938 research outputs found
Pulsar Timing Observations and Tests of General Relativity in Double-Neutron-Star Binaries
We describe the techniques used in pulsar timing observations, and show how
these observations may be applied to tests of strong-field general relativity
for double-neutron-star binary systems. We describe the tests of GR resulting
from the PSRs B1913+16 and B1534+12 systems. For the latter pulsar, 5
"Post-Keplerian" timing parameters are measurable, including the orbital period
derivative and the two Shapiro delay parameters.Comment: Talk at Marcel-Grossmann meeting IX, Rome, 2000, to be published by
World Scientific, 2 pages, no figure
The Formation of the Double Pulsar PSR J0737-3039A/B
Recent timing observations of the double pulsar J0737-3039A/B have shown that
its transverse velocity is extremely low, only 10 km/s, and nearly in the Plane
of the Galaxy. With this new information, we rigorously re-examine the history
and formation of this system, determining estimates of the pre-supernova
companion mass, supernova kick and misalignment angle between the pre- and
post-supernova orbital planes. We find that the progenitor to the recently
formed `B' pulsar was probably less than 2 MSun, lending credence to
suggestions that this object may not have formed in a normal supernova
involving the collapse of an iron core. At the same time, the supernova kick
was likely non-zero. A comparison to the history of the double-neutron-star
binary B1534+12 suggests a range of possible parameters for the progenitors of
these systems, which should be taken into account in future binary population
syntheses and in predictions of the rate and spatial distribution of short
gamma-ray burst events.Comment: To appear in MNRAS Letters. Title typo fix only; no change to pape
Pulsars: Gigantic Nuclei
What is the real nature of pulsars? This is essentially a question of the
fundamental strong interaction between quarks at low-energy scale and hence of
the non-perturbative quantum chromo-dynamics, the solution of which would
certainly be meaningful for us to understand one of the seven millennium prize
problems (i.e., "Yang-Mills Theory") named by the Clay Mathematical Institute.
After a historical note, it is argued here that a pulsar is very similar to an
extremely big nucleus, but is a little bit different from the {\em gigantic
nucleus} speculated 80 years ago by L. Landau. The paper demonstrates the
similarity between pulsars and gigantic nuclei from both points of view: the
different manifestations of compact stars and the general behavior of the
strong interaction.Comment: 8 pages, 1 figures; Comments welcome
PSR J1453+1902 and the radio luminosities of solitary versus binary millisecond pulsars
We present 3 yr of timing observations for PSR J1453+1902, a 5.79-ms pulsar
discovered during a 430-MHz drift-scan survey with the Arecibo telescope. Our
observations show that PSR J1453+1902 is solitary and has a proper motion of
8(2) mas/yr. At the nominal distance of 1.2 kpc estimated from the pulsar's
dispersion measure, this corresponds to a transverse speed of 46(11) km/s,
typical of the millisecond pulsar population. We analyse the current sample of
55 millisecond pulsars in the Galactic disk and revisit the question of whether
the luminosities of isolated millisecond pulsars are different from their
binary counterparts. We demonstrate that the apparent differences in the
luminosity distributions seen in samples selected from 430-MHz surveys can be
explained by small-number statistics and observational selection biases. An
examination of the sample from 1400-MHz surveys shows no differences in the
distributions. The simplest conclusion from the current data is that the spin,
kinematic, spatial and luminosity distributions of isolated and binary
millisecond pulsars are consistent with a single homogeneous population.Comment: 8 pages, 5 figures and 3 tables, accepted for publication by MNRA
Parametric derivation of the observable relativistic periastron advance for binary pulsars
We compute the dimensionless relativistic periastron advance parameter ,
which is measurable from the timing of relativistic binary pulsars. We employ
for the computation the recently derived Keplerian-type parametric solution to
the post-Newtonian (PN) accurate conservative dynamics of spinning compact
binaries moving in eccentric orbits. The parametric solution and hence the
parameter are applicable for the cases of \emph{simple precession}, namely,
case (i), the binary consists of equal mass compact objects, having two
arbitrary spins, and case (ii), the binary consists of compact objects of
arbitrary mass, where only one of them is spinning with an arbitrary spin. Our
expression, for the cases considered, is in agreement with a more general
formula for the 2PN accurate , relevant for the relativistic double pulsar
PSR J0737--3039, derived by Damour and Sch\"afer many years ago, using a
different procedure.Comment: 12 pages including 1 figure; submitted to PR
Model-Independent Comparisons of Pulsar Timings to Scalar-Tensor Gravity
Observations of pulsar timing provide strong constraints on scalar-tensor
theories of gravity, but these constraints are traditionally quoted as limits
on the microscopic parameters (like the Brans-Dicke coupling, for example) that
govern the strength of scalar-matter couplings at the particle level in
particular models. Here we present fits to timing data for several pulsars
directly in terms of the phenomenological couplings (masses, scalar charges,
moment of inertia sensitivities and so on) of the stars involved, rather than
to the more microscopic parameters of a specific model. For instance, for the
double pulsar PSR J0737-3039A/B we find at the 68% confidence level that the
masses are bounded by 1.28 < m_A/m_sun < 1.34 and 1.19 < m_B/m_sun < 1.25,
while the scalar-charge to mass ratios satisfy |a_A| < 0.21, |a_B| < 0.21 and
|a_B - a_A| < 0.002$. These constraints are independent of the details of the
scalar tensor model involved, and of assumptions about the stellar equations of
state. Our fits can be used to constrain a broad class of scalar tensor
theories by computing the fit quantities as functions of the microscopic
parameters in any particular model. For the Brans-Dicke and quasi-Brans-Dicke
models, the constraints obtained in this manner are consistent with those
quoted in the literature.Comment: 19 pages, 7 figure
Measurement of gravitational spin-orbit coupling in a binary pulsar system
In relativistic gravity, a spinning pulsar will precess as it orbits a
compact companion star. We have measured the effect of such precession on the
average shape and polarization of the radiation from PSR B1534+12. We have also
detected, with limited precision, special-relativistic aberration of the
revolving pulsar beam due to orbital motion. Our observations fix the system
geometry, including the misalignment between the spin and orbital angular
momenta, and yield a measurement of the precession timescale consistent with
the predictions of General Relativity.Comment: 4 pages, accepted to PRL. Version with high-resolution figure 2
available at http://www.astro.ubc.ca/people/stairs/papers/sta04b.ps.g
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