2020ApJ...903...39K

We analyze the photometry and spectra of the "redback" millisecond pulsar binary J2339-0533. These observations include new measurements from Keck and the Gamma-Ray Burst Optical/Near-infrared Detector (GROND), as well as archival measurements from the Optical and Infrared Synergetic Telescopes for Education and Research (OISTER), WIYN, Southern Astrophysical Research (SOAR), and Hobby-Eberly Telescope (HET) telescopes. The parameters derived from GROND, our primary photometric data, describe well the rest of the data sets, raising our confidence in our fitted binary properties. Our fit requires hot spots (likely magnetic poles) on the surface of the companion star, and we see evidence that these spots move over the 8 yr span of our photometry. The derived binary inclination i = 69.°3 ± 2.°3, together with the center-of-mass velocity (from the radial-velocity fits) K_C = 347.0 ± 3.7 kms^–1, give a fairly typical neutron star mass of 1.47 ± 0.09 M_☉.