[vsnet-grb-info 17509] GRB 160127A: TAROT La Silla observatory optical light curve

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18939
SUBJECT: GRB 160127A: TAROT La Silla observatory optical light curve
DATE:    16/01/27 12:14:43 GMT
FROM:    Alain Klotz at IRAP-CNRS-OMP  <Alain.Klotz at free.fr>

Klotz A., Turpin D. (IRAP-CNRS-OMP),
Boer M., Gendre B., Bardho O. (UNS-CNRS-OCA),
Gendre B. (Etelman Observatory-UVI),
Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 160127A detected by SWIFT
(trigger 671828) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 25.1s after the GRB trigger
(13.4s after the notice). The elevation of the field
increased from 42 degrees above horizon and weather
conditions were good.

We detected the candidate couterpart mentioned by
Amaral-Rogers et al. (GCNC 18938).

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We detect the OT increasing its optical flux from
t0+25s to t0+45s (R~16.9) and fading until the end of
the trail at t0+85s.

Following images were acquired in tracking mode:
t1(s) t2(s)  Rmag   d_Rmag
   99  129    17.9    0.6
  141  171    17.4    0.1
  182  212    17.1    0.7
  223  253    17.1    0.0
  306  396    17.1    0.2
  407  497    17.4    0.4
  610  700    17.6    0.1
  711  801    17.6    0.2
  914 1004    17.6    0.1
1015 1105    17.4    0.0
1742 1922   >18.4    0.6

Magnitudes were estimated with the stars:
NOMAD1 0900-0248256 ra=225.9885561 dec=+00.0840197 R=14.83
NOMAD2 0901-0246538 ra=225.9533572 dec=+00.1320336 R=14.83

Magnitudes are not corrected for galactic dust extinction.

After the first deacay observed in the trailed image from
t0+45s to t0+85s, we observed a bump (maximum flux at t0+220s
R~17.1) and we suspect a second bump (maximum flux at t0+1100s
R~17.3) followed by a steep decay. The OT become fainter
than 18.4 after t0+2000s.