Swift Observations of GRB 210204A

J.A. Kennea (PSU) for the Swift team

1. Introduction

Hurley et al. (GCN Circ. 29408) reported the GRB detection. Table 1 contains the best reported positions from Swift.

Izzo et al. (GCN Circ. 29411) determined a redshift of 1.466 from VLT, and Xu et al. (GCN Circ. 29432) determined a redshift of 0.876. 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 Kennea et al. (GCN Circ. 29413).

The light curve (Figure 2) is consistent with a constant source of mean count rate 9.1 x 10-2 ct s-1.

A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.73 (+0.31, -0.29). The best-fitting absorption column is 1.7 (+1.3, -1.1) x 1021 cm-2, in excess of the Galactic value of 3.5 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 4.0 x 10-11 (4.9 x 10-11) erg cm-2 count-1.

4. UVOT Observations and Analysis

UVOT results are not available.

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
07h48m19.37s +11°24'34.2" 1.7" XRT-final UKSSDC
07h48m19.37s +11°24'34.2" 1.7" XRT Kennea et al. GCN Circ. 29413

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Lipunov et al. 29395 Fermi GRB 210204A: Global MASTER-Net
observations report 		MASTER
Optical Izzo et al. 29411 VLT/X-shooter redshift of 1.466 for
ZTF21aagwbjr/AT2021buv, strengthening
its association with GRB 210204A		 VLT redshift
Optical Teja et al. 29414 Optical Observations from HCT Himalayan Chandra Telescope detection
Optical Belkin et al. 29417 (ZTF21aagwbjr/AT2021buv): Mondy and
AbAO optical observations		 Abastumani Astro. Obs.
Optical Rossi and Melandri 29433 LBT observations and jet break LBT detection
Optical Belkin et al. 29438 (ZTF21aagwbjr/AT2021buv): continued
Mondy optical observations		 Mondy
Optical Gupta et al. 29490 observations with the 3.6m Devasthal
Optical Telescope and possible jet
break		 Devasthal Opt.Tel. light curve
Optical Belkin et al. 29499 (ZTF21aagwbjr/AT2021buv): continued
CrAO and AbAO optical observations		 Abastumani Astro. Obs. light curve
Optical Belkin et al. 29520 (ZTF21aagwbjr/AT2021buv): continued
Assy and Mondy optical observations		 Mondy light curve
Radio Chandra et al. 29541 uGMRT radio detection GMRT detection
Gamma-ray Fermi 29390 Fermi GBM Final Real-time Localization Fermi GBM
Gamma-ray Kunzweiler et al. 29391 BALROG localization (Fermi Trigger
634112970 / GRB 210204270)		 BALROG
Gamma-ray Bissaldi 29393 Fermi GBM observation Fermi GBM Epeak=162±33 keV
T90=210 seconds
Fluence=5.76±0.04x10-6erg cm-2
(60th percentile for long GRBs)
Gamma-ray Hurley et al. 29408 IPN triangulation IPN
Gamma-ray Waratkar et al. 29410 AstroSat CZTI Detection CZTI
Gamma-ray Frederiks et al. 29415 Konus-Wind detection of GRB 210204A /
ZTF21aagwbjr		 Konus-Wind Epeak=137 (-25,+22) keV
Gamma-ray Frederiks 29424 Konus-Wind detection of GRB 210204A
(correction to GCN Circ. 29415)		 Konus-Wind Epeak=136 (-16,+21) keV
Other Li et al. 29392 GECAM detection detection
Xu et al. 29432 redshift revision of ZTF21aagwbjr/AT2021buv
(correction to GCN Circ. 29411)		 corrects Circ. 29411

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

February 23, 2021