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The XXL survey currently covers two 25 deg2 patches with XMM observations of ~10 ks. We summarize the scientific results associated with the first release of the XXL dataset, which occurred in mid-2016.We review several arguments for increasing the survey depth to 40 ks during the next decade of XMM operations. X-ray (z<2) cluster, (z<4) active galactic nuclei (AGN), and cosmic background survey science will then benefit from an extraordinary data reservoir. This, combined with deep multi-observations, will lead to solid standalone cosmological constraints and provide a wealth of information on the formation and evolution of AGN, clusters, and the X-ray background. In particular, it will offer a unique opportunity to pinpoint the z>1 cluster density. It will eventually constitute a reference study and an ideal calibration field for the upcoming eROSITA and Euclid missions. [ABSTRACT FROM AUTHOR]

Quasi-periodic oscillations (QPOs) are coherent peaks of variability power observed in the X-ray power spectra (PSDs) of stellar mass X-ray binaries (XRBs). A scale invariance of the accretion process implies they should be present in the active galactic nuclei. The first robust detection was a ∼ 1 h periodicity in the Seyfert galaxy RE J1034+396 from a ∼ 90 ks XMM- Newton observation; however, subsequent observations failed to detect the QPO in the 0.3-10.0 keV band. In this talk we present the recent detection of the ∼ 1 h periodicity in the 1.0-4.0 keV band of 4 further low-flux/spectrally-harder observations of RE J1034+396 (see Alston et al. 2014). We also present recent work on the discovery of a QPO in the Seyfert galaxy, MS 2254.9-3712, which again is only detected in energy bands associated with the primary power-law continuum emission (Alston et al. 2015). We conclude these features are most likely analogous to the high-frequency QPOs observed in XRBs. In both sources, we also see evidence for X-ray reverberation at the QPO frequency, where soft X-ray bands and Iron Kα emission lag the primary X-ray continuum. These time delays may provide another diagnostic for understanding the underlying QPO mechanism observed in accreting black holes. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Radio sources of the RCR catalogue, obtained from observational data of the 'Cold' experiment, have been identified, almost completely, with optical objects. For this purpose, we used optical, infrared, and radio sky surveys as well as archive data from the VLA (NRAO) and the 6-m telescope (SAO). According to spectroscopy and color index constraints, the identified sources are classified as galaxies and quasars; about 20 % of the sources remain unclassified because of being optically faint. We estimated radio luminosities of the sources and found that a majority (60%) of them belong to strong radio sources. Using ratios of FIRST and NVSS flux densities and angular sizes, we prepared a sample of steep spectrum compact sources. The existing infrastructure of the virtual observatory increases the effectiveness of astronomical studies like ours greatly. However, we still cannot consider the virtual observatory a completed project because it requires further development of services providing actualization of user data and better semantic compatibility of information. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]