Is there a UV/X-ray connection in IRAS 13224-3809?

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.

Other publications