Astron. Astrophys. 355, 454-460 (2000)

BeppoSAX spectrum of GRB971214: evidence of a substantial energy output during afterglow

D. Dal Fiume ¹, L. Amati ¹, L.A. Antonelli ^2,3, F. Fiore ^2,3, J. M. Muller ^2,4, A. Parmar ⁵, N. Masetti ¹, E. Pian ¹, E. Costa ⁶, F. Frontera ^1,7, L. Piro ⁶, J. Heise ⁴, R.C. Butler ⁸, A. Coletta ³, M. Feroci ⁶, P. Giommi ², L. Nicastro ⁹, M. Orlandini ¹, E. Palazzi ¹, G. Pizzichini ¹ and M. Tavani <sup>10

1</sup> Istituto di Tecnologie e Studio delle Radiazioni Extraterrestri (TeSRE), C.N.R., via Gobetti 101, 40129 Bologna, Italy
² Beppo-SAX Scientific Data Center, Via Corcolle 19, 00131 Roma, Italy
³ Osservatorio Astronomico di Roma, Via Frascati 33, 00044 Roma, Italy
⁴ Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁵ Astrophysics Division, Space Science Department of ESA, ESTEC, P.O. Box 299, 2200 AG Noordwijk, The Netherlands
⁶ Istituto di Astrofisica Spaziale (IAS), C.N.R., Via Fosso del Cavaliere, 00133 Roma, Italy
⁷ Dipartimento di Fisica, Università di Ferrara, Via Paradiso 12, 44100 Ferrara, Italy
⁸ Agenzia Spaziale Italiana, Viale Regina Margherita 202, 00198 Roma, Italy
⁹ Istituto di Fisica Cosmica con Applicazioni all'Informatica (IFCAI), C.N.R., Via U. La Malfa 153, 90139, Palermo, Italy
¹⁰ Istituto di Fisica Cosmica "G. P. S. Occhialini", C.N.R., via Bassini 15, 20133 Milano, Italy

Received 4 August 1999 / Accepted 26 November 1999

Abstract

We report the X/-ray spectrum of GRB971214 and of its afterglow. The afterglow was measured few hours after the main event and for an elapsed time of more than two days. The measure of this GRB and afterglow is relevant due to its extreme, cosmological distance (z=3.42). The prompt event shows a hard photon spectrum, consistent with a broken power law with photon indices 0.1 below 20 keV and 1.3 above 60 keV. The afterglow spectrum, measured with the MECS and LECS BeppoSAX telescopes, is consistent with a power law with spectral photon index =1.6. Within the statistical accuracy of our measure no spectral evolution is detected during the observation of the afterglow. When integrated during the time span covered by BeppoSAX observations, the power in the afterglow emission, even with very conservative assumptions, is at least comparable with the power in the main event. The IR-to-X rays broad band spectrum is also presented, collecting data from the literature and adding them to the BeppoSAX measure. It shows that the predictions from synchrotron emission models is qualitatively confirmed. The BeppoSAX measurement of the X and ray spectrum of this GRB/afterglow is discussed in the framework of current theoretical models

Key words: gamma rays: bursts gamma rays: observations X-rays: general

Send offprint requests to: D. Dal Fiume - daniele@tesre.bo.cnr.it

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Contents

• 1. Introduction
• 2. Observations
• 3. The broad band spectrum of the afterglow
• 4. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: March 9, 2000
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