A search for early optical emission from short- and long-duration gamma-ray bursts

Gamma-ray bursts of short duration may harbor vital clues to the range of phenomena producing bursts. However, recent progress from the observation of optical counterparts has not benefited the study of short bursts. We have searched for early optical emission from six gamma-ray bursts using the telephoto array on the Robotic Optical Transient Search Experiment I. Three of these events were of short duration, including GRB 980527, which is among the brightest short bursts yet observed. The data consist of unfiltered CCD optical images taken in response to Burst and Transient Source Experiment triggers delivered via the GRB Coordinates Network. For the first time, we have analyzed the entire 16 degrees x 16 degrees field covered for five of these bursts. In addition, we discuss a search for the optical counterpart to GRB 000201, a well-localized long burst. Single-image sensitivities range from 13th to 14th magnitude around 10 s after the initial burst detection and from 14 to 15.8 mag 1 hr later. No new optical counterparts were discovered in this analysis suggesting short-burst optical and gamma-ray fluxes are uncorrelated.