We discuss preliminary results from a joint XMM-Newton and NuSTAR monitoring program on the active galactic nucleus NGC 4593, consisting of 5×20 ks observations, spaced by two days, performed in January 2015. The source is found to be variable, both in flux and spectral shape, on time scales as short as a few ks. The spectrum clearly softens when the source brightens. A simple timing analysis suggests the presence of a variable soft excess that correlates with the primary continuum.
Ursini, F., Petrucci, P.O., Matt, G., Bianchi, S., Cappi, M., De Marco, B., et al. (2016). High-energy monitoring of Seyfert galaxies: The case of NGC 4593. ASTRONOMISCHE NACHRICHTEN, 337(4-5), 552-556 [10.1002/asna.201612346].