TITLE:   GCN CIRCULAR
NUMBER:  17313
SUBJECT: GRB 150120A: Gemini-North optical imaging
DATE:    15/01/20 07:51:01 GMT
FROM:    Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>

W. Fong (U. Arizona), R. Chornock (Ohio U.) and D. Fox (PSU) report:

"We observed the location of the possibly short GRB 150120A (D'Elia et al.,
GCN 17310) with the Gemini Multi-Object Spectrograph (GMOS) mounted on the
Gemini-North 8-m telescope starting on 2015 Jan 20.206 UT (2.0 hr after the
BAT trigger). We obtained 1800-sec in each of the riz-bands in 0.5" seeing.
Within the enhanced XRT position (Evans, GCN 17311), we do not detect any
optical sources in our images. Tied to SDSS, we calculate a 3-sigma limit
of r>26.3 AB mag.

We clearly detect two sources on the outskirts of the XRT position (Sources
A and B from P60 observations; Perley et al., GCN 17312), both of which
appear extended in our images. We do not find any evidence for variability
of these sources over the duration of our observations.

We thank Gemini observers and staff Sabrina Pakzad, Katherine Roth, Joe
Burchett, and Rongmon Bordoloi for the quick scheduling and execution of
these observations."