2017ApJ...850..100A

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.