[vsnet-grb-info 11160] GRB 111117A: further NOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12572
SUBJECT: GRB 111117A: further NOT observations
DATE:    11/11/19 10:35:25 GMT
FROM:    Giorgos Leloudas at Dark Cosmology Centre  <giorgos at dark-cosmology.dk>

Giorgos Leloudas, Daniele Malesani (DARK) and Dong Xu (WIS) report on behalf of a larger collaboration:

We have continued observing GRB 111117A (Mangano et al., GCN 12559) using ALFOSC on the Nordic Optical Telescope (NOT).
In addition, we have made a more careful analysis of the data reported in Andersen et al. (GCN  12563).
Our R-band photometry, calibrated to USNO B1, can be summarized in the following table:

Stack 			mid-time		R			
5x300 s 			7.93 hr		23.36+-0.15	
5x300 s		 	9.88 hr		23.98+-0.24	
8x300 s 			36.38 hr		23.74+-0.20  

If we instead stack all the images obtained during the first night (10x300s, mid-time 8.91 hr after the GRB), we obtain R = 23.81+-0.17.

Based on the NOT observations only, we suggest that there is some evidence of fading (albeit at low significance) between the observations obtained at 7.93 hr and later, indicating that at that time there was some contribution from the GRB afterglow to the underlying host galaxy light.

We are grateful to the NOT observers, Kristian Vida (Konkoly Observatory) and
Heidi Korhonen (U. Copenhagen) for obtaining these observations.