Swift Observations of GRB 220627A

J.D. Gropp (PSU) and M.H. Siegel (PSU) for the Swift team

1. Introduction

Lalla et al. (GCN Circ. 32283) reported the GRB detection. Table 1 contains the best reported positions from Swift.

de Wet et al. (GCN Circ. 32289) reported the position from MeerLICHT for the optical afterglow of this GRB. Izzo et al. (GCN Circ. 32291) determined a redshift of 3.084 from VLT. 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 Gropp et al. (GCN Circ. 32296). Fourteen uncatalogued X-ray sources are detected, of which one ("Source 3") is fading with >3-sigma significance, and is therefore likely the GRB afterglow.

The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=1.4 (+0.8, -0.5).

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations (Siegel GCN Circ. 32302) of the field of GRB 220627A 130224 s after the LAT trigger (Di Lalla, et al., GCN Circ. 32283). No optical afterglow consistent with the optical position (de Wet et al., GCN Circ. 32289, Izzo et al., GCN Circ. 33391) or X-ray afterglow (Gropp et al., GCN Circ. 32296) 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 E_B-V of 0.047 mag. in the direction of the GRB (Schlegel et al. 1998).

Figure 1. The BAT light curve is not available.

RA (J2000) Dec (J2000) Error Note Reference

13^h25^m28.51^s -32°25'34.5" 3.1" XRT Gropp et al. GCN Circ. 32296

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Lipunov et al. 32280 Fermi GRB 220627A: Global MASTER-Net
observations report MASTER

Optical Groot et al. 32281 MeerLICHT detection of two afterglow
candidates MeerLICHT detection

Optical de Wet et al. 32289 MeerLICHT candidate optical afterglow MeerLICHT detection

Optical Izzo et al. 32291 VLT MUSE redshift VLT redshift

Optical Guelbenzu et al. 32304 GROND observations GROND detection

Radio Leung et al. 32341 ATCA detection of radio counterpart ATCA detection

Radio Giarratana et al. 32454 MeerKAT radio observations

Gamma-ray Lalla et al. 32283 Fermi-LAT detection Fermi LAT E_max=15.7 GeV

Gamma-ray Roberts et al. 32288 Fermi GBM Detection of a possible
Lensed or Ultra-long GRB Fermi GBM E_peak=410±16 keV
T₉₀=138 seconds
Fluence=7.88±0.13x10^-5erg cm^-2
(brighter than 97.0% of long GRBs)

Gamma-ray Frederiks et al. 32295 Konus-Wind detection Konus-Wind E_peak=250 (-49,+60) keV

Gamma-ray Suresh et al. 32316 AstroSat CZTI detection CZTI

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

Filter T_start(s) T_stop(s) Exp(s) Mag

u 130224 148828 4854 >22.0

RA (J2000)	Dec (J2000)	Error	Note	Reference
13^h25^m28.51^s	-32°25'34.5"	3.1"	XRT	Gropp et al. GCN Circ. 32296

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Lipunov et al.	32280	Fermi GRB 220627A: Global MASTER-Net observations report	MASTER
Optical	Groot et al.	32281	MeerLICHT detection of two afterglow candidates	MeerLICHT	detection
Optical	de Wet et al.	32289	MeerLICHT candidate optical afterglow	MeerLICHT	detection
Optical	Izzo et al.	32291	VLT MUSE redshift	VLT	redshift
Optical	Guelbenzu et al.	32304	GROND observations	GROND	detection
Radio	Leung et al.	32341	ATCA detection of radio counterpart	ATCA	detection
Radio	Giarratana et al.	32454	MeerKAT radio observations
Gamma-ray	Lalla et al.	32283	Fermi-LAT detection	Fermi LAT	E_max=15.7 GeV
Gamma-ray	Roberts et al.	32288	Fermi GBM Detection of a possible Lensed or Ultra-long GRB	Fermi GBM	E_peak=410±16 keV T₉₀=138 seconds Fluence=7.88±0.13x10^-5erg cm^-2 (brighter than 97.0% of long GRBs)
Gamma-ray	Frederiks et al.	32295	Konus-Wind detection	Konus-Wind	E_peak=250 (-49,+60) keV
Gamma-ray	Suresh et al.	32316	AstroSat CZTI detection	CZTI

Filter	T_start(s)	T_stop(s)	Exp(s)	Mag
u	130224	148828	4854	>22.0

Table 3. UVOT observation reported by Siegel (GCN Circ. 32302). The start and stop time of the exposure are given in seconds since the BAT trigger. The preliminary 3-σ upper limit is given. No correction has been made for extinction in the Milky Way.

August 11, 2022