AAS 207th Meeting, 8-12 January 2006
Session 183 Radio and X-Ray Pulsars
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[183.03] The Mass of a Millisecond Pulsar

B. A. Jacoby (Naval Research Laboratory), A. W. Hotan, M. Bailes (Swinburne University of Technology), S. M. Ord (University of Sydney), S. R. Kulkarni (California Institute of Technology)

We report on two years of timing observations of the low-mass binary millisecond pulsar PSR J1909-3744 with the Caltech-Parkes-Swinburne Recorder II (CPSR2), a new instrument that gives unprecedented timing precision. Daily observations give a weighted rms residual of 74 ns. Since their discovery, the masses of the rapidly rotating millisecond pulsars have remained a mystery, with the recycling hypothesis arguing for heavy objects, and the accretion-induced collapse of a white dwarf more consistent with neutron stars less than the Chandrashkar limit. Our data have allowed the measurement of Shapiro delay in this edge-on system, giving the first precise determination of a millisecond pulsar mass, 1.438 ±0.024 solar masses. The mass of PSR J1909-3744 is at the upper edge of the range observed in mildly recycled pulsars in double neutron star systems, consistent with the the recycling hypothesis. It appears that the production of millisecond pulsars is possible with the accretion of less than 0.2 solar masses.

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