Radio Pulsation Searches of Two Redback Binary MSP Candidates with the GBT

We report on searches for radio pulsations of two redback binary millisecond pulsar (MSP) candidates: Fermi LAT gamma-ray sources 3FGL J0212.1+5320 and 3FGL J0838.8-2829. Having both optical and X-ray counterparts, they exhibit properties strikingly similar to those of the sample of confirmed redback MSPs. We conducted five observations of 3FGL J0212.1+5320 from 2022 April – September using the Robert C. Byrd Green Bank Telescope at L-band (1 - 2 GHz), where we successfully detect the long-suspected pulsar. We repeat the same strategy for 3FGL J0838.8-2829, and plan to conduct the first observation in 2023 February. We present a multi-wavelength analysis of these two sources, motivated by our blind radio pulsation search results and derived parameters, if any, and complemented by existing X-ray and optical data. We explain the implications of our findings, including variability at different orbital phases, and ongoing efforts to learn more about each source.