J.D. Gropp (PSU), A.P. Beardmore (U. Leicester) and K.K. Simpson (PSU) for the Swift team
At 05:12:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190109A (trigger=882747) (Gropp et al. GCN Circ. 23642). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 114° from the Sun (6.9 hours East) and 83° from the 9%-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 Sakamoto et al. (GCN Circ. 23653),
the BAT ground-calculated position is RA, Dec = 33.213, 38.111 deg, which is RA(J2000) = 0
The mask-weighted light curve (Figure 1) shows several overlapping peaks starting at ~T+1 s, peaking at ~T+40 s, and returning to baseline at ~T+200 s.
The time-averaged spectrum from T+5.86 to T+205.36 s (with a 1.03 s gap in the data at T+111.97 s) is best fit by a power law with an exponential cutoff.
This fit gives a photon index 0.36 ± 0.47, and
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/882747/BA/.
Analysis of the initial XRT data was reported by Beardmore et al. (GCN Circ. 23645). We have analysed 19 ks of XRT data for GRB 190109A, from 175 s to 184.7 ks after the BAT trigger. The data comprise 291 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 23643).
The late-time light curve (Figure 2) (from T0+4.8 ks) can be modelled with a power-law decay with a decay index of α=1.34 (+0.12, -0.11).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.87 ± 0.04. The best-fitting absorption column is 9.5 (+1.3, -1.2) x 1
A summary of the PC-mode spectrum is thus:
Total column: 5.4 (+3.9, -0.3) x 1
Galactic foreground: 5.1 x 1
Excess significance: <1.6 σ
Photon index: 1.84 (+0.15, -0.10)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00882747.
The Swift/UVOT began settled observations of the field of GRB 190109A 181 s after the BAT trigger
(Simpson and Gropp GCN Circ. 23663).
No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 23644) 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
The Swift/UVOT began settled observations of the field of GRB 190109A 181 s after the BAT trigger
( GCN Circ. 23673).
No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 23644) 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 |
+38°06'29.7" | 1.4" | XRT-final | UKSSDC |
0 |
+38°06'30.7" | 1.8" | XRT-enhanced | Osborne et al. GCN Circ. 23644 |
0 |
+38°06'39.5" | 1.0' | BAT-refined | Sakamoto et al. GCN Circ. 23653 |
Band | Authors | GCN Circ. | Subject | Observatory | Notes |
---|---|---|---|---|---|
Optical | Oeda et al. | 23649 | MITSuME Akeno optical upper limits | MITSuME Akeno | upper limits |
Gamma-ray | von Kienlin | 23658 | Fermi GBM observation | Fermi GBM | Fluence=7.6±0.4x1 (6 |
Filter | Exp(s) | Mag | ||
---|---|---|---|---|
whit |
181 | 331 | 147 | >21.60 |
white | 181 | 12997 | 1291 | >20.27 |
v | 670 | 6867 | 490 | >16.8 |
b | 596 | 18739 | 1727 | >18.6 |
u | 340 | 24226 | 2551 | >17.5 |
w1 | 720 | 23954 | 2223 | >17.4 |
m2 | 695 | 23048 | 1357 | >18.1 |
w2 | 646 | 6662 | 491 | >17.9 |
Table 3. UVOT observations reported by (GCN Circ. 23673). 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 12, 2019