Anomalous behaviour of the UV-optical continuum bands in NGC 5548
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During the 2014 HST/Swift and ground-based multi-wavelength monitoring campaign of NGC 5548 (AGN STORM), the UV–optical broad emission lines exhibited anomalous, decorrelated behaviour relative to the far-UV continuum flux variability. Here, we use key diagnostic emission lines (Lyα and He ii) for this campaign to infer a proxy for the all important, variable driving EUV continuum incident upon BLR clouds. The inferred driving continuum provides a crucial step towards the recovery of the broad emission line response functions in this AGN. In particular, the ionising continuum seen by the BLR was weaker and softer during the anomalous period than during the first third of the campaign, and apparently less variable than exhibited by the far-UV continuum. We also report the first evidence for anomalous behaviour in the longer wavelength (relative to λ1157Å) continuum bands. This is corroborative evidence that a significant contribution to the variable UV–optical continuum emission arises from a diffuse continuum emanating from the same gas that emits the broad emission lines.
Goad , M R , Knigge , C , Korista , K T , Cackett , E , Horne , K , Starkey , D A , Peterson , B M , De Rosa , G , Kriss , G A , Edelson , R & Fausnaugh , M 2019 , ' Anomalous behaviour of the UV-optical continuum bands in NGC 5548 ' , Monthly Notices of the Royal Astronomical Society . https://doi.org/10.1093/mnras/stz1186
Monthly Notices of the Royal Astronomical Society
© 2019, 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 the publisher's policies. This is the author created accepted version manuscript following peer review and as such may differ slightly from the final published version. The final published version of this is available at https://doi.org/10.1093/mnras/stz1186
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