<i>Swift</i> monitoring of NGC 5548: X-ray reprocessing and short-term UV/optical variability

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dc.contributor.authorMcHardy, I. M.
dc.contributor.authorCameron, D. T.
dc.contributor.authorDwelly, T.
dc.contributor.authorConnolly, S.
dc.contributor.authorLira, P.
dc.contributor.authorEmmanoulopoulos, D.
dc.contributor.authorGelbord, J.
dc.contributor.authorBreedt, E.
dc.contributor.authorArevalo, P.
dc.contributor.authorUttley, P.
dc.date.accessioned2025-01-23T21:42:21Z
dc.date.available2025-01-23T21:42:21Z
dc.date.issued2014
dc.description.abstractLags measured from correlated X-ray/UV/optical monitoring of AGN allow us to determine whether UV/optical variability is driven by reprocessing of X-rays or X-ray variability is driven by UV/optical seed photon variations. We present the results of the largest study to date of the relationship between the X-ray, UV and optical variability in an AGN with 554 observations, over a 750 d period, of the Seyfert 1 galaxy NGC 5548 with Swift. There is a good overall correlation between the X-ray and UV/optical bands, particularly on short time-scales (tens of days). The UV/optical bands lag the X-ray band with lags which are proportional to wavelength raised to the power 1.23 +/- 0.31. This power is very close to the power (4/3) expected if short time-scale UV/optical variability is driven by reprocessing of X-rays by a surrounding accretion disc. The observed lags, however, are longer than expected from a standard Shakura-Sunyaev accretion disc with X-ray heating, given the currently accepted black hole mass and accretion rate values, but can be explained with a slightly larger mass and accretion rate, and a generally hotter disc. Some long-term UV/optical variations are not paralleled exactly in the X-rays, suggesting an additional component to the UV/optical variability arising perhaps from accretion rate perturbations propagating inwards through the disc.
dc.fuente.origenWOS
dc.identifier.doi10.1093/mnras/stu1636
dc.identifier.eissn1365-2966
dc.identifier.issn0035-8711
dc.identifier.urihttps://doi.org/10.1093/mnras/stu1636
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/101658
dc.identifier.wosidWOS:000342926300033
dc.issue.numero2
dc.language.isoen
dc.pagina.final1474
dc.pagina.inicio1469
dc.revistaMonthly notices of the royal astronomical society
dc.rightsacceso restringido
dc.subjectaccretion, accretion discs
dc.subjectradiation mechanisms: general
dc.subjectgalaxies: active
dc.subjectgalaxies: Seyfert
dc.subjectultraviolet: galaxies
dc.subjectX-rays: galaxies
dc.title<i>Swift</i> monitoring of NGC 5548: X-ray reprocessing and short-term UV/optical variability
dc.typeartículo
dc.volumen444
sipa.indexWOS
sipa.trazabilidadWOS;2025-01-12
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