GCN Circular 2897
Subject
GRB 041218: optical observations
Date
2004-12-23T17:25:42Z (19 years ago)
From
Graziella Pizzichini at IASF/CNR,Bologna <pizzichini@bo.iasf.cnr.it>
P. Ferrero (IASF/CNR- Bologna/ Osservatorio e Universita' di Teramo),
G. Pizzichini (IASF/CNR- Bologna), G. Greco, C. Bartolini, A. Guarnieri,
and A. Piccioni(Universita' di Bologna), and R.Gualandi (INAF/ Bologna Observatory)
report:
We observed the optical afterglow of INTEGRAL GRB 041218 (Mereghetti et
al.,GCN 2858) detected by Torii (GCN 2860) and Gorosabel et al. (GCN
2861), using the 152 cm telescope in Loiano (Bologna University) on
December, 18 (Greco et al., GCN 2863) in clear sky conditions and strong
winds (seeing ~3).
Our photometric analysis of the images gives the following results:
----------------------------------------------------
Filter UT mean magOT exp
----------------------------------------------------
Rc Dec 18.758 19.74 +- 0.07 600s
Rc Dec 18.765 19.74 +- 0.06 600s
Rc Dec 18.781 20.04 +- 0.07 600s
Rc Dec 18.792 20.27 +- 0.07 600s
Rc Dec 18.800 20.58 +- 0.09 600s
Rc Dec 18.807 20.45 +- 0.09 600s
Rc Dec 18.814 20.64 +- 0.09 600s
Rc Dec 18.824 20.63 +- 0.09 600s
Rc Dec 18.840 20.81 +- 0.08 2x600s
Rc Dec 18.854 20.90 +- 0.10 2x600s
Rc Dec 18.872 20.75 +- 0.09 3x600s
V Dec 18.906 >19.1 (1 sigma) 600s
Rc Dec 18.913 >21 (1 sigma) 600s
B Dec 18.895 >20.4 600s
----------------------------------------------------
In the time interval of our observations we find the same decay index
alpha = 1.4 given by D'Avanzo et al., GCN 2879, with the possible
exception of the Rc magnitude at UT 18.872, which is however still within
3 sigmas of the extrapolation from the other points.
The following stars have been used:
R.A.: 24.853910 Decl.:+71.385923
R.A.: 24.801607 Decl.:+71.360825
R.A.: 24.831858 Decl.:+71.343547
for Rc photometry;
R.A.: 24.909680 Decl.:+71.278967
for V upper limit (Henden, GCN 2869);
R.A.: 24.903450 Decl.:+71.379872
for B upper limit (USNOA.2).
This message can be quoted.