Gamma-ray Burst 200901A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 20 03:47:48 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     994143,   Seg_Num: 0
GRB_RA:           61.758d {+04h 07m 02s} (J2000),
                  61.848d {+04h 07m 23s} (current),
                  61.540d {+04h 06m 10s} (1950)
GRB_DEC:         -59.880d {-59d 52' 47"} (J2000),
                 -59.826d {-59d 49' 31"} (current),
                 -60.012d {-60d 00' 43"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4543 [cnts]    Image_Peak=371 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   147     E_range: 25-100 keV
BKG_INTEN:       20200 [cnts]
BKG_TIME:        13638.44 SOD {03:47:18.44} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19093 TJD;   245 DOY;   20/09/01
GRB_TIME:        13651.56 SOD {03:47:31.56} UT
GRB_PHI:         136.36 [deg]
GRB_THETA:        39.89 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     44.00 [sigma]
IMAGE_SIGNIF:    17.50 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +5  +0  +0 +20  +0 
SUN_POSTN:       160.76d {+10h 43m 03s}   +8.13d {+08d 07' 39"}
SUN_DIST:        101.50 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      330.72d {+22h 02m 52s}  -16.67d {-16d 40' 25"}
MOON_DIST:        76.20 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.53,-43.47 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       14.53,-75.80 [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 = 147.77,-10.24 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(4.0<100sec) coincident with the FERMI_GBM event (trignum=620624852).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 01 Sep 20 03:47:52 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     620624852
GRB_RA:           61.667d {+04h 06m 40s} (J2000),
                  61.789d {+04h 07m 09s} (current),
                  61.372d {+04h 05m 29s} (1950)
GRB_DEC:         -54.633d {-54d 37' 59"} (J2000),
                 -54.579d {-54d 34' 43"} (current),
                 -54.766d {-54d 45' 57"} (1950)
GRB_ERROR:       12.38 [deg radius, statistical plus systematic]
GRB_INTEN:       130 [cnts/sec]
DATA_SIGNIF:     5.80 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        19093 TJD;   245 DOY;   20/09/01
GRB_TIME:        13647.62 SOD {03:47:27.62} UT
GRB_PHI:          48.00 [deg]
GRB_THETA:       155.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.59
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      64%  Distant Particles
2nd_MOST_LIKELY:  34%  GRB
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       160.76d {+10h 43m 03s}   +8.13d {+08d 07' 39"}
SUN_DIST:        101.81 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      330.72d {+22h 02m 53s}  -16.67d {-16d 40' 24"}
MOON_DIST:        77.09 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      264.65,-45.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       27.51,-71.96 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200901158/quicklook/glg_lc_medres34_bn200901158.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 186.23,-25.18 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(4.0<100sec) coincident with the SWIFT_BAT event (trignum=994143).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 01 Sep 20 04:24:53 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     620624852
GRB_RA:           65.170d {+04h 20m 41s} (J2000),
                  65.274d {+04h 21m 06s} (current),
                  64.919d {+04h 19m 41s} (1950)
GRB_DEC:         -57.000d {-56d 59' 59"} (J2000),
                 -56.952d {-56d 57' 05"} (current),
                 -57.117d {-57d 07' 02"} (1950)
GRB_ERROR:       3.04 [deg radius, statistical only]
GRB_DATE:        19093 TJD;   245 DOY;   20/09/01
GRB_TIME:        13647.62 SOD {03:47:27.62} UT
GRB_PHI:          48.83 [deg]
GRB_THETA:       151.94 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       160.79d {+10h 43m 09s}   +8.12d {+08d 07' 05"}
SUN_DIST:         99.80 [deg]   Sun_angle= 6.4 [hr] (West of Sun)
MOON_POSTN:      331.04d {+22h 04m 09s}  -16.57d {-16d 34' 27"}
MOON_DIST:        78.43 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      266.99,-42.75 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       27.67,-75.03 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200901158/quicklook/glg_lc_medres34_bn200901158.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2020/bn200901158/quicklook/glg_locplot_all_bn200901158.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 has human-in-the-loop processing.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(4.0<100sec) coincident with the SWIFT_BAT event (trignum=994143).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 20 03:51:51 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     994143,   Seg_Num: 0
GRB_RA:           61.758d {+04h 07m 02s} (J2000),
                  61.848d {+04h 07m 23s} (current),
                  61.540d {+04h 06m 10s} (1950)
GRB_DEC:         -59.880d {-59d 52' 47"} (J2000),
                 -59.826d {-59d 49' 31"} (current),
                 -60.012d {-60d 00' 43"} (1950)
GRB_DATE:        19093 TJD;   245 DOY;   20/09/01
GRB_TIME:        13651.56 SOD {03:47:31.56} UT
TRIGGER_INDEX:   147
GRB_PHI:         136.36 [deg]
GRB_THETA:        39.89 [deg]
DELTA_TIME:      -31.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     44.00 [sigma]
IMAGE_SIGNIF:    17.50 [sigma]
LC_URL:          sw00994143000msb.lc
SUN_POSTN:       160.77d {+10h 43m 04s}   +8.13d {+08d 07' 35"}
SUN_DIST:        101.50 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      330.75d {+22h 03m 01s}  -16.66d {-16d 39' 46"}
MOON_DIST:        76.19 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.53,-43.47 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       14.53,-75.80 [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 = 147.77,-10.24 [deg].

GCN Circular #28334
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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB200901.16 (trigger No 994143,04h 07m 01.92s , -59d 52m 48.0s, R=0.05) errorbox 25 sec after notice time and 46 sec after trigger time at 2020-09-01 03:48:18 UT, with upper limit up to 16.9 mag. The observations began at zenith distance = 65 deg. The sun altitude is -64.8 deg.
The galactic latitude b = -43 deg., longitude l = 271 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1431471
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      52 |         MASTER-OAFA |   C |    10 | 16.4 |        
      81 |         MASTER-OAFA |   C |    10 | 16.5 |        
     116 |         MASTER-OAFA |   C |    20 | 16.9 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #28335
K. K. Simpson (PSU), S. D. Barthelmy (GSFC), J.D. Gropp (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team:
At 03:47:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200901A (trigger=994143). Swift did not slew immediately due to an observing constraint. The BAT on-board calculated location is RA, Dec 61.758, -59.880 which is
```
   RA(J2000) = 04h 07m 02s
   Dec(J2000) = -59d 52' 47"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+47.5 minutes. There will be no XRT or UVOT data until this time.
This source lies within the current (Sector 29) field-of-view of TESS camera 3.
Burst Advocate for this burst is K. K. Simpson (kira.simpson1984 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 20 04:38:45 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     994143,   Seg_Num: 0
POINT_RA:         61.649d {+04h 06m 36s} (J2000)
POINT_DEC:       -59.846d {-59d 50' 46"} (J2000)
IMG_START_DATE:  19093 TJD;   245 DOY;   20/09/01
IMG_START_TIME:  16701.96 SOD {04:38:21.96} UT,   3050.4 [sec] since BAT Trigger Time
COUNTS:          33    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:     Tue 01 Sep 20 04:41:20 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     994143,   Seg_Num: 0
POINT_RA:         61.649d {+04h 06m 36s} (J2000)
POINT_DEC:       -59.847d {-59d 50' 47"} (J2000)
POINT_ROLL:      93.787d
IMG_START_DATE:  19093 TJD;   245 DOY;   20/09/01
IMG_START_TIME:  16704.21 SOD {04:38:24.21} UT,   3052.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.389
N_STARS:         28
X_OFFSET:        951 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1910 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00994143000msufc3052.fits
SUN_POSTN:       160.80d {+10h 43m 11s}   +8.11d {+08d 06' 50"}
SUN_DIST:        101.56 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      331.18d {+22h 04m 43s}  -16.53d {-16d 31' 48"}
MOON_DIST:        76.05 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.51,-43.54 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       14.49,-75.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 20 04:41:36 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     994143,   Seg_Num: 0
POINT_RA:         61.649d {+04h 06m 36s} (J2000)
POINT_DEC:       -59.847d {-59d 50' 47"} (J2000)
POINT_ROLL:      93.787d
IMG_START_DATE:  19093 TJD;   245 DOY;   20/09/01
IMG_START_TIME:  16704.21 SOD {04:38:24.21} UT,   3052.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.389
N_STARS:         28
X_OFFSET:        951 [pixels]
Y_OFFSET:        544 [pixels]
X_MAX:           1910 [pixels]
Y_MAX:           1503 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00994143000msufc3052.fits
SUN_POSTN:       160.80d {+10h 43m 11s}   +8.11d {+08d 06' 50"}
SUN_DIST:        101.56 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      331.18d {+22h 04m 43s}  -16.53d {-16d 31' 46"}
MOON_DIST:        76.04 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.51,-43.54 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       14.49,-75.74 [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 01 Sep 20 04:42:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     994143,   Seg_Num: 0
POINT_RA:         61.649d {+04h 06m 36s} (J2000)
POINT_DEC:       -59.847d {-59d 50' 47"} (J2000)
ROLL:            93.787d
IMG_START_DATE:  19093 TJD;   245 DOY;   20/09/01
IMG_START_TIME:  16704.21 SOD {04:38:24.21} UT,   3052.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     620627929
X_OFFSET:        1270 [pixels]
Y_OFFSET:        863 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1430
Y_GRB_POS:       1023
BINNING_INDEX:   1
IM_URL:          sw00994143000msuni3078.fits
SUN_POSTN:       160.80d {+10h 43m 12s}   +8.11d {+08d 06' 49"}
SUN_DIST:        101.56 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      331.19d {+22h 04m 45s}  -16.53d {-16d 31' 36"}
MOON_DIST:        76.04 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.51,-43.54 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       14.49,-75.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 01 Sep 20 04:42:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     994143,   Seg_Num: 0
POINT_RA:         61.649d {+04h 06m 36s} (J2000)
POINT_DEC:       -59.847d {-59d 50' 47"} (J2000)
ROLL:            93.787d
IMG_START_DATE:  19093 TJD;   245 DOY;   20/09/01
IMG_START_TIME:  16704.21 SOD {04:38:24.21} UT,   3052.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     620627929
X_OFFSET:        1270 [pixels]
Y_OFFSET:        863 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1430
Y_GRB_POS:       1023
BINNING_INDEX:   1
IM_URL:          sw00994143000msuni3078.fits
SUN_POSTN:       160.80d {+10h 43m 12s}   +8.11d {+08d 06' 49"}
SUN_DIST:        101.56 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      331.19d {+22h 04m 46s}  -16.53d {-16d 31' 32"}
MOON_DIST:        76.04 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:      271.51,-43.54 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       14.49,-75.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #28336
D.N. Burrows (PSU), J.A. Kennea (PSU), M. Perri (ASDC), G. Tagliaferri (INAF-OAB), P.A. Evans (U. Leicester) and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 200901A at 04:38:21.9 UT, 3050.4 seconds after the BAT trigger. No source was detected in 1.9 ks of promptly downlinked data, which covered 54% of the BAT error circle. We are waiting for the full dataset to detect and localise the XRT counterpart.
GCN Circular #28340
P. Veres, R. Hamburg and C. Meegan (all UAH) report on behalf of the Fermi GBM Team:
"At 03:47:27.62 UT on 1 September 2020, the Fermi Gamma-Ray Burst Monitor (GBM) triggered on GRB 200901A (trigger 620624852 / 200901158) which was also detected by the Swift/BAT (Simpson et al., GCN 28335). The GBM on-ground location is consistent with the Swift position.
The event was classified as particle activity by the flight software, but it is in fact a GRB.
The angle from the Fermi LAT boresight at the GBM trigger time is 151 degrees.
The GBM light curve consists of overlapping pulses with a duration (T90) of about 10.2 s (50-300 keV). The time-averaged spectrum from T0-0.9 s to T0+10.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.52 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 410 +/- 150 keV.
The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.54)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 11.2 +/- 0.96 ph/s/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 #28341
J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU) and K. K. Simpson (PSU) report on behalf of the Swift-XRT team:
We have analysed 2.5 ks of XRT data for GRB 200901A (Simpson et al. GCN Circ. 28335), from 3.1 ks to 11.1 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. Using 1707 s of PC mode data and 4 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 61.78319, -59.89084 which is equivalent to:
```
RA (J2000): 04h 07m 07.97s
Dec(J2000): -59d 53' 27.0"
```
with an uncertainty of 1.8 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.95 (+0.28, -0.24).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.31 (+0.30, -0.28). The best-fitting absorption column is 2.2 (+0.9, -0.8) x 10^21 cm^-2, in excess of the Galactic value of 1.5 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.0 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.2 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^20 cm^-2
Excess significance: 4.2 sigma
Photon index:	     2.31 (+0.30, -0.28)
```
If the light curve continues to decay with a power-law decay index of 0.95, the count rate at T+24 hours will be 7.9 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x 10^-13 (3.8 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/00994143.
This circular is an official product of the Swift-XRT team.
GCN Circular #28342
A. A. Breeveld (UCL-MSSL) and K. K. Simpson (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 200901A 3053 s after the BAT trigger (Simpson et al., GCN Circ. 28335). A possible optical afterglow consistent with the XRT position (Kennea et al., GCN Circ. 28341) is detected in the initial UVOT exposures in the white filter only. It is not clear whether the source is fading. Preliminary detections and 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          3053         3202          147         20.6 +/- 0.3
white             3916         4115          197         20.5 +/- 0.2
v                 4326         4526          197         >19.1
b                 3711         3910          197         >20.4
u                 3211         4987          290         >20.0
w1                4736         4936          197         >19.1
m2                4531         4731          197         >19.1
w2                4121         4321          197         >19.3
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #28344
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), D. M. Palmer (LANL), K. K. Simpson (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200901A (trigger #994143) (Simpson et al., GCN Circ. 28335). The BAT ground-calculated position is RA, Dec = 61.759, -59.901 deg which is
```
   RA(J2000)  =  04h 07m 02.3s
   Dec(J2000) = -59d 54' 03.4"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 21%.
The mask-weighted light curve shows several overlapping pulses that start at ~T-5 s and end at ~T+27 s. The main peak occurs at ~T0. The burst location went out of the BAT field of view at ~T+514 s. T90 (15-350 keV) is 20.37 +- 7.55 sec (estimated error including systematics).
The time-averaged spectrum from T-4.43 to T+26.59 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.11. The fluence in the 15-150 keV band is 2.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.01 sec in the 15-150 keV band is 7.7 +- 0.6 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/994143/BA/
GCN Circular #28348
V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, A.Kuznetsov, K.Zhirkov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, 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 (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-OAFA robotic telescope (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, v.2010, 30L) started in alert mode (Lipunov et al. GCN 28334) Swift GRB 200901A (Simpson et al. GCN 28335, Sakamoto et al. GCN 28344) errorbox observation 25s after notice time (46s after trigger time) at 2020-09-01 03:48:18 UT.
There is OT at XRT (Kennea et al. GNC 28341) and UVOT (Breeveld et al. GCN 28342) position first 20 minutes after trigger time.
Data analysis will continue.
GCN Circular #28767
Martin Jelinek, Jan Strobl (ASU CAS Ondrejov, CZ), Martin Masek, Petr Janecek, Sergey Karpov, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ)
report:
The 30cm robotic telescope FRAM-Auger in Malargue (Argentina) reacted robotically to the Swift/BAT alert of GRB200901A (Simpson et al., GCNC 28335, Burrows et al., GCNC 28336, Kennea et al., GCNC 28341, and Breeveld et al., GCNC 28342).
The weather was cloudy but as the clouds moved, we could select some good images, in particular there is a continuous set of 14 exposures between 4:00 and 4:17 UT, where the position could be well identified.
We do not detect any new or strongly variable source at or around the reported X-ray errorbox at single frames or a combined 14 x 20s R-band image with the exposure mid-time 21.3 min after the initial trigger. The combined exposure has a limiting magnitude R(Vega) = 17.8, as calibrated against the Atlas Catalogue.

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Jochen Greiner, last update: 24-Oct-2020 [Disclaimer]