Spectral evolution of gamma-ray bursts with BeppoSAX and correlation with X-ray afterglow properties

¹ Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, Via Gobetti 101, 40129 Bologna, Italy
² Dipartimento di Fisica, Università di Ferrara, Via Paradiso 11, 44100 Ferrara, Italy
³ LAEFF, Madrid, Spain
⁴ Istituto Astrofisica Spaziale, CNR, Via Fosso del Cavaliere, 00133 Roma, Italy
⁵ Space research Organization in the Netherlands, Utrecht, NL, The Netherlands
⁶ BeppoSAX Scientific Data Center, Via Corcolle, 00100 Roma, Italy
⁷ Istituto Fisica Cosmica e Informatica, CNR, Palermo, Italy
⁸ Istituto di Fisica Cosmica e Teconologie Relative, CNR, Via Bassini 15/A, 20133 Milano, Italy
⁹ Columbia Astrophysics Laboratory, New York, U.S.A.

Received: 21 January 1999
Accepted: 21 April 1999

Abstract

We report some comparative results of an investigation devoted to study the spectral evolution of a sample of Gamma-Ray Bursts. They were simultaneously detected with both the Gamma-Ray Burst Monitor and the Wide Field Cameras aboard the BeppoSAX satellite and were reobserved with the Narrow Field Instruments aboard the same satellite.