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A Refined Orbital Solution for Swift J1749.4-2807

ATEL # 2569; T. E. Strohmayer (NASA/GSFC), C. B. Markwardt (U. Maryland & NASA/GSFC)
on 16 Apr 2010; 21:29 UT
Password Certification: Tod Strohmayer (

Subjects: X-ray, Binaries, Neutron Stars, Pulsars, Transients
Referred to by ATEL #: 2576

We report a refined orbital solution for the new accreting ms pulsar Swift J1749.4-2807 (ATEL #2548, #2567, #2568), using 14 ks of barycenter-corrected RXTE data spanning the time range 2010-04-14T21:12 to 2010-04-16T17:24 (UTC).

We obtained a coherent, phase connected timing solution with a circular orbit model. We find an orbital period of 31740.345 +- 0.04 s (8.8168 hr), a projected semi-major axis of a sin(i) = 1899.53 +- 0.01 lt-ms, and a barycentric pulse frequency for the first harmonic of the pulsar (twice the spin frequency) of 1035.840025 +- 0.4 micro-Hz. The time of the ascending node is 2455301.1522672 0.0000014 JD (TDB).

This solution implies a mass function of 0.05463 +- 0.00018 M_sol, and a minimum companion mass of 0.475 (for a 1.4 M_sol neutron star). The most recent observations indicate that the amplitude of the fundamental has increased again. Additional RXTE observations are planned. Observations at other wavelengths are encouraged.

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