GRB 131218A

D. Gotz (CEA Saclay), S. Mereghetti (IASF-Milano), E. Bozzo, C. Ferrigno, R. Farinelli, (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the  IBAS Localization Team report:

a gamma ray burst lasting about 6 s has been detected by IBAS in the IBIS/ISGRI data at  21:05:32 U.T. on December 18.
Its refined  coordinates (J2000)  are:

  R.A.: 113.7807 deg
  DEC.: -64.7373 deg

with an uncertainty of 1.8 arc min (90% c.l.).

A preliminary estimation of the burst fluence is 5x10^-7 erg/cmsq in the 20-200 keV energy band.

A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html

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

We imaged the field of GRB 131218A detected by INTEGRAL
(trigger 6409) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 3.41h after the GRB trigger
which occured during day. The elevation of the field
increased from 26 degrees above horizon and weather
conditions were good.

We co-added a series of exposures but we do not
detect any OT with a limiting magnitude of:

t0+3.41h to t0+4.98h : Rlim = 19.6

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

N.B. Galactic coordinates are lon=276.4490 lat=-19.8751
and the galactic extinction in R band is about 0.4 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.

A. Klotz (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D. Coward (UWA),
B. Gendre, M. Boer, K. Siellez, H. Dereli , O. Bardho (UNS-CNRS-OCA),
A. Williams (PO-UWA), R. Martin (PO-UWA), D. Turpin (IRAP-CNRS-OMP)
report:

We imaged the field of GRB 131218A detected by INTEGRAL
(trigger 6409) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations are R filtered, started 0.87 day after
the GRB trigger. The limiting magnitude of the co added
image is Rlim = 20.5.

In the error box provided by INTEGRAL notice we detect
only one faint candidate not present on the DSS atlas:

RA(J2000.0) = 07h 35m 10.50s
DEC(J2000.0) = -64d 43' 19.4"

OT was R~20.0 0.87 day after GRB.

We have no more images so we cannnot conclude if it
is a fading source or not. Additional images are
programmed to be recorded in the next nights.

V. D'Elia (ASDC) and F.E. Marshall (NASA/GSFC)
report on behalf of the Swift team:


We report on Swift observations of the field of the INTEGRAL discovered GRB131218A (Gotz et al. GCN Circ 15601
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 ), starting 17.5 hours after the trigger. Due to an observing constraint, only a very short exposure was carried out.

XRT began observing the field on 2013-12-19 at 14:32:15 UT, i.e.,  62803 s after the trigger, for a total of 99 s. No source is detected within the INTEGRAL error circle. The 3-sigma upper limit on the count rate is ~9E-02 cts/s.

The Swift/UVOT began settled observations of the field of GRB 131218A 62782 s after the trigger. No optical afterglow consistent with the optical position (Klotz et al., GCN Circ. 15603
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 ) is detected in the initial UVOT exposure.
The preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposure is:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

v                62782        62900          116         >19.8

The magnitude in the table is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.17 in the direction of the burst (Schlegel et al. 1998).

D. A. Kann, M. Tanga (both MPE Garching), S. Klose, S. Schmidl (both TLS
Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND
collaboration:

We observed the field of GRB 131218A (INTEGRAL-6409, Gotz et al., GCN
#15601
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 ) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG telescope at La Silla Observatory
(Chile).

A first series of observations (integration time 6750 sec in the optical,
5400 sec in the NIR, midtime 0.24 days after the trigger, seeing 1".0 and
airmass 1.5) yield the following image depths (AB magnitudes):

g' > 24.6,
r' > 24.9,
i' > 24.5,
z' > 24.4,
J > 22.4,
H > 21.8, and
K > 20.8.

A second set of observations (integration time 3750 sec in the optical,
3000 sec in the NIR, midtime 2.31 days after the trigger, seeing 0".9 and
airmass 1.3) yield somewhat deeper limits in the optical, while they are
somewhat shallower in the NIR.

Image subtraction between these two epochs shows no evidence for variable
sources, both in the INTEGRAL error circle and around it, and therefore we
can only place upper limits on the presence of any afterglow.

Magnitudes are calibrated against GROND zeropoints (g'r'i'z') and 2MASS
stars (JHK), and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.17 mag in the direction of the
burst (Schlegel et al. 1998).