A Multiwavelength Study of Nearby Millisecond Pulsar PSR J1400-1431: Improved Astrometry and an Optical Detection of Its Cool White Dwarf Companion
Ray, P. S.; Kaplan, D. L.; Lorimer, D. R.; McLaughlin, M. A.; Stovall, K.; Kondratiev, V. I.; Barlow, B. N.; Bogdanov, S.; Lynch, R.; Istrate, A.; Hegedus, R. J.; Rosen, R.; Bellm, E. C.; Swiggum, J. K.; Gentile, P.; Heatherly, S. A.; Vasquez Soto, A.; Clancy, P.; Penprase, B.
United States, Netherlands, Russia
Abstract
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 (1×1029 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^\circ .