H.E.S.S. observations of composite Seyfert–starburst galaxies

Acharyya, A.; Stawarz, Ł.; Hinton, J. A.; Boisson, C.; Lazarevic, S.; Moulin, E.; Zhong, W.; Khélifi, B.; Unbehaun, T.; Ashkar, H.; Rieger, F.; Mehta, A.; Said, W. Si; Lefranc, V.; Shapopi, J. N. S.; Chernyakova, M.; van Eldik, C.; Venter, C.; Bolmont, J.; Berge, D.; Tanaka, T.; Grondin, M.-H.; Mbarubucyeye, J. Damascene; Kostunin, D.; O'Brien, P.; Pühlhofer, G.; Filipovic, M. D.; Chibueze, O.; Böttcher, M.; Bruno, B.; Backes, M.; Aharonian, F.; Punch, M.; Wach, T.; Holler, M.; Pensec, U.; Prokhorov, D. A.; Marchegiani, P.; Egg, K.; Steinmassl, S.; Sabri, K.; Cotter, G.; Rudak, B.; Hess, B.; Cornejo, B.; Djuvsland, J.; Kasai, E.; Reimer, O.; Holch, T. L.; Quirrenbach, A.; Ebrahim, R.; Fontaine, G.; Liniewicz, P.; Katarzynski, K.; Funk, S.; Burger-Scheidlin, C.; Reimer, A.; Olivera-Nieto, L.; de Assis Scarpin, J.; Collins, T.; Jung-Richardt, I.; Feijen, K.; Salzmann, H.; Dmytriiev, A.; Moghadam, M. O.; Taylor, A. M.; H. E. S. S. Collaboration; Tsirou, M.; Regeard, M.; Parsons, R. D.; Moderski, R.; Chibueze, J. O.; de Lavergne, M. de Bony; Vink, J.; Chen, A.; Mitchell, A. M. W.; Casanova, S.; Kasprzak, K.; Luashvili, A.; Mackey, J.; Ren, H.; Marandon, V.; Panny, S.; Niemiec, J.; Komin, N.; Sasaki, M.; Terrier, R.; Brun, F.; de Naurois, M.; Djannati-Ataï, A.; Chandra, S.; Zech, A.; Batzofin, R.; Jamrozy, M.; Barbosa Martins, V.; Jankowsky, F.; Mayer, M.; Mohrmann, L.; Malyshev, D.; Kerszberg, D.; Horns, D.; Lenain, J.-P.; Kosack, K.; Borowska, J.; de Oña Wilhelmi, E.; Wierzcholska, A.; Becherini, Y.; Vecchi, M.; Gabici, S.; Glicenstein, J. F.; Escañuela Nieves, C.; Lang, R. G.; Cerruti, M.; Colafrancesco, S.; Schüssler, F.; Celic, J.; Spencer, S.; Goswami, P.; Sahakian, V.; Glombitza, J.; Panter, M.; Giler, A. G. Delgado

Preprint

PUBDB-2026-02387

H.E.S.S. observations of composite Seyfert–starburst galaxies

Acharyya, A. ; Aharonian, F. ; Ashkar, H. ; Backes, M. ; Barbosa Martins, V.DESY* ; Batzofin, R. ; Becherini, Y. ; Berge, D. ; Böttcher, M. ; Boisson, C. ; Bolmont, J.DESY* ; Borowska, J. ; Brun, F. ; Bruno, B. ; Burger-Scheidlin, C. ; Casanova, S. ; Celic, J. ; Cerruti, M. ; Chandra, S. ; Chen, A. ; Chernyakova, M. ; Chibueze, J. O. ; Chibueze, O. ; Colafrancesco, S. ; Collins, T. ; Cornejo, B. ; Cotter, G. ; Mbarubucyeye, J. D. ; de Assis Scarpin, J. ; de Lavergne, M. d. B. ; de Naurois, M. ; de Oña Wilhelmi, E. ; Giler, A. G. D. ; Djannati-Ataï, A. ; Djuvsland, J. ; Dmytriiev, A. ; Ebrahim, R. ; Egg, K. ; Escañuela Nieves, C. ; Feijen, K. ; Filipovic, M. D. ; Fontaine, G. ; Funk, S. ; Gabici, S. ; Glicenstein, J. F. ; Glombitza, J. ; Goswami, P. ; Grondin, M.-H. ; Hess, B. ; Hinton, J. A. ; Holch, T. L. ; Holler, M. ; Horns, D. ; Jamrozy, M. ; Jankowsky, F. ; Jung-Richardt, I. ; Kasai, E. ; Kasprzak, K. ; Katarzynski, K. ; Kerszberg, D. ; Khélifi, B. ; Komin, N. ; Kosack, K. ; Kostunin, D.DESY* ; Lang, R. G. ; Lazarevic, S. ; Lefranc, V. ; Lenain, J.-P. ; Liniewicz, P. ; Luashvili, A. ; Mackey, J. ; Malyshev, D. ; Malyshev, D. ; Marandon, V. ; Marchegiani, P. ; Mayer, M.Extern* ; Mehta, A. ; Mitchell, A. M. W. ; Moderski, R. ; Moghadam, M. O. ; Mohrmann, L.XFEL.EU* ; Moulin, E. ; Niemiec, J. ; O'Brien, P. ; Olivera-Nieto, L. ; Panny, S. ; Panter, M. ; Parsons, R. D. ; Pensec, U. ; Prokhorov, D. A. ; Pühlhofer, G. ; Punch, M. ; Quirrenbach, A. ; Regeard, M. ; Reimer, A. ; Reimer, O. ; Ren, H. ; Rieger, F. ; Rudak, B. ; Sabri, K. ; Sahakian, V. ; Salzmann, H. ; Sasaki, M. ; Schüssler, F. ; Shapopi, J. N. S. ; Said, W. S. ; Spencer, S. ; Stawarz, Ł. ; Steinmassl, S. ; Tanaka, T. ; Taylor, A. M.DESY* ; Terrier, R. ; Tsirou, M. ; Unbehaun, T. ; van Eldik, C. ; Vecchi, M. ; Venter, C. ; Vink, J. ; Wach, T. ; Wierzcholska, A. ; Zech, A. ; Zhong, W. ; H. E. S. S. Collaboration (Collaboration author)DESY*

2026

(2026)

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Report No.: arXiv:2603.21912

Abstract: Context. Composite galaxies that contain both Seyfert and starburst components may produce very high-energy (VHE; > 100 GeV) γ-ray emission at a wide range of spatial scales, from a few Schwarzschild radii of a supermassive black hole (SMBH; RS = 10−6 pc for MSMBH = 107 M⊙) to dimensions of kiloparsec-size jet-driven outflows. In addition to supernova remnants, various sources have been suggested to explain data collected on composite galaxies, including multi-messenger neutrino and ultra-high-energy cosmic-ray data.Aims. The closest composite Seyfert–starburst galaxies (NGC 1068, the Circinus galaxy, and NGC 4945) are observed with the High Energy Stereoscopic System (H.E.S.S.) to provide constraints on cosmic-ray populations in these systems.Methods. Data obtained in H.E.S.S. observations have been analyzed to search for VHE γ-ray counterparts to the GeV γ-ray signals detected with Fermi-LAT and for potential spectral components in the VHE range.Results. No significant signals have been found in these H.E.S.S. data. Upper limits on the VHE γ-ray fluxes were applied to constrain theoretical models involving different spectral components.Key words: relativistic processes / ISM: jets and outflows / galaxies: Seyfert / galaxies: starburst / gamma rays: galaxies★★ The authors honor the memory of Sergio Colafrancesco, who brought us together in pursuit of this study during his final years.

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