GCN Circular 8501

P. D'Avanzo, S. Covino, L.A. Antonelli, D. Malesani, D. Fugazza, L.  
Calzoletti,  S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini,  
V. D'Elia,  F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta,  C.  
Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E.J.A.  
Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella,  
G. Stratta, G. Tagliaferri, G. Tosti, V. Testa, S.D. Vergani, F.  
Vitali report on behalf of the REM team:

The robotic 60-cm REM telescope located at La Silla (Chile) observed  
automatically the field of the GRB 081109 (Immler et al. GCN 8500
Not found
 
 
) on  
Nov 09 starting about 52 s after the burst.  Observations were  
carried out at high airmass (~ 6). We clearly detect an object in our  
first K-band image inside the XRT error box (Immler et al. GCN 8500
Not found
 
 
)  
at the following coordinates (J2000):

R.A. = 22:03:09.72
Dec = -54:42:39.5

with an uncertainty of 1.0". The object is not visible in the single  
RJH images taken approximately at the same epoch. Coadding all the  
available RJH images taken around the same epoch we obtain the  
following results:

Mean_obs         texp   #frames_coadd    Filter    Mag

Nov 09.30604 UT  780 s     11   R    > 16.5 (3sigma)
Nov 09.30707 UT   65 s      4    J    > 15.8 (3sigma)
Nov 09.29936 UT   75 s      7    H    15.47 � 0.26
Nov 09.30145 UT   10 s      1    K    14.51 � 0.27

The object subsequently brightened, reaching K = 14.27 � 0.16 on Nov  
09.30612 UT. No object is detected at this position in the 2MASS and  
USNO catalogs. We propose this is the NIR afterglow of GRB 081109. We  
cannot indeed exclude the possibility that the lack of detection  
blueward of the H band is due to an high-redshift nature of this  
event. We note, however, that the large airmass badly affects the  
images in the J and R bands, so that our limits are not very  
constraining

Further deep optical/NIR observations are encouraged.