[vsnet-grb-info 21340] GRB 181123B: Gemini-North optical detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23439
SUBJECT: GRB 181123B: Gemini-North optical detection
DATE:    18/11/23 20:30:11 GMT
FROM:    Wen-fai Fong at Northwestern U  <wfong at northwestern.edu>

W. Fong (Northwestern Univ.), N. R. Tanvir (U. Leicester) and A. J. Levan (U. Warwick) report on behalf of a larger collaboration:

"We observed the location of the short-duration GRB 181123B (Lien et al., GCN 23432) with the Gemini Multi-Object Spectrograph (GMOS) mounted on the Gemini-North 8-meter telescope. We obtained 18x90-sec each in the i-band at a mid-time of 2018 November 23.618 UT (9.2 hr post-burst). The observations have an airmass range of 1.4-1.9, 0.9” seeing, and were taken in thick, variable clouds. We detect a faint source consistent with the UVOT-enhanced XRT position (Evans et al., GCN 23433; Osborne et al., GCN 23434) at the position:

RA(J2000) = 12:17:27.95
Dec(J2000) = +14:35:52.5
+/- 0.05" in each coordinate

The source has a preliminary magnitude of i~23.32 +/- 0.25 AB mag, not corrected for Galactic extinction. Both astrometry and photometry are calibrated to SDSS. The source appears to be marginally extended; however, at present it is too weak of a detection to make a strong conclusion.

Further observations are planned. We thank the Gemini staff, and in particular observers Julia Scharwaechter and Michael Hoenig, for their assistance with these observations."