N. D'Amico

We present the first optical observations of the unique system J0737-3039 (composed of two pulsars, hereafter PSR-A and PSR-B). Ultra-deep optical observations, performed with the High Resolution Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope, could not detect any optical emission from the system down to m _F435W = 27.0 and m _F606W = 28.3. The estimated optical flux limits are used to constrain the three-component (two thermal and one non-thermal) model recently proposed to reproduce the XMM-Newton X-ray spectrum. They suggest the presence of a break at low energies in the non-thermal power-law component of PSR-A and are compatible with the expected blackbody emission from the PSR-B surface. The corresponding efficiency of the optical emission from PSR-A's magnetosphere would be comparable to that of other Myr-old pulsars, thus suggesting that this parameter may not dramatically evolve over a timescale of a few Myr.

Millisecond pulsars in southern globular clusters have been regularly observed for timing pourposes with the Parkes radio telescope. To date, several pulsars have data spanning more than 6 years, and their peculiarities are now recognisable via their timing analysis. In this paper we briefly summarise the state of the art of the timing for the eclipsing binary PSR J1701‐3006B in the clobular cluster NGC6266 and for all the millisecond pulsars in the globualr cluster NGC6752.

The timing of radio pulsars provides a tool for studying a wide range of funda- mental physical and astrophysical problems. The best results are obtained by regular, fre- quent timing observations of a large number of sources at various frequencies. We describe a project which aims to improve on all of the above parameters by combining timing data from the pulsar timing programs of 4 European groups to form the so-called EPTA. These data will be used to study, amongst other things, relativistic binari es and gravitational waves.

We report the discovery of a radio pulsar with a characteristic age of 7300 yr, making it one of the 10 apparently youngest Galactic pulsars known. PSR J1357-6429, with a spin period of P = 166 ms and spin-down luminosity of 3.1 × 10³⁶ ergs s^-1, was detected during the Parkes multibeam survey of the Galactic plane. We have measured a large rotational glitch in this pulsar, with ΔP/P = -2.4 × 10^-6, similar in magnitude to those experienced occasionally by the Vela pulsar. At a nominal distance of only ~2.5 kpc, based on the measured free electron column density of 127 cm^-3 pc and the electron distribution model of Cordes & Lazio, this may be, after the Crab, the nearest very young pulsar known. The pulsar is located near the radio supernova remnant candidate G309.8-2.6.

We report on a 10 ks observation of the double pulsar system J0737-3039 obtained with the Chandra X-Ray Observatory's Advanced CCD Imaging Spectrometer. We detect the system as a point source with coordinates (J2000.0) R.A. = 07^h37^m5123, decl. = -30°39'409, making this the first double neutron star system to be detected at X-ray energies. Only 77 source counts are detected. The data are represented satisfactorily by a power-law spectrum with photon index Γ = 2.9 ± 0.4. The inferred 0.2-10 keV luminosity is ≈2 × 10³⁰ ergs s^-1 for a distance of 0.5 kpc. We do not detect any significant variability with orbital phase in these data, which span one full orbit. These results are consistent with the X-ray emission originating solely from the magnetosphere of the energetic A pulsar, with an efficiency for conversion of rotational energy to X-rays in this band of ~0.04%, although we cannot exclude other possibilities.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

By means of high-resolution spectra, we have measured radial velocities of the companion (hereafter COM J1740-5340) to the eclipsing millisecond pulsar PSR J1740-5340 in the galactic globular cluster NGC 6397. The radial velocity curve fully confirms that COM J1740-5340 is orbiting the pulsar, and this enables us to derive the most accurate mass ratio (M-PSR/M-COM = 5.85 +/- 0.13) for any nonrelativistic binary system containing a neutron star. Assuming a pulsar mass in the range 1.3-1.9 M-., the mass of COM J1740-5340 spans the interval 0.22-0.32 M-., the inclination of the system is constrained within, and the Roche lobe 56degrees greater than or similar to i greater than or similar to 47degrees and the Roche lobe radius is r(RL) similar to1.5-1.7 R-.. A preliminary chemical abundance analysis confirms that COM J1740-5340 has a metallicity compatible with that measured for other stars in this metal-poor globular, but the unexpected detection of strong He I absorption lines implies the existence of regions at K, which are significantly warmer T > 10,000 than the rest of the star. The intensity of this line correlates with the orbital phase, suggesting the presence of a region on the companion surface, heated by the millisecond pulsar flux

A high-frequency survey of the Galactic plane for radio pulsars is in progress, using the multibeam receiver on the 64-m Parkes radiotelescope. We describe the survey motivations, the observing plan and the inital results. The survey is discovering many pulsars, more than 500 so far. Eight of the new pulsars are binary, one with a massive companion. At least eight are young, with characteristic ages of less than 100 kyr. Two of these (Kaspi et al., this Conference) have surface dipole magnetic field strengths greater than any other known radio pulsar.