2004/10/01 by P. Arévalo, P. Arevalo, I. E. Papadakis +3
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.1051/0004-6361:20041801
published as Astron.Astrophys. 430 (2005) 435-442 · 9 pages, 8 figures, accepted for publication in A&A
arxiv created 2004/10/01 · openalex publication_date 2005/01/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We used a ∼300 ks long XMM-Newton observation of the Seyfert 1 galaxy MCG–6-30-15 to study the correlation between the 0.2–10 keV X-ray and the 3000–4000 Å U bands. We found a significant correlation peak at a time lag of ks where the UV flux variations preceded the variations in the X-ray band. We interpret this result as evidence in favour of Comptonisation models where the observed X-rays are produced through Compton up-scattering of thermal UV seed photons from an accretion disc, as this process naturally predicts the UV variations to precede similar flux variations in the X-rays. The length of the time lag favours models where the observed UV and the seed-photon-emitting regions are connected by perturbations of the accretion flow traveling inwards through the disc, affecting first the main U-band-emitting radii and then the innermost region where the bulk of the seed photons is expected to be produced. Finally, the absence of significant features in the correlation function with X-ray flux variations preceding those in the UV indicates that the observed U-band photons are not mainly produced through reprocessing of hard X-rays in this source.