GCN Circular 2535

G. Tagliaferri, D. Fugazza, S. Covino, N. Cucchiara, P. D'Avanzo,
S. Kalogerakos, A. Simoncelli, F.M. Zerbi (INAF-OAB);
G. Chincarini  (UNIMIB & INAF-OAB); O. Hainaut (ESO-La Silla);
G.L. Israel, L. Stella (INAF-OAR); D. Malesani (SISSA);
on behalf of a larger collaboration report:

We observed the field of the INTEGRAL GRB 040223 (Gotz et al. GCN 2525
Not found
 
 
)
with SofI at the ESO-NTT telescope in the JHKs filters. We observed this
field three times, at Feb 24.258, Feb 24.383 and Feb 25.361 UT (i.e. 0.70,
0.82, and 1.8 days after the GRB). In the Ks-band the seeing was of 1.0,
0.6 and 0.7 arcsec, respectively.

We detect 32 sources with Ks magnitude between 15.0 and 19.9  within a
square box of 12.5 arcsec, which corresponds to the XMM-Newton error
circle  (Breitfellner et al. GCN 2530
Not found
 
 
). The brightest five have the 
following
magnitudes (calibrated to the 2MASS):

 Ra(2000)   Dec(2000)    K1s              K2s             K3s
-----------------------------------------------------------------------
16:39:30.2 -41:56:03.3  14.91 +/- 0.11   14.93 +/- 0.08  15.00 +/- 0.10
16:39:29.3 -41:56:01.2  15.48 +/- 0.11   15.44 +/- 0.08  15.52 +/- 0.10
16:39:29.5 -41:55:59.8  15.55 +/- 0.12   15.58 +/- 0.09  15.61 +/- 0.10
16:39:29.6 -41:56:08.8  16.28 +/- 0.12   16.15 +/- 0.08  16.25 +/- 0.10
16:39:29.5 -41:56:06.2  16.70 +/- 0.12   16.62 +/- 0.09  16.76 +/- 0.10

We do not observe significant variability for the sources detected in the
XMM-Newton error box between the three exposures. Therefore, we have no
indication of a transient associated with the XMM-Newton source. A full
analysis of these data is in progress. More observations at ESO are not
planned.

For the NTT SofI Ks finding charts and the list of sources detected in 
the XMM-Newton
error box, see http://www.merate.mi.astro.it/~taglia/GRB040223/grb.html

We thank the ESO La Silla staff for their prompt reaction and support.
This message can be cited.