1. Evidence for variability time-scale-dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469.
- Author
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Pahari, Mayukh, McHardy, I M, Vincentelli, Federico, Cackett, Edward, Peterson, Bradley M, Goad, Mike, Gültekin, Kayhan, and Horne, Keith
- Subjects
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LIGHT curves , *OPTICAL telescopes , *SEYFERT galaxies , *SOUND reverberation , *X-rays , *MATHEMATICAL continuum - Abstract
Using 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 UVW 2, 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. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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