3,937 research outputs found

    Relativistic Gravity and Binary Radio Pulsars

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    Following a summary of the basic principles of pulsar timing, we present a review of recent results from timing observations of relativistic binary pulsars. In particular, we summarize the status of timing observations of the much celebrated original binary pulsar PSR B1913+16, draw attention to the recent confirmation of strong evidence for geodetic precession in this system, review the recent measurement of multiple post-Keplerian binary parameters for PSR B1534+12, and describe the Parkes Multibeam survey, a major survey of the Galactic Plane which promises to discover new relativistic binary pulsar systems.Comment: 12 pages, 3 EPS figures, proceedings of 8th Canadian Conference on General Relativity and Relativistic Astrophysics, held June 1999, McGill University, Montreal, Quebec, Canad

    On the continuity of local times of Borel right Markov processes

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    The problem of finding a necessary and sufficient condition for the continuity of the local times for a general Markov process is still open. Barlow and Hawkes have completely treated the case of the L\'{e}vy processes, and Marcus and Rosen have solved the case of the strongly symmetric Markov processes. We treat here the continuity of the local times of Borel right processes. Our approach unifies that of Barlow and Hawkes and of Marcus and Rosen, by using an associated Gaussian process, that appears as a limit in a CLT involving the local time process.Comment: Published at http://dx.doi.org/10.1214/009117906000000980 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

    The High-Velocity Outflow of PG1211+143 May Not be That Fast

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    We analyze the X-ray spectrum of the quasar PG1211+143 observed with the CCD and grating spectrometers on board XMM-Newton. Using an ion by ion fitting model we find an outflow component of about 3000 km/s that includes absorption lines of K-shell and L-shell ions of the astrophysically abundant elements. We also identify and include in our model broad (FWHM = 6000 km/s) emission lines from H-like ions of C, N, O, and Ne, and He-like ions of O, Ne, and Mg. The outflow velocity we find is an alternative interpretation of the data and is in contrast with the ultra high velocity of ~24000 km/s reported previously for this object. Nevertheless, we can not completely rule out the presence of a high velocity component due to the poor signal-to-noise ratio of the data.Comment: 7 pages, 2 figures, emulateapj, accepted for publication in The Astrophysical Journa

    A characterization of the infinitely divisible squared Gaussian processes

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    We show that, up to multiplication by constants, a Gaussian process has an infinitely divisible square if and only if its covariance is the Green function of a transient Markov process.Comment: Published at http://dx.doi.org/10.1214/009117905000000684 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org
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