In order to measure the predicted “optical end” of the GRB emission, we designed and are building the Burst Simultaneous Three-channel Instrument, the BSTI, shown on the left figure. It consists of

• Separate waveband to each camera via dichroics

• High time resolution without noise penalty via Electron Multiplied CCD cameras – allows cross-correlation with gamma-ray signal to determine if from same emission source

• Three filters, Sloan i’,r’,g’ allows measurement of power law slope, determination of synchrotron self-absorption frequency.

Through 2019 we (especially Research-Engineer Zhanat Maksut) are working hard on fabricating the BSTI and automating the measurement response of the telescope to GRB position alerts.

Synchrotron models which reproduce the gamma-ray spectrum of GRBs have clear predictions for optical emission (e.g. Shen & Zhang 2009). By measuring the optical slopes with multi-channel cameras, we can verify or eliminate this important model. The spectral slope of prompt GRB emission has never been measured in the optical bands before.

For more details, see Grossan, Kumar and Smoot, 2019 (submitted to JHEA https://arxiv.org/abs/1909.02152).