[vsnet-grb-info 11476] GRB 120119A: TAROT La Silla observatory optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12883
SUBJECT: GRB 120119A: TAROT La Silla observatory optical observations
DATE:    12/01/20 09:47:40 GMT
FROM:    Alain Klotz at CESR-CNRS  <Alain.Klotz at free.fr>

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 120119A detected by SWIFT
(trigger 512035) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 33.0s after the GRB trigger
(9.2s after the notice) using the trigger time origin
at 04:04:30.21 UT (Beardmore et al. GCNC 12859).
The elevation of the field increased from
67 degrees above horizon and weather conditions
were good. We observed during 4.35h until the
dawn allowing a continuous follow up of the afterglow
discovered by Beardmore et al. (GCNC 12859).

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 during the fading of the
gamma emission. We extracted three measurements from
the trail.

A first magnitude extraction is reported in the following
table. As noticed by LaCluyze et al. (GCNC 12864), the
optical emission decreased slowly in the range 33s to 200s,
then it increased to reach a maximum R=16.8 at 850 +/- 50s.
A decay phase alpha=1.3 occured between 10^3 and 10^4 seconds.
As noticed by Elenin et al. (GCNC 12871) the begining of a
plateau is suspected after 10^4 seconds. The end of the
night over Chile does not allow to conclude definitively.

Note that the GRB was also observed at TAROT Calern (France)
but data are poor due to the low elevation of the field.
However, the afterglow is also detected in the TAROT Calern
images.

------------------------------------------
  t1(min)    t2(min)     mag    dmag
------------------------------------------
     0.55       0.85    16.96    0.30
     0.85       1.15    17.15    0.30
     1.15       1.55    17.05    0.30
     1.67       2.17    17.32    0.16
     2.34       2.84    17.37    0.12
     3.01       3.51    17.58    0.22
     3.67       4.17    17.53    0.17
     4.34       4.84    17.27    0.17
    10.36      11.86    17.02    0.26
    12.03      13.53    16.87    0.20
    13.70      15.20    17.03    0.15
    15.37      16.87    16.94    0.18
    17.03      18.53    17.19    0.29
    18.70      20.20    17.19    0.11
    21.31      22.81    17.27    0.24
    22.97      24.47    17.37    0.16
    24.64      26.14    17.35    0.09
    26.31      27.81    17.32    0.19
    27.98      29.48    17.40    0.06
    29.64      31.14    17.59    0.05
    35.98      38.98    17.65    0.05
    39.15      42.15    18.00    0.21
    45.48      48.48    18.09    0.06
    48.65      51.65    18.31    0.25
    55.66      58.66    18.39    0.15
    58.83      61.83    18.58    0.26
    42.32      84.94    18.51    0.12
    65.16      91.28    19.10    0.15
    95.40     126.40    19.51    0.09
   129.73     195.34    19.78    0.12
   199.45     261.71    19.90    0.08