TITLE:   GCN CIRCULAR
NUMBER:  15605
SUBJECT: GRB 131218A: Swift XRT and UVOT observations
DATE:    13/12/20 15:32:27 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

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), 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) 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).