Deep optical observations contemporaneous with emission from the periodic FRB 180916.J0158+65

TL;DR

This study conducted deep optical observations of FRB 180916.J0158+65 during its active phase, finding no optical counterpart and constraining models of the burst environment and energy.

Contribution

First simultaneous deep optical observations of FRB 180916+65 during its active phase, setting limits on optical emission and circumburst environment models.

Findings

No optical transient detected at m_i=24.7 mag within 2.2 to 1938.1 seconds after burst

Constraints on burst energy >1e44 erg and circumburst density >1e4 cm^-3

Limits inform models of the burst environment and emission mechanisms

Abstract

We present deep Apache Point Observatory optical observations within seconds of the outburst of the periodic fast radio burst (FRB) 180916.J0158+65 obtained on 3 September 2020. 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), we did not detect any transient optical emission at m_i=24.7~mag (3-sigma) from 2.2 to 1938.1 seconds 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 >1e44 erg and the circumburst density was >1e4 cm-3.