Journal Article

Fermi-detection ofγ -ray Emissions from the Hot Coronae of Radio-quiet Active Galactic Nuclei

Morselli, A, Maldera, S, Monzani, M.E, Blandford, R.D, Kuss, M, Cutini, S, Orestano, P. Cristarella, Buson, S, Sanchez-Conde, M, d'Ammando, F, Fegan, S.J, Martí-Devesa, G, Sgro, C, Negro, M, Fusco, P, Di Lalla, N, Gonzalez, J. Becerra, Ormes, J.F, Funk, S, Gasbarra, C, Laviron, A, Lorusso, L, Orlando, E, Parkinson, P.M. Saz, Gasparrini, D, Hou, Xian, Di Venere, L, Karwin, C, Rani, B, Bissaldi, E, Porter, T.A, Niwa, R, Hashizume, M, Hays, E, Persic, M, Li, Jian, Longo, F, Spandre, G, Loparco, F, Moskalenko, I.V, Gargano, F, Panzarini, G, Chiaro, G, Dinesh, A, Bellazzini, R, Grenier, I.A, Michelson, P.F, Principe, G, Cavazzuti, E, Horan, D, Giroletti, M, Razzano, M, Hewitt, J.W, Kayanoki, T, Bruel, P, Spinelli, P, Raino, S, Berenji, B, Fukazawa, Y, Rando, R, Germani, S, Green, D, Lemoine-Goumard, M, Abdollahi, S, Paneque, D, Cameron, R.A, Ajello, M, Lubrano, P, Orienti, M, Fiori, A, Bartolini, C, Franckowiak, A, Mirabal, N, Bonino, R, Giglietto, N, Giordano, F, Ciprini, S, Reimer, O, Morishita, T, Mitthumsiri, W, Pillera, R, Bastieri, D, Serini, D, Giliberti, M, Siskind, E.J, Reimer, A, Guiriec, S, Marcotulli, L, Pesce-Rollins, M, Domínguez, A, Batista, R. Alves, Ca

2025

Overview

Relativistic jets around supermassive black holes (SMBHs) are well-known powerfulγ -ray emitters. In absence of the jets in radio-quiet active galactic nuclei (AGNs), how the SMBHs work inγ -ray bands is still unknown despite of great observational efforts made in the last 3 decades. Considering the previous efforts, we carefully select an AGN sample composed of 37 nearby Seyfert galaxies with ultra-hard X-rays for the goals ofγ -ray detections by excluding all potential contamination in this band. Adopting a stacking technique, here we report the significantγ -ray detection ( \\rm TS=30.6 , or5.2 σ ) from the sample using 15-year Fermi-Large Area Telescope (LAT) observation. We find an averageγ -ray luminosity of the sample as(1.5±1.0)×10⁴⁰ \\rm erg s⁻¹at energies from 1-300 GeV. Limited by the well-known pair production from the interaction ofγ -rays with low energy photons,≳several GeVγ -rays are found to originate from an extended corona ( ∼ 2.7× 10⁶ R_(\\rm g) ), whereas the canonical much more compact X-ray corona ( ∼ 10 R_(\\rm g) ) is responsible for 1 to several GeVγ -rays. The finding of the compact region lends to strong supports to the long-time theoretical expectations, but the extended corona is beyond all the existing models. One promising scenario is that the electron-positron pairs produced in the compact X-ray corona would expand as fireball, similar to that inγ -ray bursts, forming the structure of extended corona.

• Publisher: Nature Publishing Group
• Subject: Astrophysics / Physics