10,804 research outputs found
Spectral observations of X Persei: Connection between H-alpha and X-ray emission
We present spectroscopic observations of the Be/X-ray binary X Per obtained
during the period 1999 - 2018. Using new and published data, we found that
during "disc-rise" the expansion velocity of the circumstellar disc is 0.4 -
0.7 km/s. Our results suggest that the disc radius in recent decades show
evidence of resonant truncation of the disc by resonances 10:1, 3:1, and 2:1,
while the maximum disc size is larger than the Roche lobe of the primary and
smaller than the closest approach of the neutron star. We find correlation
between equivalent width of H-alpha emission line () and the X-ray
flux, which is visible when . The
correlation is probably due to wind Roche lobe overflow.Comment: Accepted for publication in Astronomy & Astrophysic
Two atoms in an anisotropic harmonic trap
We consider the system of two interacting atoms confined in axially symmetric
harmonic trap. Within the pseudopotential approximation, we solve the
Schroedinger equation exactly, discussing the limits of quasi-one and
quasi-two-dimensional geometries. Finally, we discuss the application of an
energy-dependent pseudopotential, which allows to extend the validity of our
results to the case of tight traps and large scattering lengths.Comment: RevTeX 4 pages, 2 figure
Wind regime peculiarities in the lower thermosphere in the winter of 1983/84
Temporal variations of prevailing winds at 90 to 100 km obtained from measurements carried out in winter 1983 to 1984 at three sites in the USSR and two sites in East Germany are reported. These variations are compared with those of the thermal stratospheric regime. Measurements were carried out using the drifts D2 method (meteor wind radar) and the D1 method (ionospheric drifts). Temporal variations of zonal and meridional prevailing wind components for all the sites are given. Also presented are zonal wind data obtained using the partial reflection wind radar. Wind velocity values were obtained by averaging data recorded at between 105 and 91 km altitude. Wind velocity data averaged in such a way can be related to about the same height interval to which the data obtained by the meteor radar and ionospheric methods at other sites, i.e., the mean height of the meteor zone (about 95 km). The results presented show that there are significant fluctuations about the seasonal course of both zonal and meridional prevailing winds
Analytical solutions for the dynamics of two trapped interacting ultracold atoms
We discuss exact solutions of the Schroedinger equation for the system of two
ultracold atoms confined in an axially symmetric harmonic potential. We
investigate different geometries of the trapping potential, in particular we
study the properties of eigenenergies and eigenfunctions for quasi-one- and
quasi-two-dimensional traps. We show that the quasi-one- and the
quasi-two-dimensional regimes for two atoms can be already realized in the
traps with moderately large (or small) ratios of the trapping frequencies in
the axial and the transverse directions. Finally, we apply our theory to
Feshbach resonances for trapped atoms. Introducing in our description an
energy-dependent scattering length we calculate analytically the eigenenergies
for two trapped atoms in the presence of a Feshbach resonance.Comment: RevTeX, 15 pages, 15 figure
The Schwarzschild black hole as a point particle
The description of a point mass in general relativity (GR) is given in the
framework of the field formulation of GR where all the dynamical fields,
including the gravitational field, are considered in a fixed background
spacetime. With the use of stationary (not static) coordinates non-singular at
the horizon, the Schwarzschild solution is presented as a point-like field
configuration in a whole background Minkowski space. The requirement of a
stable -causality stated recently in [J.B.Pitts and W.C.Schieve, Found.
Phys., v. 34, 211 (2004)] is used essentially as a criterion for testing
configurations.Comment: LATEX, 8 pages, no figure
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