One-week optical observations of pulsed emission from the Crab pulsar with IMONY on the 3.8 m Seimei telescope

Abstract

We report our optical observations of the Crab pulsar using the Imager of MPPC-based Optical photoN counter from Yamagata (IMONY), a high-time-resolution photon-counting imager with 100 ns timing resolution, mounted on the 3.8 m Seimei telescope in Japan (f/D~6). The detector format was upgraded from a $4\times 4$ to an $8\times 8$ GAPD array with larger pixels ($100$ to $200\mu m$), resulting in a 14".5 field of view on the Seimei telescope. We conducted nightly optical observations for one week, including two nights of simultaneous optical and radio observations with the 64 m Usuda radio telescope. Thanks to the large diameter of the Seimei telescope and the high time resolution of IMONY, we successfully detected optical Single Pulses (SPs) emitted in each rotation. Moreover, we found an optical peak timing drift of $30\pm 7.9\mu \mathrm{s}$ over three days, with a significance of $3.9\sigma$. The corresponding emission region size is 9.1 km, which is equivalent to 0.006 times the light cylinder radius of the Crab pulsar. We ruled out the possibility of a pulsar glitch and suggested that the optical pulsed emission region of the Crab pulsar may fluctuate due to the spatial drift and variations in the magnetospheric caustics.

References in corpus (13)

• Radio Emission Signatures in the Crab Pulsar
• Observation of Pulsed Gamma-rays Above 25 GeV from the Crab Pulsar with MAGIC
• PINT: A Modern Software Package for Pulsar Timing
• Pulsar Radio Emission Mechanism: Radio Nanoshots as a Low Frequency Afterglow of Relativistic Magnetic Reconnection
• Optical polarisation of the Crab pulsar: precision measurements and comparison to the radio emission
• Bright Giant Pulses from the Crab Nebula Pulsar: Statistical Properties, Pulse Broadening and Scattering due to the Nebula
• Simultaneous Absolute Timing of the Crab Pulsar at Radio and Optical Wavelengths
• Enhanced X-ray Emission Coinciding with Giant Radio Pulses from the Crab Pulsar
• Aqueye+: a new ultrafast single photon counter for optical high time resolution astrophysics
• Wide-Band Spectra of Giant Radio Pulses from the Crab Pulsar
• Short time scale pulse stability of the Crab pulsar in the optical band
• Development of an optical photon-counting imager with a monolithic Geiger APD array
• Optical photon-counting observation of the Crab pulsar with Kanata telescope using prototype IMONY