[vsnet-grb-info 15775] GRB 141109A: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17063
SUBJECT: GRB 141109A: TAROT La Silla observatory optical observations
DATE:    14/11/12 23:17:57 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

Klotz A., Turpin D. (IRAP-CNRS-OMP),
Boer M., Gendre B., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA),
Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 141109A detected by SWIFT
(trigger 618024) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 93s after the GRB trigger
(18s after the notice). The elevation of the field increased from
10 degrees above horizon and weather conditions were good.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
This image was obtained when the gamma emission was still
very active. We do not detect any OT with a limiting magnitude of:

t0+93s to t0+153s : Rlim = 12.9

The optical afterglow reported by Covino (GCNC 17039)
is detected in co added images (in tracking mode):

  t0+465s to  t0+655s : Rlim = 17.3
  t0+665s to  t0+868s : R = 16.8
  t0+879s to t0+1069s : R = 16.1
t0+1093s to t0+1283s : R = 16.7
t0+1293s to t0+1497s : Rlim = 17.2

The TAROT photometry indicates that the optical afterglow
reached the maximum of light about 16 minutes after the
Swift trigger.

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.