AAS 205th Meeting, 9-13 January 2005
Session 76 X-Ray Binaries, and Pulsars
Oral, Tuesday, January 11, 2005, 10:00-11:30am, Royal Palm 1-3

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[76.06] A Method of Measuring the Mass of 4U0900-40 Dynamically

J. F. Dolan (Lab. Astron. & Solar Phys., NASA's GSFC), P. B. Etzel (San Diego State Univ.), P. T. Boyd (Univ. Md. Baltimore County & Lab. High Energy Astrophys., NASA's GSFC)

Accurate measurements of neutron star masses are needed to constrain the equation of state of neutron star matter and to identify the evolutionary track of the progenitor stars that form neutron stars. The best measured values of the mass of 4U0900-40 (= Vela XR-1), 1.86 ± 0.16 and 1.93 ± 0.20 solar masses, make it the most massive neutron star known. The direct relationship between the maximum mass of neutron stars and the equation of state of dense matter makes 4U0900-40 the single most important neutron star mass to determine accurately. Previous mass estimates of 4U0900-40 have been obtained using non-dynamical methods. We describe here a dynamical method for determining the mass of 4U0900-40 using the reprocessed UV pulses emitted by its B0.5Ib companion, in which knowledge of the primary's rotational speed or the pattern of its X-ray illumination are unnecessary.

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© 2004. The American Astronomical Society.