Results from GROCSE, A Real-Time Search for \\ the Optical Counterparts of Gamma-Ray Bursts

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Session 111 -- Gamma Ray Bursts
Oral presentation, Thursday, 12, 1995, 10:00am - 11:30am

[111.07] Results from GROCSE, A Real-Time Search for \\ the Optical Counterparts of Gamma-Ray Bursts

Carl Akerlof, Brian Lee (Univ.~of Michigan), Scott Barthelmy, Thomas Cline, Neil Gehrels (NASA/Goddard SFC), Elden Ables, Richard Bionta, Linda Ott, Hye-Sook Park (LLNL), Gerald Fishman, Chryssa Kouveliotou, Charles Meegan (NASA/Marshall SFC), Donald Ferguson (WorldView Imaging Corporation)

Since January 12, 1994, an experiment called GROCSE (Gamma-Ray Optical Counterpart Search Experiment) has been monitoring the night sky for the optical counterparts of gamma-ray bursts. The basic detector consists of an 8.9 cm aperture electronic camera attached to a rapid slewing computer-controlled mount. This device is activated by the real-time telemetry data stream from the BATSE instrument onboard the Compton Gamma-Ray Observatory. The BATSE signals are filtered and broadcast via the BACODINE network to Lawrence Livermore National Laboratory using the UNIX socket communication protocol linked via Internet. The typical response time to obtain the first image is approximately 15 seconds following the initial burst detection. The field of view of the camera is restricted to 0.18 sterdians to match the online angular position errors associated with the BACODINE GRB coordinate estimates. Under dark skys, the limiting detection magnitude is 8.5. By October 1994, the GROCSE camera has been triggered by seven BATSE bursts. Data from these events are being analyzed to provide either a detection or an upper limit for GRB optical luminosity. Results will be presented for the ratio of optical to gamma-ray intensity. A second generation camera system is currently under development that is expected to push the limiting magnitude to approximately $m_v$ = 13. The status of this effort will be briefly reported.

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