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GCN Circular 985

Subject
GRB010222, possible increase of optical decay slope
Date
2001-02-24T18:59:09Z (23 years ago)
From
Nicola Masetti at ITeSRE,CNR,Bologna <masetti@tesre.bo.cnr.it>
N. Masetti, E. Palazzi (ITeSRE, CNR, Bologna), E. Pian (Oss. Astron. Trieste),
A. Zacchei, A. Magazzu, M. Pedani, F. Ghinassi (TNG) and M. Mignoli
(Oss. Astron. Bologna), on behalf of a larger collaboration, report:


"We observed the optical transient (Henden, GCNs #961, #962) associated
with GRB010222 (Piro, GCNs #959, #960) in the R band with TNG+Dolores
on 2001 Feb. 24.236 UT (i.e. ~2 days after the GRB). The total exposure
time was 4 minutes; seeing was 0.9 arcsec.

Using star `A' by Stanek et al. (GCN #970) as reference, we note that our
measurement, R = 20.88 +- 0.03, is ~0.4 mag fainter than the extrapolation
of the t^{-0.9} decay measured by Price et al. (GCN #973), Fynbo et al.
(GCN #975) and Stanek et al. (GCN #983). 

The power-law decay between our TNG measurement and that made in the R
filter by Stanek et al. (GCN #983) on Feb. 23.45 has an index ~1.3. Thus,
our data seem to suggest that a break occurred at ~1 day after the GRB in 
the R-band light curve of the afterglow.

Further observations are strongly encouraged to confirm (or reject) this
result.".

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