855 research outputs found
A post-Newtonian diagnosis of quasiequilibrium configurations of neutron star-neutron star and neutron star-black hole binaries
We use a post-Newtonian diagnostic tool to examine numerically generated
quasiequilibrium initial data sets for non-spinning double neutron star and
neutron star-black hole binary systems. The PN equations include the effects of
tidal interactions, parametrized by the compactness of the neutron stars and by
suitable values of ``apsidal'' constants, which measure the degree of
distortion of stars subjected to tidal forces. We find that the post-Newtonian
diagnostic agrees well with the double neutron star initial data, typically to
better than half a percent except where tidal distortions are becoming extreme.
We show that the differences could be interpreted as representing small
residual eccentricity in the initial orbits. In comparing the diagnostic with
preliminary numerical data on neutron star-black hole binaries, we find less
agreement.Comment: 17 pages, 6 tables, 8 figure
Physical libration of a deformable moon theory I Semiannual progress report, Aug. 29, 1966 - Feb. 28, 1967
Lunar gravity field and physical librations of moo
`Similar' coordinate systems and the Roche geometry. Application
A new equivalence relation, named relation of 'similarity' is defined and
applied in the restricted three-body problem. Using this relation, a new class
of trajectories (named 'similar' trajectories) are obtained; they have the
theoretical role to give us new details in the restricted three-body problem.
The 'similar' coordinate systems allow us in addition to obtain a unitary and
an elegant demonstration of some analytical relations in the Roche geometry. As
an example, some analytical relations published in Astrophysical Journal by
Seidov in 2004 are demonstrated.Comment: 9 pages (preprint format), 9 figures, published in Astrophysics and
Space Scienc
The precession and nutation of deformable bodies IV - Deformation of self-gravitating elastic solids
Equivalent equations which govern deformations of self-gravitating elastic bodies of nonuniform internal temperatur
The Rossiter-McLaughlin effect and analytic radial velocity curves for transiting extrasolar planetary systems
A transiting extrasolar planet sequentially blocks off the light coming from
the different parts of the disk of the host star in a time dependent manner.
Due to the spin of the star, this produces an asymmetric distortion in the line
profiles of the stellar spectrum, leading to an apparent anomaly of the radial
velocity curves, known as the Rossiter - McLaughlin effect. Here, we derive
approximate but accurate analytic formulae for the anomaly of radial velocity
curves taking account of the stellar limb darkening. The formulae are
particularly useful in extracting information of the projected angle between
the planetary orbit axis and the stellar spin axis, \lambda, and the projected
stellar spin velocity, V sin I_s. We create mock samples for the radial curves
for the transiting extrasolar system HD209458, and demonstrate that constraints
on the spin parameters (V sin I_s, \lambda) may be significantly improved by
combining our analytic template formulae and the precision velocity curves from
high-resolution spectroscopic observations with 8-10 m class telescopes. Thus
future observational exploration of transiting systems using the Rossiter -
McLaughlin effect is one of the most important probes to better understanding
of the origin of extrasolar planetary systems, especially the origin of their
angular momentum.Comment: 39 pages, 16 figures, Accepted to ApJ. To match the published version
(ApJ 623, April 10 issue
Structure and evolution of rotationally and tidally distorted stars
This paper aims to study the configuration of two components caused by
rotational and tidal distortions in the model of a binary system. The
potentials of the two distorted components can be approximated to 2nd-degree
harmonics. Furthermore, both the accretion luminosity () and the
irradiative luminosity are included in stellar structure equations. The
equilibrium structure of rotationally and tidally distorted star is exactly a
triaxial ellipsoids. A formula describing the isobars is presented, and the
rotational velocity and the gravitational acceleration at the primary surface
simulated. The results show the distortion at the outer layers of the primary
increases with temporal variation and system evolution. Besides, it was
observed that the luminosity accretion is unstable, and the curve of the
energy-generation rate fluctuates after the main sequence in rotation
sequences. The luminosity in rotation sequences is slightly weaker than that in
non-rotation sequences. As a result, the volume expands slowly. Polar ejection
is intensified by the tidal effect. The ejection of an equatorial ring may be
favoured by both the opacity effect and the -effect in
the binary system.Comment: 10 pages, 17 figures,Accepted by Astronomy and Astrophysic
Relativistic tidal properties of neutron stars
We study the various linear responses of neutron stars to external
relativistic tidal fields. We focus on three different tidal responses,
associated to three different tidal coefficients: (i) a gravito-electric-type
coefficient G\mu_\ell=[length]^{2\ell+1} measuring the \ell^{th}-order mass
multipolar moment GM_{a_1... a_\ell} induced in a star by an external
\ell^{th}-order gravito-electric tidal field G_{a_1... a_\ell}; (ii) a
gravito-magnetic-type coefficient G\sigma_\ell=[length]^{2\ell+1} measuring the
\ell^{th} spin multipole moment G S_{a_1... a_\ell} induced in a star by an
external \ell^{th}-order gravito-magnetic tidal field H_{a_1... a_\ell}; and
(iii) a dimensionless ``shape'' Love number h_\ell measuring the distortion of
the shape of the surface of a star by an external \ell^{th}-order
gravito-electric tidal field. All the dimensionless tidal coefficients
G\mu_\ell/R^{2\ell+1}, G\sigma_\l/R^{2\ell+1} and h_\ell (where R is the radius
of the star) are found to have a strong sensitivity to the value of the star's
``compactness'' c\equiv GM/(c_0^2 R) (where we indicate by c_0 the speed of
light). In particular, G\mu_\l/R^{2\l+1}\sim k_\ell is found to strongly
decrease, as c increases, down to a zero value as c is formally extended to the
``black-hole (BH) limit'' c^{BH}=1/2. The shape Love number h_\ell is also
found to significantly decrease as c increases, though it does not vanish in
the formal limit c\to c^{BH}. The formal vanishing of \mu_\ell and \sigma_\ell
as c\to c^{BH} is a consequence of the no-hair properties of black holes; this
suggests, but in no way proves, that the effective action describing the
gravitational interactions of black holes may not need to be augmented by
nonminimal worldline couplings.Comment: 21 pages, 10 figures. Matches the published versio
Optical Observations of GRO J1655-40 in Quiescence I: A Precise Mass for the Black Hole Primary
We report photometric and spectroscopic observations of the black hole binary
GRO J1655-40 in complete quiescence. In contrast to the 1995 photometry, the
light curves from 1996 are almost completely dominated by ellipsoidal
modulations from the secondary star. Model fits to the light curves, which take
into account the temperature profile of the accretion disk and eclipse effects,
yield an inclination of i=69.50 +/- 0.08 degrees and a mass ratio of Q=2.99 +/-
0.08. The precision of our determinations of i and Q allow us to determine the
black hole mass to an accuracy of approximately 4% (7.02 +/- 0.22 solar
masses). The secondary star's mass is 2.34 +/- 0.12 solar masses. The position
of the secondary on the Hertzsprung-Russell diagram is consistent with that of
a 2.3 solar mass star which has evolved off the main sequence and is halfway to
the start of the giant branch. Using the new spectra we present an improved
value of the spectroscopic period (2.62157 +/- 0.00015 days), radial velocity
semiamplitude (228.2 +/- 2.2 km/sec), and mass function (3.24 +/- 0.09 solar
masses). Evolutionary models suggest an average mass transfer rate for such a
system of 3.4E-9 solar masses per year (2.16E+17 grams per second), which is
much larger than the average mass transfer rates implied in the other six
transient black hole systems, but still barely below the critical mass transfer
rate required for stability.Comment: 30 pages, 12 figures, LaTeX (uses orosztwo.sty), to appear in ApJ,
vol. 474 (March 10, 1997
Regularization of the circular restricted three-body problem using 'similar' coordinate systems
The regularization of a new problem, namely the three-body problem, using
'similar' coordinate system is proposed. For this purpose we use the relation
of 'similarity', which has been introduced as an equivalence relation in a
previous paper (see \cite{rom11}). First we write the Hamiltonian function, the
equations of motion in canonical form, and then using a generating function, we
obtain the transformed equations of motion. After the coordinates
transformations, we introduce the fictitious time, to regularize the equations
of motion. Explicit formulas are given for the regularization in the coordinate
systems centered in the more massive and the less massive star of the binary
system. The 'similar' polar angle's definition is introduced, in order to
analyze the regularization's geometrical transformation. The effect of
Levi-Civita's transformation is described in a geometrical manner. Using the
resulted regularized equations, we analyze and compare these canonical
equations numerically, for the Earth-Moon binary system.Comment: 24 pages, 7 figures; Accepted for publication in Astrophysics and
Space Scienc
- …