E. Sonbas (Adiyaman Univ.), P. D'Avanzo (INAF-OAB) and M.H. Siegel (PSU) for the Swift team
At 11:18:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190627A (trigger=911609) (Sonbas et al. GCN Circ. 24888). Swift slewed immediately to the burst. At the time of the trigger, the initial BAT position was 145° from the Sun (9.9 hours East) and 144° from the 30%-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.
Siegel and Sonbas (GCN Circ. 24889) reported the detection with UVOT of an optical afterglow. Leonini et al. (GCN Circ. 24893) reported the position from Montarrenti for the optical afterglow of this GRB. Japelj et al. (GCN Circ. 24916) determined a redshift of 1.942 from VLT/FORS2. 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. 24899),
the BAT ground-calculated position is RA, Dec = 244.843, -5.302 deg which is RA(J2000) = 1
The mask-weighted light curve (Figure 1) shows a single peak, visible only in the softest energy channels, with a duration of about four seconds.
The burst location went out of the BAT field soon after T+400 s due to a spacecraft slew.
The time-averaged spectrum from T+0.04 to T+1.78 s is best fit by a simple power-law model.
The power law index of the time-averaged spectrum is 2.38 ± 0.38.
The fluence in the 15-150 keV band is 9.9 ± 2.2 x 1
The results of the batgrbproduct analysis are available at https://gcn.gsfc.nasa.gov/notices_s/911609/BA/.
Analysis of the initial XRT data was reported by D'Avanzo et al. (GCN Circ. 24906). We have analysed 25 ks of XRT data for GRB 190627A, from 98 s to 631.1 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 24890).
The light curve (Figure 2) can be modelled with an initial power-law decay with an index of α=0.23 (+0.16, -0.18), followed by a break at T+24.7 ks to an α of 1.46 ± 0.12.
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.06 (+0.15, -0.07). The best-fitting absorption column is consistent with the Galactic value of 1.8 x 1
A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.8 x 1
Intrinsic column: 1.8 ± 2.7 x 1
Photon index: 2.06 (+0.15, -0.07)
The results of the XRT team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00911609.
The Swift/UVOT began settled observations of the field of GRB 190627A 115 s after the BAT trigger
(Siegel and Sonbas GCN Circ. 24889).
An uncatalogued source consistent with the BAT position 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 |
-05°17'20.8" | 0.46" | UVOT-refined | Siegel and Sonbas GCN Circ. 24889 |
| 1 |
-05°17'20.5" | 1.4" | XRT-final | UKSSDC |
| 1 |
-05°17'20.4" | 1.7" | XRT-enhanced | Evans et al. GCN Circ. 24890 |
| 1 |
-05°18'08.6" | 2.7' | BAT-refined | Barthelmy et al. GCN Circ. 24899 |
| Band | Authors | GCN Circ. | Subject | Observatory | Notes |
|---|---|---|---|---|---|
| Optical | Pozanenko et al. | 24892 | NUTTelA-TAO optical observations | NUTTelA | detection |
| Optical | Leonini et al. | 24893 | Montarrenti Observatory optical detection |
Montarrenti | detection |
| Optical | Morris et al. | 24894 | VIRT Afterglow observation | Virgin Island Robotic Telescope | |
| Optical | Lipunov et al. | 24895 | MASTER optical counterpart observation | MASTER | detection |
| Optical | Mao | 24896 | GMG observation | Gao-Mei-Gu | detection |
| Optical | Pozanenko et al. | 24900 | NUTTelA-TAO optical counterpart observations |
NUTTelA | detection |
| Optical | Kann et al. | 24901 | Optical imaging and spectroscopy from Calar Alto |
Calar Alto | spectroscopy |
| Optical | Blazek et al. | 24902 | NIR imaging from Liverpool Telescope | Liverpool Telescope | |
| Optical | Jelinek and Strobl | 24903 | Optical imaging by D50 from Ondrejov | D50 | |
| Optical | Malesani et al. | 24904 | NOT optical observations | NOT | detection |
| Optical | Mao | 24905 | GMG observation at the second epoch | Gao-Mei-Gu | |
| Optical | Xin et al. | 24907 | Xinglong 2.16m optical observation | Xinglong | |
| Optical | Volnova et al. | 24911 | Koshka Zeiss-1000 optical counterpart observations |
Zeiss-1000 | detection |
| Optical | Japelj et al. | 24916 | VLT/FORS2 spectroscopic redshift | VLT/FORS2 | redshift |
| Optical | Dichiara et al. | 24986 | Discovery Channel Telescope late time observations |
Discovery Channel | detection |
| Filter | Exp(s) | Mag | ||
|---|---|---|---|---|
| white | 115 | 144 | 29 | 18.15 ± 0.10 |
Table 3. UVOT observation reported by Siegel and Sonbas (GCN Circ. 24889). The start and stop time of the exposure are given in seconds since the BAT trigger. The preliminary detection is given. No correction has been made for extinction in the Milky Way.
July 6, 2019