Evolving optical polarisation of the black hole X-ray binary MAXI J1820+070

Aims. The optical emission of black hole transients increases by several magnitudes during the X-ray outbursts. Whether the extra light arises from the X-ray heated outer disc, from the inner hot accretion flow, or from the jet is currently debated. Optical polarisation measurements are able to distinguish the relative contributions of these components. Methods. We present the results of BVR polarisation measurements of the black hole X-ray binary MAXI J1820+070 during the period of March-April 2018. Results. We detect small, $\sim$0.7%, but statistically significant polarisation, part of which is of interstellar origin. Depending on the interstellar polarisation estimate, the intrinsic polarisation degree of the source is between $\sim$0.3% and 0.7%, and the polarisation position angle is between $\sim10\deg-30\deg$. We show that the polarisation increases after MJD 58222 (2018 April 14). The change is of the order of 0.1% and is most pronounced in the R band. The change of the source Stokes parameters occurs simultaneously with the drop of the observed V-band flux and a slow softening of the X-ray spectrum. The Stokes vectors of intrinsic polarisation before and after the drop are parallel, at least in the V and R filters. Conclusions. We suggest that the increased polarisation is due to the decreasing contribution of the non-polarized component, which we associate with the the hot flow or jet emission. The low polarisation can result from the tangled geometry of the magnetic field or from the Faraday rotation in the dense, ionised, and magnetised medium close to the black hole. The polarized optical emission is likely produced by the irradiated disc or by scattering of its radiation in the optically thin outflow.Comment: 11 pages, 12 figures, A&A in pres

Disc and wind in black hole X-ray binary MAXI J1820+070 observed through polarized light during its 2018 outburst

We describe the first complete polarimetric data set of the entire outburst of a low-mass black hole X-ray binary system and discuss the constraints for geometry and radiative mechanisms it imposes. During the decaying hard state, when the optical flux is dominated by the non-thermal component, the observed polarization is consistent with the interstellar values in all filters. During the soft state, the intrinsic polarization of the source is small, similar to 0.15 per cent in B and V filters, and is likely produced in the irradiated disc. A much higher polarization, reaching similar to 0.5 per cent in V and R filters, at a position angle of similar to 25 degrees observed in the rising hard state coincides in time with the detection of winds in the system. This angle coincides with the position angle of the jet. The detected optical polarization is best explained by scattering of the non-thermal (hot flow or jet base) radiation in an equatorial wind

Black hole spin-orbit misalignment in the x-ray binary MAXI J1820+070

If a black hole is in a close enough binary system with a star, it rips material off the companion. As that material falls into the black hole, it forms an accretion disk that is hot enough to emit optical and x-ray radiation. Poutanen et al. used optical polarimetry to determine the orbital axis of a black hole x-ray binary (see the Perspective by Patat and Mapelli). Combining these observations with previous measurements of the black hole spin showed that the two are misaligned by at least 40 degrees. This high misalignment must have been generated during the formation of the black hole, because accretion always brings the two axes closer together. —KT

Изучение электрофизиологических механизмов действия соединения ЛМГ-124

In vitro experiments performed on the isolated rats hippocampal neurons, the antiarrhythmic activity electrophysiological mechanisms of the complex compound LMG-124 containing an antiarrhythmic agent of the class I by Vaughan Williams, Lappaconitine hydrobromide, were studied. As the reference preparation, a prototype, Lappaconitine hydrobromide, was used. The electrical activity of the neurons was recorded by the patch-clamp method in the whole cell configuration. It is shown that the compound LMG-124 effectively inhibits the fast incoming Na+ current flowing through transmembrane potential-dependent fast Na+ channels. This effect of the LMG-124 connection is realized at the level of the open Na+ channel. As follows from the data obtained, the LMG-124 compound, in contrast to Lappaconitine hydrobromide, blocks not only Na+ channels, but also partially and K+ channels, so that it can be attributed to antiarrhythmic drugs potentially possessing anti-arrhythmic properties of the Ia class by Vaughan classification Williams.В экспериментах in vitro, выполненных на изолированных нейронах гиппокампа крыс, изучали электрофизиологические механизмы, лежащие в основе антиаритмической активности комплексного соединения ЛМГ-124, содержащего в своём составе антиаритмическое средство IС класса классификации Vaughan Williams - лаппаконитина гидробромид. В качестве препарата сравнения использовали прототип - лаппаконитина гидробромид. Электрическую активность нейронов регистрировали методом patch-clamp в конфигурации whole cell. Показано, что соединение ЛМГ-124 эффективно ингибирует быстрый входящий Na+ ток, протекающий через трансмембранные потенциал-зависимые быстрые Na+ каналы. Этот эффект соединения ЛМГ-124 реализуется на уровне открытого Na+ канала. Как следует из полученных данных, соединение ЛМГ-124, в отличие от лаппаконитина гидробромида, блокирует не только Na+ каналы, но частично и К+ каналы, в силу чего его можно отнести к антиаритмическим лекарственным средствам, потенциально обладающим свойствами антиаритмиков Ia класса, по классификации Vaughan Williams

Optical polarimetry: Methods, Instruments and Calibration Techniques

In this chapter we present a brief summary of methods, instruments and calibration techniques used in modern astronomical polarimetry in the optical wavelengths. We describe the properties of various polarization devices and detectors used for optical broadband, imaging and spectropolarimetry, and discuss their advantages and disadvantages. The necessity of a proper calibration of the raw polarization data is emphasized and methods of the determination and subtraction of instrumental polarization are considered. We also present a few examples of high-precision measurements of optical polarization of black hole X-ray binaries and massive binary stars made with our DiPol-2 polarimeter, which allowed us to constrain the sources of optical emission in black hole X-ray binaries and measure orbital parameters of massive stellar binaries.Comment: 33 pages, 14 figure; to be published in Astrophysics and Space Science Library 460, Astronomical Polarisation from the Infrared to Gamma Ray

Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design

N-methyl D-aspartate (NMDA) receptors in rat and human heart

This study focuses on the investigation of expression and function of N-methyl D-aspartate receptors (NMDARs) in rat myocardium and on the role these receptors play in control of autonomous heart function. NMDARs are ionotropic glutamate receptors mediating Ca2+ uptake upon their activation by co-agonists glutamate and glycine. We have detected the presence of gene transcripts of the NR1, 2A, B, C and D and 3A subunits. Expression of the NMDAR subunits and activity of the receptor complex varied substantially within the heart. In hearts of young animals maximal expression and the highest density of active NMDAR units was found in the atria and in septum. In senescent hearts up-regulation in NR2B abundance and the receptor activity was observed in the ventricles. Activation of the NMDARs in isolated ventricular myocytes resulted in an increase in the intracellular Ca2+ levels and initiation of Ca2+ transients which could be suppressed by co-administration of antagonist of the NMDAR, MK-801. Perfusion of rat hearts with autologous blood supplemented with NMDA agonists was associated with induction of tachycardia and sinus arrhythmia, and a positive inotropic effect whereas intracoronary administration of the NMDAR antagonists exerted an anti-arrhythmic effect and resulted in bradycardia. We have performed pilot studies exploring expression levels of the NMDAR subunits in biopsies collected from all four chambers of human patients undergoing mitral valve replacement surgery. Expression of NR1, NR2A, B, C and D, NR3A and B was shown. Development of decompensated hypertrophy was associated with an increase in expression. The obtained data reveal that NMDARs are expressed in rat heart and are active players in calcium handling contributing to the pacemaker function and contractile force control