High-energy Variability of PSR J1311-3430

We have studied the variability of the black-widow-type binary millisecond pulsar PSR J1311-3430 from optical to gamma-ray energies. We confirm evidence for orbital modulation in the weak off-pulse ≳200 MeV emission, with a peak at {φ }_B≈ 0.8, following pulsar inferior conjunction. The peak has a relatively hard spectrum, extending above ∼1 GeV. XMM-Newton and Swift UV observations also show that this source’s strong X-ray flaring activity is associated with optical/UV flares. With a duty cycle of ∼7%-19%, this flaring is quite prominent with an apparent power-law intensity distribution. Flares are present at all orbital phases, with a slight preference for {φ }_B=0.5{--}0.7. We explore possible connections of these variabilities with the intrabinary shock and magnetic activity on the low-mass secondary.