We have conducted an optical study of the recently discovered very fast (P∼16msec) X-ray pulsar PSR J0537-6910 in the supernova remnant N157B. Broad band imaging has been obtained to study the field around the X-ray position and a high speed photometry programme was carried out in an attempt to detect optical pulses.

The two young pulsars PSR J0537-6910 and PSR B1706-44 have been recently observed with the NTT and the VLT. Although both pulsars turned out to be undetected (V ≥ 23.4 and V ≥ 27.5 respectively) the observations provided interesting constraints on the evolution of the optical luminosity of young pulsars.

Optical data in the V-band gathered with the 8.2m ESO Very Large Telescope (VLT) at the radio interferometric position of PSR 1706-44 are presented. The pulsar is close to a bright star in projection and was not detected. The pulsar magnitude limit must be fainter than V=24.5 for a distance of ≤ from the bright star. In the outer gap model for an aligned rotor the optical flux should scale with the gammaray flux. For pulsars which emit pulsed gamma-rays but are not detected in the optical bands, the synchrotron cutoff frequency for the tertiary photons must be well below the optical frequencies and the magnetic and spin axes may be misaligned.

Observations of the 5 confirmed optical pulsars indicate that the peak emission scales according to the outer field strength. We show that this gives gives further confirmation that a simple phenomenological models such as Pacini and Salvati (1987) still have validity. Furthermore we show that the Crab pulsar exhibits unpulsed emission which further complicate any studies of the thermal emission from Isolated Neutron Stars.

OPTIMA is a small and mobile highspeed photometer which is primarily intended for the observation of young high energy pulsars at optical wavelengths. The detector system consists of a fiber fed photon counter based on avalanche photodiodes, a GPS timing receiver and an integrating CCD camera to ensure the correct positioning of the targeted object. In January 1999, OPTIMA proved its functionality by measuring the lightcurve of the Crab pulsar.

The detection of a pulsed X-ray counterpart (RX J1824.2-2R52P) of the 3.05 ms pulsar PSR 1821-24, suggests the possibility of a part of the rotational energy loss of this high spindown rate pulsar being in the optical band. Archival HST data for M28 is used here to set upper limits on the optical V-band magnitude of PSR 1821-24. The optical limit extends the multiwavelength observations for this source and provides a constraint for theoretical models of pulsar emission.

We investigate the polarization characteristics of optical emission from young pulsars. In a first attempt we search for polarization in images without time resolution in order to select suitable candidates for time-resolved studies. Polarization information constrains the nature of the faint optical emission of pulsars and will eventually allow to derive the topology of the field in those areas were optical radiation is emitted. We determine the polarization of the time-integrated optical emission of the SMC pulsar B0540-69 and the Vela pulsar B0833-45. We identify a new candidate optical counterpart for the young pulsar B1509-58 and find that the old candidate is unpolarized. The polarization of these three sources is rather high in view of the assumption that averaging over a putative swing of the polarization angle through 180 degrees will lead to depolarisation in the pulse-averaged signal.

We also detect high degrees of polarization in the synchrotron nebula surrounding the LMC pulsar B0540-69, indicating even further similarity to the Crab.

Recent X-ray observatories like ROSAT, ASCA, RXTE, BeppoSAX and Chandra have achieved important progress in neutron star and pulsar astronomy. The identification of Geminga as a rotation-powered pulsar, the discovery of X-ray emission from millisecond pulsars and the identification of cooling neutron stars are only few of the fascinating results. In the following I will give a brief review on the X-ray emission properties of rotation-powered pulsars and their wind nebulae.

We report upper limits to pulsed X-ray emissions from PSR B1951+32 in 0.5 - 250 keV based on observations of ASCA in 1993 and RXTE in 1996. Together with earlier ROSAT report, these upper limits strongly suggest a thermal pulsed component below about 1 keV. These upper limits also indicate a spectral bending occurring in 100 keV - 3 MeV, which favors an outer-magnetosphere origin for gamma-ray emissions from PSR B1951+32.

We present some preliminary results of a BeppoSAX observation of the pulsar PSR B1509–58. We discuss in detail the spectrum energy distribution and show that the high energy data can be explained by a steepening continuum spectrum.

We report on our analysis of a 300 ks observation of the Vela pulsar with the Rossi X-Ray Timing Explorer (RXTE). The double-peaked, pulsed emission at 2 - 30 keV, which we had previously detected during a 93 ks observation, is confirmed with much improved statistics. There is now clear evidence, both in the spectrum and the light curve, that the emission in the RXTE band is a blend of two separate components. The spectrum of the harder component connects smoothly with the OSSE, COMPTEL and EGRET spectrum and the peaks in the light curve are in phase coincidence with those of the high-energy light curve. The spectrum of the softer component is consistent with an extrapolation to the pulsed optical flux, and the second RXTE pulse is in phase coincidence with the second optical peak. In addition, we see a peak in the 2-8 keV RXTE pulse profile at the radio phase.

The recently discovered pulsar PSR J0537-6910 is the most rapidly rotating young pulsar known. This latest example of a Crab-like pulsar, located in the supernova remnant N157B in the Large Magellanic Cloud, is rotating twice as fast as the Crab pulsar. With a characteristic age of 5000 years, it is also the oldest known example of a Crab-like pulsar and was likely rotating close to the maximum rate for a neutron star when it was born. Here we report preliminary results from an intensive monitoring campaign of X-ray observations acquired with the Rossi X-ray Timing Explorer that began in January 1999. These observation have revealed a large glitch event in the pulse timing during the first six month of our campaign, consistent with those suggested by sparse observations dating back to 1993. The current evolution of the rotation rate of PSR J0537-6910 provides a unique probe of the internal structure of neutron stars and constraints on possible pulsar emission mechanisms.

We present the results of a phase resolved spectroscopy of the Crab pulsar in the band 0.1 - 200 keV based on many observations performed with BeppoSAX. The spectrum was found soft in the main peak and significantly harder in the Interpeak region. This behaviour is explained by means of a two component model.

We report on the spectral and temporal properties of the 50 ms pulsar PSR B0540–69 using ASCA archival data obtained during 1993 to 1995. From the spectral analysis it was found that the spectra of the whole (nebular and pulsed) emission and pulsed emission in the range 1-10 keV can be represented by a single power law of photon index, Γ = 2.00 ± 0.02 and Γpulsed = 1.7 ± 0.3 respectively. The parameters for pulse frequency change during 1993-1995 were obtained using the 9 pulse frequency measurements with ASCA. The parameters derived from the ASCA observations are consistent with the previous measurements, suggesting high stability of this pulsar, ΔΩ/Ω ≲ 0.5 × 10−7 over the past 10 years. These results confirm similarity of this pulsar with the Crab pulsar.

On behalf of a large collaboration (see Mineo et al. (1999) for details) I present the results of a BSAX observation of PSR J0218+4232 which, for the first time, provides detailed information on the pulsar temporal and spectral emission properties in the broad energy band 1–10 keV.

We present X-ray observations of PSR J1814–1744, a 4 s radio pulsar with inferred surface dipole magnetic field strength 5.5 × 1013 G recently discovered in the on-going Parkes multibeam survey. This pulsar’s spin parameters are very similar to those of anomalous X-ray pulsars (AXPs). X-ray emission is not detected from the position of the radio pulsar in observations with ROSAT and ASCA. The derived upper flux limit implies an X-ray luminosity significantly smaller than those of all known AXPs. These results argue that magnetar mechanism invoked to explain X-ray emission from AXPs must depend on more than merely the inferred surface magnetic field strength as estimated from P and .

We have examined several archival ASCA observations of Galactic radio pulsars, including PSRs B1046–58 and B1610–50. X-ray emission is detected from PSR B1046–58 with a significance of ∼5σ. We find no evidence for pulsations. We argue that the emission is from a spatially unresolved synchrotron nebula powered by the pulsar. The location of the X-ray counterpart within the 95% position error ellipse of the gamma-ray source 3EG J1048–5840 strengthens the claim of Kaspi et al. (2000) that PSR B1046–58 emit ϒ-rays. X-ray emission from PSR B1610–50 is not detected. We use the X-ray luminosity upper limit to constrain the pulsar’s velocity ≲ 200km s−1, arguing against an association with the nearby supernova remnant Kes 32. Our results for these radio pulsars contradict previous reports of detections of large (tens of arc minutes) associated synchrotron nebulae.

We report the first detection of the pulsed X-ray emission from the fastest millisecond pulsar known PSR B1937+21 (P =1.558msec) with ASCA. The pulsar is detected as a point source above ∼ 1.7keV, with no nebulosity indicated. The source flux in the energy band 2–10keV is found to be f = 4.3 × 10−13erg s−1 cm−2, which corresponds to the luminosity of Lx = 4πD2f ≈ 6.6 × 1032(D/3.6kpc)2 erg s−1, where D is the distance, and correspond to ≈ 6 × 10−4 of the rotation power of the pulsar. The pulsation is found at the period predicted by the radio ephemerides with very narrow primary peaks, the width of which is about 1/16 phase ≈ 100μs near the time resolution limit (61μs) of the observation. The pulsed luminosity within the primary peak (1/16 phase interval) is found to be fp = 4.0 × 10−12erg s−1 cm−2. Although there may be a secondary peak, its statistical significance is too low to identify. Spectra of the whole source region and the primary peak are fitted by power law models to give photon indices of about unity for both.

We report on the likely detection of pulsed high-energy γ-rays from the binary millisecond pulsar PSR J0218+4232 in 100–1000 MeV data from CGRO EGRET. Imaging analysis demonstrates that the highly significant γ-ray source 2EG J0220+4228 (∼ 10σ) is for energies > 100 MeV positionally consistent with both PSR J0218+4232 and the BL Lac 3C66A. However, above 1 GeV 3C66A is the evident counterpart, whereas between 100 and 300 MeV PSR J0218+4232 is the most likely one. Timing analysis using one ephemeris valid for all EGRET observations yields in the 100-1000 MeV range a double-pulse profile at a ∼ 3.5σ significance level. The phase separation is similar to the component separation of ∼ 0.47 observed at X-rays. A comparison of the γ-ray profile with the 610 MHz radio profile in absolute phase shows that the two γ- ray pulses coincide with two of the three emission features in the complex radio profile.

We apply a likelihood analysis to pulsar detections, pulsar upper limits, and diffuse background measurements from the OSSE and EGRET instruments to constrain the γ-rays pulsar luminosity law. We find a steeper dependence on period and magnetic field at OSSE than at EGRET energies. We also find that pulsars may be an important component of the OSSE diffuse flux, but are most likely not important for EGRET. We estimate that as many as half of the unidentified EGRET sources may be γ-rays pulsars. Furthermore, we predict that GLAST will detect roughly 1000 γ-rays pulsars, only 100 of which are currently known.