AGN X-ray coronae at high luminosity: A broadband study of RBS 229 and PG 1407+265
Abstract
Context. The X-ray emission of active galactic nuclei (AGNs) is commonly interpreted as arising from Comptonisation in a hot corona above the accretion disc. A prominent soft X-ray excess is also observed in many sources and is often explained by a warm Comptonising layer. Aims. We investigate the X-ray-emitting coronae of the luminous radio-quiet quasars PG 1407+265 (z=0.94) and RBS 229 (z=0.334), testing whether a two-corona scenario consistently describes their broadband spectra. Methods. We combine XMM-Newton EPIC and Optical Monitor data with simultaneous NuSTAR observations and long-term Swift monitoring, and model the spectra using Comptonisation models. Results. Both quasars are X-ray loud relative to the standard αOX-LUV relation, with PG 1407+265 showing the strongest deviation. Their spectra are well reproduced by a warm, optically thick Comptonising component accounting for the soft excess and a hot corona producing the hard X-ray continuum. Both sources show high-energy cut-offs at approximately 70-80 keV. RBS 229 exhibits moderate reflection and a weak neutral Fe K-alpha line, while no significant reflection features are detected in PG 1407+265. The warm-corona parameters of RBS 229 remain consistent across epochs, whereas PG 1407+265 shows strong variability, including an extreme soft-excess episode extending to approximately 3 keV in the rest frame. Conclusions. These results constrain AGN coronae in the poorly explored high-luminosity regime. The cut-offs are broadly consistent with trends in AGN luminosity and accretion rate and remain below the runaway pair-production limit. The contrasting variability suggests that the warm corona responds to changes in the accretion flow while remaining within a narrow range of physical conditions.
Versions
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BibTeX
@article{lai2026xray,
title = {{AGN X-ray coronae at high luminosity: A broadband study of RBS 229 and PG 1407+265}},
author = {Alessandro Leonardo Lai and Stefano Bianchi and Andrea Marinucci and Enrico Piconcelli and Francesco Ursini and Elena Bertola and Giorgio Lanzuisi and Pierre-Olivier Petrucci and Daniel Stern and Cristian Vignali and Luca Zappacosta},
journal = {Astron.Astrophys.},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202660733},
eprint = {2609.01265},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05735434v1},
}
RIS
TY - JOUR
TI - AGN X-ray coronae at high luminosity: A broadband study of RBS 229 and PG 1407+265
AU - Alessandro Leonardo Lai
AU - Stefano Bianchi
AU - Andrea Marinucci
AU - Enrico Piconcelli
AU - Francesco Ursini
AU - Elena Bertola
AU - Giorgio Lanzuisi
AU - Pierre-Olivier Petrucci
AU - Daniel Stern
AU - Cristian Vignali
AU - Luca Zappacosta
PY - 2026
DA - 2026/09/01
JO - Astron.Astrophys.
DO - 10.1051/0004-6361/202660733
UR - https://hal.science/hal-05735434v1
AB - Context. The X-ray emission of active galactic nuclei (AGNs) is commonly interpreted as arising from Comptonisation in a hot corona above the accretion disc. A prominent soft X-ray excess is also observed in many sources and is often explained by a warm Comptonising layer. Aims. We investigate the X-ray-emitting coronae of the luminous radio-quiet quasars PG 1407+265 (z=0.94) and RBS 229 (z=0.334), testing whether a two-corona scenario consistently describes their broadband spectra. Methods. We combine XMM-Newton EPIC and Optical Monitor data with simultaneous NuSTAR observations and long-term Swift monitoring, and model the spectra using Comptonisation models. Results. Both quasars are X-ray loud relative to the standard α_OX-L_UV relation, with PG 1407+265 showing the strongest deviation. Their spectra are well reproduced by a warm, optically thick Comptonising component accounting for the soft excess and a hot corona producing the hard X-ray continuum. Both sources show high-energy cut-offs at approximately 70-80 keV. RBS 229 exhibits moderate reflection and a weak neutral Fe K-alpha line, while no significant reflection features are detected in PG 1407+265. The warm-corona parameters of RBS 229 remain consistent across epochs, whereas PG 1407+265 shows strong variability, including an extreme soft-excess episode extending to approximately 3 keV in the rest frame. Conclusions. These results constrain AGN coronae in the poorly explored high-luminosity regime. The cut-offs are broadly consistent with trends in AGN luminosity and accretion rate and remain below the runaway pair-production limit. The contrasting variability suggests that the warm corona responds to changes in the accretion flow while remaining within a narrow range of physical conditions.
ER -