. Panny, M. Panter, R. D. Parsons, U. Pensec, S. Pita, G. Pühlhofer, M. Punch, A. Quirrenbach, M. Regeard, A. Reimer, O. Reimer. 2024-02-20. Curvature in the very-high energy gamma-ray spectrum of M87. https://doi.org/10.1051/0004-6361/202348913

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