Free Access
Astron. Astrophys. Suppl. Ser.
Volume 138, Number 3, September 1999
Gamma-Ray Bursts in the Afterglow Era Contents Rome, November 3-6, 1998
Page(s) 521 - 522
Published online 15 September 1999
DOI: 10.1051/aas:1999336

Astron. Astrophys. Suppl. Ser. 138, 521-522

Temporal evolution of the pulse width in GRBs

E. Ramirez-Ruiz12 and E.E. Fenimore2

1 - Facultad de Ciencias, Universidad Nacional Autónoma de México, Distrito Federal, 04510, Mexico
2 - Los Alamos National Laboratory, Mail Stop D436, Los Alamos, NM 87545, U.S.A.

Received December 18, 1998; accepted March 23, 1999


Many cosmological models of GRBs envision the energy source to be a cataclysmic stellar event leading to a relativistically expanding fireball. Particles are thought to be accelerated at shocks and produce nonthermal radiation. The highly variable temporal structure observed in most GRBs has significantly constrained models. By using different methods of statistical analysis in the time domain we show that the width of the pulses in GRBs time histories remain remarkably constant throughout the classic GRB phase. If the emission sites lie on a relativistically expanding shell, we determine both the amount of deceleration and the angular spread of the emitting region from the time dependency of the pulse width. We find no deceleration over at least 2/3 of the burst duration and angular spreads of the complete emitting shell that are substancially smaller than $\Gamma^{-1}$. The lack of temporal evolution of the pulse width should be explained by any fireball shock scenario.

Key words: gamma-ray: bursts

Copyright The European Southern Observatory (ESO)

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.