TOO: SEARCH FOR IR COUNTERPARTS TO GAMMA RAY BURSTS

in this discretionary time too proposal we outline a strategy for systematic iso observations of future gammaray bursts (grbs) in order to detect the infrared emission associated with the burst sources. the recent remarkable discoveries of fading (time scale of days) long wavelength afterglows (xray through to optical and radio) from a few grbs have radically improved our understanding of these enigmatic sources. the direct redshift measurement of the optical transient (ot) of grb970508 has yielded a value of z0.835 from both emission and absorption spectral features, providing the first direct evidence for the cosmological origin of grbs. these discoveries were made possible by the capability of the wide field camera (wfc) aboard the bepposax xray satellite, to rapidly localise grbs to within a virgul3. radius error circle. the fact that iso and sax, both european missions, are in orbit at the same time, provides an unprecedented opportunity to exploit this capability to the utmost. we request too observations of future grbs in the light of these new discoveries which could not have been anticipated at the time of the supplemental call. we anticipate that isocam will detect transient emission at 15microns, once the observations are made within a few days of the grb and that isophot will detect the host galaxy, which may be difficult to detect in the optical due to its likely dusty nature. as part of our strategy, we request further observations of grb970508 (requiring virgul1 hour), in order to confirm the pht detection of a faint 60um source consistent with the ot position and to further characterise the nature of this host galaxy. observations of a number of different grbs with iso will be crucial in determining the nature of the host galaxies and establishing commonalities between them and in the detection and monitoring of the mid to far infrared afterglow. this consortium has formed from a number of groups trun [truncated!, Please see actual data for full text]