Swift Observations of GRB 220527A

B. Sbarufatti (PSU) for the Swift team

1. Introduction

Bissaldi et al. (GCN Circ. 32131) reported the GRB detection. Table 1 contains the best reported positions from Swift.

(GCN Circ. 32136) reported the detection with UVOT of an optical afterglow. Xu et al. (GCN Circ. 32141) determined a redshift of 0.857 from NOT. Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.

2. BAT Observations and Analysis

BAT did not observe this burst.

3. XRT Observations and Analysis

Analysis of the initial XRT data was reported by Sbarufatti et al. (GCN Circ. 32135).

The light curve (Figure 2) is consistent with a constant source of mean count rate 3.9 x 10-1 ct s-1. A power-law fit gives an index of 0.6 (+2.5, -1.1).

A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.83 (+0.21, -0.20). The best-fitting absorption column is 9.8 (+6.1, -3.5) x 1020 cm-2, consistent with the Galactic value of 6.2 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 3.6 x 10-11 (4.2 x 10-11) erg cm-2 count-1.

4. UVOT Observations and Analysis

The Swift/UVOT began observations ( GCN Circ. 32136) of the Fermi/LAT localization (GCN Circ. 32131) of GRB 220527A , collecting 1.7 ks of u band data between T0+30.1 ks and T0+31.9 ks after the Fermi GBM detection (32133). A source consistent with the XRT afterglow position (GCN Circ. 32135) is detected in the UVOT observation. Table 3 gives preliminary magnitudes using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc., 1358, 373).

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
21h34m06.73s -14°58'18.1" 1.00" UVOT GCN Circ. 32136
21h34m06.73s +14°58'18.6" 2.6" XRT Sbarufatti et al. GCN Circ. 32135

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Lipunov et al. 32137 LAT GRB220527.39: Global MASTER-Net
observations report 		MASTER
Optical Imai et al. 32138 MITSuME Akeno optical observation MITSuME Akeno
Optical Xu et al. 32141 NOT optical photometry and
spectroscopic redshift		 NOT redshift
Optical de Wet et al. 32143 MeerLICHT afterglow observations MeerLICHT detection
Optical D'Avanzo et al. 32145 REM optical/NIR observations REM
Optical Sun et al. 32146 AST3-3 Yaoan Optical Observation Antarctic Survey Tel.
Optical Zheng et al. 32158 Lick 3m Optical Observations Pan-STARRS detection
Optical Niwano et al. 32159 MITSuME Akeno continued optical
observation		 MITSuME Akeno
Gamma-ray Ursi et al. 32129 AGILE detection AGILE
Gamma-ray Fermi 32130 Fermi GBM Final Localization Fermi GBM
Gamma-ray Bissaldi et al. 32131 Fermi-LAT detection Fermi LAT Emax=12 GeV
Gamma-ray Mangan et al. 32133 Fermi GBM Observation Fermi GBM Epeak=151.6±2.7 keV
T90=10.5 seconds
Fluence=5.69±0.04x10-5erg cm-2
(brighter than 95.8% of long GRBs)
Gamma-ray Yamaoka et al. 32139 CALET Gamma-Ray Burst Monitor detection CALET
Gamma-ray Gopalakrishnan et al. 32140 AstroSat CZTI detection CZTI
Gamma-ray Lysenko et al. 32152 Konus-Wind observation Konus-Wind Epeak=154 (-10,+10) keV
Duration=~21.3 seconds
Fluence=5.98(-0.31,+0.32)x10-5erg cm-2
Other Ruffini et al. 32169 A BdHN I with a clear UPE phase

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

Table 3. Found no UVOT observations.

June 7, 2022