[vsnet-grb-info 19839] GRB 170921A: TAROT Calern observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21903
SUBJECT: GRB 170921A: TAROT Calern observatory optical observations
DATE:    17/09/21 19:35:55 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

Klotz A., Atteia J.L. (CNRS-OMP-IRAP),
Boer, M., Laugier, R. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:

We imaged the field of GRB 170921A detected by SWIFT
(trigger 773509) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 3.86h after the GRB trigger.
The elevation of the field increased from
12 degrees above horizon and weather conditions
were good.

We co-added a series of exposures.
No OT is detected with a limiting magnitude of:

t0+3.86h to t0+4.23h : Rlim = 19.5

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.