Publication: Hybrid corona and transient soft X-ray lags in Fairall 9
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0
Issued Date
2026-01-01
Resource Type
ISSN
00358711
eISSN
13652966
Scopus ID
2-s2.0-105026341712
Journal Title
Monthly Notices of the Royal Astronomical Society
Volume
545
Issue
3
Rights Holder(s)
SCOPUS
Bibliographic Citation
Monthly Notices of the Royal Astronomical Society Vol.545 No.3 (2026)
Suggested Citation
Khanthasombat K., Chainakun P., Luangtip W., Jiang J., Young A.J. Hybrid corona and transient soft X-ray lags in Fairall 9. Monthly Notices of the Royal Astronomical Society Vol.545 No.3 (2026). doi:10.1093/mnras/staf2210 Retrieved from: https://hdl.handle.net/20.500.14740/55369
Corresponding Author(s)
Other Contributor(s)
Abstract
Fairall 9 is among the most massive Seyfert galaxies exhibiting a strong soft X-ray excess, but it is challenging to probe soft X-ray reverberation lags (if any) due to the long intrinsic time-scales expected from its large black hole mass of ~2.55 x 10<sup>8</sup> M<inf>⊙</inf>. We fit five XMM–Newton spectra of Fairall 9 using the hybrid reXcor model taking into account both hot and warm corona. The soft excess is explained by a combination of a physically motivated warm corona and the disc reflection. Then, we perform a wavelet coherence analysis of the light curves between 0.3–1 and 1–4 keV bands. The spectral fits are consistent with a rapidly spinning black hole (a = 0.99), a warm corona with optical depth ~10–30, and a hot lamp-post corona located at either 5 or 20 r<inf>g</inf>. This configuration supports a coexisting hot and warm corona scenario, allowing the disc to extend almost to the event horizon. Our wavelet analysis on combined observations reveals signatures of transient soft X-ray lags, confined to specific time–frequency intervals. The earlier observations exhibit more variable and transient lag behaviour. In contrast, the later observations display more persistent soft X-ray lags at the frequencies of ~9 x 10<sup>-6</sup>–2.5 x 10<sup>-5</sup> Hz, with amplitudes reaching ~1000 s. The results indicate a progressively stable disc–corona configuration in later observations. Given the mass and geometry of Fairall 9, the observed soft lags appears plausibly consistent in both size and time-scales with expectations from X-ray reverberation.