[vsnet-grb-info 13444] GRB 130605A: TAROT La Silla observatory optical decay

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14777
SUBJECT: GRB 130605A: TAROT La Silla observatory optical decay
DATE:    13/06/06 03:01:51 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

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

We analyzed TAROT La Silla images taken during the first hours
after the GRB 130605A (Holland et al. GCNC 14773).
We have a photometric follow-up of the afterglow
detected by Nicuesa Guelbenzu et al. (GCNC 14774).

All TAROT magnitudes are computed using the reference star
NOMAD-1 0565-0204137 (RA = 134.5240528 Dec. = -33.4675072 R=12.50).

The first TAROT image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
After substraction of an overlaped star we can mesure the
continuous photometry between 32.7 and 92.7s:

 From 32.7s to 58.5s the magnitude rises steeply until R = 14.85
 From 58.5s to 92.7s the magnitude stays at about the level R = 14.9

Then the decay is recorded using the later images:

  Tstart  Tstop  Rmag  1sig
  (sec)   (sec)
   106.3  136.3  15.20 0.02
   146.8  176.8  15.43 0.02
   187.4  217.4  15.56 0.02
   227.7  257.7  15.70 0.03
   268.5  298.5  16.10 0.02
   308.8  398.8  16.17 0.02
   409.4  499.4  16.45 0.04
   509.9  599.9  16.71 0.08
   610.5  700.5  16.98 0.04
   711.3 1161.3  17.88 0.07
  1113.3 1203.3  18.36 0.29
  1414.9 1684.9 >18.57
  1515.5 4845.5 >19.41

The light curve can be fitted in three parts implying
two breaks at 284s and 656s:

 From  76s to 284s alpha=0.65
 From 284s to 656s alpha=1.3
Beyond 656s       alpha=2.2

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