TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2535 SUBJECT: GRB 040223: Deep NIR NTT observations DATE: 04/02/26 21:21:38 GMT FROM: Gianpiero Tagliaferri at OAB-INAF 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) 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). 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.