About 100 AGNs have their black hole mass measured directly using the reverberation mapping technique over the past few decades. By now we have high enough numbers to explore unique subsamples within these objects and to study phenomena across variety of AGNs. I will review recent reverberation mapping studies which focus on high-redshift high-luminosity AGNs and on AGNs with super-Eddington accreting massive black holes. These studies enable to investigate the BLR size, mass, and luminosity relations in different subsamples of AGNs and to check whether there are differences in these relations in different types of AGNs. In particular I will discuss the following questions: Is the BLR size - luminosity relation the same over the whole AGNs luminosity range? Are there different relations for different types of AGNs? What are these studies teaching us about theory of accretion into black holes in AGNs?

We present the most up-to-date and complete multi-wavelength correlation analysis on luminosity properties of TeV BL Lacs. Correlation function (power law or linear) parameters are calculated based on linear regression method. Using the lower energy luminosities of a sample of 182 non-TeV BL Lacs and the generated functions, minimum level of VHE gamma-ray emission was calculated for each non-TeV BL Lacs. This multi wavelength prediction method gives us a list of best candidates to be observed with current generation of Imaging Air Cherenkov Telescopes.

The present work proposes a method to calculate the AGN magnetic luminosity fraction to be converted into ultra high energy cosmic rays (UHECRs) luminosities for nine UHECR AGN Seyfert sources based on the respective observation of gamma ray upper limits. The motivation for such calculation comes attached to the fact that a fraction of the magnetic luminosity (L B ) produced by Kerr black holes in some AGNs can produce the necessary energy to accelerate UHECRs beyond the GZK limit, observed, e.g., by the Auger experiment. Nevertheless, the direct detection of those UHECRs has a lack of information about the direction of the source from where those cosmic rays are coming, since charged particles are deflected by the intergalactic magnetic field. Such problem arises alternative methods to evaluate the luminosity of UHECRs from the observation of upper limits during the propagation.

Bosonic fields around a spinning black hole can be amplified via ‘superradiance’, a wave analogue of the Penrose process, which extracts energy and momentum from the black hole. For hypothetical ultra-light bosons, with Compton wavelengths on ≳ km scales, such a process can lead to the exponential growth of gravitationally bound states around astrophysical Kerr black holes. If such particles exist, as predicted in many theories of beyond Standard Model physics, then these bosonic clouds give rise to a number of potentially-observable signals. Among the most promising are monochromatic gravitational radiation signals which could be detected at Advanced LIGO and future gravitational wave observatories.

High energy photon radiations of gamma-ray bursts (GRBs) and active galactic nuclei (AGNs) are dominated by their jet radiations. It was suggested that relativistic jets powered by different mass-scale black holes may share the same physical laws. A tight relation among the peak luminosity, the peak photon energy in the νf ν spectrum, and the initial Lorentz factor is found for GRBs. With samples of GeV-TeV BL Lacs, FSRQs, and NLS1 galaxies, we show that these sources do not follow this relation. This may be attributed to the jet geometry and continuous/episodic jet as well as radiation physics for different kinds of sources.

V404 Cygni went into an outburst again on June 15, 2015 after 26 years of quietness. Soon after the notifications, we started intense optical observation campaign of this source. The spectral index between RC and IC-band was stable over the outburst, whereas that between g′ and RC-band varied violently. With the time domain analysis of the multi-color optical light curves, we successfully decomposed optical variations into three components: highly-variable component (HVC), little-variable component (LVC). The loci of the LVC in the color-color diagram is consistent with that of a single temperature blackbody radiation or a multi-color blackbody radiation from a standard accretion disk, while those of the HVC trace that of power-law spectra.

A small fraction of Tidal Disruption Events (TDE) produce relativistic jets, evidenced by their non-thermal X-ray spectra and transient radio emission. Here we present milliarcsecond-resolution imaging results on TDE J1644+5734 with the European VLBI Network (EVN). These provide a strong astrometric constraint on the average apparent jet velocity βapp < 0.27, that constrains the intrinsic jet velocity for a given viewing angle.

We review the current observational and theoretical status of the polarization measurements of Gamma-ray Bursts at all wavelengths. Gamma-Ray Bursts are thought to be produced by an ultra-relativistic jet, possibly powered by a black hole. One of the most important open point is the composition of the jet: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (Poynting flux). The polarization properties are expected to help disentangling main energy carrier. The prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry.

We analyzed the light curves (LCs) of several radio-quiet and radio-loud quasars belonging to the same parameter space volume in the 4D Eigenvector 1 (4DE1) quasar sequence, using data from the Catalina Real-time Transient Survey (CRTS). We report preliminary results on detected variability pattern, and discuss possible cases of periodic variability.

Hyperaccreting disks around black holes are the engines that drive outflows and jets in gamma ray bursts (GRBs). The torus formed after the core collapse or a compact binary merger is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrinos rather than photon emission. Hyperaccretion powers the ultra-relativistic jets, where the GRB prompt emission originates. The neutrons produced in the disk and also in the outflowing material are necessary for the production of heavier nuclei. We discuss here the observable consequences of nucleosynthesis and we also apply the scenario of hyperaccretion to the gravitational wave source, GW150914. Temporal coincidence reported by the Fermi satellite suggested that the black hole merger might be accompanied with a GRB. We propose that a collapsing massive star and a black hole in a close binary could lead to such event. Gravitational wave emission due to the merger of collapsed core and the companion black hole might then coincide with a weak GRB.

We present KETJU, a new regularized tree code based on algorithmic chain regularization and implemented into Gadget-3. This new code is able to follow simultaneously galactic-scale dynamical and astrophysical processes and the small-scale supermassive black hole binary dynamics. We present here the general idea of this new code and show a test simulation of black hole binary dynamics in a galaxy merger of two massive elliptical galaxies. The separation of the black holes at the time of the merger is several orders of magnitude smaller in KETJU than when compared to ordinary Gadget-3 simulations. The merger timescale is also longer by 100 − 200 Myr.

According to the currently favored picture, relativistic jets in active galactic nuclei (AGN) are launched in the vicinity of the black hole by magnetic fields extracting energy from the spinning black hole or the accretion disk. In the past decades, various models from shocks to magnetic reconnection have been proposed as the energy dissipation mechanism in the jets. This paper presents a short review on how linear polarization observations can be used to constrain the magnetic field structure in the jets of AGN, and how the observations can be used to constrain the various emission models.

The formation of direct collapse black hole seeds with masses ~104 − 105 ~M⊙ could help explain the assembly of supermassive black holes powering high redshift quasars. Conditions conducive to the formation of these massive initial seeds exist at high redshift. Halos hosting these massive seeds merge promptly with a nearby galaxy. These early stage mergers at high redshift produce a new class of transient galaxies that contain an accreting black hole that is over-massive compared to the newly acquired stellar component - Obese Black hole Galaxies (OBGs). During this phase, the accretion luminosity of the direct collapse black hole seed exceeds that of the acquired stellar component. Here we calculate the multi-wavelength spectrum of this short-lived OBG stage, and show that there exist unique observational signatures in long wavelengths spanning near, mid to far-infrared that should be detectable by instruments aboard the upcoming James Webb Space Telescope (JWST).

A programme of worldwide, multi-wavelength electromagnetic follow-up of sources detected by gravitational wave detectors is in place. Following the discovery of GW150914 and GW151226, wide field imaging of their sky localisations identified a number of candidate optical counterparts which were then spectrally classified. The majority of candidates were found to be supernovae at redshift ranges similar to the GW events and were thereby ruled out as a genuine counterpart. Other candidates ruled out include AGN and Solar System objects. Given the GW sources were black hole binary mergers, the lack of an identified electromagnetic counterpart is not surprising. However the observations show that it is possible to organise and execute a campaign that can eliminate the majority of potential counterparts. Finally we note the existence of a “classification gap” with a significant fraction of candidates going unclassified.

Basic questions about black holes, some of which are fairly old, include (1) What is a black hole? (2) Do black holes exist? And the answer to this depends a good deal on the answer to (1), (3) Where, when, why, and how have they formed? and (4) What are they good for? Here I attempt some elaboration of the questions and partial answers, noting that general relativity is required to described some of the phenomena, while dear old Isaac Newton is OK for others.

We study the interaction of relativistic jets with their environment, using 3-dimen- sional relativistic particle-in-cell simulations for two cases of jet composition: (i) electron-proton (e − − p +) and (ii) electron-positron (e ±) plasmas containing helical magnetic fields. We have performed simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability and the Mushroom instability. We have found that these kinetic instabilities are suppressed and new types of instabilities can grow. For the e − − p + jet, a recollimation-like instability occurs and jet electrons are strongly perturbed, whereas for the e ± jet, a recollimation-like instability occurs at early times followed by kinetic instability and the general structure is similar to a simulation without a helical magnetic field. We plan to perform further simulations using much larger systems to confirm these new findings.

The jets from active galactic nuclei exhibit stability which seems to be far superior compared to that of terrestrial and laboratory jets. They manage to propagate over distances up to a billion of initial jet radii. Yet this may not be an indication of some exotic physics but mainly a reflection of the specific environment these jets propagate through. The key property of this environment is a rapid decline of density and pressure along the jet, which promotes its rapid expansion. Such an expansion can suppress global instabilities, which require communication across the jet, and hence ensure its survival over huge distances. At kpc scales, some AGN jets do show signs of strong instabilities and even turn into plumes. This could be a result of the flattening of the external pressure distribution in their host galaxies or inside the radio lobes. In this regard, we discuss the possible connection between the stability issue and the Fanaroff-Riley classification of extragalactic radio sources. The observations of AGN jets on sub-kpc scale do not seem to support their supposed lack of causal connectivity. When interpreted using simple kinematic models, they reveal a rather perplexing picture with more questions than answers on the jets dynamics.

The first gravitational wave transient GW150914 was observed by Advanced LIGO on September 14th, 2015 at 09:50:45 Universal Time. In addition to follow-up electromagnetic observations, the detection of neutrinos will probe deeply and more on the nature of astrophysical sources, especially in the ultra-high energy regime. Neutrinos in the EeV energy range were searched in data collected at the surface detector of the Pierre Auger Observatory within ± 500 s and 1 day after the GW150914 event. No neutrino candidates were found. Based on this non-observation, we derive the first and only neutrino fluence upper limit at EeV energies for this event at 90% CL, and report constraints on existence of accretion disk around mergers.

The blazar QSO B0218+357 is the first gravitationally lensed blazar detected in the very high energy (VHE, E > 100 GeV) gamma-ray spectral range (Ahnen et al. 2016). It is gravitationally lensed by the intervening galaxy B0218+357G (z l = 0.68466 ± 0.00004, Carilli et al. 1993), which splits the blazar emission into two components, spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 days delay. In July 2014 a flare from QSO B0218+357 was observed by the Fermi-LAT (Large Area Telescope, Atwood et al. 2009, Ackermann et al. 2012), and followed-up by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, a stereoscopic system of two 17m Imaging Atmospheric Cherenkov Telescopes located on La Palma, Canary Islands (Aleksić et al. 2016a, 2016b), during the expected time of arrival of the delayed component of the emission. MAGIC could not observe the leading image due to the Full Moon. The MAGIC and Fermi-LAT observations were accompanied by optical data from KVA telescope at La Palma, and X-ray observations by Swift-XRT (Fig. 1 left). Variability in gamma-rays was of the order of one day, while no variability correlated with gamma-rays was observed at lower energies. The flux ratio of the leading to trailing image in HE gamma-rays was larger than in the flare of QSO B0218+357 observed by Fermi-LAT in 2012 (Cheung et al. 2014). Changes in the observed flux ratio can be caused by gravitational microlensing on individual stars in the host galaxy (Neronov et al. 2015), or by other compact objects like for ex. clumps in giant molecular clouds (Sitarek & Bednarek 2016).