The Library
Swift monitoring of NGC 5548 : X-ray reprocessing and short-term UV/optical variability
Tools
McHardy, I. M., Cameron, D. T., Dwelly, T., Connolly, S., Lira, P., Emmanoulopoulos, D., Gelbord, J., Breedt, E., Arevalo, P. and Uttley, P. (2014) Swift monitoring of NGC 5548 : X-ray reprocessing and short-term UV/optical variability. Monthly Notices of the Royal Astronomical Society, Volume 444 (Number 2). pp. 1469-1474. doi:10.1093/mnras/stu1636 ISSN 0035-8711.
Research output not available from this repository.
Request-a-Copy directly from author or use local Library Get it For Me service.
Official URL: http://dx.doi.org/10.1093/mnras/stu1636
Abstract
Lags 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.
Item Type: | Journal Article | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||
Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||||
Publisher: | Oxford University Press | ||||||||||
ISSN: | 0035-8711 | ||||||||||
Official Date: | 21 October 2014 | ||||||||||
Dates: |
|
||||||||||
Volume: | Volume 444 | ||||||||||
Number: | Number 2 | ||||||||||
Page Range: | pp. 1469-1474 | ||||||||||
DOI: | 10.1093/mnras/stu1636 | ||||||||||
Status: | Peer Reviewed | ||||||||||
Publication Status: | Published | ||||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||||
Adapted As: |
Request changes or add full text files to a record
Repository staff actions (login required)
View Item |