GRMHD study of accreting massive black hole binaries in astrophysical environment: a review

We present an overview of recent numerical advances in the theoretical characterization of massive binary black hole (MBBH) mergers in astrophysical environments. These systems are among the loudest sources of gravitational waves (GWs) in the universe and particularly promising candidates for multimessenger astronomy. Coincident detection of GWs and electromagnetic (EM) signals from merging MBBHs is at the frontier of contemporary astrophysics. One major challenge in observational efforts searching for these systems is the scarcity of strong predictions for EM signals arising before, during, and after merger. Therefore, a great effort in theoretical work to-date has been to characterize EM counterparts emerging from MBBHs concurrently to the GW signal, aiming to determine distinctive observational features that will guide and assist EM observations. To produce sharp EM predictions of MBBH mergers it is key to model the binary inspiral down to coalescence in a full general relativistic fashion by solving Einstein's field equations coupled with the magnetohydrodynamics equations that govern the evolution of the accreting plasma in strong-gravity. We review the general relativistic numerical investigations that have explored the astrophysical manifestations of MBBH mergers in different environments and focused on predicting potentially observable smoking-gun EM signatures that accompany the gravitational signal.Comment: 15 pages, 8 figures. Published in Astroparticle Physic

GRMHD simulations of accretion flows onto massive binary black hole mergers embedded in a thin slab of gas

We present general relativistic magnetohydrodynamic simulations of merging equal-mass, spinning black holes embedded in an equatorial thin slab of magnetized gas. We evolve black holes either non-spinning, with spins aligned to the orbital angular momentum, and with misaligned spins. The rest-mass density of the gas slab follows a Gaussian profile symmetric relative to the equatorial plane and it is initially either stationary or with Keplerian rotational support. As part of our diagnostics, we follow the accretion of matter onto the black hole horizons and the Poynting luminosity. Throughout the inspiral phase, the configurations with non-zero spins display modulations in the mass accretion rate that are proportional to the orbital frequency and its multiples. Our frequency analysis suggests that these modulations are influenced by the initial geometry and angular momentum of the gas distribution. In contrast to binary models evolved in the gas cloud scenario, we do not observe a significant increase in the mass accretion rate after the merger in any of our simulations. This observation brings attention to a potential link between the electromagnetic signatures of massive binary black hole mergers and the geometrical distribution of the surrounding gas. It also suggests the possibility of not detecting a peak luminosity at the time of merger in future electromagnetic observations.Comment: 14 pages, 7 figures, submitted to PR

A complete spectroscopic catalogue of local galaxies in the Northern spring sky -- Gas properties and nuclear activity in different environments

With the aim of providing the complete demography of galaxies in the local Universe, including their nuclear properties, we present SPRING, a complete census of local galaxies limited to the spring quarter of the Northern sky (10h< RA <16h; 0< Dec <65). The SPRING catalogue is a flux- and volume-limited sample (r < 17.7 mag, cz < 10000 km/s) of 30597 galaxies, including the Virgo, Coma and A1367 clusters. To inspect possible secular and environmental dependencies of the various nuclear excitation properties (SF vs. AGN), we perform a multidimensional analysis by dividing the sample according to (i) their position in the (NUV-i) vs. M* diagram,(ii) local galaxy density, (iii) stellar-mass, (iv) halo-mass of the group to which galaxies belong, and (v) neutral Hydrogen content. We present a new calibration of the optical diameter-based HI-deficiency parameter employing a reference sample of isolated galaxies. At intermediate distances between Virgo and Coma, we identify a ring-like structure of galaxies constituted by three large filaments. The fraction of HI-deficient galaxies within the filament suggests that filaments are a transitioning environment between field and cluster in terms of HI content. We classify the nuclear spectra according to the four-line BPT and the two-line WHAN diagrams, and investigate the variation in the fraction of AGN with stellar-mass, as well as their colours and environments. In general, we observe that the mass-dependency of the fraction of Seyfert nuclei is little sensitive to the environment, whereas the fraction of star-forming nuclei is a steeper function of M* in lower-density environments and in blue-cloud galaxies. We find that the fraction of LINERs depends on galaxy colour and, for logM* > 9.5-10, increases in galaxies belonging to the green valley.Comment: 26 pages, 22 figures. Accepted for publication in Astronomy & Astrophysic

Astrophysics with the Laser Interferometer Space Antenna

Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy as it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and other space-based instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA's first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed: ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or intermediate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help make progress in the different areas. New research avenues that LISA itself, or its joint exploitation with studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe

Misaligned Spinning Binary Black Hole Mergers in Hot Magnetized Plasma

We present general relativistic magneto-hydrodynamical simulations of equal-mass spinning black hole binary mergers embedded in a magnetized gas cloud. We focus on the effect of the spin orientation relative to the orbital angular momentum on the flow dynamics, mass accretion rate and Poynting luminosity. We find that, across the inspiral, the gas accreting onto the individual black holes concentrates into disk-like overdensities, whose angular momenta are oriented towards the spin axes and which persist until merger. We identify quasi-periodic modulations occurring in the mass accretion rate at the level of 1-20%, evolving in parallel with the gravitational wave chirp. The similarity between the accretion rate time-series and the gravitational strain is a consequence of the interplay between strong, dynamical gravitational fields and magnetic fields in the vicinity of the inspiralling black holes. This result suggests that quasi-periodicity in the pre-merger accretion rate of massive binaries is not exclusive of environments in which the black holes are embedded in a circumbinary accretion disk, and could provide an additional useful signature of electromagnetic emission concurrent to low-frequency gravitational wave detection.Comment: 9 pages, 4 figures. Accepted for publication in The Astrophysical Journal Letter

Validation of Shell Ionization Cross Sections for Monte Carlo Electron Transport

Abstract: Theoretical and semi-empirical methods to calculate electron impact ionization cross sections for atomic shells are subject to validation tests with respect to a wide collection of experimental measurements to identify the state of the art for Monte Carlo particle transport. The validation process applies rigorous statistical analysis methods. Cross sections based on the EEDL Evaluated Electron Data Library, widely used by Monte Carlo codes, and on calculations by Bote and Salvat, used in the Penelope code, are generally equivalent in compatibility with experiment. Results are also reported for various formulations of the Binary-Encounter-Bethe and Deutsch-Märk models

"Português" ou "brasileiro"? a denominação do vernáculo no sul do Brasil

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Assessment of New Evaluated Atomic Data Libraries in ENDF/B-VIII.0

Evaluated data libraries for electron-photon transport are most important components in Monte Carlo simulation and have been used in general-purpose Monte Carlo codes for decades. A new version of evaluated atomic data libraries, called EPICS2017, was released in early 2018. This paper reports an extensive assessment of EPICS2017, focused on what has changed, and evaluates the impact of using the new libraries in a Monte Carlo simulation environment. The results provide guidelines for developers and users of Monte Carlo codes wishing to use the new libraries. In addition, they also highlight opportunities for improving the data libraries in future releases

Astrophysics with the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and space-born instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA’s first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed; ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or interme-diate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help making progress in the different areas. New research avenues that LISA itself, or its joint exploitation with upcoming studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe