Multiwavelength Studies of Transitional Millisecond Pulsars: New Insights into Accretion Physics

Transitional millisecond pulsars (tMSPs) are a newly recognized population of sources that undergo sporadic transformations between clearly distinguishable non-accreting radio pulsar and accreting X-ray pulsar states. In the accreting state, these systems reside in a regime where the rotation-powered outflow and the accretion inflow are energetically comparable. As such, they can offer unique insight into the physics of accretion onto magnetized objects. I will present results from our extensive multi-wavelength campaign targeting the canonical tMSP PSR J1023+0038 and the tMSP candidate 3FGL J1544.6-1125, based on observations with NICER, XMM-Newton, Chandra, HST, NuSTAR, and the VLA. I will highlight a few key findings, including the measurement of the long-term spin-down behavior of PSR J1023+0038, the extraordinary anti-correlated X-ray/radio variability, and the detection of UV pulsations with HST.