The mag 14.7 main-belt asteroid (4288) Tokyotech, 12 km in diameter, was predicted to occult a mag 11.2 star in Aries on 2019 December 1. Observers within the 12 km wide shadow track could see a drop in brightness of 3.5 magnitudes for up to 1.4s.

My site was 10 km south of the predicted shadow zone, with an 11% probability of success. I was fortunate to record the brief disappearance of the target star, 1.12s in duration. The attached screenshot shows the analysis of the light curve using Tangra and AOTA.

    D  - 19 52 19.34 ± 0.02
    R  - 19 52 20.46 ± 0.02

This is the first chord observed across Tokyotech; there are no previous observations listed in the Occult database. These timings confirm that the asteroid is at least 9 km in diameter and the Gaia position of the target star will give high-precision astrometry of the asteroid at the mid-time of the occultation.

After I submitted my formal report to the Planoccult list server I received an interesting reply from Raoul Behrend (Geneva Observatory). He leads the CdR &CdL team which analyses asteroids' light curves, searching for binary systems. He commented that Tokyotech is a binary asteroid, and two hours before my occultation event its components were predicted to be in mutual eclipse. Because I recorded one brightness dip and not two, this would help to constrain their model of the Tokyotech system.