Swift Observations of GRB 220412B

J.D. Gropp (PSU), V. D'Elia (SSDC and INAF-OAR) and M.H. Siegel (PSU) for the Swift team

1. Introduction

At 17:06:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220412B (trigger=1102329) (Gropp et al. GCN Circ. 31886). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 60° from the Sun (4.0 hours West) and 159° from the 81%-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

Analysis of the BAT data was reported by Sakamoto and Barthelmy (GCN Circ. 31910).

The BAT light curve (Figure 1) showed a single-peaked

The time-averaged spectrum from T-0.03 to T+0.16 s is best fit by a simple

The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/1102329/BA/.

3. XRT Observations and Analysis

Analysis of the initial XRT data was reported by D'Elia et al. (GCN Circ. 31897). We have analysed 7.8 ks of Photon Counting (PC) mode XRT data for the Swift-BAT-detected burst GRB 220412B, collected between T0+4.7 ks and T0+29.1 ks.

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations of the field of GRB 220412B 89 s after the BAT trigger (Siegel and Gropp GCN Circ. 31917). No optical afterglow consistent with the BAT position (Sakamoto et al., GCN Circ. 31910) is detected in the initial UVOT exposures. 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 EB-V of 0.060 mag. in the direction of the GRB (Schlegel et al. 1998).

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
21h23m01.9s -00°15'38.5" 1.6' BAT-refined Sakamoto and Barthelmy GCN Circ. 31910

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Murata et al. 31889 MITSuME Akeno optical upper limits MITSuME Akeno upper limits
Optical Kumar et al. 31892 GIT optical upper limit GROWTH-India Tel. upper limits
Optical Lipunov et al. 31894 Swift GRB 220412B: Global MASTER-Net
observations report 		MASTER
Optical Hu et al. 31900 BOOTES-1 optical upper limit BOOTES-1 upper limits
Optical D'Avanzo et al. 31904 TNG optical observations TNG
Gamma-ray Veres and Meegan 31908 Fermi GBM observation Fermi GBM Epeak=499±116 keV
T90=0.16 seconds
Fluence=4.44±0.40x10-7erg cm-2
(brighter than 62% of short GRBs)
Gamma-ray Svinkin et al. 31909 Konus-Wind detection Konus-Wind Epeak=283 (-52,+68) keV
Fluence=3.2(-0.1,+1.2)x10-7erg cm-2

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

Filter Tstart(s) Tstop(s) Exp(s) Mag
white (fc) 89 217 128 >20.0
white 4378 4577 197 >20.3
b 4173 4373 197 >19.8
u 3968 4167 197 >19.4
w2 4584 4663 78 >19.2

Table 3. UVOT observations reported by Siegel and Gropp (GCN Circ. 31917). The start and stop times of the exposures are given in seconds since the BAT trigger. The preliminary 3-σ upper limits are given. No correction has been made for extinction in the Milky Way.

April 19, 2022