Bibcode
Masetti, N.; Palazzi, E.; Pian, E.; Mannucci, F.; Antonelli, L. A.; Di Paola, A.; Saracco, P.; Savaglio, S.; Amati, L.; Bartolini, C.; Bernabei, S.; Bettoni, D.; Covino, S.; Cristiani, S.; Desidera, S.; Di Serego Alighieri, S.; Falomo, R.; Frontera, F.; Ghinassi, F.; Guarnieri, A.; Magazzù, A.; Maiolino, R.; Mignoli, M.; Nicastro, L.; Pedani, M.; Piccioni, A.; Poggianti, B. M.; Testa, V.; Valentini, G.; Zacchei, A.
Bibliographical reference
Astronomy and Astrophysics, v.374, p.382-393 (2001)
Advertised on:
8
2001
Journal
Citations
63
Refereed citations
50
Description
The GRB010222 optical and near-infrared (NIR) afterglow was monitored at
the TNG and other Italian telescopes starting ~ 1 day after the
high-energy prompt event. The BVR light curves, which are the best
sampled, are continuously steepening and can be described by two power
laws, f(t) ~ t-alpha , of indices alpha1 ~ 0.7 and
alpha2 ~ 1.3 before and after a break occurring at about 0.5
days after the GRB start time, respectively. This model accounts well
also for the flux in the U, I and J bands, which are less well
monitored. The temporal break appears to be achromatic. The two K-band
points are not consistent with the above behaviour, and rather suggest a
constant trend. A low-resolution optical spectrum has also been taken
with TNG. In the optical spectrum we found three absorption systems at
different redshifts (0.927, 1.155 and 1.475), the highest of which
represents a lower limit to, and probably coincides with, the redshift
of the GRB. The broad-band optical spectral energy distributions do not
appear to vary with time, consistently with the achromatic behaviour of
the light curves. We compare our measurements with different afterglow
evolution scenarios and we find that they favor a transition from
relativistic to non-relativistic conditions in the shock propagation.
Based on observations collected at: the Italian Telescopio Nazionale
Galileo (TNG), operated on the island of La Palma by the Centro Galileo
Galilei of the CNAA (Consorzio Nazionale per l'Astronomia e
l'Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of
the Instituto de Astrofisica de Canarias; the Asiago Astronomical
Observatory, Italy; the Bologna Astronomical Observatory in Loiano,
Italy; the Campo Imperatore Astronomical Observatory, Italy, and TIRGO
infrared observatory, Switzerland.