Gamma-ray Burst 091020

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:36:59 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     277767405
GRB_RA:          138.133d {+09h 12m 32s} (J2000),
                 138.345d {+09h 13m 23s} (current),
                 137.045d {+09h 08m 11s} (1950)
GRB_DEC:         +67.167d {+67d 09' 60"} (J2000),
                 +67.126d {+67d 07' 33"} (current),
                 +67.372d {+67d 22' 20"} (1950)
GRB_ERROR:       14.75 [deg radius, statistical plus systematic]
GRB_INTEN:       307 [cnts/sec]
DATA_SIGNIF:     9.40 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77803.82 SOD {21:36:43.82} UT
GRB_PHI:          39.00 [deg]
GRB_THETA:       140.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      1.23
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      94%  GRB
2nd_MOST_LIKELY:   3%  Distant Particles
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 39"}
SUN_DIST:         91.29 [deg]   Sun_angle= 4.5 [hr] (West of Sun)
MOON_POSTN:      237.33d {+15h 49m 20s}  -24.19d {-24d 11' 32"}
MOON_DIST:       115.66 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.74, 38.29 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      115.56, 47.95 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 174.92,-20.17 [deg].

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:37:02 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.715d {+11h 42m 52s} (J2000),
                 175.846d {+11h 43m 23s} (current),
                 175.047d {+11h 40m 11s} (1950)
GRB_DEC:         +50.972d {+50d 58' 19"} (J2000),
                 +50.918d {+50d 55' 03"} (current),
                 +51.250d {+51d 14' 58"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       6271 [cnts]    Image_Peak=520 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   148     E_range: 25-100 keV
BKG_INTEN:       31767 [cnts]
BKG_TIME:        77786.81 SOD {21:36:26.81} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77804.66 SOD {21:36:44.66} UT
GRB_PHI:         -148.64 [deg]
GRB_THETA:        41.12 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     32.41 [sigma]
IMAGE_SIGNIF:    17.70 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +5  +0  +0 -39  +0 
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 39"}
SUN_DIST:         66.76 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.33d {+15h 49m 20s}  -24.19d {-24d 11' 32"}
MOON_DIST:        92.50 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.93, 62.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.71, 43.95 [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 = 160.64,20.43 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=277767405).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:37:16 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     277767405
GRB_RA:          165.100d {+11h 00m 24s} (J2000),
                 165.289d {+11h 01m 09s} (current),
                 164.118d {+10h 56m 28s} (1950)
GRB_DEC:         +77.650d {+77d 39' 00"} (J2000),
                 +77.597d {+77d 35' 50"} (current),
                 +77.918d {+77d 55' 06"} (1950)
GRB_ERROR:       3.81 [deg radius, statistical only]
DATA_SIGNIF:     21.70 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77803.82 SOD {21:36:43.82} UT
GRB_PHI:          19.00 [deg]
GRB_THETA:       145.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 39"}
SUN_DIST:         91.10 [deg]   Sun_angle= 2.7 [hr] (West of Sun)
MOON_POSTN:      237.33d {+15h 49m 20s}  -24.19d {-24d 11' 33"}
MOON_DIST:       109.87 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      130.18, 37.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      115.21, 60.97 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:37:10 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      57
TRIGGER_NUM:     277767405
GRB_RA:          149.617d {+09h 58m 28s} (J2000),
                 149.850d {+09h 59m 24s} (current),
                 148.410d {+09h 53m 38s} (1950)
GRB_DEC:         +75.683d {+75d 40' 60"} (J2000),
                 +75.636d {+75d 38' 10"} (current),
                 +75.922d {+75d 55' 19"} (1950)
GRB_ERROR:       5.77 [deg radius, statistical plus systematic]
GRB_INTEN:       479 [cnts/sec]
DATA_SIGNIF:     26.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77803.82 SOD {21:36:43.82} UT
GRB_PHI:          26.00 [deg]
GRB_THETA:       145.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.95
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      93%  GRB
2nd_MOST_LIKELY:   4%  Distant Particles
DETECTORS:       0,0,1, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 39"}
SUN_DIST:         92.38 [deg]   Sun_angle= 3.7 [hr] (West of Sun)
MOON_POSTN:      237.33d {+15h 49m 20s}  -24.19d {-24d 11' 33"}
MOON_DIST:       112.77 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      135.18, 37.02 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      113.10, 57.06 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 174.92,-20.17 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:37:20 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      68
TRIGGER_NUM:     277767405
GRB_RA:          170.580d {+11h 22m 19s} (J2000),
                 170.741d {+11h 22m 58s} (current),
                 169.747d {+11h 18m 59s} (1950)
GRB_DEC:         +76.020d {+76d 01' 12"} (J2000),
                 +75.966d {+75d 57' 58"} (current),
                 +76.294d {+76d 17' 40"} (1950)
GRB_ERROR:       1.82 [deg radius, statistical only]
DATA_SIGNIF:     27.30 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77803.82 SOD {21:36:43.82} UT
GRB_PHI:          18.00 [deg]
GRB_THETA:       143.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 39"}
SUN_DIST:         89.05 [deg]   Sun_angle= 2.3 [hr] (West of Sun)
MOON_POSTN:      237.33d {+15h 49m 20s}  -24.19d {-24d 11' 33"}
MOON_DIST:       108.04 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      129.79, 39.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      119.44, 61.00 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:38:45 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.7284d {+11h 42m 54.8s} (J2000),
                 175.8589d {+11h 43m 26.1s} (current),
                 175.0602d {+11h 40m 14.4s} (1950)
GRB_DEC:         +50.9788d {+50d 58' 43.6"} (J2000),
                 +50.9244d {+50d 55' 27.7"} (current),
                 +51.2563d {+51d 15' 22.7"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       99 [cnts]
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77885.50 SOD {21:38:05.50} UT,   80.8 [sec] since BAT Trigger Time
CENTROID_X:      285.27,  raw= 285  [pixels]
CENTROID_Y:      307.28,  raw= 307  [pixels]
ROLL:            147.75 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   21.88
GRB_POS_XRT_Z:   -40.12
IMAGE_URL:       sw00373458000msxps_rw.img
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 40"}
SUN_DIST:         66.77 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.35d {+15h 49m 24s}  -24.19d {-24d 11' 41"}
MOON_DIST:        92.51 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.90, 62.84 [deg] galactic lon,lat of the burst
ECL_COORDS:      150.72, 43.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:38:42 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.7284d {+11h 42m 54.8s} (J2000),
                 175.8589d {+11h 43m 26.1s} (current),
                 175.0602d {+11h 40m 14.4s} (1950)
GRB_DEC:         +50.9788d {+50d 58' 43.6"} (J2000),
                 +50.9244d {+50d 55' 27.7"} (current),
                 +51.2563d {+51d 15' 22.7"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       99 [cnts]
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77885.50 SOD {21:38:05.50} UT,   80.8 [sec] since BAT Trigger Time
CENTROID_X:      285.27,  raw= 285  [pixels]
CENTROID_Y:      307.28,  raw= 307  [pixels]
ROLL:            147.75 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   21.88
GRB_POS_XRT_Z:   -40.12
IMAGE_URL:       sw00373458000msxps_rw.img
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 40"}
SUN_DIST:         66.77 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.35d {+15h 49m 24s}  -24.19d {-24d 11' 41"}
MOON_DIST:        92.51 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.90, 62.84 [deg] galactic lon,lat of the burst
ECL_COORDS:      150.72, 43.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:38:32 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.7284d {+11h 42m 54.81s} (J2000),
                 175.8589d {+11h 43m 26.14s} (current),
                 175.0602d {+11h 40m 14.43s} (1950)
GRB_DEC:         +50.9788d {+50d 58' 43.6"} (J2000),
                 +50.9244d {+50d 55' 27.7"} (current),
                 +51.2563d {+51d 15' 22.7"} (1950)
GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.01e-09 [erg/cm2/sec]
GRB_SIGNIF:      9.94 [sigma]
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77885.50 SOD {21:38:05.50} UT,   80.8 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.21 261.43 243.67
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 40"}
SUN_DIST:         66.77 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.35d {+15h 49m 23s}  -24.19d {-24d 11' 40"}
MOON_DIST:        92.50 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.90, 62.84 [deg] galactic lon,lat of the burst
ECL_COORDS:      150.72, 43.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.64 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:40:38 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.715d {+11h 42m 52s} (J2000),
                 175.846d {+11h 43m 23s} (current),
                 175.047d {+11h 40m 11s} (1950)
GRB_DEC:         +50.972d {+50d 58' 19"} (J2000),
                 +50.918d {+50d 55' 03"} (current),
                 +51.250d {+51d 14' 58"} (1950)
GRB_DATE:        15124 TJD;   293 DOY;   09/10/20
GRB_TIME:        77804.66 SOD {21:36:44.66} UT
TRIGGER_INDEX:   148
GRB_PHI:         -148.64 [deg]
GRB_THETA:        41.12 [deg]
DELTA_TIME:      -24.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     32.41 [sigma]
IMAGE_SIGNIF:    17.70 [sigma]
LC_URL:          sw00373458000msb.lc
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 42"}
SUN_DIST:         66.77 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.37d {+15h 49m 28s}  -24.20d {-24d 11' 51"}
MOON_DIST:        92.52 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.93, 62.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.71, 43.95 [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 = 160.64,20.43 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:41:33 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.712d {+11h 42m 51s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 05"} (J2000)
POINT_ROLL:      147.751d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77894.04 SOD {21:38:14.04} UT,   89.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.262
N_STARS:         21
X_OFFSET:        568 [pixels]
Y_OFFSET:        520 [pixels]
X_MAX:           1527 [pixels]
Y_MAX:           1479 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00373458000msufc0089.fits
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 43"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.38d {+15h 49m 30s}  -24.20d {-24d 11' 56"}
MOON_DIST:        92.53 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.91, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [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 20 Oct 09 21:41:02 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.712d {+11h 42m 51s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 05"} (J2000)
POINT_ROLL:      147.751d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77894.04 SOD {21:38:14.04} UT,   89.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.262
N_STARS:         21
X_OFFSET:        568 [pixels]
Y_OFFSET:        520 [pixels]
X_MAX:           1527 [pixels]
Y_MAX:           1479 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00373458000msufc0089.fits
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 42"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.37d {+15h 49m 29s}  -24.20d {-24d 11' 53"}
MOON_DIST:        92.53 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.91, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:41:02 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.712d {+11h 42m 51s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 05"} (J2000)
POINT_ROLL:      147.751d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77894.04 SOD {21:38:14.04} UT,   89.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.262
N_STARS:         21
X_OFFSET:        568 [pixels]
Y_OFFSET:        520 [pixels]
X_MAX:           1527 [pixels]
Y_MAX:           1479 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00373458000msufc0089.fits
SUN_POSTN:       205.65d {+13h 42m 36s}  -10.63d {-10d 37' 42"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.37d {+15h 49m 29s}  -24.20d {-24d 11' 53"}
MOON_DIST:        92.53 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.91, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:43:24 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.712d {+11h 42m 51s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 05"} (J2000)
ROLL:            147.751d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77894.04 SOD {21:38:14.04} UT,   89.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277767499
X_OFFSET:        848 [pixels]
Y_OFFSET:        783 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1008
Y_GRB_POS:       943
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0095.fits
SUN_POSTN:       205.65d {+13h 42m 37s}  -10.63d {-10d 37' 44"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.39d {+15h 49m 34s}  -24.20d {-24d 12' 06"}
MOON_DIST:        92.55 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.91, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:43:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.712d {+11h 42m 51s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 05"} (J2000)
ROLL:            147.751d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77894.04 SOD {21:38:14.04} UT,   89.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277767499
X_OFFSET:        848 [pixels]
Y_OFFSET:        783 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1008
Y_GRB_POS:       943
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0095.fits
SUN_POSTN:       205.65d {+13h 42m 37s}  -10.63d {-10d 37' 45"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.40d {+15h 49m 35s}  -24.20d {-24d 12' 07"}
MOON_DIST:        92.55 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.91, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #10048
J. L. Racusin (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (MSSL), W.B Landsman (GSFC), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), A. Rowlinson (U Leicester), M. H. Siegel (PSU), E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 21:36:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091020 (trigger=373458). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 175.715, +50.972 which is
```
   RA(J2000) = 11h 42m 52s
   Dec(J2000) = +50d 58' 19"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a bright peak with a second much smaller peak at T+30 s, for a total duration of about 45 sec. The peak count rate was ~5000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 21:38:05.5 UT, 80.8 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 175.7284, +50.9788 which is equivalent to:
```
   RA(J2000)  = 11h 42m 54.81s
   Dec(J2000) = +50d 58' 43.6"
```
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 39 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
The initial flux in the 2.5 s image was 3.01e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 89 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	11:42:55.18 = 175.72993
  DEC(J2000) = +50:58:41.9  = 50.97831
```
with a 90%-confidence error radius of about 0.74 arc sec. This position is 3.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 15.73 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02.
Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 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/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:49:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78106.33 SOD {21:41:46.33} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.711
N_STARS:         18
X_OFFSET:        528 [pixels]
Y_OFFSET:        463 [pixels]
X_MAX:           1487 [pixels]
Y_MAX:           1422 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00373458000msufc0301.fits
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 50"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.45d {+15h 49m 48s}  -24.21d {-24d 12' 37"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:49:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78106.33 SOD {21:41:46.33} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.711
N_STARS:         18
X_OFFSET:        528 [pixels]
Y_OFFSET:        463 [pixels]
X_MAX:           1487 [pixels]
Y_MAX:           1422 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00373458000msufc0301.fits
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 50"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.46d {+15h 49m 49s}  -24.21d {-24d 12' 39"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [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 20 Oct 09 21:50:45 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.7279d {+11h 42m 54.69s} (J2000),
                 175.8584d {+11h 43m 26.02s} (current),
                 175.0597d {+11h 40m 14.31s} (1950)
GRB_DEC:         +50.9796d {+50d 58' 46.5"} (J2000),
                 +50.9252d {+50d 55' 30.6"} (current),
                 +51.2571d {+51d 15' 25.5"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78243.00 SOD {21:44:03.00} UT,   438.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 51"}
SUN_DIST:         66.77 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.46d {+15h 49m 51s}  -24.21d {-24d 12' 45"}
MOON_DIST:        92.58 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.90, 62.84 [deg] galactic lon,lat of the burst
ECL_COORDS:      150.72, 43.96 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:50:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
ROLL:            147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78106.33 SOD {21:41:46.33} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     277767711
X_OFFSET:        848 [pixels]
Y_OFFSET:        783 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1008
Y_GRB_POS:       943
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0307.fits
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 51"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.46d {+15h 49m 51s}  -24.21d {-24d 12' 44"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:49:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78106.33 SOD {21:41:46.33} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.711
N_STARS:         18
X_OFFSET:        528 [pixels]
Y_OFFSET:        463 [pixels]
X_MAX:           1487 [pixels]
Y_MAX:           1422 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00373458000msufc0301.fits
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 50"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.45d {+15h 49m 48s}  -24.21d {-24d 12' 37"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:50:26 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
ROLL:            147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78106.33 SOD {21:41:46.33} UT,   301.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     277767711
X_OFFSET:        848 [pixels]
Y_OFFSET:        783 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1008
Y_GRB_POS:       943
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0307.fits
SUN_POSTN:       205.66d {+13h 42m 38s}  -10.63d {-10d 37' 51"}
SUN_DIST:         66.78 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.46d {+15h 49m 51s}  -24.21d {-24d 12' 43"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:56:52 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78679.06 SOD {21:51:19.06} UT,   874.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.279
N_STARS:         34
X_OFFSET:        288 [pixels]
Y_OFFSET:        223 [pixels]
X_MAX:           1727 [pixels]
Y_MAX:           1662 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00373458000msufc0874.fits
SUN_POSTN:       205.66d {+13h 42m 39s}  -10.63d {-10d 37' 56"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.52d {+15h 50m 06s}  -24.22d {-24d 13' 17"}
MOON_DIST:        92.63 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:57:24 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78679.06 SOD {21:51:19.06} UT,   874.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.279
N_STARS:         34
X_OFFSET:        288 [pixels]
Y_OFFSET:        223 [pixels]
X_MAX:           1727 [pixels]
Y_MAX:           1662 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00373458000msufc0874.fits
SUN_POSTN:       205.66d {+13h 42m 39s}  -10.63d {-10d 37' 57"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.53d {+15h 50m 07s}  -24.22d {-24d 13' 20"}
MOON_DIST:        92.63 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [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 20 Oct 09 21:56:52 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
POINT_ROLL:      147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78679.06 SOD {21:51:19.06} UT,   874.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.279
N_STARS:         34
X_OFFSET:        288 [pixels]
Y_OFFSET:        223 [pixels]
X_MAX:           1727 [pixels]
Y_MAX:           1662 [pixels]
DET_THRESH:      17
PHOTO_THRESH:    10
SL_URL:          sw00373458000msufc0874.fits
SUN_POSTN:       205.66d {+13h 42m 39s}  -10.63d {-10d 37' 56"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.52d {+15h 50m 06s}  -24.22d {-24d 13' 17"}
MOON_DIST:        92.63 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 21:58:44 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
ROLL:            147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78679.06 SOD {21:51:19.06} UT,   874.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277768284
X_OFFSET:        847 [pixels]
Y_OFFSET:        782 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1007
Y_GRB_POS:       942
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0880.fits
SUN_POSTN:       205.66d {+13h 42m 39s}  -10.63d {-10d 37' 58"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.54d {+15h 50m 10s}  -24.22d {-24d 13' 27"}
MOON_DIST:        92.64 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [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 20 Oct 09 21:59:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373458,   Seg_Num: 0
POINT_RA:        175.708d {+11h 42m 50s} (J2000)
POINT_DEC:       +50.985d {+50d 59' 07"} (J2000)
ROLL:            147.748d
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  78679.06 SOD {21:51:19.06} UT,   874.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277768284
X_OFFSET:        847 [pixels]
Y_OFFSET:        782 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1007
Y_GRB_POS:       942
BINNING_INDEX:   1
IM_URL:          sw00373458000msuni0880.fits
SUN_POSTN:       205.66d {+13h 42m 39s}  -10.63d {-10d 37' 58"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.54d {+15h 50m 11s}  -24.22d {-24d 13' 28"}
MOON_DIST:        92.64 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.92, 62.83 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      150.70, 43.96 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 20 Oct 09 22:38:18 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     373458,   Seg_Num: 0
GRB_RA:          175.7298d {+11h 42m 55.15s} (J2000),
                 175.8603d {+11h 43m 26.47s} (current),
                 175.0616d {+11h 40m 14.77s} (1950)
GRB_DEC:         +50.9783d {+50d 58' 41.8"} (J2000),
                 +50.9239d {+50d 55' 25.9"} (current),
                 +51.2558d {+51d 15' 20.9"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         15.69 +/- 0.20 [mag]
FILTER:          10, White
IMG_START_DATE:  15124 TJD;   293 DOY;   09/10/20
IMG_START_TIME:  77813.00 SOD {21:36:53.00} UT,   8.3 [sec] since BAT Trigger Time
SUN_POSTN:       205.69d {+13h 42m 45s}  -10.64d {-10d 38' 33"}
SUN_DIST:         66.79 [deg]   Sun_angle= 2.0 [hr] (West of Sun)
MOON_POSTN:      237.92d {+15h 51m 42s}  -24.28d {-24d 16' 53"}
MOON_DIST:        92.87 [deg]
MOON_ILLUM:      8 [%]
GAL_COORDS:      146.90, 62.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      150.72, 43.96 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 3.6 arcsec from the XRT position.

GCN Circular #10050
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1088 s of XRT Photon Counting mode data and 1 UVOT images for GRB 091020, 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 = 175.73005, +50.97839 which is equivalent to:
```
RA (J2000): 11h 42m 55.21s
Dec (J2000): +50d 58' 42.2"
```
with an uncertainty of 1.8 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 #10051
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), A. M. Parsons (GSFC), J. L. Racusin (NASA/GSFC/ORAU), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091020 (trigger #373458) (Racusin, et al., GCN Circ. 10048). The BAT ground-calculated position is RA, Dec = 175.727, 50.977 deg which is
```
    RA(J2000)  =  11h 42m 54.4s
    Dec(J2000) = +50d 58' 36.6"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 43%.
The mask-weighted light curve began with a small hump at T-10 sec, rising sharply to a peak at T+2 sec and decaying exponentially out to T+50 sec, with a much smaller peak superimposed at T+30 sec. T90 (15-350 keV) is 34.6 +- 2.7 sec (estimated error including systematics).
The time-averaged spectrum from T-8.7 to T+38.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.53 +- 0.07. The fluence in the 15-150 keV band is 3.7 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.14 sec in the 15-150 keV band is 4.2 +- 0.3 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/373458/BA/
GCN Circular #10052
E. Gorbovskoy,D.Kuvshinov, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski, A. Krylov, N.Shatskiy, N.Tyurina, P.Balanutsa, V.V.Chazov,
Sternberg Astronomical Institute, Moscow State University
A. Tlatov, A.V. Parkhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
V.Krushinski, I.Zalognikh, T.Kopytova, A. Popov Ural State University, Kourovka
S.Yazev, K.Ivanov, N.M.Budnev Irkutsk State University
V.Yurkov Blagoveschensk Educational State University, Blagoveschensk
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x400 mm, 8 square degrees, 2x16Mpx Apogee CCD) located at Kislovodsk was pointed to the GRB 091020 (Racusin et al., GCN 10048) by internet 3422 s after the GRB time. The large delay was caused with technical problems on site.
We see bright optical counterpart (~17.5 mag) on the firrst images at UVOT position.
We have 130 images with 180 sec synchronous exposition each and 19.5 magnitude limit during ~4 hours in two polarization.
The power low decay with alpha ~= 1.3 during 2.5 hours is observed. This is the preliminary result. The reduction is continued.
The message may be cited.
mailto: lipunov@sai.msu.ru
GCN Circular #10053
Dong Xu, Johan P.U. Fynbo (DARK/NBI), Nial R. Tanvir (Univ. Leicester), Jens Hjorth, Giorgos Leloudas, Daniele Malesani (DARK/NBI), Pall Jakobsson (Univ. Iceland), Paul A. Wilson (NOT and Univ. Oslo), Johannes Andersen (NBI and NOT), report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 091020 (Racusin et al., GCN 10048; Gorbovskoy et al., GCN 10052) with the Nordic Optical Telescope equipped with ALFOSC. We detect the afterglow with a magnitude R ~ 20, based on a nearby USNO star, with mean time Oct 21.220 UT (0.315 days after the GRB).
We secured low-resolution spectroscopy (30 min exposure), covering the wavelength range 3500-9100 AA, starting on Oct. 21.231 UT. Wavelength calibration was carried out using archival frames.
In a preliminary analysis we detect several absorption features, which we interpret as FeII 2344, 2374, 2382, Al III 1854, 1862, Mg II 2798 (Mg II 2803 is blended with the telluric A band), all at the common z = 1.71. There is flux in the spectrum down to ~3800 AA, setting a firm upper limit z < 2.13 to the GRB redshift.
GCN Circular #10054
S. R. Oates (MSSL-UCL) and J. L. Racusin (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began observerving the field of GRB 091020 89 s after the BAT trigger (Racusin et al., GCN Circ. 10048). We detect the optical afterglow in all filters at the refined UVOT position RA, Dec 175.730, +50.97833, which is
```
     RA  (J2000)  11:42:55.20
     Dec (J2000)  50:58:42.0
```
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). This position is consistent with the enhanced XRT position (Beardmore et al., GCN 10050). The detection in the white, v, b and u filters and the weak detection in the uvw1 filter is consistent with a redshift z~1.7, which is consistent with redshift reported by NOT (Xu, et al., GCN 10053).
Preliminary magnitudes and 3 sigma upper limits are reported below.
```
Filter    T_start(s) T_stop(s)  Exposure(s)   Mag  Err
------------------------------------------------------------------------
white       89        239        147          15.73 +/- 0.01
white       874       1024       147          17.27 +/- 0.03
v           799       819        19           16.40 +/- 0.15
b           1153      1173       19           17.27 +/- 0.15
u           707       727        19           17.06 +/- 0.16
uvw1        683       6929       490          20.29 +/- 0.35
uvm2        657       6723       490          > 20.29
uvw2        608       6314       303          > 20.27
-------------------------------------------------------------------------
```
The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383,627).
GCN Circular #10056
A. P. Beardmore, P. A. Evans (U. Leicester) and J. L. Racusin (NASA/GSFC/ORAU) report on behalf of the Swift-XRT team:
We have analysed 13 ks of Swift-XRT data for GRB 091020 (Racusin et al., GCN Circ. 10048), from 87 s to 29.6 ks after the BAT trigger (#373458). The data comprise 350 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 10050).
The light curve shows an initial steep decay with an index of 3.7 +/-0.6, breaking at T+130 s to a shallower decay of slope 0.90 +/- 0.03, with a small flare superimposed at T+190s. A further break to a decay slope of 1.39 +/- 0.1 is apparent at T+6.6 ks.
The WT mode spectrum, from 87 s to 434 s after the trigger, can be fit by an absorbed power-law with a photon index of 1.99 +/- 0.07. The best-fitting absorption column is (6.08 +1.04 -0.99) x 10^21 cm^-2, at a redshift of 1.71 (Xu et al., GCN Circ 10053), in addition to the Galactic value of 1.4 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum from 436 s to 7.3 ks (with an exposure time of 3.5 ks) has a photon index of (2.15 +0.12 -0.11) and a best-fitting intrinsic absorption column of (5.1 +1.6 -1.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay at the same rate, the count rate at T+24 hours will be 0.015 count s^-1, which corresponds to an observed (unabsorbed) 0.3-10 keV flux of 4.8 x 10^-13 (6.3 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/00373458.
This circular is an official product of the Swift-XRT team.
GCN Circular #10057
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long GRB 091020 (Racusin et al., GCN 10048; Palmer et al., GCN Circ 1= 0051) triggered Konus-Wind at T0=3D77804.860s UT (21:36:44.860).
The burst light curve shows a smooth structure with a total duration of ~40 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB091020_T77804/
As observed by Konus-Wind the burst had a fluence of (1.04 =B1 0.21)x10-5 erg/cm2, and a 256-ms peak flux measured from T0 + 0.768s of (1.2 =B1 0.2)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the burst (from T0 to T0+33.024 s) is well fitted in the 20 keV - 2 MeV range by GRB (Band) model for which: the low-energy photon index alpha =3D -0.93 (> -1.57), the high energy photon index beta =3D -1.9(-0.8 / +0.2), the peak energy Ep =3D 103(-68, +248) keV (chi2 =3D 62/60 dof).
All the quoted values are preliminary. All the quoted errors are at the 90% confidence level.
Assuming z =3D 1.71 (Dong Xu et al., GCN 10053) and a standard cosmology model with H_0 =3D 70 km/s/Mpc, Omega_M =3D 0.27, Omega_Lambda =3D 0.73, the isotropic energy release E_iso ~7.9x10^52 erg, the peak luminosity (L_iso)_max ~2.5x10^52 erg/s, and Ep_rest ~280 keV.
GCN Circular #10058
D. A. Perley (UC Berkeley) reports:
I observed the location of GRB 091020 (Racusin et al, GCN 10048) starting at UT 2009-10-21 12:30 using the Nickel 40-inch telescope at Lick Observatory. A series of nine exposures in R-band were acquired, followed by five exposures in I-band and an additional sequence in R-band during morning twilight. All exposures except for the first were of 180 seconds duration.
The afterglow is marginally detected in individual frames and well-detected in a combined stack. Calibrating relative to five nearby SDSS standard stars transformed to R-band using the transformation equation of Lupton (2005), the estimated magnitude of the afterglow in the first R-band stack is:
R = 20.91 +/- 0.13 mag (t_mid = 15.17 hr)
Additional follow-up is planned if weather permits.
GCN Circular #10059
Dmitry Frederiks reports:
I made a mistake in the subject line of GCN 10057: it should be "Konus-Wind observations of GRB 091020" instead of "Konus-Wind observations of GRB 091010".
I apologize for the confusion.
GCN Circular #10060
D. A. Perley (UC Berkeley) reports:
Further to observations the previous night (GCN 10058), I re-observed the afterglow of GRB 091020 between UT 2009-10-22 12:23 and 13:25 using the Nickel 40-inch telescope at Lick Observatory in a series of seventeen 180 second exposures (51 minutes total integration) in R-band.
The afterglow is detected in in the combined stack of all frames. Calibrating relative to the same SDSS standard stars as in GCN 10058, the estimated magnitude of the afterglow at this time is:
R = 21.81 +/- 0.23 mag (t_mid = 39.29 hr)
The implied average decay index over the 24 hours since the previous observation is alpha=0.87.
GCN Circular #10076
D. A. Kann, U. Laux, M. Roeder & H. Meusinger (TLS Tautenburg) report:
We observed the afterglow of the Swift GRB 091020 (Racusin et al., GCN 10048) with the 1.34m Schmidt telescope of the Thueringer Landessternwarte Tautenburg, Germany, as soon as it had risen to an airmass of 2.2, starting 0.167 days after the GRB. We obtained 3 x 300 sec images in Z, Ic, Rc, V and B each. We detect the afterglow in all single images.
As a comparison star, we use the SDSS star at:
```
RA (J2000) =    11:42:49.2 (175.7050129)
Dec. (J2000) = +51:00:52.42 (+51.01456163)
```
For this star, using the transformation equations of Lupton (2005) (taking the mean of the two transformation equations each), and transforming the z' value to Vega mags following Fukugita (1995), we derive the magnitudes:
```
B =  19.109
V =  17.740
Rc = 16.759
Ic = 15.927
Z =  15.563
```
We derive the following afterglow magnitudes:
```
dt		Filter	mag	dmag
____________________________________
0.166947	Z	18.17	0.13
0.170987	Z	18.10	0.13
0.175038	Z	18.16	0.13
0.179181	Ic	18.45	0.06
0.183221	Ic	18.30	0.05
0.187260	Ic	18.32	0.05
0.191404	Rc	19.43	0.04
0.195444	Rc	19.40	0.04
0.199483	Rc	19.40	0.04
0.203627	V	19.90	0.10
0.207666	V	20.00	0.10
0.211706	V	20.06	0.10
0.215849	B	20.78	0.10
0.219889	B	20.71	0.08
0.223928	B	20.72	0.08
```
Using further reported magnitudes (Oates et al., GCN 10054; Gorbovskoy et al., GCN 10052, Xu et al., GCN 10053, Perley, GCN 10058, GCN 10060), we find that the Rc band light curve is very well described by a
single power-law decay with alpha = 1.12 +/- 0.06, B and V light curves agree with an achromatic light curve evolution. We find a red afterglow with spectral slope beta ~ 2, and note that the Ic - Z color is
very blue, this may be due to a filter mismatch between the SDSS z' filter and our Z filter.
This message may be cited.
GCN Circular #10080
L.P. Xin, X.F. Wang, J. Wang, Y.L. Qiu, J.Y. Wei, W.K. Zheng, J.S. Deng, and C. Wu, J.Y. Hu on behalf of EAFON report:
We observed the optical afterglow of GRB 091020 (e.g. Racusin et al., GCN 10048; Gorbovskoy et al., GCN 10052; Perley GCN 10060) with Xinglong TNT telescope from Oct. 22, 20:27:52(UT),1.952 days after the burst. The optical afterglow (Gorbovskoy et al., GCN 10052; Perley GCN 10060) was not detected in our combined image with a duration of 7*600 sec. The upper limit is estimated to be R~21.4 mag from USNO-B1.0 R2 magnitude, at the mean time of 1.974 days since the trigger.
This message may be cited.
For more information about Xinglong GRBs Follow-up observations, please visit the web-site: http://www.xinglong-naoc.org/grb/
GCN Circular #10088
Dale A. Frail (NRAO), Poonam Chandra (RMC), and Tanay Singh report on behalf of a larger collaboration:
"We used the Very Large Array (VLA) to observe the field of view towards the Swift burst GRB 091020A (GCN 10048, 10050, 10051) at a frequency of 8.46 GHz. Data has been taken at 6 different epochs: October 21.66, 22.54, 22.77, 22.99, 24.60 and 26.71 UT. The average flux density of the source during the first 4 epochs was 108 +/- 25 uJy. The source has since increased in flux, rising to 230 +/- 42 uJy on Oct 24.60 UT and 436 +/- 42 uJy on Oct. 26.71 UT. Our current best-fit position is (J2000) R.A.=11:42:55.268, Dec.=+50:58:41.36 with a conservative error of +/-0.6". Further observations are planned.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."
GCN Circular #10090
D. A. Kann, U. Laux, M. Roeder & H. Meusinger (TLS Tautenburg) report:
We observed again the afterglow of the Swift GRB 091020 (Racusin et al., GCN 10048) with the 1.34m Schmidt telescope of the Thueringer Landessternwarte Tautenburg, Germany, on the 26th of October, 5.2 days after the GRB. We obtained 11 x 600 sec images in Rc before clouds shut us down again. At the position of the afterglow, we detect a faint source in the stacked image.
We derive the following afterglow magnitudes using the same comparison star as Kann et al., GCN 10076:
```
dt		Filter	mag	dmag
____________________________________
5.213357	Rc	23.62	0.31
```
Kann et al., GCN 10076, found a single power-law decay with alpha = 1.12 +/- 0.06. Compared to the extrapolation of this fit, there is no significant evidence for a break yet.
No further observations are possible due to an instrument change.
This message may be cited.
GCN Circular #10095
V.Chaplin (UAH) reports on behalf of the Fermi GBM Team:
"At 21:36:43.82 UT on 20 October 2009, the Fermi Gamma-Ray Burst Monitor triggered on GRB 091020 (trigger 277767405 / 091020900), which was also detected by the Swift-BAT (Racusin et al., GCN 10048). The angle from the Fermi LAT boresight of the Swift-XRT position (Beardmore et al., GCN 10050) is 118 degrees.
The GBM light curve consists of a single pulse with a duration (T90) of about 37 s (8-1000 keV). The time-averaged spectrum from T0-7.7 s to T0+21 s is best fit by a Band function with Epeak = 47.9 +/- 7.1 keV, alpha = 0.2 +/- 0.4, and beta = -1.7 +/- .02.
The event fluence (8-1000 keV) in this time interval is (1.0 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.5 s in the 8-1000 keV band is 7.4 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #10109
LaCluyze, A., D. Reichart, A. Smith, D. Caton, L. Hawkins, J. Haislip, K. Ivarsen, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report:
Skynet observed the Swift/BAT localization of GRB 090920 (Racusin et al., GCN 10048) with the 14" Dark Sky Observatory telescope in North Carolina beginning 12.0 hours after the trigger in I.
We detect the afterglow (Racusin et al., GCN 10048). Stacking only images that increase the limiting magnitude yields:
```
mean                                                         1-sig.  1-sig.
time                                                         sys.    stat.
since                                             cal.       cal.    cal.
trig.  tel.    exp.      fil.  magnitude          stars*     unc.    unc.
(h)            (# x s)                                       (mag)   (mag)

12.6   DSO-14  18 x 160  I     19.75 +0.26 -0.21  13 SDSS 7  0.020   0.001
```
* Transformed using Jester et al., 2005, ApJ, 130, 873.
GCN Report 257.1
GCN_Report 257.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_257_1.pdf by J.L. Racusin at NASA-GSFC titled: "Swift Observations on GRB 091020"
GCN Circular #10231
E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov, D.Zemnukhov, M. Kornilov Sternberg Astronomical Institute, Moscow State University
V.Krushinski, I.Zalozhnih, T.Kopytova Ural State University, Kourovka
A. Tlatov, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory
K.Ivanov, S.Yazev, N.M.Budnev, E.Konstantinov, V.Lenok Irkutsk State University
S.Sergienko, V.Yurkov Blagoveschensk Educational State University, Blagoveschensk
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru, 2x400 mm, 2x 4 square degrees, 2x16Mpx Apogee CCD) located at Kislovodsk was pointed to the GRB 091020 (Racusin et al., GCN 10048) by internet 3422 s after the GRB time. The large delay was caused with technical problems on site (Gorbovskoy et al., GCN 10052).
The first 7 images was taken in R-band. The exposure each images is 180s.
West-telescope
```
GRB Time         OT Mag         Error
1.02097639      17.93           0.22
1.07643278      17.43           0.09
1.13188834      17.78           0.14
1.18734417      18.03           0.19
1.24280056      17.87           0.15
1.29825584      17.58           0.10
1.35371584      17.94           0.12
```
The result of the unfiltred polarization combined images is: West-telescope
```
GRB Time         OT Mag         Error
(Hours)

1.604558        18.65           0.10
1.983004        18.91           0.08
2.285582        19.04           0.08
2.562864        19.28           0.11
2.84015         19.36           0.09
3.117435        19.32           0.08
3.394721        19.35           0.06
3.672004        19.23           0.10
3.949285        20.07           0.16
4.226602        20.67           0.28
4.503883        20.07           0.22
```
East-telescope
```
GRB Time          GRB           Error
(Hours)

1.604718        18.60           0.06
1.983232        18.46           0.06
2.285826        19.14           0.09
2.563109        19.11           0.09
2.84039         19.56           0.10
3.117671        19.38           0.09
3.394954        19.70           0.17
3.672234        19.53           0.11
3.949516        19.92           0.16
4.226796        20.03           0.19
4.50408         19.99           0.16
```
Using all our polarizated magnitudes we find that the light curve is very well described by a single power-law decay with alpha = 1.2 +/- 0.1, that is in good agreement with the following observations (Kann et al., GCN 10076)
The light curve of our observations is available at http://observ.pereplet.ru/images/GRB091020/grb.html . The message may be cited.
mailto: lipunov@sai.msu.ru
1305.1620 from 9 May 13
E. S. Gorbovskoy et al.: The MASTER-II Network of Robotic Optical Telescopes. First Results
The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gamma- ray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was ob- served for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars.

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