D. J. K. Buisson, A. M. Lohfink, W. N. Alston, E. M. Cackett, C.-Y. Chiang, T. Dauser, B. De Marco, A. C. Fabian, L. C. Gallo, J. A. García, J. Jiang, E. Kara, M. J. Middleton, G. Miniutti, M. L. Parker, C. Pinto, P. Uttley, D. J. Walton, D. R. Wilkins. 2018. Is there a UV/X-ray connection in IRAS 13224-3809?. Monthly Notices of the Royal Astronomical Society 475, 2, 2306-2313 DOI: 10.1093/mnras/sty008
We present results from the optical, ultraviolet, and X-ray monitoring of the NLS1 galaxy IRAS 13224-3809 taken with Swift and XMM-Newton during 2016. IRAS 13224-3809 is the most variable bright AGN in the X-ray sky and shows strong X-ray reflection, implying that the X-rays strongly illuminate the inner disc. Therefore, it is a good candidate to study the relationship between coronal X-ray and disc UV emission. However, we find no correlation between the X-ray and UV flux over the available similar to 40 d monitoring, despite the presence of strong X-ray variability and the variable part of the UV spectrum being consistent with irradiation of a standard thin disc. This means either that the X-ray flux which irradiates the UV emitting outer disc does not correlate with the X-ray flux in our line of sight and/or that another process drives the majority of the UV variability. The former case may be due to changes in coronal geometry, absorption or scattering between the corona and the disc.