BATSE/OSSE rapid burst response

The BATSE and OSSE instrument teams have modified flight software to promptly (within 2 min of trigger) slew the OSSE detectors to burst locations determined on-board by BATSE. This enables OSSE to make sensitive searches for prompt and delayed post-burst line and continuum emission above 50 keV. In the best cases our sensitivity will be more than an order of magnitude better than any other search in this energy range. We expect to slew to 1–2 bursts per month, based on the OSSE FOV and BATSE event rate. Detections or limits from continued operation of this system may provide significant constraints on burst models. As an example of the observations made using this system, we present preliminary limits for post-burst emission from GRB 950223 on several time scales.     

Radio counterpart searches of gamma ray bursts

Radio observations may be one of the most promising but least explored bands of the spectrum to search for the counterparts of gamma ray bursters. We describe several ongoing experiments with demonstrated high sensitivity to monitor gamma ray bursts for evidence of a flaring or fading counterpart in the days, weeks and months following the original event.     

Osse limits on pre- and post-burst emission

The existence of either pre- or post-burst emission can provide substantial new information about the burst source and its local environment. We have data from serveral events serendipitously in or near the OSSE field of view at the time of the burst. We present pre- and post-burst flux limits from one such event, GRB 940301. The OSSE data for other periods when scheduled observations have included burst locations will enable us to search for pre- and post- burst emission on many time scales.     

Search for a radio counterpart to GRB 940301 with westerbork

The COMPTEL instrument onboard theCompton Gamma-Ray Observatory imaged the bright gamma-ray burst GRB 940301 within 1.6 hours of the event, with a mean 1 error radius of 1.5°. The error region was subsequently refined by combining the COMPTEL location with the arc derived from differences in the event arrival time at the Ulysses and BATSE detectors. Westerbork observations of the COMPTEL error region began on March 4 1994 at 21 cm, however coverage of the refined position was not obtained until 32 days after the GRB occurrence, by which time the operating wavelength had changed to 92 cm. We have constrained the level of variability of sources within the triangulation arc-COMPTEL 2 error box region to be less than 40 mJy (5 upper limit) at 92 cm 41 days after the burst.     

Preliminary results of optical searches of IPN3 localizations

We present preliminary results from deep optical searches of small (5 arcmin²) GRB error boxes determined using the Third Interplanetary Network (IPN³). Two of these fields also have been found to have historical OT events located within the IPN³ error boxes. We compare the preliminary results of these searches to those reported for the larger IPN¹ error boxes. The small size of the IPN³ error boxes should allow a test of the hypothesis suggested by the IPN¹ study that there are excess QSOs associated with the GRB fields.     

Observations of GRBs with the Explosive Transient Camera

The Explosive Transient Camera (ETC) has been performing automatic observations of the night sky since 1990. Since the launch of the Compton Gamma-Ray Observatory, the times and localizations of-ray bursts detected by the Burst and Transient Source Experiment (BATSE) have been compared with ETC observations to determine whether the ETC had observed a -ray burst in progress. To date, six temporal and spatial correlations have been found, but no new optical radiation has been detected. In this paper, we present current results of ETC/BATSE correlated observations and describe plans for future observations.     

Ground-based optical CCD experiments for GRB and optical transient detection

We present details of one operational ground-based experiment for optical detection of GRBs and two which are under consideration/development. The wide-field CCD camera is already in manual burst alert operation with promising results. The Optical Transient Monitor is a CCD-based double monitor suitable for network use for reliable detection of short-lived phenomena in the sky. The system is well suited for correlated efforts with GRB projects. The third experiment is a robotic telescope with automatic response to GRB burst alert messages received via the Internet link. It is expected to get CCD frames with a FOV of 20 deg (needed for BACODINE triggers) of positions of newly detected GRBs within 1 minute.