Multi-Wavelength Observations of a New Redback Millisecond Pulsar 4FGL J1910.7−5320

We present the study of multi-wavelength observations of an unidentified Fermi Large Area Telescope (LAT) source, 4FGL J1910.7−5320 (J1910), a new candidate redback millisecond pulsar binary. In the 4FGL 95% error region of J1910, we find a possible binary with a 8.36-hr orbital period from the Catalina Real-Time Transient Survey (CRTS), confirmed by optical spectroscopy using the SOAR telescope. We fit the optical spectral energy distributions of J1910 with a blackbody model, inferring a maximum distance of 4.1 kpc by assuming that the companion fills its Roche-lobe with a radius of R = 0.7 R_sun. Using a 12.6 ks Chandra X-ray observation, we identified an X-ray counterpart for J1910, with a spectrum that can be described by an absorbed power- law with a photon index of 1.0 ± 0.4. The spectrally hard X-ray emission shows tentative evidence for orbital variability. Using more than 12 years of Fermi-LAT data, we refined the position of the γ-ray source, and the optical candidate still lies within the 68% positional error circle. These observational facts all suggest that 4FGL J1910.7−5320 is a redback millisecond pulsar.