Abstract

We present deep Apache Point Observatory optical observations within seconds of radio emission from the periodic fast radio burst (FRB) 180916.J0158+65 obtained on 2020 September 3. FRB 180916.J0158+65 is located in a nearby spiral galaxy 150 Mpc away and has an "active phase" with a well-measured period of approximately 16.3.days. Targeting the FRB at the peak of its expected active phase and during a recent 30.minute observing window by the Canadian Hydrogen Intensity Mapping Experiment (CHIME) in which a radio burst was detected, we did not detect any transient optical emission at m(i) approximate to 24.7 mag (3 sigma) from 2.2 to 1938.1.s after the burst arrival time in optical bands (corrected for dispersion). Comparing our limiting magnitudes to models of a synchrotron maser formed in the circumburst environment of FRB 180916+J0158.65, we constrain scenarios where the burst energy was >1044 erg and the circumburst density was >10(4).cm(-3).