Precise gamma-ray burst (GRB) sources with rapid alerts

Gamma-ray burst afterglow studies in the optical and radio bands resulting from the source localization capabilities of BeppoSAX have revolutionized t he GRB discipline. More source locations, defined to minutes of are and wit h delays of only hours, are needed for additional follow-on and afterglow m easurements. The new, three-cornered, long-baseline interplanetary GRB netw ork (IPN) was created in late August, 1998, with the turn-on of the Near Ea rth Asteroid Rendezvous (NEAR) gamma ray monitor. The great distances invol ved in this system will make possible GRB source localizations of adequate precision for immediate small-field astronomical studies. The rate of produ ction should be over 20 per year. Alerts will be delayed by up to 27 hours per event, however, due to the fact of daily transmission from deep space v ehicles, but some fraction of the delays will be only a few hours. The IPN now includes Ulysses, at distances of up to 6 AU, the NEAR, now over 1.3 AU away, the GGS-Wind Konus at several tight-seconds distance, and the CGRO B ATSE gamma ray and RXTE x-ray experiments. Results will be distributed rapi dly and automatically using the well-known GRB coordinates distribution net work (GCN), that is currently processing CGRO BATSE and other GRB data to e nable rapid wide-angle counterpart searches (see, e.g., S. Barthelmy et al. , this Workshop). The spectacular 1979-March-5-like SGR event of 1998 Augus t 27 was the first event found with the renewed IPN (Cline at al., IAUC 700 2; Hurley et al., IAUC 7004; Marshall et al., IAUC 7005). This event, with the precisely known source direction of SGR 1900+14, confirmed the system c alibration. No classical GRBs were observed in the few weeks between August turn-on and preparation for this Workshop in early September, 1998, howeve r. Details are outlined below.