TITLE:   GCN CIRCULAR
NUMBER:  31507
SUBJECT: GRB 220118A: 2.2m CAHA/CAFOS detections
DATE:    22/01/20 17:33:32 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), D. B. Malesani (Radboud Univ. and DAWN/NBI), 
A. de Ugarte Postigo (Obs. Cote d'Azur), C. C. Thoene (HETH/ASU CAS 
Ondrejov), M. Blazek (HETH), J. F. Agui Fernandez (HETH/IAA-CSIC), A. 
Guijarro, and A. Fernandez (both CAHA) report:

We observed the afterglow of GRB 220118A (Swift detection: Klingler et 
al., GCN #31490; Fermi/GBM Detection: Fletcher et al., GCN #31506; 
afterglow detections: Hosokawa et al., GCN #31493; Kumar et al., GCN 
#31496; Belles & Klingler, GCN #31498) with CAFOS, mounted on the 2.2 m 
telescope, at the Calar Alto Observatory (Almeria, Spain). The 
observation started at 01:09:11 UT on 19 January 2022 (6.81 hr after the 
GRB) and consisted of 10 x 150 s integrations in the r' band and 9 x 150 
s in the i' band. Observations were hampered by the Wolf Moon, but 
otherwise conditions were very good (1".1 seeing, very good 
transparency).

The afterglow is faintly detected in the stacked images in each filter. 
Against several Pan-STARRS stars, we measure:

r' = 22.40 +/- 0.18 mag at 0.29916 d after trigger, and

i' = 22.07 +/- 0.17 mag at 0.32064 d after trigger.

No further observations are planned.