Swift Observations of GRB 201203A

S. Dichiara (NASA/GSFC/UMCP) and V. D'Elia (ASDC) for the Swift team

1. Introduction

At 06:52:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 201203A (trigger=1010946) (Dichiara et al. GCN Circ. 28985). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 122° from the Sun (9.9 hours East) and 83° from the 92%-illuminated Moon. Table 1 contains the best reported positions from Swift.

Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

Standard analysis products for this burst are available at https://gcn.gsfc.nasa.gov/swift_gnd_ana.html.

2. BAT Observations and Analysis

As reported by Sakamoto et al. (GCN Circ. 28995), the BAT ground-calculated position is RA, Dec = 38.055, -26.505 deg which is RA(J2000) = 02h32m13.1s Dec(J2000) = -26°30'19.2" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%.

The BAT light curve (Figure 1) showed a complex structure with a duration of about ~20 s. T90 (15-350 keV) is 12.18 ± 2.10 s (estimated error including systematics).

The time-averaged spectrum from T-2.73 to T+12.84 s is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.78 ± 0.26. The fluence in the 15-150 keV band is 2.9 ± 0.5 x 10-7 erg cm-2. This fluence is larger than that of 12% of the long GRBs in the Second BAT GRB Catalog (Sakamoto et al. 2011). The 1-s peak photon flux measured from T+11.49 s in the 15-150 keV band is 0.5 ± 0.1 ph cm-2 s-1. All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/1010946/BA/.

3. XRT Observations and Analysis

Analysis of the initial XRT data was reported by D'Elia et al. (GCN Circ. 28990).

The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=1.4 (+1.3, -1.1).

A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.7, -0.4). The best-fitting absorption column is consistent with the Galactic value of 1.8 x 1020 cm-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10-11 (1.6 x 10-11) erg cm-2 count-1.

4. UVOT Observations and Analysis

UVOT results are not available.

BAT light curve

Figure 1. The BAT mask-weighted light curve in the four individual and total energy bands. The units are counts s-1 illuminated-detector-1. The vertical green dash-dotted lines show the T50 interval, the vertical black dashed lines show the T90 interval, and vertical blue (orange) solid lines show the start (stop) of slews.

RA (J2000) Dec (J2000) Error Note Reference
02h32m13.34s -26°31'06.1" 3.5" XRT-final UKSSDC
02h32m13.25s -26°31'05.5" 3.3" XRT D'Elia et al. GCN Circ. 28990
02h32m13.1s -26°30'19.2" 1.9' BAT-refined Sakamoto et al. GCN Circ. 28995

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Jelinek et al. 28986 FRAM-Auger optical limit FRAM upper limits
Optical Watson et al. 28987 DDOTI Observations Deca-Degree Optical Imager
Optical Zheng and Filippenko 28988 KAIT Optical Upper Limit KAIT upper limits
Optical Lipunov et al. 28991 Swift GRB 201203A: Global MASTER-Net
observations report 		MASTER
Optical Niwano et al. 28992 MITSuME Okayama optical upper limits MITSuME Okayama upper limits
Optical Kumar et al. 28993 GROWTH-India Telescope optical upper
limit.		 GROWTH-India upper limits
Optical Kumar et al. 29030 1.3m DFOT, optical upper limits Devasthal Opt.Tel. upper limits
Optical Pankov et al. 29032 Zeiss-1000 (Koshka observatory) optical
upper limit		 Zeiss-1000 upper limits

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

December 13, 2020