Detectability Of Optical Transients With Timescales Of Subseconds

We search for optical transient sources with durations of similar to 0.1 to similar to 1.3 s using a data set obtained in the Organized Autotelescopes for Serendipitous Event Survey (OASES) observation campaign. Since the OASES observations were carried out using two independent wide-field and high-cadence observation systems monitored the same field simultaneously, the obtained data set provides a unique opportunity to develop a robust detection method for subsecond optical transients. In the data set of a selected field around the ecliptic and the Galactic plane, we find no astronomical event candidate that satisfies our detection criteria. From the nondetection result, we derive an upper limit on the event rate of subsecond transients around the ecliptic and the Galactic plane for the first time, obtaining similar to 0.090 and similar to 0.38 hr(-1) deg(-2) for m = 12 and 13 Vmag, respectively. In addition, future prospects of the subsecond-scale transient event surveys are discussed.