Exploring jet properties in magnetohydrodynamics with gravity

Om de overeenkomsten en verschillen tussen systemen met zwarte gaten met de massa van de zon en diegene met massa's die ongeveer een miljoen tot een miljard keer groter zijn, te kunnen gebruiken om meer over deze objecten te weten te komen, moeten we de gerichte uitstromen van plasma die ze produceren, goed begrijpen. Uit waarnemingen blijkt dat ergens in deze uitstroom deeltjes een hogere energie krijgen. Door deze uitstromen te modelleren door vloeistofdynamica met magneetvelden en zwaartekracht, kunnen we deze locatie koppelen aan de eigenschappen rond het zwarte gat. Hierdoor zijn we voor het eerst in staat uit waarnemingen van deze locatie informatie over het zwarte gat te weten te komen

Fermi-LAT counterparts of IceCube neutrinos above 100 TeV

The IceCube Collaboration has published four years of data and the observed neutrino flux is significantly in excess of the expected atmospheric background. Due to the steeply falling atmospheric background spectrum, events at the highest energies are most likely extraterrestrial. In our previous approach we have studied blazars as the possible origin of the High-Energy Starting Events (HESE) neutrino events at PeV energies. In this work we extend our study to include all HESE neutrinos (which does not include IC 170922A) at or above a reconstructed energy of 100 TeV, but below 1 PeV. We study the X-ray and $\gamma$-ray data of all ($\sim200$) 3LAC blazars that are positionally consistent with the neutrino events above 100 TeV to determine the maximum neutrino flux from these sources. This larger sample allows us to better constrain the scaling factor between the observed and maximum number of neutrino events. We find that when we consider a realistic neutrino spectrum and other factors, the number of neutrinos is in good agreement with the detected number of IceCube HESE events. We also show that there is no direct correlation between \Fermi-LAT $\gamma$-ray flux and the IceCube neutrino flux and that the expected number of neutrinos is consistent with the non-detection of individual bright blazars.Comment: accepted for publication by A&

The accretion-ejection coupling in the black hole candidate X-ray binary MAXI J1836-194

We present the results of our quasi-simultaneous radio, submm, infrared, optical and X-ray study of the Galactic black hole candidate X-ray binary MAXI J1836-194 during its 2011 outburst. We consider the full multiwavelength spectral evolution of the outburst, investigating whether the evolution of the jet spectral break (the transition between optically thick and optically thin synchrotron emission) is caused by any specific properties of the accretion flow. Our observations show that the break does not scale with the X-ray luminosity or with the inner radius of the accretion disc, and is instead likely to be set by much more complex processes. We find that the radius of the acceleration zone at the base of the jet decreases from ˜106 gravitational radii during the hard intermediate state to ˜103 gravitational radii as the outburst fades (assuming a black hole mass of 8 M?), demonstrating that the electrons are accelerated on much larger scales than the radius of the inner accretion disc and that the jet properties change significantly during outburst. From our broad-band modelling and high-resolution optical spectra, we argue that early in the outburst, the high-energy synchrotron cooling break was located in the optical band, between ˜3.2 × 10^14 and 4.5 × 10^14 Hz. We calculate that the jet has a total radiative power of ˜3.1 × 10^36 erg s-1, which is ˜6 per cent of the bolometric radiative luminosity at this time. We discuss how this cooling break may evolve during the outburst, and how that evolution dictates the total jet radiative power. Assuming the source is a stellar mass black hole with canonical state transitions, from the measured flux and peak temperature of the disc component we constrain the source distance to be 4-10 kpc

Polarimetry of binary systems: polars, magnetic CVs, XRBs

Polarimetry provides key physical information on the properties of interacting binary systems, sometimes difficult to obtain by any other type of observation. Indeed, radiation processes such as scattering by free electrons in the hot plasma above accretion discs, cyclotron emission by mildly relativistic electrons in the accretion shocks on the surface of highly magnetic white dwarfs and the optically thin synchrotron emission from jets can be observed. In this review, I will illustrate how optical/near-infrared polarimetry allows one to estimate magnetic field strengths and map the accretion zones in magnetic Cataclysmic Variables as well as determine the location and nature of jets and ejection events in X-ray binaries.Comment: 26 pages, 16 figures; to be published in Astrophysics and Space Science Library 460, Astronomical Polarisation from the Infrared to Gamma Rays, Editors: Mignani, R., Shearer, A., S{\l}owikowska, A., Zane,

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

Relativistic plasma jets are observed in many accreting black holes. According to theory, coiled magnetic fields close to the black hole accelerate and collimate the plasma, leading to a jet being launched. Isolating emission from this acceleration and collimation zone is key to measuring its size and understanding jet formation physics. But this is challenging because emission from the jet base cannot be easily disentangled from other accreting components. Here, we show that rapid optical flux variations from a Galactic black-hole binary are delayed with respect to X-rays radiated from close to the black hole by ~0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these sub-second optical variations has hitherto been controversial. Not only does our work strongly support a jet origin for the optical variations, it also sets a characteristic elevation of <~10$^3$ Schwarzschild radii for the main inner optical emission zone above the black hole, constraining both internal shock and magnetohydrodynamic models. Similarities with blazars suggest that jet structure and launching physics could potentially be unified under mass-invariant models. Two of the best-studied jetted black hole binaries show very similar optical lags, so this size scale may be a defining feature of such systems

European Green Deal as a matter of security

Abstract The European Green Deal (EGD) is a set of policy initiatives by the European Union with the overarching and ambitious aim of making Europe climate neutral in 2050. Being world’s first ‘climate-neutral bloc’ and fulfilling other goals extending to many different sectors, including construction, biodiversity, energy, transport, food and others has also an impact on different sectors of security. The implementation of the tasks set out in the EGD requires taking into account the necessity of sustainability in reaching the goals, including not violating sectoral security in the EU Member States. Nexus approach might be useful in the processes of finding and implementation of particular solutions.</jats:p

Single burst age and metallicity from HB, Mg b and <Fe> for model and observed elliptical galaxies

In this paper a method is presented to calculate the single starburst population (SSP) age and metalicity directly from the spectrum of an observed galaxy, using the Lick/IDS index system.

Condition of urban park infrastructure in the context of perceived security of park users

Abstract Personal security is one of the key aspects affected by the perception of urban greenery, which plays an important role for city dwellers. The survey conducted in Poland in 2020 (N=394) aimed to check how important for park users in context of perceived security are selected factors related to maintenance of different types of park infrastructure (condition of equipment and pavement, also condition of greenery), level of park cleanliness (filling of the rubbish bins, litter on the ground, and graffiti on different types of facilities), and elements related to the use of park space (paths, varied topography, functional aids, and water). The condition of equipment was assessed as a factor of high impact (average of 4.13 in 5-point Likert scale), as well as the presence of park paths (4.02). The results indicate that all 10 of the examined factors are recognized as important (3 and higher). They also show that both women (compared to men) and older respondents (compared to those under 60) assessed higher the importance of factors related to the condition of elements of infrastructure and pavement, as well as the level of cleanliness in urban parks in shaping their personal sense of security.</jats:p

The optimal locations for shock acceleration in MHD jets

Jets can contribute to the spectra of X-ray binaries (XRBs) and active galactic nuclei (AGN) from the radio through the γ-ray bands; thus understanding their physics is key for interpreting the data. Recent VLBI observations suggest that jets begin to accelerate particles into power-law distributions at a point offset from the black hole by ~104 rg, possibly via a collimation shock. Spectral fitting of simultaneous, broadband data from both XRBs and AGN in jet-dominated states corroborates this picture. From a magnetohydrodynamical (MHD) point of view, it is natural to associate the onset of particle acceleration with the final MHD critical point in the flow, the modified fast point (MFP), where causal contact with the upstream flow is broken. In this way a standing disruption like a shock can form, and this location might vary with the physical parameters of the jet. In order to study this issue, we have used the self-similar formalism of Vlahakis & Königl (2003, hereafter VK03) to simplify the MHD equations and to derive solutions that cross the critical points. We have found a new parameter space of solutions that cross the MFP at a finite height above the disc and are relativistic, spanning a range of Lorentz factors Γ ≤ 10 (Polko et al. 2010). We present these results, as well as preliminary work connecting the relativistic formalism to the non-relativistic conditions with gravity near the base of the jets