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dc.contributor.authorPahari, Mayukh
dc.contributor.authorMcHardy, Ian M.
dc.contributor.authorVincentelli, Federico
dc.contributor.authorCackett, Edward M.
dc.contributor.authorPeterson, Bradley M.
dc.contributor.authorGoad, Michael R.
dc.contributor.authorGültekin, Kayhan
dc.contributor.authorHorne, Keith
dc.identifier.citationPahari , M , McHardy , I M , Vincentelli , F , Cackett , E M , Peterson , B M , Goad , M R , Gültekin , K & Horne , K 2020 , ' Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469 ' , Monthly Notices of the Royal Astronomical Society , vol. 494 , no. 3 , pp. 4057-4068 .
dc.identifier.otherPURE: 269474355
dc.identifier.otherPURE UUID: 3c403198-ed18-4ffe-9c6f-f99a92bb7b5c
dc.identifier.otherWOS: 000535882100075
dc.identifier.otherScopus: 85101306792
dc.descriptionMP acknowledges Royal Society-SERB Newton International Fellowship support funded jointly by the Royal Society, UK and the Science and Engineering Board of India (SERB) through Newton–Bhabha Fund. IMcH acknowledges support from a Royal Society Leverhulme Trust Research Fellowship LT160006 and from STFC grant ST/M001326/1. EMC gratefully acknowledges support from the National Science Foundation through award number AST-1909199. KH acknowledges support from STFC grant ST/R000824/1.en
dc.description.abstractUsing a month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220-1970 Å, we performed a detailed time-lag study of the Seyfert 1 galaxy NGC 7469. Our cross-correlation analysis confirms previous results showing that the X-rays are delayed relative to the UV continuum at 1315 Å by 3.49 ± 0.22 d, which is possibly caused by either propagating fluctuation or variable Comptonization. However, if variations slower than 5 d are removed from the X-ray light curve, the UV variations then lag behind the X-ray variations by 0.37 ± 0.14 d, consistent with reprocessing of the X-rays by a surrounding accretion disc. A very similar reverberation delay is observed between Swift/XRT X-ray and Swift/UVOT UVW2, U light curves. Continuum light curves extracted from the Swift/GRISM spectra show delays with respect to X-rays consistent with reverberation. Separating the UV continuum variations faster and slower than 5 d, the slow variations at 1825 Å lag those at 1315 Å by 0.29 ± 0.06 d, while the fast variations are coincident (0.04 ± 0.12 d). The UV/optical continuum reverberation lag from IUE, Swift, and other optical telescopes at different wavelengths are consistent with the relationship: τ ∝  λ4/3, predicted for the standard accretion disc theory while the best-fitting X-ray delay from RXTE and Swift/XRT shows a negative X-ray offset of ∼0.38 d from the standard disc delay prediction.
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen
dc.rightsCopyright © 2020 the Author(s). Published by Oxford University Press on behalf of the 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
dc.subjectAccretion, accretion discsen
dc.subjectBlack hole physicsen
dc.subjectGalaxies: individual: NGC 7469en
dc.subjectGalaxies: Seyferten
dc.subjectX-rays: galaxiesen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleEvidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469en
dc.typeJournal articleen
dc.contributor.sponsorScience & Technology Facilities Councilen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.contributor.institutionUniversity of St Andrews. St Andrews Centre for Exoplanet Scienceen
dc.description.statusPeer revieweden

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