Porquet, D.D.PorquetHagen, S.S.HagenGrosso, N.N.GrossoLobban, A.A.LobbanReeves, J. N.J. N.ReevesBRAITO, ValentinaValentinaBRAITODone, C.C.Done2025-01-272025-01-2720240004-6361http://hdl.handle.net/20.500.12386/35724Context. The X-ray broadband spectra of the bare active galactic nucleus (AGN) Mrk 110, obtained by simultaneous XMM-Newton and NuSTAR observations performed in November 2019 and April 2020, are characterised by the presence of a prominent and absorption-free smooth soft X-ray excess, moderately broad O VII and Fe Kα emission lines, and a lack of a strong Compton hump. The disc-corona system is almost viewed face-on as inferred from the O VII accretion disc lines. While relativistic reflection as the sole emission is ruled out, a simplified combination of soft and hard Comptonisation (using COMPTT) from a warm and a hot corona, plus mild relativistic disc reflection (occuring at a few 10 s R<SUB>g</SUB>) reproduces the data very well. <BR /> Aims: We aim to confirm the physical origin of the soft X-ray excess of Mrk 110 and to determine its disc-corona system properties from its energetics using two new sophisticated models: REXCOR and RELAGN, respectively. <BR /> Methods: We applied these models to the 0.3-79 keV X-ray broadband spectra and to the spectral energy distribution (SED) from UV to hard X-rays, respectively. <BR /> Results: At both epochs, the inferred high values of the warm-corona heating from the X-ray broadband spectral analysis using REXCOR confirm that the soft X-ray excess of Mrk 110 mainly originates from a warm corona rather than relativistic reflection. The intrinsic best-fit SED determined at both epochs using RELAGN show a high X-ray contribution relative to the UV and are very well reproduced by a warm and hot corona plus mild relativistic reflection. The outer radii of the hot and warm corona are located at a few 10 s and ∼100 R<SUB>g</SUB>, respectively. Moreover, combining the inferred low Eddington ratio (approximatively a few percent) from this work, and previous multi-wavelength spectral and timing studies suggest that Mrk 110 could be classified as a moderate changing-state AGN. <BR /> Conclusions: Our analysis confirms the existence of a warm corona as a significant contribution to the soft X-ray excess and UV emission in Mrk 110, adding to growing evidence that AGN accretion deviates from standard disc theory. This strengthens the importance of long-term multi-wavelength monitoring on both single targets and large AGN surveys to reveal the real nature of the disc-corona system in AGNs.STAMPAenArticle10.1051/0004-6361/2023472022-s2.0-85182020638https://api.elsevier.com/content/abstract/scopus_id/85182020638https://www.aanda.org/articles/aa/full_html/2024/01/aa47202-23/aa47202-23.html2024A&A...681A..40PFIS/05 - ASTRONOMIA E ASTROFISICA