1. Implications of a VLBI distance to the double pulsar J0737-3039A/B - Deller, A. T.; Bailes, M.; Tingay, Steven J.
The double pulsar J0737-3039A/B is a unique system with which to test gravitational theories in the strong-field regime. However, the accuracy of such tests will be limited by knowledge of the distance and relative motion of the system. Here, we present very long baseline interferometry observations which reveal that the distance to PSR J0737-3039A/B is 1150 (+220/-160) pc, more than double previous estimates, and confirm its low transverse velocity (∼9 km s–1). Combined with a decade of pulsar timing, these results will allow tests of gravitational radiation emission theories at the 0.01% level, putting stringent constraints on theories which predict...

2. Implications of a VLBI distance to the double pulsar J0737-3039A/B - Deller, A. T.; Bailes, M.; Tingay, Steven J.
The double pulsar J0737-3039A/B is a unique system with which to test gravitational theories in the strong-field regime. However, the accuracy of such tests will be limited by knowledge of the distance and relative motion of the system. Here, we present very long baseline interferometry observations which reveal that the distance to PSR J0737-3039A/B is 1150 (+220/-160) pc, more than double previous estimates, and confirm its low transverse velocity (∼9 km s–1). Combined with a decade of pulsar timing, these results will allow tests of gravitational radiation emission theories at the 0.01% level, putting stringent constraints on theories which predict...

3. Pulsar/Supernova Remnant Associations - Victoria M. Kaspi
. We review proposed pulsar/supernova remnant associations, summarize recent highlights, including searches for young pulsars, searches for remnants, studies of previously proposed associations, and attempts at pulsar/remnant association syntheses. We argue that most proposed pulsar/supernova remnant associations require additional investigation before they can be considered secure. Existing evidence from secure associations implies pulsars are born with large magnetic fields, but do not necessarily have particularly large radio luminosities. We argue that the evidence for large space velocities from associations is ambiguous. 1. Introduction No review of pulsar/supernova remnant (PSR/SNR) associations should begin without praising Baade & Zwicky (1934), who, long before neutron stars were discovered, hypothesized they are born in supernova explosions...

4. Pulsar Searches At Arecibo - David J. Nice
The large collecting area of the Arecibo Observatory has made it a particularly powerful instrument for pulsar searches. We describe some important characteristics of the Arecibo telescope, and we give detailed summaries of two millisecond pulsar search projects. THE ARECIBO OBSERVATORY Pulsar searches have been undertaken at numerous radio observatories throughout the world. The sensitivities of these searches are directly proportional to the collecting areas of the telescopes used. It comes as no surprise, then, that the largest radio telescope, the 305 m instrument of the Arecibo Observatory (see figure I), has been especially productive for such observations. The primary reflector of the Arecibo telescope is spherical in shape and...

5. Effelsberg Multifrequency Pulsar Polarimetry - A. Von Hoensbroech,K. M. Xilouris
. The polarization characteristics of pulsar emission have recently proved to be a useful tool in locating the altitude of radio-emitting regions in pulsar magnetospheres. We have used both adding and multiplying polarimeters to perform wide-bandwidth pulsar polarimetry at cm-wavelengths with the Effelsberg radio telescope and processed these measurements to derive emission altitudes from regions closer to the stellar surface than ever before. A gain analysis of these devices is presented, together with the dynamic calibration procedure we used to eliminate instrumental errors. A sample of 62 calibrated profiles is presented here, while the dependency of emission altitude with frequency is considered in an accompanying paper. The data presented here comprise a reliable high...

6. Plasma Processes in Pulsar Magnetospheres and Eclipsing Binary Pulsar Systems - Qinghuan Luo
Plasma processes that may be responsible for pulsar radio emission and for eclipses observed for binary pulsars are discussed. High brightness temperature of pulsar radio emission implies that the radiation mechanism must be coherent. Several emission mechanisms are discussed. The high brightness temperature of radio emission also implies that nonlinear effect on wave propagation through pulsar magnetospheric plasmas is important and may result in radio pulse microstructure or cause fluctuation in dispersion measure. The discovery of eclipsing binary pulsars provides us with an opportunity to study nonlinear wave-wave interactions in electron-ion plasmas in the winds (or magnetospheres) of companion stars. 1 Introduction Pulsars are thought to be rotating, strongly magnetized neutron...

7. Tensor--Scalar Gravity and Binary-Pulsar Experiments - Thibault Damour
Some recently discovered nonperturbative strong-field effects in tensor--scalar theories of gravitation are interpreted as a scalar analog of ferromagnetism: "spontaneous scalarization". This phenomenon leads to very significant deviations from general relativity in conditions involving strong gravitational fields, notably binary-pulsar experiments. Contrary to solar-system experiments, these deviations do not necessarily vanish when the weak-field scalar coupling tends to zero. We compute the scalar "form factors" measuring these deviations, and notably a parameter entering the pulsar timing observable fl through scalar-field-induced variations of the inertia moment of the pulsar. An exploratory investigation of the confrontation between tensor--scalar theories and binary-pulsar experiments shows that nonperturbative scalar field effects are already very tightly constrained by...

8. High-Precision Metrology From Pulsar - R. S. Foster,F. Camilo,A. Wolszczan
The binary millisecond pulsar J1713+0747 after 22 months of timing appears to be the most stable millisecond pulsar yet observed. Current timing precision now rivals the best results obtained from pulsars B1937+21 and B1855+09. We summarize recent results from timing which include measurement of the pulsar's annual parallax, proper motion, and the relativistic "Shapiro delay." We use these observations to place limits on the mass of the neutron star and its companion. With a post-fit weighted root-mean-square timing residual of approximately 0:4 ¯s, and a characteristic age of roughly 9 Theta 10 9 yr, this pulsar may prove to be an important celestial clock in the construction of a pulsar...

9. On the Evolution of Pulsar Beams - T. M. Tauris
We have analyzed polarization data for a large number of isolated pulsars to investigate the evolution of pulsar radio beams. Assuming that a circular beam is directed along the axis of a dipolar magnetic field, we demonstrate that the distribution of magnetic inclination angles for the parent population of all pulsars is not flat but highly concentrated towards small inclination angles and that, consequently, the average beaming fraction is only ¸ 10 per cent. Furthermore, we find that there is a tendency for the beam axis to align with the rotational axis on a time-scale of ¸ 10 7 yr. This has interesting consequences for statistical studies of the...

10. Electron Energy Losses Near Pulsar Polar Caps - Steven J. Sturner
We present results of a model for the energetics of electrons accelerated by the large electric fields generated by a rotating highly magnetized neutron star. The energy loss mechanisms we consider in our calculations include magnetic Compton scattering of thermal x-ray photons, triplet pair production, and curvature radiation emission. The electron acceleration mechanism is assumed to operate only to a height above the polar cap approximately equal to the polar cap radius. We find several interesting results. First, magnetic Compton scattering is the dominant energy loss process when the electron Lorentz factors are ! fewTheta10 6 for typical gamma-ray pulsar magnetic fields and surface temperatures measured by ROSAT. The amount...

11. Radio Emission Altitude in Pulsar Magnetospheres - J. Kijak
A geometrical analysis of the pulse-profile widths at 0.43 and 1.42 GHz (Arecibo) as well as at 1.41 GHz (Effelsberg) is presented. We have measured the profile pulsewidths at the lowest possible intensity level. An empirical relationship for the pulsar radio emission altitudes is proposed. We argue that for the millisecond pulsars the emission region lies close to the polar cap, as opposed to the long period pulsars where the radiation originates few hundreds km away from the surface of the neutron star. Key words: radio pulsars: general, emission altitudes 1 INTRODUCTION The hypothesis known as "radius-to-frequency" mapping (RFM) explains the systematic increase of component separation and profile widths with...

12. Predictions of Glitch Behavior from Pulsar Models - Fronefield Crawford Iii
Current neutron star theories use a two-component model of the star interior, which is believed to consist of a degenerate neutron superfluid core surrounded by a rigid crust of iron nuclei in a sea of free electrons. At the extremely high densities near the center of the star (10 11 to 10 15 g/cm 3 ), the characteristics of the matter are largely unknown. We have created several models of the neutron star interior employing different equations of state in order to place restrictions on the possible equations of state of the matter. We have been able to set limits on the mass, radius, and central density from these models. We have also...

13. Psr J0045--7319: A Dual-Line Binary Radio Pulsar - J. F. Bell; Bell Bessell; M. Bailes; V. M. Kaspi
Binary radio pulsars are superb tools for mapping binary orbits, because of the precision of the pulse timing method (e.g Taylor & Weisberg 1989). To date, all orbital parameters for binary pulsars have been derived from observations of the pulsar alone. We present the first observations of the radial velocity variations due to the binary motion of a companion to a radio pulsar. Our results demonstrate that the companion to the Small Magellanic Cloud pulsar PSR J0045--7319 is the B1V star identified by Kaspi et al. (1994). The mass ratio of the system is 6:3 \Sigma 1:2, which, for a...

14. Giant Radio Pulses from a Millisecond Pulsar - I. Cognard,J. A. Shrauner,J. H. Taylor,S. E. Thorsett
We have observed 1.7 million individual pulses from the millisecond pulsar PSR B1937+21. About one pulse in ten thousand has more than 20 times the mean "pulse on" flux density, and individual pulses as large as 300 times the average were observed. Comparable behavior has previously been observed only for the Crab pulsar. Giant pulses from PSR B1937+21 are seen in both the main pulse and interpulse components, and their amplitude distribution has roughly a power law shape. Strong pulses differ greatly from the average emission: they are narrower, systematically delayed by some 40--50 ¯s, and many are nearly 100% circularly polarized. In addition to their potential importance...

15. Pulsar Bound on the Photon Electric Charge Reexamined - Georg Raffelt
If photons had a small electric charge Q fl their path in the galactic magnetic field would be curved, leading to a time delay between photons of different frequency from a distant source. Cocconi's previous application of this argument led to a limit which is too restrictive by a factor of about 200; the corrected bound is Q fl =e ¸ ! 10 Gamma29 . Astronomical time-of-flight methods allow one to set powerful limits on hypothetical electric charges of neutrinos and photons. Their path in the galactic magnetic field would be curved, leading to an energy-dependent time delay. The absence of an anomalous spread of the neutrino arrival times from SN 1987A allowed...

16. TeV gamma-rays from Galactic objects: pulsars, pulsar - T. Kifune
Pulsar nebula, supernova remnant and nucleus of active galaxy are found as TeV gamma ray emitter, and the number of such sources is now approaching 10. All of them so far evidenced are explained by electron progenitor. The emission process in the TeV energy region is characterized and controlled by the particle interaction of high energy photons and electrons. The radiation by electrons implies a tight link of emission in the TeV region to the other bands, raising importance of the `multiwavelengths analysis' in order to investigate production, acceleration and interaction of energetic particles. The absoption of TeV gamma rays due to pair creation of electron and positron becomes more serious for...

17. Spark Model for Pulsar Radiation Modulation Patterns - J. A. Gil,M. Sendyk
A non-stationary polar gap model rst proposed by Ruderman & Sutherland (1975) is modied and applied to spark{associated pulsar emission at radio wavelengths. It is argued that under physical and geometrical conditions prevailing above pulsar polar cap, highly non-stationary spark discharges do not occur at random positions. Instead, sparks should tend to operate in well determined preferred regions. At any instant the polar cap is populated as densely as possible with a number of two-dimensional sparks with a characteristic dimension as well as a typical distance between adjacent sparks being about the polar gap height. Our model diers, however, markedly from its original hollow cone" version. The key...

18. Osse Observations Of The Vela Pulsar - J. D. Kurfess,D. A. Grabelsky
The OSSE detector on board the Compton Gamma Ray Observatory observed the Vela Pulsar (PSR 0833-45) during August-September 1991 and April-May 1992. Pulsed emission was detected at the 4-5oe level in the 0.06-0.57 MeV band in the sum of the two observing periods, as well as in each individual observation at lower significance. There is no significant variability observed. Light curves have a peak structure similar to that observed at higher energies. The spectrum is hard at lower energies and appears to require a break in the 0.5-2 MeV region. OBSERVATIONS The OSSE detectors on board the Compton Gamma Ray Observatory (CGRO) were used to observe the Vela Pulsar...

19. Osse Limits On Pulsar Gamma-Ray Emission - M. P. Ulmer,P. C. Schroeder
. This paper reports a summary of the GRO/OSSE pulsar survey and presents new upper limits to low-energy gamma ray emission for fifteen pulsars. These limits are used to reject simple correlations between the gamma-ray luminosity and other measured properties of gamma-ray pulsars. 1. Introduction For over two years the Compton Gamma-Ray Observatory Oriented Scintillation Spectrometer Experiment (GRO/OSSE) has collected data from many known radio and X-ray pulsars. Five pulsars (Crab, Vela, PSR B1706-44, PSR B1055-52, and Geminga) have been detected by the GRO Energetic Gamma-Ray Experiment Telescope (EGRET) and three (Crab, Vela, and PSR B1509-58) have been detected by OSSE. Here we present OSSE 2oe upper limits on fifteen...

20. The Binary Pulsar PSR1908+00 in NGC6760 - J. Middleditch,S. B. Anderson,T. A. Prince
We present orbital parameters of the 3.6 ms binary pulsar 1908+00 in the globular cluster NGC 6760. The orbital period is 3.4 hr and the mass function is 3 Theta 10 Gamma6 M fi , implying a minimum companion mass of 0.018 M fi . The companion is probably degenerate; and if it is hydrogen, it is close to overflowing its Roche lobe. The only other millisecond binary radio pulsar systems with orbital period ! 10 hr and mass function below 10 Gamma3 M fi are the eclipsing pulsars 1957+20 and 1744Gamma24A, and the very low-mass binary 0021Gamma72J. These pulsars are ablating their companions, and may be the progenitors of...

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