Swift Observations of GRB 200608A

M.J. Moss (GWU) for the Swift team

1. Introduction

At 17:28:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200608A (trigger=976692) (Moss et al. GCN Circ. 27906). Swift did not slew due to an observing constraint. At the time of the trigger, the initial BAT position was 133° from the Sun (8.5 hours West) and 13° from the 90%-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 Lien et al. (GCN Circ. 27913), the BAT ground-calculated position is RA, Dec = 309.628, -31.194 deg which is RA(J2000) = 20h38m30.7s Dec(J2000) = -31°11'39.4" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 53%.

The mask-weighted light curve (Figure 1) shows several overlapping pulses that start at ~T+20 s and ends at ~T+150 s. The two main peaks occur at ~T+18 s and ~T+70 s, respectively. There may be an additional weak pulse at ~T-100 s. T90 (15-350 keV) is 119.2 ± 34.7 s (estimated error including systematics).

The time-averaged spectrum from T+18.09 to T+147.94 s is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.05 ± 0.22. The fluence in the 15-150 keV band is 1.5 ± 0.2 x 10-6 erg cm-2. This fluence is larger than that of 52% of the long GRBs in the Second BAT GRB Catalog (Sakamoto et al. 2011). The 1-s peak photon flux measured from T+70.29 s in the 15-150 keV band is 0.7 ± 0.3 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/976692/BA/.

3. XRT Observations and Analysis

XRT refined results are not available.

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
20h38m30.7s -31°11'39.4" 2.3' BAT-refined Lien et al. GCN Circ. 27913

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Hu et al. 27907 BOOTES-3 and BOOTES-4 optical upper
limit		 BOOTES-3 upper limits
Optical Lipunov et al. 27908 Swift GRB 200608A: Global MASTER-Net
observations report 		MASTER

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

June 10, 2020