M.G. Bernardini (INAF-OAB), M. Perri (ASDC) and F.E. Marshall (NASA/GSFC) for the Swift team
At 19:26:28 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200107B (trigger=948219) (Bernardini et al. GCN Circ. 26661). Swift did not slew immediately due to an observing constraint. At the time of the trigger, the initial BAT position was 74° from the Sun (11.9 hours East) and 104° from the 90%-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.
Analysis of the BAT data was reported by Barthelmy et al. (GCN Circ. 26670).
G. Bernardini et al., GCN Circ. 26661).
The BAT ground-calculated position is RA, Dec = 107.067, -83.716 deg which is RA(J2000) = 0
The mask weighted light curve (Figure 1) shows complex multi-peak structures with a duration of ~100 s.
The overall structure starts at ~T-40 s and lasts till ~T+80s.
The time-averaged spectrum from T-29.86 to T+77.04 s is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 1.41 ± 0.10.
The fluence in the 15-150 keV band is 3.0 ± 0.2 x 1
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/948219/BA/.
Analysis of the initial XRT data was reported by Perri et al. (GCN Circ. 26685). We have analysed 4.2 ks of XRT data for GRB 200107B, from 908 s to 163.3 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode.
The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=1.0 (+0.3, -0.4).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.5, -0.4). The best-fitting absorption column is 2.8 (+2.4, -1.3) x 1
A summary of the PC-mode spectrum is thus:
Total column: 2.8 (+2.4, -1.3) x 1
Galactic foreground: 1.5 x 1
Excess significance: <1.6 σ
Photon index: 1.9 (+0.5, -0.4)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00948219.
The Swift/UVOT began settled observations of the field of GRB 200107B 903 s after the BAT trigger
(Marshall and Bernardini GCN Circ. 26693).
Some of the exposures are affected by poor attitude control, but we have selected observing times for which this is not a significant issue.
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 |
-83°42'58.3" | 4.0" | XRT-final | UKSSDC |
0 |
-83°42'58.3" | 4.0" | XRT-refined | Perri et al. GCN Circ. 26685 |
0 |
-83°42'56.5" | 1.2' | BAT-refined | Barthelmy et al. GCN Circ. 26670 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Lipunov et al. | 26672 | Swift GRB 200107B: Global MASTER-Net observations report |
MASTER | |
Gamma-ray | Fermi | 26659 | Fermi GBM Final Real-time Localization | Fermi GBM | |
Gamma-ray | Lesage and Meegan | 26671 | Fermi GBM observation | Fermi GBM | Fluence=1.29±0.15x1 (8 |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
whit |
903 | 1052 | 55 | 19.3 (+0.5/-0.4) |
v | 1059 | 1079 | 19 | >18.6 |
b | 1157 | 1177 | 19 | >18.6 |
u | 1133 | 3144 | 179 | >19.7 |
w1 | 2777 | 2976 | 197 | >19.5 |
w2 | 1208 | 1228 | 19 | >18.2 |
Table 3. UVOT observations reported by Marshall and Bernardini (GCN Circ. 26693). 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.
January 10, 2020