Excess Optical Enhancement Observed with ARCONS for Early Crab Giant Pulses

TL;DR

This study reveals a significant correlation between optical and radio pulses in the Crab pulsar, showing optical enhancement linked to radio giant pulses with high temporal precision, suggesting a causal connection.

Contribution

We provide high time-resolution observations demonstrating a direct optical-radio correlation in the Crab pulsar, extending understanding of pulsar emission mechanisms.

Findings

Optical flux increases by 11.3% with accompanying radio giant pulses.

Optical main pulse peak is enhanced by 2.8% during radio giant pulses.

No spectral differences found between optical pulses with or without radio counterparts.

Abstract

We observe an extraordinary link in the Crab pulsar between the enhancement of an optical pulse and the timing of the corresponding giant radio pulse. At optical through infrared wavelengths, our observations use the high time resolution of ARCONS, a unique superconducting energy-resolving photon-counting array at the Palomar 200-inch telescope. At radio wavelengths, we observe with the Robert C. Byrd Green Bank Telescope and the GUPPI backend. We see an $11.3\pm2.5\%$ increase in peak optical flux for pulses that have an accompanying giant radio pulse arriving near the peak of the optical main pulse, in contrast to a $3.2\pm0.5\%$ increase when an accompanying giant radio pulse arrives soon after the optical peak. We also observe that the peak of the optical main pulse is $2.8\pm0.8\%$ enhanced when there is a giant radio pulse accompanying the optical interpulse. We observe no statistically significant spectral differences between optical pulses accompanied by and not accompanied by giant radio pulses. Our results extend previous observations of optical-radio correlation to the time and spectral domains. Our refined temporal correlation suggests that optical and radio emission are indeed causally linked, and the lack of spectral differences suggests that the same mechanism is responsible for all optical emission.