679 research outputs found
Constraints on the collimated X-ray emission of SS 433 from the reflection on molecular clouds
We calculate X-ray signal that should arise due to reflection of the putative
collimated X-ray emission of the Galactic supercritical accretor SS 433 on
molecular clouds in its vicinity. The molecular gas distribution in the region
of interest has been constructed based on the data of the BU-FCRAO GRS in
CO emission line, while the collimated emission was
assumed to be aligned with the direction of the relativistic jets, which are
continuously launched by the system. We consider all the available
observations covering the regions possibly containing the reflection signal and
put constraints on the apparent face-on luminosity of SS 433 above 4 keV. No
signatures of the predicted signal have been found in the analysed regions down
to a 4-8 keV surface brightness level of erg/s/cm/deg.
This translates into the limit on the apparent face-on 2-10 keV luminosity of
SS 433 erg/s, provided that the considered
clouds do fall inside the illumination cone of the collimated emission. This,
however, might not be the case due to persisting uncertainty in the
line-of-sight distances to SS 433 (4.5-5.5 kpc) and to the
considered molecular clouds. For half-opening angle of the collimation cone
larger than or comparable to the amplitude of the jets' precession
(), the stringent upper limit quoted above is most relevant if
kpc, provided that the kinematic distances to the considered
molecular clouds are sufficiently accurate. Dropping the last assumption, a
more conservative constraint is erg/s for
kpc (and yet worse outside this range). We conclude that
SS 433 is not likely to belong to the brightest ultraluminous X-ray sources if
it could be observed face-on, unless its X-ray emission is highly collimated.
(Abridged)Comment: Astronomy Letters, in press; 16 pages, 8 figure
An upper limit on nickel overabundance in the supercritical accretion disk wind of SS 433 from X-ray spectroscopy
We take advantage of a long (with a total exposure time of 120 ks) X-ray
observation of the unique Galactic microquasar SS 433, carried out with the
XMM-Newton space observatory, to search for a fluorescent line of neutral (or
weakly ionized) nickel at the energy 7.5 keV. We consider two models of the
formation of fluorescent lines in the spectrum of SS 433: 1) due to reflection
of hard X-ray radiation from a putative central source on the optically thick
walls of the accretion disk "funnel"; and 2) due to scattering of the radiation
coming from the hottest parts of the jets in the optically thin wind of the
system. It is shown, that for these cases, the photon flux of Ni I K
fluorescent line is expected to be 0.45 of the flux of Fe I K
fluorescent line at 6.4 keV, for the relative nickel overabundance , as observed in the jets of SS 433. For the continuum model without the
absorption edge of neutral iron, we set a 90 per cent upper limit on the flux
of the narrow Ni I K line at the level of ph
s cm. For the continuum model with the absorption edge, the
corresponding upper limit is ph s cm. At the
same time, for the Fe I K line, we measure the flux of
ph s cm. Taken at the face
value, the results imply that the relative overabundance of nickel in the wind
of the accretion disc should be at least 1.5 times less than the corresponding
excess of nickel observed in the jets of SS 433.Comment: 17 pages, 12 figures, 4 tables, Astronomy Letters, in press, 2018,
Volume 44, Issue
Quantum interference in the classically forbidden region: a parametric oscillator
We study tunneling between period two states of a parametrically modulated
oscillator. The tunneling matrix element is shown to oscillate with the varying
frequency of the modulating field. The effect is due to spatial oscillations of
the wave function and the related interference in the classically forbidden
region. The oscillations emerge already in the ground state of the oscillator
Hamiltonian in the rotating frame, which is quartic in the momentum.Comment: Submitted to PR
Research of high-current pulsed electron beam energy distribution in depth of sheet of water
Distribution of the absorbed doze and energy of the high-current pulsed electron beam formed by accelerator TEU-500 (350...500 kV, 60 ns, current density 0,3...0,4 kA/sm2) in water sheet depth has been measured. The high-resolution measurement technique of doze and energy distribution with application of dosimetric film based on lavsan with phenazine covering was used. Spatial resolution at registration of the absorbed doze in the range of 5...100 kGr amounts to 20...30 mkm. It was shown that at absorption of electron beam with high current density (in conditions of track overlapping on surface of the absorbing layer) distribution of the absorbed doze in thedepth within the limits of ±10 % coincides with distribution obtained for low-current bea
Multiphoton antiresonance in large-spin systems
We study nonlinear response of a spin with easy-axis anisotropy. The
response displays sharp dips or peaks when the modulation frequency is
adiabatically swept through multiphoton resonance. The effect is a consequence
of a special symmetry of the spin dynamics in a magnetic field for the
anisotropy energy . The occurrence of the dips or peaks is
determined by the spin state. Their shape strongly depends on the modulation
amplitude. Higher-order anisotropy breaks the symmetry, leading to sharp steps
in the response as function of frequency. The results bear on the dynamics of
molecular magnets in a static magnetic field.Comment: Submitted to PR
Propagation and interaction of ultrashort electromagnetic pulses in nonlinear media with a quadratic-cubic nonlinearity
Propagation of extremely short unipolar pulses of electromagnetic field
("videopulses") is considered in the framework of a model in which the material
medium is represented by anharmonic oscillators (approximating bound electrons)
with quadratic and cubic nonlinearities. Two families of exact analytical
solutions (with positive or negative polarity) are found for the moving
solitary pulses. Direct simulations demonstrate that the pulses are very robust
against perturbations. Two unipolar pulses collide nearly elastically, while
collisions between pulses with opposite polarities and a small relative
velocity are inelastic, leading to emission of radiation and generation of a
small-amplitude additional pulse.Comment: 12 pages, 10 figure
Several New Active Galactic Nuclei Among X-ray Sources Detected by INTEGRAL and SWIFT Observatories
We present the results of the optical identifications of a set of X-ray
sources from the all-sky surveys of INTEGRAL and SWIFT observatories. Optical
data were obtained with Russian-Turkish 1.5-m Telescope (RTT150). Nine X-ray
sources were identified as active galactic nuclei (AGNs). Two of them are
hosted by nearby, nearly exactly edge-on, spiral galaxies MCG -01-05-047 and
NGC 973. One source, IGR J16562-3301, is most probably BL Lac object (blazar).
Other AGNs are observed as stellar-like nuclei of spiral galaxies, with broad
emission lines in their spectra.
For the majority of our hard X-ray selected AGNs, their hard X-ray
luminosities are well-correlated with the luminosities in [OIII],5007 optical
emission line. However, the luminosities of some AGNs deviate from this
correlation. The fraction of these objects can be as high as 20%. In
particular, the flux in [OIII] line turns to be lower in two nearby edge-on
spiral galaxies, which can be explained by the extinction in their galactic
disks.Comment: 9 pages, 3 figures, accepted for publication in Astronomy Letters,
the original text in Russian can be found at
http://hea.iki.rssi.ru/~rodion/poptid.pd
Gravitational orientation of the orbital complex, Salyut-6--Soyuz
A simple mathematical model is proposed for the Salyut-6-Soyuz orbital complex motion with respect to the center of mass under the one-axis gravity-gradient orientation regime. This model was used for processing the measurements of the orbital complex motion parameters when the above orientation region was implemented. Some actual satellite motions are simulated and the satellite's aerodynamic parameters are determined. Estimates are obtained for the accuracy of measurements as well as that of the mathematical model
Double-layered monopolar order in Tb2Ti2O7 spin liquid
Ho2Ti2O7 and Dy2Ti2O7 spin ices exhibit elementary excitations akin to
magnetic monopoles. Here we focus on Tb2Ti2O7 spin liquid, where correlated
magnetic moments keep fluctuating down to very low temperatures. Using a
monopole picture, we have re-analyzed the field-induced magnetic structure
previously determined by neutron diffraction in Tb2Ti2O7. We show that under a
high field applied along a [110] direction, Tb2Ti2O7 orders as a three
dimensional arrangement of monopole and antimonopole double layers. In
contrast, Ho2Ti2O7 spin ice in the same conditions behaves as a monopole-free
state. By symmetry analysis we derived the distortions compatible with the
observed magnetic structure of Tb2Ti2O7 which can be related to the appearance
of the double-layered monopolar order.Comment: 6 pages, 6 figures, submitted for publicatio
X-ray line formation in the spectrum of SS 433
The mechanisms for the formation of X-ray lines in the spectrum of SS 433 are
investigated by taking into account the radiative transfer inside the jets. The
results of Monte Carlo numerical simulations are presented. The effect of a
decrease in line intensity due to scattering inside the jet turns out to be
pronounced, but it does not exceed 60% in magnitude on the entire grid of
parameters. The line broadening due to scattering, nutational motion, and the
contribution of satellites can lead to overestimates of the jet opening angle
from the line widths in Chandra X-ray observations. The fine structure
of the lines turns out to be very sensitive to the scattering effects. This
makes its investigation by planned X-ray observatories equipped with
high-resolution spectrometers (primarily Astro-H) a powerful tool for
diagnosing the parameters of the jets in SS 433.Comment: 23 pages, 14 figures, to be published in Astronomy Letters, v. 38, n.
7, p. 443 (2012
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