Negative X-ray reverberation time delays from MCG–6-30-15 and Mrk 766

Abstract

Abstract We present an X-ray time lag analysis, as a function of Fourier frequency, for MCG–6-30-15 and Mrk 766 using long-term XMM–Newton light curves in the 0.5–1.5 and the 2–4 keV energy bands, together with some physical modelling of the corresponding time lag spectra. Both the time lag spectra of MCG–6-30-15 and Mrk 766 show negative values (i.e. soft band variations lag behind the corresponding hard band variations) at high frequencies, around 10−3 Hz, similar to those previously observed from 1H 0707−495. The remarkable morphological resemblance between the time lag spectra of MCG–6-30-15 and Mrk 766 indicate that the physical processes responsible for the observed soft time delays are very similar in the two sources, favouring a reflection scenario from material situated very nearby to the central black hole.