Gamma-ray Burst 190823A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Notice

TITLE:           GCN/MAXI NOTICE
NOTICE_DATE:     Fri 23 Aug 19 14:01:53 UT
NOTICE_TYPE:     MAXI Unknown Source Position
EVENT_ID_NUM:    718431354
EVENT_RA:        279.18d {+18h 36m 43s} (J2000),
                 279.53d {+18h 38m 08s} (current),
                 278.28d {+18h 33m 07s} (1950)
EVENT_DEC:       -43.50d {-43d 29' 55"} (J2000),
                 -43.48d {-43d 28' 51"} (current),
                 -43.54d {-43d 32' 28"} (1950)
EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX:      682.0 +- 0.0 [mCrab]
EVENT_DATE:      18718 TJD;   235 DOY;   19/08/23
EVENT_TIME:      48639.00 SOD {13:30:39.00} UT
EVENT_TSCALE:    30s
EVENT_EBAND:     Low, 2-4 keV
SUN_POSTN:       152.25d {+10h 09m 00s}  +11.41d {+11d 24' 42"}
SUN_DIST:        124.54 [deg] 
MOON_POSTN:       58.23d {+03h 52m 56s}  +16.41d {+16d 24' 39"}
MOON_DIST:       135.83 [deg] 
MOON_ILLUM:      51 [%] 
GAL_COORDS:      351.73,-15.81 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.09,-20.29 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.

GCN Notice

 
TITLE:           GCN/MAXI NOTICE
NOTICE_DATE:     Fri 23 Aug 19 14:14:42 UT
NOTICE_TYPE:     MAXI Unknown Source Position
EVENT_ID_NUM:    718431354
EVENT_RA:        279.28d {+18h 37m 07s} (J2000),
                 279.63d {+18h 38m 32s} (current),
                 278.38d {+18h 33m 30s} (1950)
EVENT_DEC:       -43.44d {-43d 26' 19"} (J2000),
                 -43.42d {-43d 25' 15"} (current),
                 -43.48d {-43d 28' 53"} (1950)
EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX:      322.0 +- 0.0 [mCrab]
EVENT_DATE:      18718 TJD;   235 DOY;   19/08/23
EVENT_TIME:      48639.00 SOD {13:30:39.00} UT
EVENT_TSCALE:    30s
EVENT_EBAND:     Low, 2-4 keV
SUN_POSTN:       152.26d {+10h 09m 02s}  +11.41d {+11d 24' 31"}
SUN_DIST:        124.62 [deg] 
MOON_POSTN:       58.35d {+03h 53m 23s}  +16.44d {+16d 26' 30"}
MOON_DIST:       135.89 [deg] 
MOON_ILLUM:      51 [%] 
GAL_COORDS:      351.81,-15.85 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      277.17,-20.23 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.

GCN Circular #25456
W. Iwakiri(Chuo U.), M. Serino(AGU), H. Negoro, M. Nakajima, W. Maruyama, M. Aoki, K. Kobayashi (Nihon U.), T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Nishida, A. Yoshida (AGU), Y. Tsuboi, R. Sasaki, H. Kawai, T. Sato (Chuo U.), M. Shidatsu (Ehime U.), N. Kawai, M. Sugizaki, M. Oeda, K. Shiraishi (Tokyo Tech), S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, N.Isobe, R. Shimomukai, M. Tominaga (JAXA), Y. Ueda, A. Tanimoto, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake (Kyoto U.), H. Tsunemi, T. Yoneyama, K. Asakura, S. Ide (Osaka U.), M. Yamauchi, S. Iwahori, Y. Kurihara, K. Kurogi, K. Miike (Miyazaki U.), T. Kawamuro (NAOJ), K. Yamaoka (Nagoya U.), Y. Kawakubo (LSU) report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 13:30:22 UT on 2019 August 23. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (279.278 deg, -43.439 deg) = (18 37 06, -43 26 19) (J2000) with a 90% C.L. statistical error of 0.17 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius).
Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners:
```
(R.A., Dec) = (280.193, -43.737) deg = (18 40 46, -43 44 13) (J2000)
(R.A., Dec) = (280.285, -43.434) deg = (18 41 08, -43 26 02) (J2000)
(R.A., Dec) = (278.903, -43.205) deg = (18 35 36, -43 12 17) (J2000)
(R.A., Dec) = (278.804, -43.508) deg = (18 35 12, -43 30 28) (J2000) 
```
The X-ray flux averaged over the scan was 322 +- 29 mCrab (4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 11:57 with an upper limit of 20 mCrab.
GCN Circular #25459
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 190823A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00085
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular #25476
E. Ambrosi (INAF-IASFPA), A. DAi (INAF-IASFPA) and V. D Elia (ASDC) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 190823A (Iwakiri et al. GCN circ. 25456) in a series of observations tiled on the sky.
Total exposure time is 1.8 ks, distributed over 7 tiles. The data were collected between T0+12.1 ks and T0+18 ks.
One uncatalogued X-ray source has been detected, with the following details:
```
RA (J2000.0):      279.68736d = 18:38:44.97
Dec (J2000.0):    -43.52789d = -43:31:40.4
```
Error: 8.6 arcsec (radius, 90% conf.)
Count-rate: 4.1 (+1.7, -1.3) ×10^-2 ct s^ -1
Distance: 18.6 arcmin from MAXI position
The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00085/ .
This circular is an official product of the Swift-XRT team.
GCN Circular #25541
R. Gaikwad, M. Chavan, V. Sharma and D. Bhattacharya and A. Vibhute (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data showed the detection of a GRB 190823A, which was also detected by Swift-XRT (E. Ambrosi et al., GCN #25476) and Tiled Swift observations (Evans P. A. et al., GCN #25459).
The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple pulses of emission with the strongest peak at 2019-08-23 13:30:05.0 UT. The measured peak count rate associated with the burst is 287 cts/s above the background in the combined data of four quadrants, with a total of 1445 cts. The local mean background count rate was 460 cts/s. Using cumulative rates, we measure a T90 of 7.3 s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.
GCN Circular #25680
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A. Tohuvavohu (U Toronto), J.A. Kennea (PSU), B. Sbarufatti (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed further observations of the MAXI-detected burst GRB 190823A (Iwakiri et al. GCN Circ. 25456). The observations now extend from T0+12.3 ks and T0+1148.9 ks with a total exposure time of 4.1 ks in Photon Counting (PC) mode.
The source previously reported by Ambrosi et al. (GCN Circ. 25476) is fading with 3-sigma significance, and is therefore likely the GRB afterglow. Using 147 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 279.68735, -43.52789 which is equivalent to:
```
RA (J2000): 18h 38m 44.97s
Dec(J2000): -43d 31' 40.4"
```
with an uncertainty of 8.7 arcsec (radius, 90% confidence). This position is 18.6 arcmin from the MAXI position. The source is fading with alpha >0.7.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020932. The results of the full analysis of the tiled XRT observations are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00085.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 06-Sep-2019 [Disclaimer]