We present the discovery of a likely new redback millisecond pulsar binary associated with the Fermi \gamma -ray source 4FGL J2333.1–5527 .
Using optical photometric and spectroscopic observations from the SOAR telescope , we identify a low-mass , main sequence-like companion in a 6.9-hr , highly inclined orbit around a suspected massive neutron star primary .
Archival XMM-Newton X-ray observations show this system has a hard power-law spectrum \Gamma = 1.6 \pm 0.3 and L _ { X } \sim 5 \times 10 ^ { 31 } erg s ^ { -1 } , consistent with redback millisecond pulsar binaries .
Our data suggest that the system harbors a massive ( 1.88 \pm 0.24 M _ { \odot } ) neutron star whose properties can be much better constrained with its future detection as a millisecond radio pulsar .
This work shows that a bevy of nearby compact binaries still await discovery , and that unusually massive neutron stars continue to be common in redbacks .