Swift Observations of GRB 210704A

A. D'Ai (INAF-IASFPA) and A.A. Breeveld (UCL-MSSL) for the Swift team

1. Introduction

Berretta et al. (GCN Circ. 30375) reported the GRB detection. Table 1 contains the best reported positions from Swift.

Kim et al. (GCN Circ. 30384) reported the position from Assy-Turgen Obs. for the optical afterglow of this GRB. de Ugarte Postigo et al. (GCN Circ. 30392) determined a redshift of 2.34 from GTC, and Minaev et al. (GCN Circ. 30452) determined a redshift of 0.11. 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'Ai et al. (GCN Circ. 30379). We cannot determine at the present time whether the source is fading.

4. UVOT Observations and Analysis

The Swift/UVOT began settled observations (Breeveld and Lien GCN Circ. 30389) of the field of GRB 210704A 53458 s after the LAT trigger (Kunzweiler et al., GCN Circ. 30369). No optical afterglow consistent with the XRT position (D'Ai et al. GCN Circ. 30379) nor the optical positions given by Kim et al., (GCN Circ. 30384) and D'Avanzo et al., (GCN Circ. 30385) 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 EB-V of 0.007 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
10h36m05.18s +57°12'59.0" 2.6" XRT-final UKSSDC
10h36m05.33s +57°12'58.9" 3.2" XRT D'Ai et al. GCN Circ. 30379

Table 1. Positions from the Swift instruments.

Band Authors GCN Circ. Subject Observatory Notes
Optical Dichiara et al. 30383 DDOTI upper limit Deca-Degree Optical Imager upper limits
Optical Kim et al. 30384 Assy optical afterglow candidate Assy-Turgen Obs. detection
Optical D'Avanzo et al. 30385 TNG detection of the optical afterglow
candidate		 TNG detection
Optical Troja et al. 30390 RATIR optical upper limits RATIR upper limits
Optical Kann et al. 30391 CAHA 2.2m Afterglow Detection CAHA detection
Optical de Ugarte Postigo et al. 30392 OSIRIS/GTC spectroscopy GTC spectroscopy
Optical Kann et al. 30401 OAJ T80 multi-color detections Obs. Astro. de Javalambre detection
Optical Sun et al. 30411 CAHA 2.2m telescope optical limit CAHA upper limits
Optical D'Avanzo et al. 30432 further TNG optical observations TNG light curve
Optical Rastinejad et al. 30433 Gemini-North Infrared Source Detection Gemini detection
Optical Watson et al. 30436 OSIRIS/GTC Observations and Archival
Detection of the Possible Host Galaxy 		GTC
Optical Pankov et al. 30440 Assy optical afterglow upper limit Assy-Turgen Obs. upper limits
Optical Troja et al. 30442 Gemini near-infrared upper limits Gemini upper limits
Optical Kann et al. 30443 NOT optical observations and color
change		 NOT
Optical Fong and Rastinejad 30445 Continued Gemini-North NIR K-band
Detections		 Gemini detection
Optical O'Connor et al. 30451 Lowell Discovery Telescope Optical
Observations		 detection
Optical Volnova et al. 30465 Zeiss-1000/SAO-RAS optical observations Zeiss-1000 marginal detection
Gamma-ray Kunzweiler et al. 30369 BALROG localization (Fermi Trigger
647120009 / GRB 210704815)		 BALROG
Gamma-ray Ursi et al. 30372 AGILE/MCAL detection AGILE
Gamma-ray Berretta et al. 30375 Fermi-LAT detection Fermi LAT Emax=16 GeV
Gamma-ray Prasad et al. 30378 AstroSat CZTI detection CZTI
Gamma-ray Malacaria and Meegan 30380 Fermi GBM detection Fermi GBM Epeak=286.1±6.4 keV
T90=4.7 seconds
Fluence=1.95±0.02x10-5erg cm-2
(86th percentile for long GRBs)
Gamma-ray Ridnaia et al. 30388 Konus-Wind detection Konus-Wind Epeak=271 (-14,+14) keV
Fluence=2.25(-0.12,+0.14)x10-5erg cm-2
Gamma-ray Minaev et al. 30444 INTEGRAL observations INTEGRAL
Other Minaev et al. 30452 classification as long GRB and redshift
estimating		 redshift

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

Filter Tstart(s) Tstop(s) Exp(s) Mag
v 53458 72068 3038 >21.1

Table 3. UVOT observation reported by Breeveld and Lien (GCN Circ. 30389). 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.

July 18, 2021