A.Y. Lien (GSFC/UMBC), B. Sbarufatti (INAF-OAB/PSU) and A.A. Breeveld (UCL-MSSL) for the Swift team
At 21:03:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190103B (trigger=881709) (Lien et al. GCN Circ. 23602). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 89° from the Sun (4.8 hours West) and 70° from the 5%-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 Markwardt et al. (GCN Circ. 23606),
the BAT ground-calculated position is RA, Dec = 212.561, 35.254 deg which is RA(J2000) = 1
The mask-weighted light curve (Figure 1) shows several overlapping pulses that starts at ~T-10 s and ends at ~T+16 s.
The main peak occurs at ~
The time-averaged spectrum from T-10.43 to T+16.18 s is best fit by a power law with an exponential cutoff.
This fit gives a photon index 0.99 ± 0.29, and
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/881709/BA/.
Analysis of the initial XRT data was reported by Sbarufatti et al. (GCN Circ. 23604). We have analysed 32 ks of XRT data for GRB 190103B, from 99 s to 498.7 ks after the BAT trigger. The data comprise 437 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 23603).
The late-time light curve (Figure 2) (from T0+4.2 ks) can be modelled with a power-law decay with a decay index of α=1.21 ± 0.04.
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.38 ± 0.06. The best-fitting absorption column is 4.27 (+0.28, -0.27) x 1
A summary of the PC-mode spectrum is thus:
Total column: 4.1 ± 0.5 x 1
Galactic foreground: 1.4 x 1
Excess significance: 13.7 σ
Photon index: 1.93 (+0.10, -0.09)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00881709.
The Swift/UVOT began settled observations of the field of GRB 190103B 103 s after the BAT trigger
(Breeveld and Lien GCN Circ. 23684).
No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 23603) 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 |
+35°15'39.7" | 1.4" | XRT-final | UKSSDC |
1 |
+35°15'39.6" | 1.7" | XRT-enhanced | Evans et al. GCN Circ. 23603 |
1 |
+35°15'13.4" | 1.3' | BAT-refined | Markwardt et al. GCN Circ. 23606 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Quadri | 23607 | Bassano Bresciano observatory upper limit |
Bassano Bresciano Obs. | upper limits |
Gamma-ray | Tsvetkova et al. | 23612 | Konus-Wind observation | Konus-Wind | Duration=~27 seconds Fluence=1.96(-0.08,+0.08)x1 |
Gamma-ray | Tezuka et al. | 23631 | CALET Gamma-Ray Burst Monitor detection | CALET |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
whit |
103 | 253 | 147 | >20.5 |
316 | 565 | 246 | >19.5 | |
white | 103 | 23827 | 1860 | >21.8 |
v | 646 | 40393 | 2202 | >20.6 |
b | 571 | 46547 | 2987 | >21.5 |
u | 316 | 46101 | 3922 | >21.3 |
w1 | 4776 | 45188 | 3715 | >21.2 |
m2 | 4570 | 41036 | 2792 | >21.1 |
w2 | 4161 | 39480 | 1904 | >21.0 |
Table 3. UVOT observations reported by Breeveld and Lien (GCN Circ. 23684). 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 15, 2019