المؤلفون: Champion, D. J., Hobbs, G. B., Manchester, R. N., Edwards, R. T., Backer, D. C., Bailes, M., Bhat, N. D. R., Burke-Spolaor, S., Coles, W., Demorest, P. B., Ferdman, R. D., Folkner, W. M., Hotan, A. W., Kramer, M., Lommen, A. N., Nice, D. J., Purver, M. B., Sarkissian, J. M., Stairs, I. H., van Straten, W.

المصدر: AIP Conference Proceedings; 8/18/2011, Vol. 1357 Issue 1, p93-96, 4p

مصطلحات موضوعية: PULSAR detection, MASS (Physics), PLANETARY orbits, ASTRONOMICAL observations, SPACE vehicles, SOLAR system, MEASUREMENT, SUN

مستخلص: High-precision pulsar timing relies on a solar system ephemeris in order to convert times of arrival (TOAs) of pulses measured at an observatory to the solar system barycenter. Any error in the conversion to the barycentric TOAs leads to a systematic variation in the observed timing residuals; specifically, an incorrect planetary mass leads to a predominantly sinusoidal variation having a period and phase associated with the planet's orbital motion about the Sun. By using an array of pulsars (PSRs J0437-4715, J1744-1134, J1857+0943, J1909-3744), the masses of the planetary systems from Mercury to Saturn have been determined. These masses are consistent with the best-known masses determined by spacecraft observations, with the mass of the Jovian system, 9.547921(2)×10^-4M⊙, being significantly more accurate than the mass determined from the Pioneer and Voyager spacecraft, and consistent with but less accurate than the value from the Galileo spacecraft. While spacecraft are likely to produce the most accurate measurements for individual solar system bodies, the pulsar technique is sensitive to planetary system masses and has the potential to provide the most accurate values of these masses for some planets. [ABSTRACT FROM AUTHOR]

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المؤلفون: Freire, P. C. C., Bassa, C. G., Wex, N., Stairs, I. H., Champion, D. J., Ransom, S. M., Lazarus, P., Kaspi, V. M., Hessels, J. W. T., Kramer, M., Cordes, J. M., Verbiest, J. P. W., Podsiadlowski, P., Nice, D. J., Deneva, J. S., Lorimer, D. R., Stappers, B. W., McLaughlin, M. A., Camilo, F.

المصدر: Monthly Notices of the Royal Astronomical Society; Apr2011, Vol. 412 Issue 4, p2763-2780, 18p, 1 Black and White Photograph, 2 Charts, 10 Graphs

مصطلحات موضوعية: STELLAR evolution, BINARY stars, PULSARS, ASTRONOMICAL observations, STAR formation, STELLAR mass, STELLAR magnetic fields, STELLAR orbits, NEUTRON stars

مستخلص: PSR J1903+0327, a millisecond pulsar in an eccentric () 95-d orbit with an companion poses a challenge to our understanding of stellar evolution in binary and multiple-star systems. Here we describe optical and radio observations which rule out most of the scenarios proposed to explain formation of this system. Radio timing measurements of three post-Keplerian effects yield the most precise measurement of the mass of a millisecond pulsar to date: solar masses (99.7 per cent confidence limit). This rules out some equations of state for superdense matter; furthermore, it is consistent with the spin-up of the pulsar by mass accretion, as suggested by its short spin period and low magnetic field. Optical spectroscopy of a proposed main-sequence counterpart shows that its orbital motion mirrors the pulsar's 95-d orbit; being therefore its binary companion. This finding rules out a previously suggested scenario which proposes that the system is presently a hierarchical triple. Conventional binary evolution scenarios predict that, after recycling a neutron star into a millisecond pulsar, the binary companion should become a white dwarf and its orbit should be nearly circular. This suggests that if PSR J1903+0327 was recycled, its present companion was not responsible for it. The optical detection also provides a measurement of the systemic radial velocity of the binary; this and the proper motion measured from pulsar timing allow the determination of the systemic 3D velocity in the Galaxy. We find that the system is always within 270 pc of the plane of the Galaxy, but always more than 3 kpc away from the Galactic Centre. Thus an exchange interaction in a dense stellar environment (like a globular cluster or the Galactic Centre) is not likely to be the origin of this system. We suggest that after the supernova that formed it, the neutron star was in a tight orbit with a main-sequence star and the present companion was a tertiary farther out. The neutron star then accreted matter from its evolving inner companion, forming a millisecond pulsar. The inner companion then disappeared, either due to a chaotic three-body interaction with the outer star (caused by the expansion of the inner orbit that necessarily results from mass transfer), or in the case of a very compact inner system, due to ablation/accretion by the newly formed millisecond pulsar. We discuss in detail the possible evolution of such a system before the supernova. [ABSTRACT FROM AUTHOR]

: Copyright of Monthly Notices of the Royal Astronomical Society is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)