A pulsar in disguise: coolest, dimmest redback yet found

Astronomers identified a mysterious Fermi source as a redback system: a neutron star with a close companion star. Using optical data spanning 6.6 years, they confirmed a 5.6-hour orbital period and determined the companion is an M-type star with mass ~0.5 solar masses and temperature ~3600 K—the coolest and most massive known in this class. The system also ranks among the dimmest redbacks in both X-rays and gamma rays, suggesting hidden diversity in neutron star binaries.