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Register a new userTiming Measurements of the Relativistic Binary Pulsar PSR B1913+16
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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, $mu_{alpha} = -1.43pm0.13$, $mu_{delta}=-0.70pm0.13$ mas yr$^{-1}$. The pulsar exhibited a small timing glitch in May 2003, with ${Delta f}/f=3.7times10^{-11}$, and a smaller timing peculiarity in mid-1992. A relativistic solution for orbital parameters yields improved mass estimates for the pulsar and its companion, $m_1=1.4398pm0.0002 M_{sun}$ and $m_2=1.3886pm0.0002 M_{sun}$. The systems orbital period has been decreasing at a rate $0.997pm0.002$ 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 Einsteins theory.
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We present relativistic analyses of 9257 measurements of times-of-arrival from the first binary pulsar, PSR B1913+16, acquired over the last thirty-five years. The determination of the Keplerian orbital elements plus two relativistic terms completely characterizes the binary system, aside from an unknown rotation about the line of sight; leading to a determination of the masses of the pulsar and its companion: 1.438 $pm$ 0.001 solar masses and 1.390 $pm$ 0.001 solar masses, respectively. In addition, the complete system characterization allows the creation of tests of relativistic gravitation by comparing measured and predicted sizes of various relativistic phenomena. We find that the ratio of observed orbital period decrease due to gravitational wave damping (corrected by a kinematic term) to the general relativistic prediction, is 0.9983 pm 0.0016; thereby confirming the existence and strength of gravitational radiation as predicted by general relativity. For the first time in this system, we have also successfully measured the two parameters characterizing the Shapiro gravitational propagation delay, and find that their values are consistent with general relativistic predictions. We have also measured for the first time in any system the relativistic shape correction to the elliptical orbit, $delta_{theta}$,although its intrinsic value is obscured by currently unquantified pulsar emission beam aberration. We have also marginally measured the time derivative of the projected semimajor axis, which, when improved in combination with beam aberration modelling from geodetic precession observations, should ultimately constrain the pulsars moment of inertia.
We describe results derived from thirty years of observations of PSR B1913+16. Together with the Keplerian orbital parameters, measurements of the relativistic periastron advance and a combination of gravitational redshift and time dilation yield the stellar masses with high accuracy. The measured rate of change of orbital period agrees with that expected from the emission of gravitational radiation, according to general relativity, to within about 0.2 percent. Systematic effects depending on the pulsar distance and on poorly known galactic constants now dominate the error budget, so tighter bounds will be difficult to obtain. Geodetic precession of the pulsar spin axis leads to secular changes in pulse shape as the pulsar-observer geometry changes. This effect makes it possible to model the two-dimensional structure of the beam. We find that the beam is elongated in the latitude direction and appears to be pinched in longitude near its center.
We report the discovery of a new binary pulsar, PSR J1829+2456, found during a mid-latitude drift-scan survey with the Arecibo telescope. Our initial timing observations show the 41-ms pulsar to be in a 28-hr, slightly eccentric, binary orbit. The advance of periastron, omegadot = 0.28 +/- 0.01 deg/yr is derived from our timing observations spanning 200 days. Assuming that the advance of periastron is purely relativistic and a reasonable range of neutron star masses for PSR J1829+2456 we constrain the companion mass to be between 1.22 Msun and 1.38 Msun, making it likely to be another neutron star. We also place a firm upper limit on the pulsar mass of 1.38 Msun. The expected coalescence time due to gravitational-wave emission is long (~60 Gyr) and this system will not significantly impact upon calculations of merger rates that are relevant to upcoming instruments such as LIGO.
We report on the high precision timing analysis of the pulsar-white dwarf binary PSR J1012+5307. Using 15 years of multi-telescope data from the European Pulsar Timing Array (EPTA) network, a significant measurement of the variation of the orbital period is obtained. Using this ideal strong-field gravity laboratory we derive theory independent limits for both the dipole radiation and the variation of the gravitational constant.
We report a dramatic orbital modulation in the scintillation timescale of the relativistic binary pulsar J1141--6545 that both confirms the validity of the scintillation speed methodology and enables us to derive important physical parameters. We have determined the space velocity, the orbital inclination and even the longitude of periastron of the binary system, which we find to be in good agreement with that obtained from pulse timing measurements. Our data permit two equally-significant physical interpretations of the system. The system is either an edge-on binary with a high space velocity ($sim 115$ km s$^{-1}$) or is more face-on with a much slower velocity ($sim 45$ km s$^{-1}$). We favor the former, as it is more consistent with pulse timing and the distribution of known neutron star masses. Under this assumption, the runaway velocity of 115 km s$^{-1}$ is much greater than is expected if pulsars do not receive a natal kick at birth. The derived inclination of the binary system is (76pm 2.5^{circ}) degrees, implying a companion mass of 1.01 (pm )~0.02 M(_{odot}) and a pulsar mass of 1.29 (pm)~0.02 M(_{odot}). Our derived physical parameters indicate that this pulsar should prove to be an excellent laboratory for tests of gravitational wave emission.
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