953 research outputs found
Fraction of the radial velocity stable stars in the early observations of the Grid Giant Star Survey
The GGSS is a partially-filled, all-sky survey to identify K-giant stars with
low level of RV-variability. We study histograms of the radial velocity (RV)
variability obtained in the early phase of the Grid Giant Star Survey (GGSS,
Bizyaev et al., 2006). This part of the survey has been conducted with a very
limited nubmer of observations per star, and rough accuracy. We apply the
Monte-Carlo simulations to infer a fraction of the RV-stable stars in the
sample. Our optimistic estimate is that 20% of all considered K-giants have
RV-variability under 30 m s. Different assumptions of intrinsic
RV-variability for our stars give 12 -- 20 % of RV-stable K-giants in the
studied sample.Comment: 3 pages, 2 figures, to be published in PAS
Structural Parameters of Stellar Disks from 2MASS Images of Edge-on Galaxies
We present results of an analysis of the J, H, and K 2MASS images of 139
spiral edge-on galaxies selected from the Revised Flat Galaxies Catalog. The
basic structural parameters scalelength (h), scaleheight (z_0), and central
surface brightness of the stellar disks (mu_0) are determined for all selected
galaxies in the NIR bands. The mean relative ratios of the scaleheights of the
thin stellar disks in the J:H:K bands are 1.16:1.08:1.00, respectively.
Comparing the scaleheights obtained from the NIR bands for the same objects, we
estimate the scaleheights of the thin stellar disks corrected for the internal
extinction. We find that the extinction-corrected scaleheight is, on average,
11% smaller than that in the K-band. Using the extinction-corrected structural
parameters, we find that the dark-to-luminous mass ratio is, on average, 1.3
for the galaxies in our sample within the framework of a simplified galactic
model. The relative thicknesses of the stellar disks z_0/h correlates with
their face-on central surface brightnesses obtained from the 2MASS images. We
also find that the scaleheight of the stellar disks shows no systematic growth
with radius in most of our galaxies.Comment: To be published in Astrophysical Journa
On the Routh sphere problem
We discuss an embedding of a vector field for the nonholonomic Routh sphere
into a subgroup of commuting Hamiltonian vector fields on six dimensional phase
space. The corresponding Poisson brackets are reduced to the canonical Poisson
brackets on the Lie algebra e(3). It allows us to relate nonholonomic Routh
system with the Hamiltonian system on cotangent bundle to the sphere with
canonical Poisson structure.Comment: LaTeX with AMSFonts, 11 page
The Hess-Appelrot system and its nonholonomic analogs
This paper is concerned with the nonholonomic Suslov problem and its
generalization proposed by Chaplygin. The issue of the existence of an
invariant measure with singular density (having singularities at some points of
phase space) is discussed
Hamiltonization of Elementary Nonholonomic Systems
In this paper, we develop the Chaplygin reducing multiplier method; using
this method, we obtain a conformally Hamiltonian representation for three
nonholonomic systems, namely, for the nonholonomic oscillator, for the
Heisenberg system, and for the Chaplygin sleigh. Furthermore, in the case of an
oscillator and the nonholonomic Chaplygin sleigh, we show that the problem
reduces to the study of motion of a mass point (in a potential field) on a
plane and, in the case of the Heisenberg system, on the sphere. Moreover, we
consider an example of a nonholonomic system (suggested by Blackall) to which
one cannot apply the reducing multiplier method
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