Swift Observations of GRB 211106A

V. D'Elia (SSDC and INAF-OAR) and N.P. Kuin (UCL-MSSL) for the Swift team

1. Introduction

Tohuvavohu et al. (GCN Circ. 31049) reported the GRB detection. Swift/BAT did not trigger on GRB 211106A (T0: 2021-11-06T04:37:31.2 UTC, INTEGRAL/SPI-ACS #9504). Table 1 contains the best reported positions from Swift.

Christensen et al. (GCN Circ. 31075) determined a redshift of 1.012. Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

2. BAT Observations and Analysis

BAT refined results are not available.

3. XRT Observations and Analysis

Analysis of the initial XRT data was reported by D'Elia et al. (GCN Circ. 31068). Of the sources reported by D'Elia et al. (GCN Circ. 31051), "Source 2" is fading with 2.5 sigma significance and thus is believed to be the GRB afterglow.

The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=0.7 (+0.5, -0.4).

4. UVOT Observations and Analysis

The Swift/UVOT observed the field of the Swift/BAT-GUANO localisation (Kuin and Tohuvavohu GCN Circ. 31079) Tohuvavohu et al. GCN Circ. 31049) of the INTEGRAL/SPI-ACS #9504 discovery of the short GRB211106A using the white filter. The GRB was also reported by Fermi GBM (Fletcher, GCN Circ. 31055), Konus-Wind (Ridnaia et al., GCN Circ. 31054). 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 0.09 mag. in the direction of the GRB (Schlegel et al. 1998).

Figure 1. The BAT light curve is not available.

XRT light curve

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

RA (J2000) Dec (J2000) Error Note Reference
22h54m20.45s -53°13'49.0" 3.4" XRT-final UKSSDC
22h54m20.45s -53°13'49.0" 3.4" XRT D'Elia et al. GCN Circ. 31068
22h54m34.32s -53°14'00.9" 7' BAT-GUANO Tohuvavohu et al. GCN Circ. 31049

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical de Wet et al. 31063 MeerLICHT follow-up MeerLICHT
Optical Guelbenzu et al. 31069 GROND observations GROND upper limits
Optical Malesani et al. 31070 VLT/FORS2 optical observations VLT/FORS2
Optical 31146 HST Observations HST
Optical Kilpatrick et al. 31157 Second HST Observation HST
Optical Kilpatrick et al. 31300 Third HST Observation HST
X-ray Berger et al. 31145 Chandra Observations Chandra
X-ray Escorial et al. 31259 XMM-Newton monitoring campaign
detections		 XMM detection
Gamma-ray Ridnaia et al. 31054 Konus-Wind detection Konus-Wind Epeak=196 (-45,+78) keV
Duration=~0.5 seconds
Fluence=6.09(-1.22,+1.41)x10-7erg cm-2
Gamma-ray Fletcher 31055 Fermi GBM Sub-Threshold Detection Fermi GBM Epeak=230 keV
Gamma-ray Svinkin et al. 31078 IPN triangulation of GRB 211106A
(short)		 IPN
Gamma-ray Zhang et al. 31150 GECAM detection GECAM
Other Christensen et al. 31075 Short GRB 211106A: spectroscopy of
galaxies in the field		 spectroscopy

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

Table 3. Found no UVOT observations.

December 25, 2021