3,605 research outputs found
A strong correlation in radio pulsars with implications for torque variations
We present an analysis of the spin-down parameters for 131 radio pulsars for
which has been well determined. These pulsars have characteristic
ages ranging from yr and spin periods in the range 0.4--30 s;
nearly equal numbers of pulsars have as . We find a
strong correlation of with , {\em independent of the sign
of} . We suggest that this trend can be accounted for by small,
stochastic deviations in the spin-down torque that are directly proportional
(in magnitude) to the spin-down torque.Comment: MNRAS, 4 pages, 2 figures. Minor editorial changes and typos
correcte
Timing Measurements of the Relativistic Binary Pulsar PSR B1913+16
We present results of more than three decades of timing measurements of the
first known binary pulsar, PSR B1913+16. Like most other pulsars, its
rotational behavior over such long time scales is significantly affected by
small-scale irregularities not explicitly accounted for in a deterministic
model. Nevertheless, the physically important astrometric, spin, and orbital
parameters are well determined and well decoupled from the timing noise. We
have determined a significant result for proper motion, , mas yr. The pulsar exhibited
a small timing glitch in May 2003, with , and a
smaller timing peculiarity in mid-1992. A relativistic solution for orbital
parameters yields improved mass estimates for the pulsar and its companion,
m_1=1.4398\pm0.0002 \ M_{\sun} and m_2=1.3886\pm0.0002 \ M_{\sun}. The
system's orbital period has been decreasing at a rate times
that predicted as a result of gravitational radiation damping in general
relativity. As we have shown before, this result provides conclusive evidence
for the existence of gravitational radiation as predicted by Einstein's theory.Comment: Published in APJ, 722, 1030 (2010
Arecibo HI Absorption Measurements of Pulsars and the Electron Density at Intermediate Longitudes in the First Galactic Quadrant
We have used the Arecibo telescope to measure the HI absorption spectra of
eight pulsars. We show how kinematic distance measurements depend upon the
values of the galactic constants R_o and Theta_o, and we select our preferred
current values from the literature. We then derive kinematic distances for the
low-latitude pulsars in our sample and electron densities along their lines of
sight. We combine these measurements with all others in the inner galactic
plane visible from Arecibo to study the electron density in this region. The
electron density in the interarm range 48 degrees < l < 70 degrees is [0.017
(-0.007,+0.012) (68% c.l.)] cm^(-3). This is 0.75 (-0.22,+0.49) (68% c.l.) of
the value calculated by the Cordes & Lazio (2002) galactic electron density
model. The model agrees more closely with electron density measurements toward
Arecibo pulsars lying closer to the galactic center, at 30 degrees<l<48
degrees. Our analysis leads to the best current estimate of the distance of the
relativistic binary pulsar B1913+16: d=(9.0 +/- 3) kpc.
We use the high-latitude pulsars to search for small-scale structure in the
interstellar hydrogen observed in absorption over multiple epochs. PSR B0301+19
exhibited significant changes in its absorption spectrum over 22 yr, indicating
HI structure on a ~500 AU scale.Comment: Accepted by Astrophysical Journal September 200
The 1973 solar occultation of the Crab Nebula pulsar
The mean electron density of the solar corona was determined by measuring the dispersion of radiofrequency pulses from pulsar NP 0532 during the June 1973 solar occultation. Trends continued which were noticed in 1971 as solar activity declined. Model fitting results suggest that the corona continued to become even more concentrated toward the equator in 1973 than in 1971. The number density of electrons in most regions decreased. The best model of the distribution of corona electrons is suggested to be one with zero density at the poles. K-corona isophotes and contours of equal path-integrated density are presented for several models. Electron density versus date and position in the corona are tabulated. It is seen that there is no simple relationship between the onset of major solar activity and density or scattering enhancements
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