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Astron. Astrophys. 345, L51-L54 (1999)

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Letter to the Editor

Lightcurves of cosmological gamma-ray bursts

E.V. Derishev, V. V. Kocharovsky and Vl.V. Kocharovsky

Institute of Applied Physics, Russian Academy of Science, 46 Ulyanov st., 603600 Nizhny Novgorod, Russia (derishev, kochar@appl.sci-nnov.ru)

Received 30 March 1999 / Accepted 17 April 1999


It is shown that in a typical fireball of cosmological GRB a neutron component is initially present and has the energy of the order of the proton-electron component. Free neutrons change essentially the dynamics of a relativistic shock formed by the ejected material in the surrounding medium. The neutron flow may decouple from the proton one or may not. Also, neutrons may decay before the shock of proton origin decelerates significantly or after that. According to these possibilities there are four types of bursts possessing lightcurves with different global appearance. We point out a number of lightcurve features expected to be correlated. For example, the height, delay time and duration of the secondary pulse are related to each other. We show that two-peaked lightcurves may be as common as single-peaked ones.

Key words: gamma rays: bursts – ISM: jets and outflows – shock waves

© European Southern Observatory (ESO) 1999

Online publication: April 28, 1999