Astron. Astrophys. Suppl. Ser. 138, 463-464

BeppoSAX detection and follow-up of GRB 980425

E. Pian¹ - L. Amati¹ - L.A. Antonelli² - R.C. Butler³ - E. Costa⁴ - G. Cusumano⁵ - J. Danziger⁶ - M. Feroci⁴ - F. Fiore⁷ - F. Frontera^1,8 - P. Giommi⁷ - N. Masetti¹ - J.M. Muller⁷ - T. Oosterbroek⁹ - A. Owens⁹ - E. Palazzi¹ - L. Piro⁴ - A. Castro-Tirado¹⁰ - A. Coletta⁷ - D. Dal Fiume¹ - S. Del Sordo⁵ - J. Heise¹¹ - L. Nicastro⁵ - M. Orlandini¹ - A. Parmar⁹ - P. Soffitta⁴ - V. Torroni⁷ - J.J.M. in 't Zand¹¹

Send offprint request: pian@tesre.bo.cnr.it

1 - Istituto Te.S.R.E., CNR, via Gobetti 101, I-40129 Bologna, Italy
2 - Osservatorio Astronomico di Roma, sede di Monteporzio Catone, Via Frascati 33, 00040 Monteporzio Catone, Italy
3 - Agenzia Spaziale Italiana, Viale Regina Margherita 120, Roma, Italy
4 - I.A.S., C.N.R., Via Fosso del Cavaliere, Area della Ricerca di Tor Vergata, I-00131 Rome, Italy
5 - I.F.C.A.I., CNR, via Ugo La Malfa 153, I-90146 Palermo, Italy
6 - Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, I-34131 Trieste, Italy
7 - BeppoSAX Scientific Data Center, Via Corcolle 19, I-00131 Rome, Italy
8 - Dip. di Fisica, Univ. di Ferrara, Via Paradiso 11, I-44100 Ferrara, Italy
9 - Astrophysics Division, SSD of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands
10 - IAA-CSIC, Granada, Spain and LAEFF-INTA, Madrid, Spain
11 - Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Received March 16; accepted July 5, 1999

Abstract:

We present BeppoSAX GRBM and WFC light curves of GRB 980425 and NFI follow-up data taken in 1998 April, May, and November. The first NFI observation has detected within the $8^{\prime}$ radius error box of the GRB an X-ray source positionally consistent with the supernova SN 1998bw, exploded within a day of GRB 980425, and a fainter X-ray source, not consistent with the position of the supernova. The former source is detected in the following NFI pointings and exhibits a decline of a factor of two in six months. If it is associated with SN 1998bw, this is the first detection of hard X-ray emission from a Type I supernova. The latter source exhibits only marginally significant variability. Based on these data, it is not possible to select either source as a firm candidate for the GRB counterpart.

Key words: gamma-rays: bursts