D. R. Lorimer

A double-pulsar system: A rare laboratory for relativistic gravity and plasma physics

The clocklike properties of pulsars moving in the gravitational fields of their unseen neutron-star companions have allowed unique tests of general relativity and provided evidence for gravitational radiation. We report here the detection of the 2.8-second pulsar J0737–3039B as the companion to the 23-millisecond pulsar J0737–3039A in a highly relativistic double neutron star system, allowing unprecedented tests of fundamental gravitational physics. We observed a short eclipse of J0737–3039A by J0737–3039B and orbital modulation of the flux density and the pulse shape of J0737–3039B, probably because of the influence of J0737–3039As energy flux on its magnetosphere. These effects will allow us to probe magneto-ionic properties of a pulsar magnetosphere.

An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system.

The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737–3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737–3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).

The Parkes Multibeam Pulsar Survey – III. Young pulsars and the discovery and timing of 200 pulsars

The Parkes Multibeam Pulsar Survey has unlocked vast areas of the Galactic plane, which were previously invisible to earlier low-frequency and less-sensitive surveys. The survey has discovered more than 600 new pulsars so far, including many that are young and exotic. In this paper we report the discovery of 200 pulsars for which we present positional and spin-down parameters, dispersion measures, flux densities and pulse profiles. A large number of these new pulsars are young and energetic, and we review possible associations of γ -ray sources with the sample of about 1300 pulsars for which timing solutions are known. Based on a statistical analysis, we estimate that about 19 ± 6 associations are genuine. The survey has also discovered 12 pulsars with spin properties similar to those of the Vela pulsar, nearly doubling the known population of such neutron stars. Studying the properties of all known ‘Vela-like’ pulsars, we find their radio luminosities to be similar to normal pulsars, implying that they are very inefficient radio sources. Finally, we review the use of the newly discovered pulsars as Galactic probes and discuss the implications of the new NE2001 Galactic electron density model for the determination of pulsar distances and luminosities.

THE PROBABILITY DISTRIBUTION OF BINARY PULSAR COALESCENCE RATES. I. DOUBLE NEUTRON STAR SYSTEMS IN THE GALACTIC FIELD

Estimates of the Galactic coalescence rate () of close binaries with two neutron stars (NS-NS) are known to be uncertain by large factors (about 2 orders of magnitude) mainly because of the small number of systems detected as binary radio pulsars. We present an analysis method that allows us to estimate the Galactic NS-NS coalescence rate using the current observed sample and, importantly, to assign a statistical significance to these estimates and calculate the allowed ranges of values at various confidence levels. The method involves the simulation of selection effects inherent in all relevant radio pulsar surveys and a Bayesian statistical analysis for the probability distribution of the rate. The most likely values for the total Galactic coalescence rate (peak) lie in the range 2-60 Myr-1 depending on different pulsar population models. For our reference model 1, in which the most likely estimates of pulsar population properties are adopted, we obtain tot = 8 Myr-1 at a 68% statistical confidence level. The corresponding ranges of expected detection rates of NS-NS inspiral are 3 × 10-3 yr-1 for the initial LIGO and 18 yr-1 for the advanced LIGO.

Pulsar Birthrates from the Parkes Multibeam Survey

We investigate the pulsar birthrate from a sample of 815 nonrecycled pulsars detected by the Parkes multibeam survey, accounting as accurately as possible for all known selection effects. We find that pulsars with magnetic fields greater than G account for more than half of the total birthrate in spite of comprising only 12 2.5 # 10 about 5%–10% of the total Galactic population. While we do not find evidence for a significant population of pulsars “injected” into the population with spin periods of ∼0.5 s, we do find that many, perhaps 40%, are born with periods in the range 0.1–0.5 s. The absolute number and birthrate of Galactic pulsars is strongly dependent on the assumed models for pulsar beaming and Galactic electron distribution. Adopting the most recent models, we find the total pulsar birthrate to be between 0.9 and 1.9 pulsars per century for 1400 MHz luminosities greater than 1 mJy kpc 2 , and the total Galactic population of active radio pulsars above this luminosity limit to be between 70,000 and 120,000. Subject headings: pulsars: general — stars: evolution

PSR J1829+2456: a relativistic binary pulsar

We report the discovery of a new binary pulsar, PSR J1829+2456, found during a midlatitude drift-scan survey with the Arecibo telescope. Our initial timing observations show the 41-ms pulsar to be in a 28-h, slightly eccentric, binary orbit. The advance of periastron ˙ ω = 0. ◦ 28 ± 0. ◦ 01 yr −1 is derived from our timing observations spanning 200 d. 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 and 1.38 M� , making it likely to be another neutron star. We also place a firm upper limit on the pulsar mass of 1.38 M� . 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.

Pulsar discovery by global volunteer computing

Einstein@Home, a distributed computing project, discovered a rare, isolated pulsar with a low magnetic field. Einstein@Home aggregates the computer power of hundreds of thousands of volunteers from 192 countries to mine large data sets. It has now found a 40.8-hertz isolated pulsar in radio survey data from the Arecibo Observatory taken in February 2007. Additional timing observations indicate that this pulsar is likely a disrupted recycled pulsar. PSR J2007+2722’s pulse profile is remarkably wide with emission over almost the entire spin period; the pulsar likely has closely aligned magnetic and spin axes. The massive computing power provided by volunteers should enable many more such discoveries.

Erratum: “The Cosmic Coalescence Rates for Double Neutron Star Binaries”(ApJ, 601, L179 [2004])

A radiation image sensing apparatus includes an image sensing, a circuit component, a supporting plate including first and second faces and configured to support the image sensing panel with the first face and support the circuit component with the second face, a connecting portion configured to connect the image sensing panel and the circuit component, and a housing configured to enclose the image sensing panel, the circuit component, the supporting plate and the connecting portion. An outer periphery of the supporting plate includes a concave portion and a projecting portion, and the connecting portion connects the image sensing panel and the circuit component through outside the concave portion. The outer edge of the concave portion is positioned inside an outer edge of the image sensing panel upon orthogonal projection onto the first face.This manuscript is an updated version of Kalogera et al. (2004) published in ApJ Letters to correct our calculation of the Galactic DNS in-spiral rate. The details of the original erratum submitted to ApJ Letters are given in page 6 of this manuscript. We report on the newly increased event rates due to the recent discovery of the highly relativistic binary pulsar J0737--3039 (Burgay et al. 2003). Using a rigorous statistical method, we present the calculations reported by Burgay et al., which produce a in-spiral rate for Galactic double neutron star (DNS) systems that is higher by a factor of 5-7 compared to estimates made prior to the new discovery. Our method takes into account known pulsar-survey selection effects and biases due to small-number statistics. This rate increase has dramatic implications for gravitational wave detectors. For the initial Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, the most probable detection rates for DNS in-spirals are one event per 10-630 yr; at 95% confidence, we obtain rates up to one per 3 yr. For the advanced LIGO detectors, the most probable rates are 10-500 events per year. These predictions, for the first time, bring the expectations for DNS detections by the initial LIGO detectors to the astrophysically relevant regime. We also use our models to predict that the large-scale Parkes Multibeam pulsar survey with acceleration searches could detect an average of four binary pulsars similar to those known at present.

The Double Pulsar System J0737‐3039A/B as Testbed for Relativistic Gravity

The double pulsar system J0737‐3039A/B is one of the most intriguing pulsar discoveries of the last decade. This binary system, with an orbital period of only 2.4‐hr, provides a truly unique laboratory for relativistic gravity. Its discovery enhances of about an order of magnitude the estimate of the merger rate of double neutron stars systems, opening new possibilities for the current generation of gravitational wave detectors. In this contribution we summarize the present results and look at the prospects of future observations.

Erratum: "The Cosmic Coalescence Rates for Double Neutron Star Binaries"([URL ADDRESS="/cgi-bin/resolve?2004ApJ...601L.179K" STATUS="OKAY"]ApJ, 601, L179 [2004][/URL])

A radiation image sensing apparatus includes an image sensing, a circuit component, a supporting plate including first and second faces and configured to support the image sensing panel with the first face and support the circuit component with the second face, a connecting portion configured to connect the image sensing panel and the circuit component, and a housing configured to enclose the image sensing panel, the circuit component, the supporting plate and the connecting portion. An outer periphery of the supporting plate includes a concave portion and a projecting portion, and the connecting portion connects the image sensing panel and the circuit component through outside the concave portion. The outer edge of the concave portion is positioned inside an outer edge of the image sensing panel upon orthogonal projection onto the first face.This manuscript is an updated version of Kalogera et al. (2004) published in ApJ Letters to correct our calculation of the Galactic DNS in-spiral rate. The details of the original erratum submitted to ApJ Letters are given in page 6 of this manuscript. We report on the newly increased event rates due to the recent discovery of the highly relativistic binary pulsar J0737--3039 (Burgay et al. 2003). Using a rigorous statistical method, we present the calculations reported by Burgay et al., which produce a in-spiral rate for Galactic double neutron star (DNS) systems that is higher by a factor of 5-7 compared to estimates made prior to the new discovery. Our method takes into account known pulsar-survey selection effects and biases due to small-number statistics. This rate increase has dramatic implications for gravitational wave detectors. For the initial Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, the most probable detection rates for DNS in-spirals are one event per 10-630 yr; at 95% confidence, we obtain rates up to one per 3 yr. For the advanced LIGO detectors, the most probable rates are 10-500 events per year. These predictions, for the first time, bring the expectations for DNS detections by the initial LIGO detectors to the astrophysically relevant regime. We also use our models to predict that the large-scale Parkes Multibeam pulsar survey with acceleration searches could detect an average of four binary pulsars similar to those known at present.