Gamma-ray burst 980329 and its X-ray afterglow

The gamma-ray burst (GRB) 980329 is the brightest gamma-ray burst detected so far with the Wide Field Cameras aboard BeppoSAX, in both gamma rays and X-rays. With respect to its fluence (2.6 × 10-5 ergs s-1 cm-2 in 50-300 keV), it would be in the top 4% of gamma-ray bursts in the 4B catalog (Meegan et al.). The time-averaged burst spectrum from 2 to 20 keV and from 70 to 650 keV can be well described by the empirical model of Band et al. The resulting photon index above the break energy is exceptionally hard at -1.32 ± 0.03. An X-ray afterglow was detected with the narrow-field instruments aboard BeppoSAX 7 hr after the event within the error box as determined with the Wide Field Cameras. Its peak flux is (1.4 ± 0.2) × 10-12 ergs s-1 cm-2 (2-10 keV). The afterglow decayed according to a power-law function with an index of -1.35 ± 0.03. GRB 980329 is characterized by being bright and hard and by lacking strong spectral evolution. © 1998. The American Astronomical Society. All rights reserved.