A New Likely Redback Millisecond Pulsar Binary with a Massive Neutron Star: 4FGL J2333.1-5527
Strader, Jay; Dage, Kristen C.; Chomiuk, Laura; Urquhart, Ryan; Aydi, Elias; Orosz, Jerome A.; Shishkovsky, Laura; Salinas, Ricardo; Swihart, Samuel J.; Kawash, Adam M.
United States, Chile
Abstract
We present the discovery of a likely new redback millisecond pulsar (MSP) binary associated with the Fermi γ-ray source 4FGL J2333.1-5527. Using optical photometric and spectroscopic observations from the Southern Astrophysical Research 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 Γ = 1.6 ± 0.3 and LX ∼ 5 × 1031 erg s-1, consistent with redback MSP binaries. Our data suggest that for secondary masses typical of redbacks, the mass of the neutron star is likely well in excess of ∼1.4 M⊙, but future timing of the radio pulsar is necessary to bolster this tentative conclusion. 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.