Swift Observations of GRB 130623A

J.R. Cummings () and D. Grupe (PSU) for the Swift team

1. Introduction

At 11:42:44.7 UTC, the time of Fermi-GBM trigger 393680570, Swift was executing a pre- planned slew (Cummings GCN Circ. 14921). Table 1 contains the best reported positions from Swift.

Varela et al. (GCN Circ. 15080) reported the position from GROND 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

with an estimated 90% confidence radius of 4 arcmin. The burst was a long GRB with 3 distinct peaks. T₉₀ was about 15 ± 2 s.

The spectrum from T₀ to T₀+15 s is best fit by a simple powerlaw with a photon index of 1.8 ± 0.2. The fluence from T₀ to T+15 was (5.4 ± 1.1) x 10^-0.7 ergs/cm². The 1-second peak flux from T+0.6 s was 1.4 ± 0.3 photons/cm² s^-1.

3. XRT Observations and Analysis

We have analysed 15 ks of XRT data for the Swift/BAT-detected burst: GRB 130623A, from 100.4 ks to 649.6 ks after the Swift/BAT trigger. The data are entirely in Photon Counting (PC) mode. An X-ray source is detected within the Swift/BAT error circle. We cannot determine at the present time whether the source is fading.

The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020284.

4. UVOT Observations and Analysis

Analysis of the UVOT data was reported by Grupe et al. (GCN Circ. 14926). Swift UVOT observed the field of GRB 130623A for 4611s. There is no source at the X-ray position in the white image. 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 0.05 mag. in the direction of the GRB (Schlegel et al. 1998).

Figure 1. The BAT light curve is unavailable.

XRT light curve

Figure 2. The XRT light curve. Any data from a cross-hatched region are not included in the fit.

RA (J2000) Dec (J2000) Error Note Reference

01^h23^m24.83^s -77°46'24.2" 4.5" XRT-final UKSSDC

01^h23^m24.83^s -77°46'24.2" 4.5" XRT Grupe et al. GCN Circ. 14926

01^h22^m53.5^s -77°47'04" BAT-ground Cummings GCN Circ. 14921

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Varela et al. 15080 GROND detection of the optical/NIR afterglow GROND detection

Gamma-ray Byrne et al. 14940 Fermi GBM detection Fermi GBM E_peak = 26.11 ± 4.67 keV

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

RA (J2000)	Dec (J2000)	Error	Note	Reference
01^h23^m24.83^s	-77°46'24.2"	4.5"	XRT-final	UKSSDC
01^h23^m24.83^s	-77°46'24.2"	4.5"	XRT	Grupe et al. GCN Circ. 14926
01^h22^m53.5^s	-77°47'04"		BAT-ground	Cummings GCN Circ. 14921

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Varela et al.	15080	GROND detection of the optical/NIR afterglow	GROND	detection
Gamma-ray	Byrne et al.	14940	Fermi GBM detection	Fermi GBM	E_peak = 26.11 ± 4.67 keV

Table 3. Found no UVOT observations.

August 8, 2013