GCN Circular 31341

D A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (Obs. Cote d'Azur), C. 
C. Thoene, M. Blazek (both HETH), J. F. Agui Fernandez (HETH/IAA-CSIC),  
and S. Gongora (CAHA) report:

We observed the localization of GRB 211227A (Swift detection: Beardmore 
et al., GCN #31316; Enhanced XRT position: Goad et al., GCN #31322; 
MAXI/GSC Detection: Tominaga et al., GCN #31319) with CAFOS, mounted on 
the 2.2 m telescope, at the Calar Alto Observatory (Almeria, Spain). The 
observation started at 00:08:45 UT on 28 December 2021 (36.65 min after 
the GRB) and consisted of 30 x 90 s integrations in the i' band. 
Observing conditions were mediocre (wind, some clouds, 3" seeing).

Our combined image is centered at 0.04233 d after the trigger. No 
afterglow is detected in the XRT error circle, in agreement with other 
observations (Lipunov et al., GCN #31315; Hu et al., GCN #31318; Fu et 
al., GCN #31320; Strausbaugh et al., GCN #31321; Perley, GCN #31323; 
Malesani et al., GCN #31324; Belles et al., GCN #31328). This area is 
affected by the outer PSF wing of a bright nearby star, causing a 
variable background. Using an isolated SDSS star, we measure a limit 
away from the stellar PSF of i' > 23.4 mag, but caution this limit will 
be somewhat less deep in the XRT error circle.

Assuming the GRB is associated with the nearby galaxy at redshift z = 
0.228 (Malesani et al., GCN #31324), a comparison with the light curve 
of GRB 060614 (Kann et al. 2011, ApJ, 734, 96) reveals this limit is 
about 3 magnitudes fainter than the equivalent afterglow magnitude for 
GRB 060614 at the same redshift.