TITLE:   GCN CIRCULAR
NUMBER:  21311
SUBJECT: GRB 170710A: Gemini-S candidate counterpart
DATE:    17/07/10 11:04:40 GMT
FROM:    Antonino Cucchiara at UVI  <antonino.cucchiara@uvi.edu>

A. Cucchiara (U. of the Virgin Islands) reports on
behalf of a larger collaboration:

"On July 10.17UT we imaged the field of GRB 170710A
(Evans et al. GCN 21308, 21309, Osborne et al. GCN 21310)
with the Gemini-South Telescope equipped with the GMOS camera.
We obtained 4x900s spectra covering the 5660-10300 Angstrom
wavelength range.
In our single 180 seconds acquisition image in i' band centered
on the Swift-XRT position we identified an uncatalogued
point-like sources at the edge of the refined position:

RA= +15:27:16.87
Dec= -38:29:06.0

Using nearby USNO-B1 stars for calibration, we measure a
magnitude of i' = 21.13 +/- 0.05.
At this point it is not possible to assess the variability
of this possible counterpart.

Preliminary analysis of the spectra reveals a faint trace
clearly visible down to the blue end of the spectrum.
No clear absorption or emission features are evident,
but more detailed analysis of the data is in progress.

We thank the Gemini staff for the prompt response, in particular
Veronica Firpo."