Gamma-ray Burst 220907A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:05:40 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1123129,   Seg_Num: 0
GRB_RA:          268.870d {+17h 55m 29s} (J2000),
                 269.207d {+17h 56m 50s} (current),
                 268.126d {+17h 52m 30s} (1950)
GRB_DEC:         -20.315d {-20d 18' 54"} (J2000),
                 -20.317d {-20d 19' 02"} (current),
                 -20.308d {-20d 18' 28"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2822 [cnts]    Image_Peak=170 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       16678 [cnts]
BKG_TIME:        50714.18 SOD {14:05:14.18} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19829 TJD;   250 DOY;   22/09/07
GRB_TIME:        50725.76 SOD {14:05:25.76} UT
GRB_PHI:         174.47 [deg]
GRB_THETA:        25.03 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     13.96 [sigma]
IMAGE_SIGNIF:    8.52 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -1  +0  +1 +23  +0 
SUN_POSTN:       166.13d {+11h 04m 31s}   +5.93d {+05d 55' 54"}
SUN_DIST:        104.30 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
MOON_POSTN:      310.13d {+20h 40m 30s}  -23.54d {-23d 32' 27"}
MOON_DIST:        37.97 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:        8.55,  2.49 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      268.94,  3.12 [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 = 142.69,-19.19 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=684252331).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:05:56 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     684252331
GRB_RA:          265.783d {+17h 43m 08s} (J2000),
                 266.086d {+17h 44m 21s} (current),
                 265.117d {+17h 40m 28s} (1950)
GRB_DEC:          -5.417d {-05d 25' 00"} (J2000),
                  -5.426d {-05d 25' 31"} (current),
                  -5.395d {-05d 23' 40"} (1950)
GRB_ERROR:       14.77 [deg radius, statistical plus systematic]
GRB_INTEN:       115 [cnts/sec]
DATA_SIGNIF:     7.50 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        19829 TJD;   250 DOY;   22/09/07
GRB_TIME:        50726.48 SOD {14:05:26.48} UT
GRB_PHI:          89.00 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.72
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      94%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,1,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:       166.13d {+11h 04m 31s}   +5.93d {+05d 55' 54"}
SUN_DIST:        100.43 [deg]   Sun_angle= -6.7 [hr] (East of Sun)
MOON_POSTN:      310.13d {+20h 40m 31s}  -23.54d {-23d 32' 24"}
MOON_DIST:        46.07 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       20.07, 12.54 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      265.59, 17.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_lc_medres34_bn220907587.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 138.58,4.55 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1123129).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:06:13 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     684252331
GRB_RA:          269.620d {+17h 58m 29s} (J2000),
                 269.953d {+17h 59m 49s} (current),
                 268.886d {+17h 55m 33s} (1950)
GRB_DEC:         -18.620d {-18d 37' 11"} (J2000),
                 -18.620d {-18d 37' 13"} (current),
                 -18.616d {-18d 36' 58"} (1950)
GRB_ERROR:       5.58 [deg radius, statistical only]
DATA_SIGNIF:     8.50 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        19829 TJD;   250 DOY;   22/09/07
GRB_TIME:        50726.48 SOD {14:05:26.48} UT
GRB_PHI:          99.00 [deg]
GRB_THETA:        75.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       166.13d {+11h 04m 31s}   +5.93d {+05d 55' 53"}
SUN_DIST:        104.96 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
MOON_POSTN:      310.13d {+20h 40m 32s}  -23.54d {-23d 32' 22"}
MOON_DIST:        37.69 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       10.38,  2.73 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      269.64,  4.82 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_lc_medres34_bn220907587.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_684252331.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1123129).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:14:55 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     684252331
GRB_RA:          269.620d {+17h 58m 29s} (J2000),
                 269.953d {+17h 59m 49s} (current),
                 268.885d {+17h 55m 32s} (1950)
GRB_DEC:         -18.700d {-18d 41' 59"} (J2000),
                 -18.700d {-18d 42' 01"} (current),
                 -18.696d {-18d 41' 46"} (1950)
GRB_ERROR:       6.86 [deg radius, statistical only]
GRB_DATE:        19829 TJD;   250 DOY;   22/09/07
GRB_TIME:        50726.48 SOD {14:05:26.48} UT
GRB_PHI:          99.00 [deg]
GRB_THETA:        75.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       166.14d {+11h 04m 33s}   +5.93d {+05d 55' 45"}
SUN_DIST:        104.96 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
MOON_POSTN:      310.22d {+20h 40m 54s}  -23.52d {-23d 31' 04"}
MOON_DIST:        37.76 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:       10.31,  2.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      269.64,  4.74 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_lc_medres34_bn220907587.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_locplot_all_bn220907587.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Short GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1123129).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:07:03 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1123129,   Seg_Num: 0
POINT_RA:        268.878d {+17h 55m 31s} (J2000)
POINT_DEC:       -20.308d {-20d 18' 29"} (J2000)
IMG_START_DATE:  19829 TJD;   250 DOY;   22/09/07
IMG_START_TIME:  50816.50 SOD {14:06:56.50} UT,   90.7 [sec] since BAT Trigger T
ime
COUNTS:          45    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 07 Sep 22 14:09:43 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1123129,   Seg_Num: 0
GRB_RA:          268.870d {+17h 55m 29s} (J2000),
                 269.207d {+17h 56m 50s} (current),
                 268.126d {+17h 52m 30s} (1950)
GRB_DEC:         -20.315d {-20d 18' 54"} (J2000),
                 -20.317d {-20d 19' 02"} (current),
                 -20.308d {-20d 18' 28"} (1950)
GRB_DATE:        19829 TJD;   250 DOY;   22/09/07
GRB_TIME:        50725.76 SOD {14:05:25.76} UT
TRIGGER_INDEX:   146
GRB_PHI:         174.47 [deg]
GRB_THETA:        25.03 [deg]
DELTA_TIME:      -37.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.96 [sigma]
IMAGE_SIGNIF:    8.52 [sigma]
LC_URL:          sw01123129000msb.lc
SUN_POSTN:       166.13d {+11h 04m 32s}   +5.93d {+05d 55' 50"}
SUN_DIST:        104.29 [deg]   Sun_angle= -6.9 [hr] (East of Sun)
MOON_POSTN:      310.17d {+20h 40m 41s}  -23.53d {-23d 31' 50"}
MOON_DIST:        38.01 [deg]
MOON_ILLUM:      89 [%]
GAL_COORDS:        8.55,  2.49 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      268.94,  3.12 [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 = 142.69,-19.19 [deg].

GCN Circular #32524
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (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 (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB220907.59 (trigger No 1123129,17h 55m 28.80s , -20d 18m 55.1s, R=0.05) errorbox 67 sec after notice time and 83 sec after trigger time at 2022-09-07 14:06:49 UT, with upper limit up to 13.9 mag. The observations began at zenith distance = 75 deg. The sun altitude is -21.4 deg.
The galactic latitude b = 2 deg., longitude l = 9 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2082082
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      85 |        MASTER-Tunka |   C |     1 | 13.9 |        
      91 |        MASTER-Tunka |   C |     1 | 13.8 |        
      97 |        MASTER-Tunka |   C |     1 | 13.8 |        
     103 |        MASTER-Tunka |   C |     1 | 13.9 |        
     109 |        MASTER-Tunka |   C |     1 | 13.9 |        
     115 |        MASTER-Tunka |   C |     1 | 13.8 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #32525
The Fermi GBM team reports the detection of a likely SHORT GRB
At 14:05:26 UT on 7 Sep 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220907A (trigger 684252331.480966 / 220907587).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 269.6, Dec = -18.7 (J2000 degrees, equivalent to J2000 17h 58m, -18d 41'), with a statistical uncertainty of 6.9 degrees.
The angle from the Fermi LAT boresight is 75.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_skymap_all_bn220907587.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_healpix_all_bn220907587.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_lc_medres34_bn220907587.gif
GCN Circular #32526
K. L. Page (U Leicester), P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB), M. H. Siegel (PSU), A. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 14:05:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220907A (trigger=1123129). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 268.870, -20.315 which is
```
   RA(J2000) = 17h 55m 29s
   Dec(J2000) = -20d 18' 54"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex peak structure with a duration of about 20 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 14:06:56.5 UT, 90.7 seconds after the BAT trigger. No source was detected in 188 s of promptly downlinked data. We are waiting for the full dataset to detect and localise the XRT counterpart.
No prompt UVOT data products are available.
Although there is no counterpart found in the (short) XRT exposure, the high significance of the BAT detection (8.5 sigma) and the simultaneous detection by Fermi/GBM (GCN #32525) indicates that this is an astrophysical event.
Burst Advocate for this burst is K. L. Page (kimlpage1978 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 #32527
K. L. Page and P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 678 s of XRT data for GRB 220907A (Page et al. GCN Circ. 32526), from 74 s to 4.1 ks after the BAT trigger. An X-ray source is now detected within the BAT error circle. The refined XRT position is RA, Dec = 268.8714, -20.2879 which is equivalent to:
```
RA (J2000): 17 55 29.14
Dec(J2000): -20 17 16.6
```
with an uncertainty of 5.0 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.
GCN Circular #32530
K. L. Page (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 5.6 ks of XRT data for GRB 220907A (Page et al. GCN Circ. 32526), from 100 s to 21.5 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. Using 188 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 = 268.87315, -20.28950 which is equivalent to:
```
RA (J2000): 17h 55m 29.56s
Dec(J2000): -20d 17' 22.2"
```
with an uncertainty of 4.0 arcsec (radius, 90% confidence). The source is fading with alpha >0.4.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01123129.
This circular is an official product of the Swift-XRT team.
GCN Circular #32531
S. R. Oates (U. Birmingham) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 220907A 95 s after the BAT trigger (Page et al., GCN Circ. 32526). No optical afterglow consistent with the enhanced XRT position (Page and Evans GCN Circ. 32530) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            95          245          147         >20.2
white               95         5001          298         >20.6
v                 3823         4023          197         >18.6
b                 4644         4844          197         >19.7
u                 4438         4638          197         >19.4
w1                4234         4433          197         >19.2
m2                4028         4228          197         >19.2
w2                3618         3818          197         >19.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.637 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #32532
Z.P. Zhu (NAOC,HUST), S.Y. Fu(NAOC), S.Q. Jiang, X. Liu, T.H. Lu, D. Xu, X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 220907A detected by Swift (Page et al., GCN 32526) and Fermi/GBM (GCN 32525) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained a series of frames in the Sloan r-band and Sloan z-band, starting at 14:07:13 UT on 2022-09-07, i.e., 108s after the BAT trigger.
No uncatalogued optical source is detected in our stacked images at the XRT position (Page eta al., GCN32527), with upper limits as follows:
```
T_mid-T0 (min)    Filter   Upper limit(3-sigma)
    15.5                 r          >19.5
    34.5                 z          >18.1
```
calibrated with the nearby PanSTARRS field and not corrected for Galactic extinction.
GCN Circular #32533
S. Dalessi, C. Meegan and P. Veres (all UAH) report on behalf of the Fermi GBM Team:
"At 14:05:26.48 UT on 07 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220907A (trigger 684252331 / 220907587), which was also detected by the Swift/BAT (Page et al. 2022, GCN 32526, 32530). The Fermi GBM Final Real-time Localization (GCN 32525) is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees.
The GBM light curve shows a single peak with a duration (T90) of about 9 s (50-300 keV). The time-averaged spectrum from T0-2.8 s to T0+5.4 s is best fit by a power law function with index = -1.48 +/- 0.07.
The event fluence (10-1000 keV) in this time interval is (1.13 +/- 0.12)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.02 s in the 10-1000 keV band is 2.32 +/- 0.24 ph/s/cm^2.
A power law function with an exponential high-energy cutoff fits the spectrum equally well. The power law index is -1.01 +/- 0.29 and the cutoff energy, parameterized as Epeak, is 320 +/- 170 keV and fluence (1.02 +/-0.22)E-6 erg/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #32537
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), (i.e. the Swift-BAT team): Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 220907A (trigger #1123129) (Page, et al., GCN Circ.32526). The BAT ground-calculated position is RA, Dec = 268.869, -20.303 deg which is
```
   RA(J2000)  =  17h 55m 28.6s
   Dec(J2000) = -20d 18' 10.8"
```
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 90%. The mask-weighted light curve shows a single peak of ten seconds approximate duration starting at T-1 sec. A spacecraft maneuver took the source out of the BAT field of view at approximately 400 seconds. T90 (15-350 keV) is 8.49 +- 1.56 sec (estimated error including systematics). The time-averaged spectrum from T-0.60 to T+10.29 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.99 +- 0.24. The fluence in the 15-150 keV band is 4.1 +- 0.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.70 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. 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/1123129/BA/

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Jochen Greiner, last update: 22-Sep-2022 [Disclaimer]