E. Troja (NASA/GSFC/UMCP), A. Tohuvavohu (U. Toronto) and N.P.M. Kuin (UCL-MSSL) for the Swift team
At 04:25:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210212A (trigger=1032183) (Troja et al. GCN Circ. 29487). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 108° from the Sun (7.1 hours East) and 102° from the 0%-illuminated Moon. Table 1 contains the best reported positions from Swift, and the latest XRT position can be viewed at http://www.swift.ac.uk/xrt_positions.
Table 2 is a summary of GCN Circulars about this GRB from observatories other than Swift.
Standard analysis products for this burst are available at https://gcn.gsfc.nasa.gov/swift_gnd_ana.html.
As reported by Palmer et al. (GCN Circ. 29491),
the BAT ground-calculated position is RA, Dec = 72.249, 7.215 deg which is RA(J2000) = 0
The mask-weighted light curve (Figure 1) showed a broad peak with some underlying structure.
It began around T-10 s, peaked around T+5 s and returned to background by T+90 s.
The time-averaged spectrum from T-15.51 to T+80.49 s is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 1.85 ± 0.23.
The fluence in the 15-150 keV band is 8.0 ± 1.2 x 1
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/1032183/BA/.
Analysis of the initial XRT data was reported by Tohuvavohu et al. (GCN Circ. 29495). We have analysed 24 ks of XRT data for GRB 210212A, from 95 s to 577.9 ks after the BAT trigger. The data comprise 337 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 29489).
The light curve (Figure 2) can be modelled with an initial power-law decay with an index of α=2.52 (+0.15, -0.14), followed by a break at T+331 s to an α of 7.2 (+0.8, -0.6).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.55 (+0.13, -0.12). The best-fitting absorption column is 1.6 (+0.6, -0.5) x 1
A summary of the WT-mode spectrum is thus:
Total column: 1.6 (+0.6, -0.5) x 1
Galactic foreground: 1.1 x 1
Excess significance: <1.6 σ
Photon index: 1.55 (+0.13, -0.12)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01032183.
The Swift/UVOT began settled observations of the field of GRB 210212A 112 s after the BAT trigger
(Kuin and Troja GCN Circ. 29492).
No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 29489) 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
Figure 1. The BAT
mask-weighted light curve in the four individual and total
energy bands. The units are counts
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 |
---|---|---|---|---|
0 |
+07°16'10.8" | 3.6" | XRT-final | UKSSDC |
0 |
+07°16'10.8" | 3.7" | XRT-enhanced | Beardmore et al. GCN Circ. 29489 |
0 |
+07°12'52.6" | 1.9' | BAT-refined | Palmer et al. GCN Circ. 29491 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Hu et al. | 29494 | BOOTES-4/MET optical upper limit | BOOTES-4 | upper limits |
Optical | Murata et al. | 29496 | MITSuME Akeno optical upper limits | MITSuME Akeno | upper limits |
Optical | Lipunov et al. | 29497 | Swift GRB 210212A: Global MASTER-Net observations report |
MASTER | |
Optical | Heintz et al. | 29498 | Possible host galaxy counterpart with the NOT |
NOT | |
Optical | Dichiara and Troja | 29507 | Gemini South optical observations | Gemini | |
Optical | Gupta et al. | 29510 | 1.3m DFOT Optical upper limit | Devasthal Opt.Tel. | upper limits |
Optical | Belkin et al. | 29522 | Mondy optical observations | Mondy | |
Optical | D'Avanzo et al. | 29527 | REM early-time optical/NIR upper limits | REM | upper limits |
Other | Dichiara and Troja | 29540 | Lowell Discovery Telescope observations |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
whit |
112 | 262 | 147 | >20.6 |
271 | 520 | 246 | >20.3 | |
white | 112 | 930 | 242 | >20.8 |
v | 600 | 4588 | 236 | >19.0 |
b | 526 | 720 | 39 | >19.3 |
u | 271 | 868 | 285 | >20.4 |
w1 | 650 | 4851 | 90 | >19.1 |
m2 | 626 | 4793 | 235 | >19.7 |
w2 | 93 | 4383 | 245 | >19.7 |
Table 3. UVOT observations reported by Kuin and Troja (GCN Circ. 29492). The start and stop times of the exposures are given in seconds since the BAT trigger. The preliminary 3-σ upper limits are given. No correction has been made for extinction in the Milky Way.
February 20, 2021