TITLE:   GCN CIRCULAR
NUMBER:  31157
SUBJECT: GRB 211106A: Second HST Observation
DATE:    21/12/02 17:42:39 GMT
FROM:    Charles Kilpatrick at Northwestern U  <ckilpatrick@northwestern.edu>

C. D. Kilpatrick (Northwestern), E. Berger (Harvard), and W. Fong (Northwestern) report on behalf of a larger collaboration:

"We re-observed the location of the short GRB 211106A (GCNC #31049) with the Hubble Space Telescope starting on 2021 December 1.46 (25.26 days post-trigger; 6.1 days after Visit 1 - GCNC #31146) using WFC3/F110W for 2 orbits, as part of program 16303 (PI: Berger).  

The source identified in our first HST observation (GCNC #31146) is still detected, with an unchanged magnitude of m(F110W) ~ 25.6.  Digital image subtraction between the two epochs does not reveal any emission at the location of the source to a 5-sigma limit of ~27 mag.

The lack of fading over the 6-day time baseline suggests that this source is not an afterglow or kilonova.  Instead, it is likely to be either the host galaxy of GRB 211106A, or an unrelated background galaxy if the GRB itself is associated with the galaxy at z=0.097. The absolute magnitude of the NIR source if it is also located at z=0.097 is M(F110W) ~ -12.7,  too luminous to be a globular cluster."