522 research outputs found
Details of the spatial structure and kinematics of the Castor and Ursa Major streams
A list of the Castor stream members is compiled based on the data from
various authors. The membership probabilities for some stars are revised based
on the individual apex, multiplicity, observational errors, and peculiarity.
The apex of the Castor moving group is determined using the apex diagram
method. The parameters of the Castor and Ursa Major streams are compared and
the positions of the two streams on the apex diagram are found to differ by
225deg, implying that the two groups move in almost opposite directions. Stars
of both moving groups are intermixed in space, the Castor stream occupies a
smaller volume than the UMa stream and is located inside it. Our results can be
useful for understanding the morphology of the Galactic disk in the Sun's
vicinity
Radial velocity dispersions of star groups in M 67
High-precision measurements of radial velocities of the M 67 cluster members
are used to calculate the radial-velocity dispersions in the stellar groups
found earlier in the cluster's corona. The previously detected feature in one
of the groups (Group 60) consisting of stars with almost identical space
velocities was confirmed. The possibility of more accurate future studies of
the parameters of star groups using the Gaia catalogues is discussed.Comment: 7 pages, 2 figure
Qualitative Approach to Semi-Classical Loop Quantum Cosmology
Recently the mechanism was found which allows avoidance of the cosmological
singularity within the semi-classical formulation of Loop Quantum Gravity.
Numerical studies show that the presence of self-interaction potential of the
scalar field allows generation of initial conditions for successful slow-roll
inflation. In this paper qualitative analysis of dynamical system,
corresponding to cosmological equations of Loop Quantum Gravity is performed.
The conclusion on singularity avoidance in positively curved cosmological
models is confirmed. Two cases are considered, the massless (with flat
potential) and massive scalar field. Explanation of initial conditions
generation for inflation in models with massive scalar field is given. The
bounce is discussed in models with zero spatial curvature and negative
potentials.Comment: Online at http://www.iop.org/EJ/abstract/1475-7516/2004/07/01
Graphoanalytical method for determining the indicators of thermal-oxidative stability of lubricating oils
Approach of the NGC 1977 star cluster to the TOI-2796 host star
We study of possible encounters in past epochs of the open star cluster NGC
1977 with host stars. For this purpose, the age of the cluster was determined
based on our catalog data. Stars with planetary systems were selected from the
NASA Archive. The age of the cluster was determined using the color - absolute
magnitude diagram and the isochron system. By extending the track of the
movement of the cluster and stars in past epochs, 10 Myr. The time of the
maximum approach 32 pc of the host star with planetary system TOI-2796 with the
NGC 1977 are found. The place of approach in the sky is shown, this point can
be considered as the place of appearance of interstellar comets. Thus, the
result of our work is that the we found approach of the host star to the
cluster entailed effects associated with the gravitational influence of the
cluster on the nuclei of comets located in the outer parts of the Oort cloud of
the planetary system. The effect of approach on comets is estimated
Effect of pressure on the Raman modes of antimony
The effect of pressure on the zone-center optical phonon modes of antimony in
the A7 structure has been investigated by Raman spectroscopy. The A_g and E_g
frequencies exhibit a pronounced softening with increasing pressure, the effect
being related to a gradual suppression of the Peierls-like distortion of the A7
phase relative to a cubic primitive lattice. Also, both Raman modes broaden
significantly under pressure. Spectra taken at low temperature indicate that
the broadening is at least partly caused by phonon-phonon interactions. We also
report results of ab initio frozen-phonon calculations of the A_g and E_g mode
frequencies. Presence of strong anharmonicity is clearly apparent in calculated
total energy versus atom displacement relations. Pronounced nonlinearities in
the force versus displacement relations are observed. Structural instabilities
of the Sb-A7 phase are briefly addressed in the Appendix.Comment: 10 pages, 8 figure
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