Issue |
A&A
Volume 438, Number 3, August II 2005
|
|
---|---|---|
Page(s) | 821 - 827 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20042534 | |
Published online | 18 July 2005 |
The puzzling case of GRB 990123: multiwavelength afterglow study
1
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy (formerly IASF/CNR, Bologna) e-mail: maiorano@bo.iasf.cnr.it
2
INAF - Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40126 Bologna, Italy
3
Dipartimento di Fisica, Università di Ferrara, via Paradiso 12, 44100 Ferrara, Italy
4
INAF - Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34100 Trieste, Italy
5
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Palermo, via La Malfa 153, 90146 Palermo, Italy (formerly IASF/CNR, Palermo)
6
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica, Sezione di Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy (formerly IASF/CNR, Roma)
7
Astrophysics Research Institute – Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK
8
INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
9
SRON, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
10
ESTEC/ESA, SCI-SDG, Keplerlaan 1, 2201 AZ, Noordwijk, The Netherlands
Received:
14
December
2004
Accepted:
15
April
2005
We report on the BeppoSAX data analysis of the afterglow of
Gamma-Ray Burst (GRB) 990123, one of the brightest GRBs detected by BeppoSAX.
Mainly due to its exceptional brightness, this is the only source for
which the Wide Field Cameras have allowed an early detection of the X-ray
afterglow between ~20 and 60 min after the GRB trigger. Besides,
again for the first time, high-energy emission from the afterglow was
detected up to 60 keV. For the X-ray afterglow we found a power-law decay
with index ; the spectrum has a power-law shape
with photon index
. The backward extrapolation of the
afterglow decay smoothly reconnects with the late GRB emission, thus
suggesting that both emissions are produced by the same phenomenon. An
extensive set of multiwavelength observations for the GRB 990123
afterglow made during the BeppoSAX pointing was collected from the
literature. The hard X-ray to radio range coverage allowed to construct a
spectral flux distribution and to perform an analysis of the GRB afterglow
in the context of the “fireball” model. We also report the results of
temporal and spectral analysis of an X-ray source serendipitously
observed about 22' north of the GRB afterglow, along with the optical
spectroscopy of its possible counterpart to establish the nature of this
source.
Key words: X-rays: general / gamma rays: bursts / radiation mechanisms: non-thermal / cosmology: observations
© ESO, 2005
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