2017ApJ...847...25S

In 2012, five high-school students involved in the Pulsar Search Collaboratory discovered the millisecond pulsar (MSP) PSR J1400-1431, and initial timing parameters were published in Rosen et al. a year later. Since then, we have obtained a phase-connected timing solution spanning five years, resolving a significant position discrepancy and measuring {dot}P, proper motion, parallax, and a monotonic slope in dispersion measure over time. Due to PSR J1400-1431's proximity and significant proper motion, we use the Shklovskii effect and other priors to determine a 95% confidence interval for PSR J1400-1431's distance, d=270_–80⁺¹³⁰ pc. With an improved timing position, we present the first detection of the pulsar's low-mass white dwarf (WD) companion using the Goodman Spectrograph on the 4.1 m SOAR telescope. Deeper imaging suggests that it is a cool DA-type WD with T_eff=3000±100 K and R/R_☉=(2.19±0.03)×10^–2 (d/270 pc). We show a convincing association between PSR J1400-1431 and a γ-ray point source, 3FGL J1400.5-1437, but only weak (3.3σ) evidence of pulsations after folding γ-ray photons using our radio timing model. We detect an X-ray counterpart with XMM-Newton, but the measured X-ray luminosity (1x10²⁹ erg s^–1) makes PSR J1400-1431 the least X-ray luminous rotation-powered MSP detected to date. Together, our findings present a consistent picture of a nearby (d~230 pc) MSP in a 9.5-day orbit around a cool ∼0.3 M_☉ WD companion, with orbital inclination i 60^○.