High-precision timing of PSR J1713+0747: Shapiro delay

We present results based on timing of the binary millisecond pulsar J1713+0747 for 22 months through 1994 February. We have measured its annual parallax, π = (0.9 ± 0.3) mas, as well as its proper motion, μ = (6.4 ± 1.0) milliarcsec (mas) yr^-1. We detect a signature in the timing residuals that is most naturally interpreted as the general relativisitic "Shapiro delay;" at the 2 σ confidence level, we find the companion mass, m₂ > 0.27 M_⊙, while the pulsar mass, m₁ > 1.2 M_⊙. Upper limits on both masses can only be obtained by imposing additional constraints on the system, such as requiring that general relativity be valid in the strongfield limit. With a post-fit weighted root mean square timing residual of approximately 0.4 μs, and a characteristic age of roughly 9 × 10⁹ yr, this pulsar is potentially the most stable celestial clock among all known pulsars.