Swift Observations of GRB 131218A

V. D'Elia (ASDC) for the Swift team

1. Introduction

Gotz et al. (GCN Circ. 15601) reported the GRB detection. a gamma ray burst lasting about 6 s has been detected by IBAS in the IBIS/ISGRI data at 21:05:32 U.T. Table 1 contains the best reported positions from Swift.

Klotz et al. (GCN Circ. 15603) reported the position from Zadko for the optical afterglow of this GRB. Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

2. BAT Observations and Analysis

BAT results are not available.

3. XRT Observations and Analysis

We have analysed xx ks of XRT data for the INTEGRAL-detected burst: GRB 131218A, from 0 s to 0 s after the INTEGRAL trigger. The data are entirely in Photon Counting (PC) mode. We cannot determine at the present time whether the source is fading.

If the light curve (Figure 2) continues to decay with a power-law decay index of , the count rate at T+24 hours will be 0.27 count s^-1

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations of the field of GRB 131218A 62782 s after the trigger (D'Elia and Marshall GCN Circ. 15605). No optical afterglow consistent with the optical position (Klotz et al., GCN Circ. 15603) is detected in the initial UVOT exposure. Table 3 gives preliminary magnitudes using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc., 1358, 373). No correction has been made for the expected extinction in the Milky Way corresponding to a reddening of E_B-V of 0.17 mag. in the direction of the GRB (Schlegel et al. 1998).

Figure 1. The BAT light curve is not available.

RA (J2000) Dec (J2000) Error Note Reference

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Klotz et al. 15602 TAROT La Silla observatory optical
observations TAROT

Optical Klotz et al. 15603 Zadko observatory - Gingin optical candidate Zadko detection

Optical Kann et al. 15606 GROND Upper Limits GROND upper limits

Gamma-ray Gotz et al. 15601 a long GRB detected with INTEGRAL INTEGRAL detection

Table 2. Summary of GCN Circulars from other observatories sorted by band and then circular number.

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

v 62782 62900 116 >19.8

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Klotz et al.	15602	TAROT La Silla observatory optical observations	TAROT
Optical	Klotz et al.	15603	Zadko observatory - Gingin optical candidate	Zadko	detection
Optical	Kann et al.	15606	GROND Upper Limits	GROND	upper limits
Gamma-ray	Gotz et al.	15601	a long GRB detected with INTEGRAL	INTEGRAL	detection

Filter	T_start(s)	T_stop(s)	Exp(s)	Mag
v	62782	62900	116	>19.8

Table 3. UVOT observation reported by D'Elia and Marshall (GCN Circ. 15605). The start and stop time of the exposure are given in seconds since the BAT trigger. The preliminary 3-σ upper limit is given. No correction has been made for extinction in the Milky Way.

December 22, 2013