Revisiting the continuum reverberation lags in the AGN PKS 0558−504

ABSTRACT We present a revised analysis of the photometric reverberation mapping campaign of the narrow-line Seyfert 1 galaxy PKS 0558 − 504 carried out with the Swift Observatory during 2008–2010. Previously, Gliozzi et al. (2013) found using the Discrete Correlation Function (DCF) method that the s...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2022-08, Vol.515 (2), p.2890-2900
Main Authors: González-Buitrago, D H, Santisteban, J V Hernández, Barth, A J, Jimenez-Bailón, E, Li, Yan-Rong, García-Díaz, Ma T, Vargas, A Lopez, Herrera-Endoqui, M
Format: Article
Language:English
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Summary:ABSTRACT We present a revised analysis of the photometric reverberation mapping campaign of the narrow-line Seyfert 1 galaxy PKS 0558 − 504 carried out with the Swift Observatory during 2008–2010. Previously, Gliozzi et al. (2013) found using the Discrete Correlation Function (DCF) method that the short-wavelength continuum variations lagged behind variations at longer wavelengths, the opposite of the trend expected for thermal reprocessing of X-rays by the accretion disc, and they interpreted their results as evidence against the reprocessing model. We carried out new DCF measurements that demonstrate that the inverted lag-wavelength relationship found by Gliozzi et al. resulted from their having interchanged the order of the driving and responding light curves when measuring the lags. To determine the inter-band lags and uncertainties more accurately, we carried out new measurements with four independent methods. These give consistent results showing time delays increasing as a function of wavelength, as expected for the disc reprocessing scenario. The slope of the re-analysed delay spectrum appears to be roughly compatible with the predicted τ ∝ λ4/3 relationship for reprocessing by an optically thick and geometrically thin accretion disc, although the data points exhibit a large scatter about the fitted power-law trend.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stac1945