Pulsar Timing Constraints on the Fermi Massive Black-Hole Binary Blazar Population

Blazars are a sub-population of quasars whose jets are nearly aligned with the line-of-sight, which tend to exhibit multi-wavelength variability on a variety of timescales. Quasi-periodic variability on year-like timescales has been detected in a number of bright sources, and has been connected to the orbital motion of a putative massive black hole binary. If this were indeed the case, those blazar binaries would contribute to the nanohertz gravitational-wave stochastic background. We test the binary hypothesis for the blazar population observed by the \textit{Fermi} Gamma-Ray Space Telescope, which consists of BL Lacertae objects and flat-spectrum radio quasars. Using mock populations informed by the luminosity functions for BL Lacertae objects and flat-spectrum radio quasars with redshifts $z \le 2$, we calculate the expected gravitational wave background and compare it to recent pulsar timing array upper limits. The two are consistent only if a fraction $\lesssim 10^{-3}$ of blazars hosts a binary with orbital periods $<5$ years. We therefore conclude that binarity cannot significantly explain year-like quasi-periodicity in blazars.Comment: 5 pages, 4 figures, accepted by MNRAS Letter

Quasi-periodicities of BL Lac Objects

We review the reports of possible year-long quasi-periodicities of BL Lac objects in the $\gamma$-ray and optical bands, and present a homogeneous time analysis of the light curves of PKS2155$-$304, PG1553+113, and BL Lac. Based on results from a survey covering the entire Fermi $\gamma$-ray sky we have estimated the fraction of possible quasi-periodic BL Lac objects. We compared the cyclical behaviour in BL Lac objects with that derived from the search of possible optical periodicities in quasars, and find that at z$\lesssim$1 the cosmic density of quasi-periodic BL Lac objects is larger than that of quasi-periodic quasars. If the BL Lac quasi-periodicities were due to a supermassive binary black hole (SBBH) scenario, there could be a tension with the upper limits on the gravitational wave background measured by the pulsar timing array. The argument clearly indicates the difficulties of generally associating quasi-periodicities of BL Lac objects with SBBHs.Comment: In publication on A&A, 6 pages, 4 figure (11 plots). Minor corrections adde

Automatic Configuration of OPC UA for Industrial Internet of Things Environments

This work has been funded partially by the Software Engineering Department of the University of Granada.We would like to acknowledge the participation of Dzmitry Basalai in this research paper for his helping in the elaboration of the prototype carried out in this workSoftware technologies play an increasingly significant role in industrial environments, especially for the adoption of Industrial Internet of Things (IIoT). In this context, the application of mechanisms for the auto-configuration of industrial systems may be relevant for reducing human errors and costs in terms of time and money, improving the maintenance and the quality control. OPC UA (OLE for Process Control Unified Architecture) systems are usually integrated into an industrial system to provide a standard way for setting a secure and reliable data exchange between industrial devices of multiple vendors and software systems. In this paper, a novel mechanism for the auto-configuration of OPC UA systems is proposed from an initial setup of industrial devices interconnected to a basic Ethernet network. The auto-configuration of the OPC UA is self-managed over the TCP/IP protocol. This mechanism allows automating the configuration process of the OPC UA server automatically from the programmable logic controller (PLC) devices connected to a basic Ethernet network. Once the PLC devices are identified, they exchange information directly with OPC using a Modbus protocol over the same Ethernet network. To test the feasibility of this approach, a case study is prepared and evaluated

Radiative Shock Solutions with Multigroup Discrete-Ordinates Transport.

We obtain semi-analytic planar radiative shock solutions using a multigroup discrete-ordinates (Sn) radiation transport model. Comparisons are made to the grey nonequilibrium diffusion solutions of Lowrie and Edwards and the grey-Sn transport solutions of Ferguson, Morel, and Lowrie. Our solutions can be used to verify radiation-hydrodynamics codes. The material opacity is assumed to be constant and we apply a multigroup discretization to the O(u/c) steady-state frequency-integrated Sn transport equation in order to investigate the structure of the group radiation temperatures. From the structures of the group radiation temperatures, we show that anti-diffusive-like behavior can be due to frequency dependence of the Planck function and not just the angular dependence of the radiation field

Associating host galaxy candidates to massive black hole binaries resolved by pulsar timing arrays

We propose a novel methodology to select host galaxy candidates of future pulsar timing array (PTA) detections of resolved gravitational waves (GWs) from massive black hole binaries (MBHBs). The method exploits the physical dependence of the GW amplitude on the MBHB chirp mass and distance to the observer, together with empirical MBH mass–host galaxy correlations, to rank potential host galaxies in the mass–redshift plane. This is coupled to a null-stream based likelihood evaluation of the GW amplitude and sky position in a Bayesian framework that assigns to each galaxy a probability of hosting the MBHB generating the GW signal. We test our algorithm on a set of realistic simulations coupling the likely properties of the first PTA resolved GW signal to synthetic all-sky galaxy maps. For a foreseeable PTA sky-localization precision of 100 deg2, we find that the GW source is hosted with 50%(90%) probability within a restricted number of ≲ 50( ≲ 500) potential hosts. These figures are orders of magnitude smaller than the total number of galaxies within the PTA sky error-box, enabling extensive electromagnetic follow-up campaigns on a limited number of targets