TITLE:   GCN CIRCULAR
NUMBER:  35762
SUBJECT: GRB 240218A: LBT H-band detection
DATE:    24/02/20 16:04:34 GMT
FROM:    Elisabetta Maiorano at INAF <elisabetta.maiorano@inaf.it>

A. Rossi, E. Maiorano, G. Stratta (INAF-OAS), P. D'Avanzo (INAF-OAB) report on behalf of the CIBO collaboration:

We observed the field of the long GRB 240218A, detected by Swift-BAT (Page et al., GCN 35742), Fermi-GBM (Veres and Meegan, GCN 35755) and Konus-Wind (Svinkin et al., GCN 35758), and with spectroscopic redshift of z=6.782 (Saccardi et al., GCN 35756).

We obtained 40 min of J-, 1 hr of H- and 1.2 hr of Ks-band imaging with the LUCI cameras mounted on LBT (Mt. Graham, AZ, USA) on 2024-02-19 (mid-time 08:20:00 UT), 1.3 days after the burst trigger. 

We clearly detect the NIR afterglow (D'Avanzo et al., GCN 35747, Malesani et al., GCN 35749) and measure a preliminary H-band magnitude of H ~ 20.2 AB, calibrated against 2MASS field stars, and not corrected for the foreground Galactic extinction.

We acknowledge the excellent support of A. Cardwell e J. Williams from the LBTO staff and E. Marini from LBT-INAF staff, in obtaining these observations.