A Lower Mass Estimate for PSR J0348+0432 Based on CHIME/Pulsar Precision Timing

Abstract The binary pulsar J0348+0432 was previously shown to have a mass of approximately 2 M ⊙ , based on the combination of radial-velocity and model-dependent mass parameters derived from high-resolution optical spectroscopy of its white-dwarf companion. We present follow-up timing observations that combine archival observations with data acquired by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) pulsar instrument. We find that the inclusion of CHIME/Pulsar data yields an improved measurement of the variation of the orbital period ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> </mml:msub> </mml:math> ) that is 1.2 σ consistent with the original values published by J. Antoniadis et al. while being roughly 6 times more precise due to the extended baseline. Assuming that this <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>P</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>b</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:math> is due to gravitational wave damping, and that the latter is as predicted by general relativity, we obtain new constraints on the mass of the pulsar and companion. When combined with the mass ratio determined from phase-resolved optical spectroscopy we determine a pulsar mass of 1.806(37) M ⊙ . For the first time for this pulsar, timing alone significantly constrains the pulsar mass. If confirmed, our mass estimates indicate that the original analysis of the optical data has overestimated the mass of the companion (and by extension the mass of the pulsar) by about 10%.