91 research outputs found
Millisecond and Binary Pulsars as Nature's Frequency Standards. II. Effects of Low-Frequency Timing Noise on Residuals and Measured Parameters
Pulsars are the most stable natural frequency standards. They can be applied
to a number of principal problems of modern astronomy and time-keeping
metrology. The full exploration of pulsar properties requires obtaining
unbiased estimates of the spin and orbital parameters. These estimates depend
essentially on the random noise component being revealed in the residuals of
time of arrivals (TOA). In the present paper, the influence of low-frequency
("red") timing noise with spectral indices from 1 to 6 on TOA residuals,
variances, and covariances of estimates of measured parameters of single and
binary pulsars are studied. In order to determine their functional dependence
on time, an analytic technique of processing of observational data in time
domain is developed which takes into account both stationary and non-stationary
components of noise. Our analysis includes a simplified timing model of a
binary pulsar in a circular orbit and procedure of estimation of pulsar
parameters and residuals under the influence of red noise. We reconfirm that
uncorrelated white noise of errors of measurements of TOA brings on gradually
decreasing residuals, variances and covariances of all parameters. On the other
hand, we show that any red noise causes the residuals, variances, and
covariances of certain parameters to increase with time. Hence, the low
frequency noise corrupts our observations and reduces experimental
possibilities for better tests of General Relativity Theory. We also treat in
detail the influence of a polynomial drift of noise on the residuals and
fitting parameters. Results of the analitic analysis are used for discussion of
a statistic describing stabilities of kinematic and dynamic pulsar time scales.Comment: 40 pages, 1 postscript figure, 1 picture, uses mn.sty, accepted to
Mon. Not. Roy. Astron. So
Testing Relativistic Effect of Propagation of Gravity by Very-Long Baseline Interferometry
It is shown that the finite speed of gravity affects very-long baseline
interferometric observations of quasars during the time of their line-of-sight
close angular encounter with Jupiter. The next such event will take place in
2002, September 8. The present Letter suggests a new experimental test of
general relativity in which the effect of propagation of gravity can be
directly measured by very-long baseline interferometry as an excess time delay
in addition to the logarithmic Shapiro time delay (Shapiro, I. I., 1964, Phys.
Rev. Lett., 13, 789).Comment: 11 pages, accepted to ApJ Letter
Beyond the Standard IAU Framework
We discuss three conceivable scenarios of extension and/or modification of
the IAU relativistic resolutions on time scales and spatial coordinates beyond
the Standard IAU Framework. These scenarios include: (1) the formalism of the
monopole and dipole moment transformations of the metric tensor replacing the
scale transformations of time and space coordinates; (2) implementing the
parameterized post-Newtonian formalism with two PPN parameters - beta and
gamma; (3) embedding the post-Newtonian barycentric reference system to the
Friedman-Robertson-Walker cosmological model.Comment: 9 pages, no figures, submitted to the proceedings of the IAU 261
Symposium "Relativity in Fundamental Astronomy: Dynamics, Reference Frames,
and Data Analysis"", Virginia Beach, USA; May 200
The Measurement of the Light Deflection from Jupiter: Theoretical Interpretation
Equations of light, propagating from quasar to observer on earth, are
integrated in the time-dependent gravitational field of the solar system by
making use of either retarded or advanced solutions of the Einstein field
equations. This technique allows to separate explicitly the effects associated
with the propagation of gravity from those associated with light in the
integral expression for the relativistic time delay of light. We prove that the
relativistic correction to the Shapiro time delay discovered by Kopeikin (ApJ,
556, L1, 2001) changes sign if one retains direction of the light propagation
but replaces retarded with advanced solution of the gravitational field
equations. Hence, this correction is due to the propagation of gravity and
allows to measure its speed. Relativistic VLBI experiment conducted by Fomalont
and Kopeikin in September 2002 proves that the propagation of gravitational
field is characterized by the retarded potentials.Comment: 14 pages, 1 figur
The Speed of Gravity in General Relativity and Theoretical Interpretation of the Jovian Deflection Experiment
Recent measurements of the propagation of the quasar's radio signal past
Jupiter are directly sensitive to the time-dependent effect from the geometric
sector of general relativity which is proportional to the speed of propagation
of gravity but not the speed of light. It provides a first confirmative
measurement of the fundamental speed of the Einstein general principle of
relativity for gravitational field.Comment: 45 pages, 6 figures, publishe
- …