F.E. Marshall (NASA/GSFC), K.L. Page (U. Leicester) and S.R. Oates (U.Warwick) for the Swift team
At 14:15:23 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191106A (trigger=933515) (Marshall et al. GCN Circ. 26177). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 76° from the Sun (3.2 hours East) and 87° from the 70%-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 Barthelmy et al. (GCN Circ. 26198),
the BAT ground-calculated position is RA, Dec = 269.356, 46.046 deg which is RA(J2000) = 1
The mask-weighted light curve (Figure 1) shows many overlapping pulses.
The burst emission starts at ~T-1.3 s and ends at ~T+2.4 s.
The time-averaged spectrum from T-1.31 to T+2.38 s is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 0.89 ± 0.17.
The fluence in the 15-150 keV band is 3.2 ± 0.3 x 1
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/933515/BA/.
Analysis of the initial XRT data was reported by Page et al. (GCN Circ. 26190). We have analysed 12 ks of XRT data for GRB 191106A, from 56 s to 75.6 ks after the BAT trigger. The data comprise 30 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve (Figure 2) can be modelled with a power-law decay with a decay index of α=2.72 (+0.11, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.3 (+0.6, -0.5). The best-fitting absorption column is 4.1 (+3.2, -2.2) x 1
A summary of the PC-mode spectrum is thus:
Total column: 4.1 (+3.2, -2.2) x 1
Galactic foreground: 4.4 x 1
Excess significance: 2.7 σ
Photon index: 2.3 (+0.6, -0.5)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00933515.
The Swift/UVOT began settled observations of the field of GRB 191106A 132 s after the BAT trigger
(Oates and Marshall GCN Circ. 26199).
No optical afterglow consistent with the XRT position (Page et al., GCN Circ. 26190) 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 |
---|---|---|---|---|
1 |
+46°02'05.5" | 3.7" | XRT-final | UKSSDC |
1 |
+46°02'06.9" | 2.3" | XRT-refined | Page et al. GCN Circ. 26190 |
1 |
+46°02'44.7" | 1.7' | BAT-refined | Barthelmy et al. GCN Circ. 26198 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Lipunov et al. | 26178 | MASTER optical observation | MASTER | |
Optical | Hu et al. | 26179 | BOOTES-4/MET optical limit | BOOTES-4 | upper limits |
Optical | Belkin et al. | 26180 | Mondy optical upper limit | Mondy | upper limits |
Optical | Zhu et al. | 26191 | NOT optical upper limit | NOT | upper limits |
Gamma-ray | Gaikwad et al. | 26201 | AstroSat CZTI detection | CZTI |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
whit |
4987 | 5137 | 147 | >20.0 |
132 | 381 | 246 | >20.1 | |
white | 4987 | 6775 | 541 | >21.0 |
v | 437 | 7186 | 549 | >19.9 |
b | 387 | 12533 | 1264 | >21.3 |
u | 132 | 11621 | 1631 | >20.8 |
w1 | 486 | 7510 | 464 | >20.0 |
m2 | 461 | 7391 | 510 | >20.0 |
w2 | 412 | 13245 | 1223 | >20.6 |
Table 3. UVOT observations reported by Oates and Marshall (GCN Circ. 26199). 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.
November 9, 2019