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[en] The period of the 50 ms pulsar PSR 0540 - 69 in the Large Magellanic Cloud was determined using five separate X-ray observations with the Exosat satellite in the interval August 12, 1984 to June 30, 1985. Together with Einstein observations and contemporaneous optical data, the Exosat periods can be fitted well to a quadratic curve yielding a braking index of 2.74 + or - 0.10. This behavior is not compatible with the optical and X-ray observations commencing about a year after Exosat, indicating the PSR 0540 - 69 is susceptible to discontinuous changes in its spin-down behavior. 15 refs

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[en] The observations of the COS-B satellite have been analyzed for evidence of high-energy gamma-ray emission (70MeV< E<5GeV) from the X-ray binary, Vela X-1. The X-ray detector on board was used for a precise determination of the rotation phase which allowed for a coherent addition of the gamma ray measurements of different epochs. The data do not show the 283 second rotational periodicity of Vela X-1. This implies a 95% confidence upper limit for pulsed gamma ray flux (E>100MeV) of N<0.5 10^-6 cm^-2s^-1. Also, the data do not show the X-ray eclipse. This implies an upper limit for gamma ray flux from the neutron star of N<0.6 10^-6 cm^-2s^-1

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No abstract available

[en] A young pulsar cools rapidly by neutrino emission. The resulting thermal contraction leads to spin-up in the earliest epochs when the effect dominates over spin-down by magnetic dipole radiation. This initial spin-up may last several years. The characteristic time dependence of the neutrino luminosity can also dominate in the second derivative of the rotation rate for as long as thousands of years with favorable initial conditions. 14 refs

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[en] High energy (E>35 MeV) gamma ray data of SAS-2 satellite has been used to compare the intensity distribution of gamma rays with that of neutral hydrogen (HI) density along the line of sight, at high galactic latitudes (/β/>30⁰). A model has been constructed where the observed gamma ray intensity has been assumed to be the bum of a galactic component proportional to the HI distribution plus an isotropic extra-galactic emission. The X²-test of the model parameters indicate that about 40% of the total high latitude emission may originate within the galaxy. (author)

[en] Optical astronometry and photometry in the Vela pulsar field is presented, investigating the proper motion of the pulsar and the optical counterpart of the 2-arcmin-diameter compact nebula seen in X-rays. Fitting the relative position measurements together with previously published data yields mu(alpha) = 26 + or - 6 marcsec (1sigma) and mu(delta) = 28 + or - 6 marcsec/yr (1 sigma) as the proper motion of the pulsar. After a star-detection algorithm is used to detect and subtract the stellar contribution, a diffuse nebula centered around the pulsar is clearly distinguishable in the V and B exposures; several wisplike structures can be recognized in the images. The optical size of the compact nebula, 2-6 x 10 to the 17th cm, is comparable to that in X-rays, and the optical intensity can be connected to the X-ray points by a power-law-type emission with photon number index gamma = about 2. 25 refs