EDP Sciences
Free access
Issue A&A
Volume 393, Number 2, October II 2002
Page(s) 409 - 423
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20021038

A&A 393, 409-423 (2002)
DOI: 10.1051/0004-6361:20021038

Time resolved spectral analysis of bright gamma ray bursts

G. Ghirlanda1, A. Celotti1 and G. Ghisellini2

1  SISSA/ISAS, Trieste - V. Beirut 2-4, 34014 Trieste, Italy
2  Osservatorio Astronomico di Brera, via Bianchi 46, Merate (LC), Italy

(Received 15 January 2002 / Accepted 27 June 2002)

We present the time integrated and time resolved spectral analysis of a sample of bright bursts selected with $F_{\rm peak} \ge 20\
\mathrm{phot\ cm^{-2}\ s^{-1}}$ from the BATSE archive. We fitted four different spectral models to the pulse time integrated and time resolved spectra. We compare the low energy slope of the fitted spectra with the prediction of the synchrotron theory [ predicting photon spectra softer than $N(E)\propto E^{-2/3}$] , and test, through direct spectral fitting, the synchrotron shock model. We point out that differences in the parameters distribution can be ascribed to the different spectral shape of the models employed and that in most cases the spectrum can be described by a smoothly curved function. The synchrotron shock model does not give satisfactory fits to the time averaged and time resolved spectra. Finally, we derive that the synchrotron low energy limit is violated in a considerable number of spectra both during the rise and decay phase around the peak.

Key words: gamma rays: bursts -- methods: data analysis -- radiation mechanisms: non-thermal

Offprint request: G. Ghirlanda, ghirland@sissa.it

SIMBAD Objects

© ESO 2002

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)