Swift Observations of GRB 210406A

V. D'Elia (SSDC and INAF-OAR) for the Swift team

1. Introduction

Mereghetti et al. (GCN Circ. 29767) reported the GRB detection. A gamma ray burst lasting about 60 s has been detected by IBAS in the IBIS/ISGRI data at 17:11:22 UT of April 6, 2021. Table 1 contains the best reported positions from Swift.

Belkin et al. (GCN Circ. 29775) reported the position from Mondy for the optical afterglow of this GRB. 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 D'Elia et al. (GCN Circ. 29785). One uncatalogued X-ray source has been detected consistent with being within 148 arcsec of the INTEGRAL position, it is below the RASS limit and shows no definitive signs of fading.

4. UVOT Observations and Analysis

UVOT results are not available.

Figure 1. The BAT light curve is not available.

RA (J2000) Dec (J2000) Error Note Reference

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes

Optical Lipunov et al. 29766 Integral GRB210406.72: Global
MASTER-Net observations report MASTER

Optical Hu et al. 29768 BOOTES-4/MET optical upper limit BOOTES-4 upper limits

Optical Vinko et al. 29769 Konkoly Obs. optical upper limit Konkoly upper limits

Optical Pankov et al. 29770 Mondy optical upper limit Mondy upper limits

Optical Belkin et al. 29775 Mondy optical afterglow candidate Mondy detection

Optical Hu et al. 29799 10.4m GTC follow-up observation GTC

Gamma-ray Mereghetti et al. 29767 A long GRB detected by INTEGRAL INTEGRAL

Gamma-ray Malacaria and Meegan 29771 Fermi GBM detection Fermi GBM E_peak=195.6±18.8 keV
T₉₀=17.4 seconds
Fluence=9.1±0.5x10^-6erg cm^-2
(73^rd percentile for long GRBs)

Gamma-ray Ridnaia et al. 29772 Konus-Wind detection Konus-Wind E_peak=176 (-36,+54) keV
Fluence=9.13(-1.16,+1.40)x10^-6erg cm^-2

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

Band	Authors	GCN Circ.	Subject	Observatory	Notes
Optical	Lipunov et al.	29766	Integral GRB210406.72: Global MASTER-Net observations report	MASTER
Optical	Hu et al.	29768	BOOTES-4/MET optical upper limit	BOOTES-4	upper limits
Optical	Vinko et al.	29769	Konkoly Obs. optical upper limit	Konkoly	upper limits
Optical	Pankov et al.	29770	Mondy optical upper limit	Mondy	upper limits
Optical	Belkin et al.	29775	Mondy optical afterglow candidate	Mondy	detection
Optical	Hu et al.	29799	10.4m GTC follow-up observation	GTC
Gamma-ray	Mereghetti et al.	29767	A long GRB detected by INTEGRAL	INTEGRAL
Gamma-ray	Malacaria and Meegan	29771	Fermi GBM detection	Fermi GBM	E_peak=195.6±18.8 keV T₉₀=17.4 seconds Fluence=9.1±0.5x10^-6erg cm^-2 (73^rd percentile for long GRBs)
Gamma-ray	Ridnaia et al.	29772	Konus-Wind detection	Konus-Wind	E_peak=176 (-36,+54) keV Fluence=9.13(-1.16,+1.40)x10^-6erg cm^-2

April 12, 2021