Volume 490, Number 2, November I 2008
|Page(s)||753 - 761|
|Section||Stellar structure and evolution|
|Published online||11 September 2008|
Multi-telescope timing of PSR J1518+4904
Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands e-mail: email@example.com
2 Stichting ASTRON, Postbus 2, 7990 AA Dwingeloo, The Netherlands e-mail: Ben.Stappers@manchester.ac.uk
3 University of Manchester, Jodrell Bank Observatory, Macclesfield Cheshire, SK11 9DL, UK
4 Physics Department, Bryn Mawr College, Bryn Mawr, PA 19010, USA
5 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
6 Laboratoire de Physique et Chimie de l'Environnement, CNRS, 3A Avenue de la Recherche Scientifique, 45071 Orléans Cedex 2, France
Accepted: 9 August 2008
Context. PSR J1518+4904 is one of only 9 known double neutron star systems. These systems are highly valuable for measuring the masses of neutron stars, measuring the effects of gravity, and testing gravitational theories.
Aims. We determine an improved timing solution for a mildly relativistic double neutron star system, combining data from multiple telescopes. We set better constraints on relativistic parameters and the separate masses of the system, and discuss the evolution of PSR J1518+4904 in the context of other double neutron star systems.
Methods. PSR J1518+4904 has been regularly observed for more than 10 years by the European Pulsar Timing Array (EPTA) network using the Westerbork, Jodrell Bank, Effelsberg and Nançay radio telescopes. The data were analysed using the updated timing software tempo2.
Results. We have improved the timing solution for this double neutron star system. The periastron advance has been refined and a significant detection of proper motion is presented. It is not likely that more post-Keplerian parameters, with which the individual neutron star masses and the inclination angle of the system can be determined separately, can be measured in the near future.
Conclusions. Using a combination of the high-quality data sets present in the EPTA collaboration, extended with the original GBT data, we have constrained the masses in the system to mp < 1.17 and mc > 1.55 (95.4% confidence), and the inclination angle of the orbit to be less than 47 degrees (99%). From this we derive that the pulsar in this system possibly has one of the lowest neutron star masses measured to date. From evolutionary considerations it seems likely that the companion star, despite its high mass, was formed in an electron-capture supernova.
Key words: stars: neutron / pulsars: general / pulsars: individual: PSR J1518+4904
© ESO, 2008
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