Heated Poles on the Companion of Redback PSR J2339$-$0533

Understand

We analyze photometry and spectra of the "redback" millisecond pulsar binary J2339$-$0533.

• These observations include new measurements from Keck and GROND, as well as archival measurements from the OISTER, WIYN, SOAR, and HET telescopes.
• The parameters derived from GROND, our primary photometric data, describe well the rest of the datasets, 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.