SCUBA sub-millimeter observations of gamma-ray bursters - I. GRB 970508, 971214, 980326, 980329, 980519, 980703, 981220, 981226

We discuss our ongoing program of Target of Opportunity observations of gam ma-ray bursts (GRBs) using the SCUBA instrument on the James Clerk Maxwell Telescope. We present observations of GRB 970508, 971214, 980326, 980329, 9 80519, 980703, 981220, and 981226. Our most important result to date is the detection of a fading counterpart to GRB 980329 at 850 mu m. Although it proved to be difficult to find the i nfrared counterpart to this burst, the sub-millimeter flux was relatively b right. This indicates that the brightness of this counterpart (corrected fo r absorption) was very similar to GRB 970508. The radio through sub-millime ter spectrum of GRB 980329 is well fit by a power law with index alpha = +0 .9. However, we cannot exclude a nu(1/3) power law attenuated by synchrotro n self-absorption. An alpha similar to +1 VLA-SCUBA power law spectrum is d efinitely ruled out for GRB 980703, and possibly also for GRB 980519. We cannot rule out that part of the sub-millimeter flux from GRB 980329 com es from a dusty star-forming galaxy at high redshift, such as the ones rece ntly discovered by SCUBA. Any quiescent dust contribution will be much larg er at submillimeter than at radio wavelengths. Both a high redshift and lar ge dust extinction would help explain the reddening of the counterpart to G RB 980329. The large intensity of this burst might then indicate that beami ng is important.