Iron K and Compton hump reverberation in SWIFT J2127.4+5654 and NGC 1365 revealed by NuSTAR and XMM-Newton

Abstract

In the past five years, a flurry of X-ray reverberation lag measurements of accreting supermassive black holes have been made using the XMM-Newton telescope in the 0.3-10 keV energy range. In this work, we use the NuSTAR telescope to extend the lag analysis up to higher energies for two Seyfert galaxies, SWIFT J2127.4+5654 and NGC 1365. X-ray reverberation lags are due to the light travel time delays between the direct continuum emission and the reprocessed emission from the inner radii of an ionised accretion disc. XMM-Newton has been particularly adept at measuring the lag associated with the broad Fe K emission line, where the gravitationally redshifted wing of the line is observed to respond before the line centroid at 6.4 keV, produced at larger radii. Now we use NuSTAR to probe the lag at higher energies, where the spectrum shows clear evidence for Compton reflection, known as the Compton 'hump'. The XMM-Newton data show Fe K lags in both SWIFT J2127.4+5654 and NGC 1365. The NuSTAR data provide independent confirmation of these Fe K lags, and also show evidence for the corresponding Compton hump lags, especially in SWIFT J2127.4+5654. These broadband lag measurements confirm that the Compton hump and Fe K lag are produced at small radii. At low-frequencies in NGC 1365, where the spectrum shows evidence for eclipsing clouds in the line of sight, we find a clear negative (not positive) lag from 2--10 keV, which can be understood as the decrease in column density from a neutral eclipsing cloud moving out of our line of sight during the observation.

14 Pages, 12 figures, accepted to MNRAS

References in corpus (10)

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Cited by in corpus (10)

• Discovery of a ~2 hr high frequency X-ray QPO and iron K alpha reverberation in the active galaxy MS 2254.9-3712
• The Multi-Layer Variable Absorbers in NGC 1365 Revealed by XMM-Newton and NuSTAR
• Theoretical modelling of the AGN iron-line vs continuum time-lags in the lamp-post geometry
• AGN Coronae Through A Jet Perspective
• The Compton hump and variable blue wing in the extreme low-flux NuSTAR observations of 1H0707-495
• Direct probe of the inner accretion flow around the supermassive black hole in NGC 2617
• Broad Iron Emission from Gravitationally Lensed Quasars Observed by Chandra
• Centrally Concentrated X-ray Radiation from an Extended Accreting Corona in Active Galactic Nuclei
• Origin of the Characteristic X-ray Spectral Variations of IRAS 13224$-$3809
• Using Simulations of Black Holes to Study General Relativity and the Properties of Inner Accretion Flow