WIDGET: System Performance and GRB Prompt Optical Observations

TL;DR

WIDGET is an automated wide-field telescope system designed to detect prompt optical emissions from GRBs, providing valuable data on their optical behavior before gamma-ray triggers and analyzing the rarity of bright events.

Contribution

This paper introduces the WIDGET system for real-time, wide-field optical monitoring of GRBs and reports on its operational performance and observational results since 2004.

Findings

No bright optical emission similar to GRB 080319B detected

WIDGET's synchronized observation efficiency is four times higher with HETE-2 than with Swift

GRB 080319B is identified as a rare event

Abstract

The WIDeField telescope for Gamma-ray burst Early Timing (WIDGET) is used for a fully automated, ultra-wide-field survey aimed at detecting the prompt optical emission associated with Gamma-ray Bursts (GRBs). WIDGET surveys the HETE-2 and Swift/BAT pointing directions covering a total field of view of 62 degree x 62 degree every 10 secounds using an unfiltered system. This monitoring survey allows exploration of the optical emission before the gamma-ray trigger. The unfiltered magnitude is well converted to the SDSS r' system at a 0.1 mag level. Since 2004, WIDGET has made a total of ten simultaneous and one pre-trigger GRB observations. The efficiency of synchronized observation with HETE-2 is four times better than that of Swift. There has been no bright optical emission similar to that from GRB 080319B. The statistical analysis implies that GRB080319B is a rare event. This paper summarizes the design and operation of the WIDGET system and the simultaneous GRB observations obtained with this instrument.