Key system parameters (Table 1): spin period 3.15 ms; orbital period 8.6866194196(2) d; eccentricity 1.30(4)e-6; sin i = 0.999894(5); companion mass 0.500(6) Msun; 2,206 pulse times of arrival, rms residual 1.1 us; reduced chi^2 = 1.4 (2165 dof). MCMC error analysis; orbital dispersion-measure variation limited to < 2e-4 pc cm^-3 (delays < 0.4 us), and three conjunction epochs over 2 months give consistent results. Unlike X-ray or periastron-advance mass determinations, the Shapiro-delay measurement involves essentially no astrophysical model assumptions.
Methodology
Radio timing of PSR J1614-2230 with the GBT and the GUPPI backend: a dense orbital campaign in March 2010 (three superior-conjunction epochs over two months) plus long-term 2002-2010 timing; 2,206 pulse times of arrival, rms residual 1.1 us, reduced chi^2 = 1.4 (2165 dof). The nearly edge-on orbit (sin i = 0.999894(5)) produces a strong Shapiro delay whose shape yields companion mass and inclination — hence the pulsar mass — from general relativity alone, with essentially no astrophysical model assumptions; MCMC error analysis, orbital dispersion-measure variation bounded to < 2e-4 pc cm^-3 (delays < 0.4 us), and the three conjunction epochs give mutually consistent results.
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