3 Follow up observations with BeppoSAX and other Satellites

Beside GRB 960720 (whose direction was observed after 6 weeks) 12 GRB direction were observed with NFI with delays ranging from 6.0 to 16.0 hours. GRB 980109 was not observed because of a poor aspect and GRB 980326 could not be pointed because of solar angle constraints. The detection of two afterglow sources starting from a BATSE trigger is only a part of the new scenario where BeppoSAX has now become part of a network that has significantly boosted its capability to produce new Gamma-Ray Burst science. In this moment BeppoSAX can be alerted by triggers originated from:

• a) BeppoSAX GRBM,
• b) BeppoSAX GRBM/WFC Quick Look Analysis (possibly helped from a GCN message).

BeppoSAX WFCs positions are distributed by e-mail to more than 200 addresses. These directions have been pointed by ASCA, ROSAT, XTE, ISO, XUV, HST plus numerous, ground based, optical, IR and Radio Telescopes.

BeppoSAX Narrow Field Instruments can also be pointed on directions provided by:

• a) RXTE All Sky Monitor, in one- or two-dimensional mode or PCA,
• b) IPN with Ulysses, BATSE, BeppoSAX, Wind and, more recently, NEAR,
• c) a combinations of these.

Partially stimulated by the BeppoSAX results other satellites have played a role in the game. An important improvement has been the implementation of the new LOCBURST capability. The prompt availability of BATSE coordinates with a precision below 2 degrees, via the GCN network (Barthelmy et al. 1998) made possible other strategies and procedures. RXTE is particularly suitable to make fast TOO pointing. In this short time the afterglow could be strong enough to be detected by PCA and actually a certain number of BATSE positions have been observed. Another important contribution has been the fast distribution of coordinates of GRB detected by ASM. Last but not least IPN-3 has become much faster. As mentioned above SAX itself could benefit of these developments but also ASCA (Murakami et al. 1998). The two major results not started from BeppoSAX WFCs have been, so far, an afterglow source (970828) from RXTE/ASM/PCA plus IPN plus ASCA and an afterglow source (980703) from RXTE/ASM plus SAX.