X-Ray and Radio Studies of the Candidate Millisecond Pulsar Binary 4FGL J0935.3+0901

Abstract

4FGL J0935.5+0901, a γ-ray source recently identified as a candidate redback-type millisecond pulsar (MSP) binary, shows an interesting feature of having double-peaked emission lines in its optical spectrum. This feature would further suggest the source is a transitional MSP system in the sub-luminous disk state. We have observed the source with XMM-Newton and Five-hundred-meter Aperture Spherical radio Telescope (FAST) at X-ray and radio frequencies respectively for further studies. From the X-ray observation, a bimodal count-rate distribution, which is a distinctive feature of the transitional MSP systems, is not detected, but the properties of X-ray variability and power-law spectrum are determined for the source. These results help establish the consistency of it being a redback in the radio pulsar state. However no radio pulsation signals are found in the FAST observation, resulting in an upper limit on the flux density of ∼4 μJy. Implications of these results are discussed.