99 research outputs found
Non-Steady State Accretion Disks in X-Ray Novae: Outburst Models for Nova Monocerotis 1975 and Nova Muscae 1991
We fit outbursts of two X-ray novae (Nova Monocerotis 1975=A0620-00 and Nova
Muscae GS 1991=1124-683) using a time-dependent accretion disk model. The model
is based on a new solution for a diffusion-type equation for the
non-steady-state accretion and describes the evolution of a viscous alpha-disk
in a binary system after the peak of an outburst, when matter in the disk is
totally ionized. The accretion rate in the disk decreases according to a power
law. We derive formulas for the accretion rate and effective temperature of the
disk. The model has three free input parameters: the mass of the central object
M, the turbulence parameter alpha, and the normalization parameter delta t.
Results of the modeling are compared with the observed X-ray and optical B and
V light curves. The resulting estimates for the turbulence parameter
are similar: 0.2-0.4 for A 0620-00 and 0.45-0.65 for GS 1124-683, suggesting a
similar nature for the viscosity in the accretion disks around the compact
objects in these sources. We also derive the distances to these systems as
functions of the masses of their compact objects.Comment: 10 pages, 7 figures; style improve
Synthesis and sorption properties of filled fibrous sorbents with immobilized hetarylformazan groups
New sorbents were prepared by immobilization of structurally different sulfur-containing hetaryl-formazans on nonwoven polyacrylonitrile fiber tilled with AV-17 anion exchanger. Sorption of some heavy metals on these materials was studied as influenced by various factors. Sorbents for selective recovery of copper(II) in the presence of nickel(II), zinc(II), and cadmium(II) cations were found
Synthesis and catalytic properties of copper(II) 1-aryl-5-benzothiazolylformazanates
New copper(II) benzothiazolylformazane complexes were synthesized and immobilized on AN-18 anion exchanger. The influence of the composition of the coordination core of copper(II) benzthiazolylformazanates and temperature on their catalytic properties in decomposition of H2O2 and oxidation of Na2S in aqueous solution was studied
Synthesis and spectroscopic features of iron(II) 1-aryl-5-benzothiazol-2- ylformazanates
New iron(II) coordination compounds with 1-aryl-5-(benzothiazol-2-yl) formazans were prepared. Their compositions and structures were determined by electronic spectroscopy, mass spectrometry, single crystal X-ray diffraction analysis, and magnetochemical measurements. © 2008 Pleiades Publishing, Ltd.Russian Foundation for Basic Researc
The thickness of accretion α-disks: Theory and observations
Observations of X-ray binaries indicate substantial half-thicknesses for the accretion disks in these systems (up to h/R ≈ 0.25, where h is the disk half-thickness and R its radius), while standard α accretion disks predict appreciably smaller half-thicknesses. We study the theoretical vertical structure of such disks using two independent numerical methods, and show that their maximum half-thicknesses in the subcritical regime cannot exceed h/R ≈ 0.1. We consider various reasons for the apparent increase in the disk thickness, the most probable of which is the presence of matter above the disk in the form of a hot corona that scatters hard radiation from the central source and inner parts of the disk. As a result, the observed thickness of the disk and the illumination of its outer parts effectively increase. This mechanism can also explain both the optical-to-X-ray flux ratio in these systems and the observed parameters of eclipsing X-ray binaries. © 2007 Pleiades Publishing, Ltd
Light curve modeling for time-dependent accretion disks in X-ray novae with general relativity effects taken into account
We present a method of modeling X-ray and optical light curves of time-dependent accretion α-disks in X-ray novae. The model is based on an analytic solution for α-disk evolution after the outburst maximum. The method involves relativistic effects near a Kerr black hole and self-irradiation of an accretion disk. The method is applied to the outbursts of X-ray Nova Monocerotis 1975 (A 0620-00) and X-ray Nova Muscae 1991 (GRS 1124-68). Recently, narrow limits were obtained for the masses and the distances of these binaries (11 ± 2M⊙, 1.1 kpc for A 0620-00 and 7 ± 0.6M⊙, 5.1 kpc for GRS 1124-68, Gelino et al. (2001a,b)). This allows us to limit other model parameters: Kerr parameter (0.5-0.7 and ∼ 0.95 respectively for A 0620-00 and GRS 1124-68) and α-parameter (0.6-0.8 and 0.4-0.5). The inner radius of the accretion disk in GRS 1124-68 has to be few times larger than that of the last marginally stable orbit. Modeled disks in both systems should be thicker than in the standard theory and should thermalize a significant part of the incident X-ray flux (≳ 20%). Possible reasons for these results are discussed
Cyano and CF3 Derivatives of 2-Aryl- and 2-Thienylquinazoline: Synthesis and Study of Optical Properties
This work was supported by the Russian Foundation for Basic Research (grant # 18-03-00112) and Russian Science Foundation (project # 19-73-10144)
QUINAZOLINONE DERIVATIVES: SYNTHESIS AND LUMINESCENCE PROPERTIES
Benzazines are widely studied heterocyclic compounds1 its framework possesses strong electron withdrawing ability and can be used as acceptor fragment to form push-pull molecules with ITC character. Quinazolin-4(3H)-one 1 represent promising fluorescence molecule with quantum yield 71% in toluene.2 2-(2-Hydroxyphenyl)quinazolin-4(3H)-ones can serve as N, O-chelating ligand favorable for construction BF2 complexes 2.3 The introduction of methoxy group at para-position of phenol ring leads to increase in quantum yield compared to unsubstituted counterpart (from 24 to 70%).This work was supported by the Russian Foundation for Basic Research (grant # 19-33-90014)
QUINAZOLINONE CONTAINED CHROMOPHORES: TUNING OF PHOTOPHYSICAL PROPERTIES
This work was supported by the Russian Science Foundation (grant # 21-13-00304)
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