S.J. LaPorte (PSU), A. D'Ai (INAF-IASFPA) and F.E. Marshall (NASA/GSFC) for the Swift team
At 22:44:01 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190324A (trigger=894718) (LaPorte et al. GCN Circ. 23993). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 63° from the Sun (3.1 hours East) and 118° from the 81%-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.
Perley et al. (GCN Circ. 23999) determined a redshift of 1.1715 from VLT. 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 Lien et al. (GCN Circ. 24007),
the BAT ground-calculated position is RA, Dec = 49.603, -47.212 deg which is RA(J2000) = 0
The mask-weighted light curve (Figure 1) shows a precursor from ~
The time-averaged spectrum from T+0.09 to T+83.30 s is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 1.46 ± 0.06.
The fluence in the 15-150 keV band is 7.2 ± 0.2 x 1
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/894718/BA/.
Analysis of the initial XRT data was reported by D'Ai et al. (GCN Circ. 24004). We have analysed 15 ks of XRT data for GRB 190324A, from 3.3 ks to 176.6 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 24001).
The light curve (Figure 2) can be modelled with an initial power-law decay with an index of α=1.09 (+0.13, -0.26), followed by a break at T+9660 s to an α of 1.69 (+0.14, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.99 ± 0.09. The best-fitting absorption column is 8.3 (+2.2, -2.1) x 1
A summary of the PC-mode spectrum is thus:
Total column: 8.3 (+2.2, -2.1) x 1
Galactic foreground: 1.7 x 1
Excess significance: 5.1 σ
Photon index: 1.99 ± 0.09
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00894718.
Analysis of the UVOT data was reported by Marshall (GCN Circ. 23996).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 3302 seconds after the BAT trigger.
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 190324A 3302 s after the BAT trigger
(Siegel and LaPorte GCN Circ. 24014).
A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 24001) is detected in the initial UVOT exposures, consistent with the initial report of Marshall (GCN Circ. 23996).
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 |
-47°12'52.6" | 0.43" | UVOT-refined | Siegel and LaPorte GCN Circ. 24014 |
| 0 |
-47°12'54.1" | 1.4" | XRT-final | UKSSDC |
| 0 |
-47°12'53.5" | 1.5" | XRT-enhanced | Beardmore et al. GCN Circ. 24001 |
| 0 |
-47°12'42.4" | 1.0' | BAT-refined | Lien et al. GCN Circ. 24007 |
| Band | Authors | GCN Circ. | Subject | Observatory | Notes |
|---|---|---|---|---|---|
| Optical | Lipunov et al. | 23995 | SWIFT GRB190324.95 Global MASTER-Net observations report |
MASTER | |
| Optical | Perley et al. | 23999 | VLT/X-shooter redshift | VLT | redshift |
| Optical | Lipunov et al. | 24003 | MASTER OT observations | MASTER | light curve |
| Gamma-ray | Hui | 24002 | Fermi GBM observation | Fermi GBM | Fluence=1.78±0.03x1 (8 |
| Gamma-ray | Sone et al. | 24006 | CALET Gamma-Ray Burst Monitor detection | CALET | |
| Gamma-ray | Luo et al. | 24011 | Insight-HXMT/HE detection | Insight-HXMT | |
| Gamma-ray | Svinkin et al. | 24015 | Konus-Wind observation | Konus-Wind | Duration=~17.3 seconds Fluence=2.07(-0.28,+0.31)x1 |
| Other | Kunzweiler et al. | 23994 | Fermi Trigger 575160247 / GRB 190324947: BALROG localization |
| Filter | Exp(s) | Mag | ||
|---|---|---|---|---|
| white | 3302 | 3452 | 147 | 17.23 ± 0.04 |
| white | 33037 | 33944 | 885 | 19.65 ± 0.07 |
| white | 101768 | 119129 | 386 | >20.79 |
| v | 3459 | 3659 | 197 | 17.55 ± 0.11 |
| v | 28515 | 39157 | 496 | >19.48 |
| b | 4281 | 4481 | 197 | 17.98 ± 0.07 |
| b | 10929 | 11267 | 329 | 18.74 ± 0.08 |
| b | 32125 | 44180 | 1489 | 20.65 ± 0.34 |
| b | 101621 | 118983 | 386 | >20.13 |
| u | 4075 | 4275 | 197 | 16.75 ± 0.05 |
| u | 10016 | 10923 | 885 | 17.78 ± 0.05 |
| u | 22022 | 22836 | 792 | 18.86 ± 0.08 |
| u | 101474 | 118836 | 386 | >19.68 |
| uvw1 | 3870 | 4070 | 197 | 16.76 ± 0.07 |
| uvw1 | 9110 | 10010 | 885 | 17.65 ± 0.07 |
| uvw1 | 20525 | 21097 | 563 | 18.68 ± 0.16 |
| uvm2 | 3664 | 3864 | 197 | 16.79 ± 0.09 |
| uvm2 | 14888 | 15397 | 501 | 18.37 ± 0.13 |
| uvw2 | 4692 | 4892 | 197 | 17.82 ± 0.12 |
| uvw2 | 26341 | 38706 | 2052 | 19.76 ± 0.15 |
Table 3. UVOT observations reported by Siegel and LaPorte (GCN Circ. 24014). The start and stop times of the exposures are given in seconds since the BAT trigger. The preliminary detections and 3-σ upper limits are given. No correction has been made for extinction in the Milky Way.
March 27, 2019