Revisiting the continuum reverberation lags in the AGN PKS 0558−504
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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.
González-Buitrago , D H , Santisteban , J V H , Barth , A J , Jimenez-Bailón , E , Li , Y-R , García-Díaz , M T , Vargas , A L & Herrera-Endoqui , M 2022 , ' Revisiting the continuum reverberation lags in the AGN PKS 0558−504 ' , Monthly Notices of the Royal Astronomical Society , vol. 515 , no. 2 , pp. 2890-2900 . https://doi.org/10.1093/mnras/stac1945
Monthly Notices of the Royal Astronomical Society
Copyright © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the final published version of the work, which was originally published at https://doi.org/10.1093/mnras/stac1945.
DescriptionFunding: DHGB acknowledges CONACYT support #319800 and of the researchers programme for Mexico. Research by AJB is supported by National Science Foundation grant AST-1907290. JVHS acknowledges funds from a Science and Technology Facilities Council grant ST/R000824/1 research fellowship. YRL acknowledges the financial support from the National Natural Science Foundation of China through grant no. 11922304 and from the Youth Innovation Promotion Association CAS.
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