Gamma-ray Burst 200922A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:07:01 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.915d {+19h 47m 40s} (J2000),
                 297.328d {+19h 49m 19s} (current),
                 295.915d {+19h 43m 40s} (1950)
GRB_DEC:         -55.204d {-55d 12' 12"} (J2000),
                 -55.151d {-55d 09' 03"} (current),
                 -55.328d {-55d 19' 38"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       594 [cnts]    Image_Peak=96 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10418     E_range: 25-100 keV
BKG_INTEN:       17756 [cnts]
BKG_TIME:        43590.32 SOD {12:06:30.32} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19114 TJD;   266 DOY;   20/09/22
GRB_TIME:        43606.64 SOD {12:06:46.64} UT
GRB_PHI:           1.60 [deg]
GRB_THETA:        32.96 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.77 [sigma]
IMAGE_SIGNIF:    10.54 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +2  +0  +0  +0 +25  +0 
SUN_POSTN:       179.95d {+11h 59m 48s}   +0.02d {+00d 01' 16"}
SUN_DIST:        105.25 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.33d {+16h 33m 19s}  -20.55d {-20d 33' 12"}
MOON_DIST:        50.27 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.85 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      288.03,-33.44 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 193.29,-15.76 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:08:41 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.9563d {+19h 47m 49.51s} (J2000),
                 297.3694d {+19h 49m 28.66s} (current),
                 295.9563d {+19h 43m 49.50s} (1950)
GRB_DEC:         -55.2048d {-55d 12' 17.2"} (J2000),
                 -55.1521d {-55d 09' 07.6"} (current),
                 -55.3288d {-55d 19' 43.8"} (1950)
GRB_ERROR:       5.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       8.21e-10 [erg/cm2/sec]
GRB_SIGNIF:      6.48 [sigma]
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43682.21 SOD {12:08:02.21} UT,   75.6 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.18 261.68 243.68
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       179.95d {+11h 59m 48s}   +0.02d {+00d 01' 15"}
SUN_DIST:        105.27 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.35d {+16h 33m 23s}  -20.56d {-20d 33' 26"}
MOON_DIST:        50.28 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.88 [deg] galactic lon,lat of the burst
ECL_COORDS:      288.06,-33.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.42 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:08:59 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.9563d {+19h 47m 49.5s} (J2000),
                 297.3694d {+19h 49m 28.6s} (current),
                 295.9563d {+19h 43m 49.5s} (1950)
GRB_DEC:         -55.2048d {-55d 12' 17.2"} (J2000),
                 -55.1521d {-55d 09' 07.6"} (current),
                 -55.3288d {-55d 19' 43.8"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       42 [cnts]
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43682.21 SOD {12:08:02.21} UT,   75.6 [sec] since BAT Trigger Time
CENTROID_X:      338.75,  raw= 339  [pixels]
CENTROID_Y:      300.22,  raw= 300  [pixels]
ROLL:            247.35 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   5.00
GRB_POS_XRT_Z:   73.91
IMAGE_URL:       sw00997024000msxps_rw.img
SUN_POSTN:       179.95d {+11h 59m 49s}   +0.02d {+00d 01' 15"}
SUN_DIST:        105.27 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.35d {+16h 33m 24s}  -20.56d {-20d 33' 28"}
MOON_DIST:        50.28 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.88 [deg] galactic lon,lat of the burst
ECL_COORDS:      288.06,-33.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:08:49 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.9563d {+19h 47m 49.5s} (J2000),
                 297.3694d {+19h 49m 28.6s} (current),
                 295.9563d {+19h 43m 49.5s} (1950)
GRB_DEC:         -55.2048d {-55d 12' 17.2"} (J2000),
                 -55.1521d {-55d 09' 07.6"} (current),
                 -55.3288d {-55d 19' 43.8"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       42 [cnts]
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43682.21 SOD {12:08:02.21} UT,   75.6 [sec] since BAT Trigger Time
CENTROID_X:      338.75,  raw= 339  [pixels]
CENTROID_Y:      300.22,  raw= 300  [pixels]
ROLL:            247.35 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   5.00
GRB_POS_XRT_Z:   73.91
IMAGE_URL:       sw00997024000msxps_rw.img
SUN_POSTN:       179.95d {+11h 59m 49s}   +0.02d {+00d 01' 15"}
SUN_DIST:        105.27 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.35d {+16h 33m 23s}  -20.56d {-20d 33' 27"}
MOON_DIST:        50.28 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.88 [deg] galactic lon,lat of the burst
ECL_COORDS:      288.06,-33.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:11:28 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     997024,   Seg_Num: 0
POINT_RA:        296.922d {+19h 47m 41s} (J2000)
POINT_DEC:       -55.211d {-55d 12' 39"} (J2000)
POINT_ROLL:      247.347d
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43692.08 SOD {12:08:12.08} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.133
N_STARS:         155
X_OFFSET:        520 [pixels]
Y_OFFSET:        624 [pixels]
X_MAX:           1479 [pixels]
Y_MAX:           1583 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00997024000msufc0085.fits
SUN_POSTN:       179.95d {+11h 59m 49s}   +0.02d {+00d 01' 12"}
SUN_DIST:        105.25 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.37d {+16h 33m 30s}  -20.56d {-20d 33' 49"}
MOON_DIST:        50.25 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.59,-29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      288.04,-33.44 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:12:00 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.915d {+19h 47m 40s} (J2000),
                 297.328d {+19h 49m 19s} (current),
                 295.915d {+19h 43m 40s} (1950)
GRB_DEC:         -55.204d {-55d 12' 12"} (J2000),
                 -55.151d {-55d 09' 03"} (current),
                 -55.328d {-55d 19' 38"} (1950)
GRB_DATE:        19114 TJD;   266 DOY;   20/09/22
GRB_TIME:        43606.58 SOD {12:06:46.58} UT
TRIGGER_INDEX:   10418
GRB_PHI:           1.60 [deg]
GRB_THETA:        32.96 [deg]
DELTA_TIME:      -25.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     8.77 [sigma]
IMAGE_SIGNIF:    10.54 [sigma]
LC_URL:          sw00997024000msb.lc
SUN_POSTN:       179.95d {+11h 59m 49s}   +0.02d {+00d 01' 12"}
SUN_DIST:        105.25 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.38d {+16h 33m 31s}  -20.56d {-20d 33' 53"}
MOON_DIST:        50.24 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.85 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      288.03,-33.44 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 193.29,-15.76 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:11:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     997024,   Seg_Num: 0
POINT_RA:        296.922d {+19h 47m 41s} (J2000)
POINT_DEC:       -55.211d {-55d 12' 39"} (J2000)
POINT_ROLL:      247.347d
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43692.08 SOD {12:08:12.08} UT,   85.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.133
N_STARS:         155
X_OFFSET:        520 [pixels]
Y_OFFSET:        624 [pixels]
X_MAX:           1479 [pixels]
Y_MAX:           1583 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00997024000msufc0085.fits
SUN_POSTN:       179.95d {+11h 59m 49s}   +0.02d {+00d 01' 12"}
SUN_DIST:        105.25 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.38d {+16h 33m 30s}  -20.56d {-20d 33' 50"}
MOON_DIST:        50.25 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.59,-29.86 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      288.04,-33.44 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 22 Sep 20 12:26:38 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     997024,   Seg_Num: 0
GRB_RA:          296.9542d {+19h 47m 49.00s} (J2000),
                 297.3673d {+19h 49m 28.16s} (current),
                 295.9542d {+19h 43m 49.00s} (1950)
GRB_DEC:         -55.2024d {-55d 12' 08.6"} (J2000),
                 -55.1497d {-55d 08' 59.0"} (current),
                 -55.3264d {-55d 19' 35.1"} (1950)
GRB_ERROR:       4.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19114 TJD;   266 DOY;   20/09/22
IMG_START_TIME:  43813.00 SOD {12:10:13.00} UT,   206.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       179.96d {+11h 59m 51s}   +0.02d {+00d 00' 57"}
SUN_DIST:        105.26 [deg]   Sun_angle= -7.8 [hr] (East of Sun)
MOON_POSTN:      248.53d {+16h 34m 07s}  -20.60d {-20d 35' 52"}
MOON_DIST:        50.15 [deg]
MOON_ILLUM:      33 [%]
GAL_COORDS:      342.60,-29.88 [deg] galactic lon,lat of the burst
ECL_COORDS:      288.06,-33.44 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.11% < P(seren) < 0.58%.

GCN Circular #28471
M. J. Moss (GWU), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 12:06:46 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200922A (trigger=997024). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 296.915, -55.204 which is
```
   RA(J2000) = 19h 47m 40s
   Dec(J2000) = -55d 12' 12"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 10 sec. The peak count rate was ~10000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 12:08:02.2 UT, 75.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 296.95425, -55.20245 which is equivalent to:
```
   RA(J2000)  = 19h 47m 49.02s
   Dec(J2000) = -55d 12' 08.8"
```
with an uncertainty of 4.2 arcseconds (radius, 90% containment). This location is 80 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 4.71 x 10^20 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 8.21e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 85 seconds after the BAT trigger. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. There is a 14.4 mag source at (296.95361,-55.20447) 8.3 arc seconds from the center of the XRT error region. There is a much weaker source at the same position in the DSS. No correction has been made for the expected extinction corresponding to E(B-V) of 0.05.
Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #28473
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 50 s of XRT Photon Counting mode data and 1 UVOT images for GRB 200922A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 296.95259, -55.20359 which is equivalent to:
```
RA (J2000): 19h 47m 48.62s
Dec (J2000): -55d 12' 12.9"
```
with an uncertainty of 2.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #28476
A. D'Ai (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and M.J. Moss report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 200922A (Moss et al. GCN Circ. 28471), from 81 s to 23.1 ks after the BAT trigger. The data comprise 123 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. 28473).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.148 (+0.026, -0.025).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.33 (+0.18, -0.17). The best-fitting absorption column is 1.6 (+0.5, -0.4) x 10^21 cm^-2, in excess of the Galactic value of 4.7 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.18 (+0.24, -0.23) and a best-fitting absorption column of 2.4 (+0.9, -0.8) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (5.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.4 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 4.7 x 10^20 cm^-2
Excess significance: 4.3 sigma
Photon index:	     2.18 (+0.24, -0.23)
```
If the light curve continues to decay with a power-law decay index of 1.148, the count rate at T+24 hours will be 4.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x 10^-13 (2.4 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00997024.
This circular is an official product of the Swift-XRT team.
GCN Circular #28477
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200922A ( M. J. Moss et al., GCN 28471) errorbox 37015 sec after notice time and 37039 sec after trigger time at 2020-09-22 22:24:05 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 48 deg. The sun altitude is -57.9 deg.
The galactic latitude b = -30 deg., longitude l = 343 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1446564
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   37129 |         MASTER-SAAO |   C |   180 | 20.5 |        
   37129 |         MASTER-SAAO |   C |   180 | 20.4 |        
   37329 |         MASTER-SAAO |   C |   180 | 20.5 |        
   37329 |         MASTER-SAAO |   C |   180 | 20.4 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #28478
L. Izzo (DARK/NBI), D. B. Malesani (DTU Space) and D. A. Kann (HETH/IAA-CSIC) report:
We observed the field of GRB 200922A (Moss et al., GCN #28471) with the Sinistro instrument mounted on the 1-m telescope of the LCO network located at Siding Spring Observatory, Australia. Observations started on September 22 at 13:53:10 UT (1.77 hours after the GRB trigger). We obtained a series of 5x120s images in r and i filters each.
Within the UVOT-enhanced XRT position at RA (J2000) = 19:47:48.87 (296.95364), Dec. (J2000) = -55:12:15.9 (-55.20442) with an error of 1".5 (improved compared to the one reported in Osborne et al., GCN #28473) we clearly detect the source that had also been seen in the early UVOT observation (Moss et al., GCN #28471) at a white magnitude of 14.4. In our stacked image we measure i = 17.31 +- 0.04 (AB mag), calibrated against nearby SkyMapper catalog stars. This value is brighter than the archival value i = 17.74 +- 0.01 mag from the SkyMapper Data Release 2 (Onken et al., 2019, PASA 36, 33). Our result suggests variability compared to the historic value, and likely fading compared to the earlier UVOT observation. Similar fading is also measured versus archival DECam field images (i = 17.79 +- 0.02 mag, NOIRLab Prop. ID 2017A-0388; PI: A. Zenteno).
The coordinates of the source in our images are (J2000.0):
```
RA = 19:47:48.9285
Dec = -55:12:16.421
```
At this stage, it is unclear if this GRB was caused by the likely stellar source, or if it is a background GRB that happens to have occurred very close to a foreground object. Further observations are encouraged.
This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 730890.

GCN Circular #28482
M. H. Siegel (PSU) and M. J. Moss (GWU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 200922A 86 s after the BAT trigger (Moss et al., GCN Circ. 28471). We identify a fading source near the XRT position (Osborne et al. GCN Circ. 28473) and also at the location of a weak source in the DSS. The source position is:

  RA(J2000)  =	19:47:48.76 = 296.95317
  DEC(J2000) = -55:12:16.5  = -55.20457

Which is 3.0 arc-second from the enhanced XRT position.
Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               86          236          147      14.37+/-0.02
white             4770         4970          196      17.51+/-0.04
white            28889        28909           19      18.62+/-0.20
v                 3745         3945          196      17.35+/-0.10
v                 9268        23149         1460      17.79+/-0.05
b                 4566         4765          196      17.95+/-0.07
b                27982        28889          881      18.49+/-0.05
u                 4360         4560          196      17.18+/-0.06
u                15921        16791          848      18.20+/-0.06
uvw1              4156         4355          196      17.23+/-0.10
uvw1             11089        15915          887      18.26+/-0.09
uvw1             50455        56029          225      18.97+/-0.27
uvm2              3950         4150          196      17.12+/-0.12
uvm2             10182        11081          885      18.19+/-0.10
uvm2             50396        55850          223      19.26+/-0.36
uvw2              3541         5089          307      17.14+/-0.09
uvw2             21653        22553          885      18.77+/-0.12
uvw2             50338        55672          223            >19.44

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).

GCN Circular #28483
P.A. Evans (U. Leicester), A. D’ai (INAF-IASFPA) and M. J. Moss (GWU) report on behalf of the Swift-XRT team:
The enhanced-XRT position reported in GCN Circ. 28473 was a particularly poor position and has been improved and shifted by the receipt of further data, as noted by Izzo et al (GCN. Circ. 28478).
The best XRT position, available at https://www.swift.ac.uk/xrt_positions/00997024/ is RA, Dec = 296.95364, -55.20442 degrees which is equivalent to:
```
RA (J2000)  = 19h 47m 48.87s
Dec (J2000)  = -55d 12' 15.9”
```
with an uncertainty of 1.5” (radius, 90% confidence). This position is consistent with the source seen by UVOT and LCO (GCN Circs. 28471, 28478).
It is normal for the XRT position to evolve slightly as new data are received, with the website always being the source of the most recent position. In the case of this GRB, the first visibility window for Swift was very short, and the satellite attitude appears to have been less stable than usual; this resulted in the position in GCN 28473 being unusually inaccurate.
This circular is an official product of the Swift-XRT team.
GCN Circular #28484
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (GWU), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+871 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200922A (trigger #997024) (Moss et al., GCN Circ. 28471). The BAT ground-calculated position is RA, Dec = 296.954, -55.199 deg which is
```
   RA(J2000)  =  19h 47m 49.0s
   Dec(J2000) = -55d 11' 55.1"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 74%.
The mask-weighted light curve shows a single FRED-like pulse that starts at ~T-2 s, peaks at ~T+0, and ends at ~T+16 s. T90 (15-350 keV) is 10.30 +- 1.96 sec (estimated error including systematics).
The time-averaged spectrum from T-1.91 to T+16.22 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.43 +- 0.26, and Epeak of 39.3 +- 5.7 keV (chi squared 52.48 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.8 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T-0.46 sec in the 15-150 keV band is 11.4 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.12 +- 0.06 (chi squared 76.50 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/997024/BA/
GCN Circular #28490
Y. Q. Zhang, Y. G. Zheng, C. Cai, Q. Luo, S. Xiao, Q. B. Yi, C. K. Li, G. Li, X. B. Li, J. Y. Liao, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team:
At 2020-09-22T12:06:46.00 (T0), Insight-HXMT/HE detected GRB 200922A (trigger ID: HEB200922504) in a routine search of the data, which also triggered Swift/BAT (Moss et al., GCN #28471).
The Insight-HXMT/HE light curve mainly consists of single pulses with a duration (T90) of 1.87 s measured from T0+0.04 s. The 1-ms peak rate, measured from T0+0.18 s, is 629 cnts/sec. The total counts from this burst is 742 counts. URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB200922504_lc.jpg
All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org.
GCN Circular #28492
D. B. Malesani (DTU Space), L. Izzo (DARK/NBI), D. A. Kann (HETH, IAA/CSIC), A. de Ugarte Postigo (HETH, IAA/CSIC), A. J. Levan (Radboud Univ.), D. Xu (NAOC), P. D'Avanzo (INAF/OABr), and A. Rossi (INAF/OAS) report on behalf of the Stargate collaboration:
For the recent GRB 200922A, several authors have noted the presence of a bright optical afterglow, initially detected by UVOT onboard the Neil Gehrels Swift observatory (Moss et al., GCN 28471; Izzo et al., GCN 28478; Siegel & Moss, GCN 28482), superimposed on a point-like object, seen e.g. in the DSS, DECam, and SkyMapper surveys.
We retrieved the white-band UVOT images (Siegel & Moss, GCN 28482). We focused on the initial image (344 s exposure starting at 12:08:32 UT on Sep 22) and on the image taken roughly one day after (274 s exposure starting at 10:05:38 UT on Sep 23). We also retrieved for comparison the archival DECam i-band images of the same region (from 2017 August).
We remark that the position of the UVOT object is entirely consistent with the latest XRT position of the afterglow (Evans et al., GCN 28483; see also https://www.swift.ac.uk/xrt_positions/), strengthening the association between the optical transient and GRB 200922A.
We then cross-matched the astrometry between the UVOT and the archival DECam images. The scatter in the astrometric solution, computed on stars of brightness similar to the UVOT afterglow, is 0.06 and 0.10 arcsec for the initial and late exposure, respectively.
In the initial UVOT image, we measure an offset of 0.62" compared to the object seen in the archival data. While small, this offset is significant. The same comparison carried out in the late time image, however, returns no measurable offset to within the errors. Independently, we also checked that the proper motion of the star (catalogued in the Gaia DR2; Brown et al. 2018, A&A, 616, A1) is too small to play any effect in producing the offset.
We thus conclude that this is a rare case of near-perfect chance superposition between a background afterglow and a bright foreground star. In the initial UVOT image, the light was dominated by the afterglow (thus yielding the offset in the position), which subsequently faded to a level fainter than the foreground star. The light curve of the X-ray afterglow (D'Ai et al., GCN 28476) is also consistent with this interpretation, as it shows the typical behaviour of a cosmological GRB.
A spectrum of the optical transient was taken using the ESO VLT1 UT1 (Antu) equipped with the FORS2 instrument. Observations were carried out using the grisms 300V and 300I (900 s exposure each), covering the wavelength range 3500-9200 AA, and started on 2020 Sep 22.997 UT (11.8 hr after the trigger). In the acquisition image, using (old) archival zeropoints, we measure V = 18.0 (Vega). This value is roughly consistent with the archival values of the star (for example the Gaia catalog gives G = 17.85), and indicates only little contribution from the afterglow at the epoch of our spectrum (at least in the V band).
The spectrum we observe is consistent with the one of a G-type star. Absorption features are observed at z = 0 from Ca H and K, Mg I, Na I D, Hdelta, Hgamma, Hbeta, and Halpha. The ordinary type of the star supports the lack of a connection with the GRB. A search was conducted for potential emission lines from the background GRB host galaxy, but the intense and spatially-variable glare from the star does not allow us to place quantitative limits. We are thus unfortunately unable to provide constraints on the GRB redshift.
We welcome the reopening of the ESO observatory at Paranal, even if at reduced capacity. We thank the ESO staff for carrying out our observations, in particular Steffen Mieske, Claudia Cid, and Romain Thomas, as well as and the entire support team on- and off-site.
GCN Circular #28505
A. Pozanenko (IKI), S. Belkin (IKI), A. Volnova (IKI), P. Minaev (IKI), N. Pankov (HSE) report on behalf GRB IKI FuN collaboration:
We observed the field of GRB 200922A (Moss et al., GCN 28471) with RC-1000 Chilescope observatory in r'-filter starting on 2020-09-22 (UT) 23:25:05. In a single obtained image of 1200 s exposure we cannot resolve the OT reported earlier (Moss et al., GCN 28471; Izzo et al., GCN 28478; Siegel et al., GCN 28482; Malesani et al., GCN 28492). Instead we subtract the flux of nearby star from SkyMapper DR1.1 from the (nearby star + OT) photometry. Preliminary photometry of the OT after the above-mentioned procedure is following.
```
Date       UT start  t-T0    Filter Exp.  OT(AB) Err.  UL(AB)
                     (mid, days)     (s)

2020-09-22 23:25:05  0.478   r'     1200  18.92  0.05  20.7
```
The photometry is based on nearby SkyMapper DR1.1 stars.

Back to JG's homepage

Jochen Greiner, last update: 26-Sep-2020 [Disclaimer]