Gamma-ray Burst 090927

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:08:16 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     370846,   Seg_Num: 0
GRB_RA:          343.953d {+22h 55m 49s} (J2000),
                 344.121d {+22h 56m 29s} (current),
                 343.082d {+22h 52m 20s} (1950)
GRB_DEC:         -70.978d {-70d 58' 38"} (J2000),
                 -70.925d {-70d 55' 30"} (current),
                 -71.244d {-71d 14' 39"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3729 [cnts]    Image_Peak=236 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   40     E_range: 25-100 keV
BKG_INTEN:       38651 [cnts]
BKG_TIME:        36426.87 SOD {10:07:06.87} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15101 TJD;   270 DOY;   09/09/27
GRB_TIME:        36436.92 SOD {10:07:16.92} UT
GRB_PHI:         129.16 [deg]
GRB_THETA:        27.13 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     25.82 [sigma]
IMAGE_SIGNIF:    11.42 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +2  +1  +0  +0 +27  +0 
SUN_POSTN:       184.07d {+12h 16m 17s}   -1.76d {-01d 45' 43"}
SUN_DIST:        106.14 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.48d {+19h 17m 56s}  -23.17d {-23d 09' 54"}
MOON_DIST:        56.93 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.42,-43.24 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      304.33,-56.26 [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 = 14.02,-15.99 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=275738839).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:07:33 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     275738839
GRB_RA:           61.733d {+04h 06m 56s} (J2000),
                  61.739d {+04h 06m 57s} (current),
                  61.708d {+04h 06m 50s} (1950)
GRB_DEC:         -68.200d {-68d 12' 00"} (J2000),
                 -68.174d {-68d 10' 27"} (current),
                 -68.332d {-68d 19' 54"} (1950)
GRB_ERROR:       18.68 [deg radius, statistical plus systematic]
GRB_INTEN:       403 [cnts/sec]
DATA_SIGNIF:     6.60 [sigma]
INTEG_TIME:      0.256 [sec]
GRB_DATE:        15101 TJD;   270 DOY;   09/09/27
GRB_TIME:        36437.21 SOD {10:07:17.21} UT
GRB_PHI:         107.00 [deg]
GRB_THETA:       110.00 [deg]
DATA_TIME_SCALE: 0.2560 [sec]
HARD_RATIO:      0.45
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      49%  Distant Particles
2nd_MOST_LIKELY:  48%  GRB
DETECTORS:       0,0,1, 0,0,0, 0,0,0, 0,1,0, 0,0,
SUN_POSTN:       184.07d {+12h 16m 17s}   -1.76d {-01d 45' 42"}
SUN_DIST:         99.80 [deg]   Sun_angle= 8.2 [hr] (West of Sun)
MOON_POSTN:      289.48d {+19h 17m 55s}  -23.17d {-23d 09' 59"}
MOON_DIST:        82.22 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      281.56,-39.85 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      338.51,-79.11 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 132.53,-25.53 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:11:05 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     370846,   Seg_Num: 0
GRB_RA:          343.953d {+22h 55m 49s} (J2000),
                 344.121d {+22h 56m 29s} (current),
                 343.082d {+22h 52m 20s} (1950)
GRB_DEC:         -70.978d {-70d 58' 38"} (J2000),
                 -70.925d {-70d 55' 30"} (current),
                 -71.244d {-71d 14' 39"} (1950)
GRB_DATE:        15101 TJD;   270 DOY;   09/09/27
GRB_TIME:        36436.92 SOD {10:07:16.92} UT
TRIGGER_INDEX:   40
GRB_PHI:         129.16 [deg]
GRB_THETA:        27.13 [deg]
DELTA_TIME:      -44.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.82 [sigma]
IMAGE_SIGNIF:    11.42 [sigma]
LC_URL:          sw00370846000msb.lc
SUN_POSTN:       184.07d {+12h 16m 17s}   -1.76d {-01d 45' 46"}
SUN_DIST:        106.14 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.51d {+19h 18m 02s}  -23.16d {-23d 09' 36"}
MOON_DIST:        56.93 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.42,-43.24 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      304.33,-56.26 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO -- this is not a normal BAT-detected burst.  
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 = 14.02,-15.99 [deg].

GCN Circular #9945
D. Grupe (PSU), J. R. Cummings (NASA/UMBC), C. Gronwall (PSU), C. Guidorzi (U Ferrara), C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), M. H. Siegel (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team:
At 10:07:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090927 (trigger=370846). The BAT on-board calculated location is RA, Dec 343.953, -70.978 which is
```
   RA(J2000) = 22h 55m 49s
   Dec(J2000) = -70d 58' 38"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 1.5 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+33.8 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 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:     Sun 27 Sep 09 10:43:14 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.960d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38572.98 SOD {10:42:52.98} UT,   2136.1 [sec] since BAT Trigger Time
COUNTS:          35    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:     Sun 27 Sep 09 10:45:51 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.959d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
POINT_ROLL:      200.981d
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38578.20 SOD {10:42:58.20} UT,   2141.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.737
N_STARS:         48
X_OFFSET:        459 [pixels]
Y_OFFSET:        597 [pixels]
X_MAX:           1418 [pixels]
Y_MAX:           1556 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00370846000msufc2141.fits
SUN_POSTN:       184.09d {+12h 16m 23s}   -1.77d {-01d 46' 20"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.81d {+19h 19m 15s}  -23.10d {-23d 05' 52"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.23 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      304.32,-56.26 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:46:24 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.959d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
POINT_ROLL:      200.981d
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38578.20 SOD {10:42:58.20} UT,   2141.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.737
N_STARS:         48
X_OFFSET:        459 [pixels]
Y_OFFSET:        597 [pixels]
X_MAX:           1418 [pixels]
Y_MAX:           1556 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00370846000msufc2141.fits
SUN_POSTN:       184.09d {+12h 16m 23s}   -1.77d {-01d 46' 20"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.82d {+19h 19m 16s}  -23.10d {-23d 05' 48"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.23 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      304.32,-56.26 [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:     Sun 27 Sep 09 10:45:51 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.959d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
POINT_ROLL:      200.981d
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38578.20 SOD {10:42:58.20} UT,   2141.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.737
N_STARS:         48
X_OFFSET:        459 [pixels]
Y_OFFSET:        597 [pixels]
X_MAX:           1418 [pixels]
Y_MAX:           1556 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00370846000msufc2141.fits
SUN_POSTN:       184.09d {+12h 16m 23s}   -1.77d {-01d 46' 20"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.81d {+19h 19m 15s}  -23.10d {-23d 05' 52"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.23 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      304.32,-56.26 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:47:09 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.959d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
ROLL:            200.981d
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38578.20 SOD {10:42:58.20} UT,   2141.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     275740983
X_OFFSET:        778 [pixels]
Y_OFFSET:        916 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       938
Y_GRB_POS:       1076
BINNING_INDEX:   1
IM_URL:          sw00370846000msuni2147.fits
SUN_POSTN:       184.09d {+12h 16m 23s}   -1.77d {-01d 46' 21"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.82d {+19h 19m 17s}  -23.10d {-23d 05' 43"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.23 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      304.32,-56.26 [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:     Sun 27 Sep 09 10:47:29 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     370846,   Seg_Num: 0
POINT_RA:        343.959d {+22h 55m 50s} (J2000)
POINT_DEC:       -70.986d {-70d 59' 09"} (J2000)
ROLL:            200.981d
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38578.20 SOD {10:42:58.20} UT,   2141.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     275740983
X_OFFSET:        778 [pixels]
Y_OFFSET:        916 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       938
Y_GRB_POS:       1076
BINNING_INDEX:   1
IM_URL:          sw00370846000msuni2147.fits
SUN_POSTN:       184.09d {+12h 16m 23s}   -1.77d {-01d 46' 21"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.83d {+19h 19m 18s}  -23.09d {-23d 05' 41"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.23 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      304.32,-56.26 [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:     Sun 27 Sep 09 10:50:00 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     370846,   Seg_Num: 0
GRB_RA:          343.9748d {+22h 55m 53.95s} (J2000),
                 344.1427d {+22h 56m 34.24s} (current),
                 343.1038d {+22h 52m 24.90s} (1950)
GRB_DEC:         -70.9785d {-70d 58' 42.5"} (J2000),
                 -70.9264d {-70d 55' 34.9"} (current),
                 -71.2455d {-71d 14' 43.7"} (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:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38586.00 SOD {10:43:06.00} UT,   2149.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       184.10d {+12h 16m 23s}   -1.77d {-01d 46' 24"}
SUN_DIST:        106.13 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.85d {+19h 19m 23s}  -23.09d {-23d 05' 25"}
MOON_DIST:        56.90 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.24 [deg] galactic lon,lat of the burst
ECL_COORDS:      304.34,-56.26 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
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 Circular #9946
C. Gronwall and D. Grupe (PSU) report on behalf of the Swift/UVOT team:
In response to GRB090927 (Swift/BAT trigger 370846) at 10:07:16 UT, UVOT took a finding chart exposure of 150 seconds with the White filter starting 2141 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
RA(J2000) =	22:55:53.41 = 343.97255
DEC(J2000) = -70:58:49.3 = -70.98037
```
with a 90%-confidence error radius of about 0.63 arc sec. This position is 7.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.10 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 27 Sep 09 10:58:53 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     370846,   Seg_Num: 0
GRB_RA:          343.9740d {+22h 55m 53.75s} (J2000),
                 344.1419d {+22h 56m 34.05s} (current),
                 343.1029d {+22h 52m 24.70s} (1950)
GRB_DEC:         -70.9789d {-70d 58' 44.0"} (J2000),
                 -70.9268d {-70d 55' 36.3"} (current),
                 -71.2459d {-71d 14' 45.2"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38586.00 SOD {10:43:06.00} UT,   2149.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       184.10d {+12h 16m 24s}   -1.78d {-01d 46' 32"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.92d {+19h 19m 42s}  -23.07d {-23d 04' 27"}
MOON_DIST:        56.89 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.24 [deg] galactic lon,lat of the burst
ECL_COORDS:      304.33,-56.26 [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:     Sun 27 Sep 09 10:59:37 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     370846,   Seg_Num: 0
GRB_RA:          343.9725d {+22h 55m 53.40s} (J2000),
                 344.1404d {+22h 56m 33.69s} (current),
                 343.1014d {+22h 52m 24.33s} (1950)
GRB_DEC:         -70.9804d {-70d 58' 49.4"} (J2000),
                 -70.9283d {-70d 55' 41.7"} (current),
                 -71.2474d {-71d 14' 50.6"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         19.10 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  15101 TJD;   270 DOY;   09/09/27
IMG_START_TIME:  38581.00 SOD {10:43:01.00} UT,   2144.1 [sec] since BAT Trigger Time
SUN_POSTN:       184.10d {+12h 16m 25s}   -1.78d {-01d 46' 33"}
SUN_DIST:        106.12 [deg]   Sun_angle= -10.7 [hr] (East of Sun)
MOON_POSTN:      289.93d {+19h 19m 43s}  -23.07d {-23d 04' 22"}
MOON_DIST:        56.89 [deg]
MOON_ILLUM:      62 [%]
GAL_COORDS:      315.41,-43.24 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      304.33,-56.26 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN Circular #9950
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1424 s of XRT Photon Counting mode data and 3 UVOT images for GRB 090927, 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 = 343.97291, -70.98032 which is equivalent to:
```
RA (J2000): 22h 55m 53.50s
Dec (J2000): -70d 58' 49.2"
```
with an uncertainty of 2.0 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 #9952
D. Grupe and L. Vetere (PSU) report on behalf of the Swift-XRT team:
Due to an observing constraint, the Swift XRT started observing the field of GRB 090927 Grupe et al., GCN Circ. 9945) delayed at 10:43:03 UT, 2147s after the BAT trigger.
XRT found a faint, fading, uncatalogued X-ray source at
```
RA (J2000): 22h 55m 53.50s
Dec (J2000): -70d 58' 49.2"
```
with an uncertainty of 2.0 arcsec (radius, 90% confidence) as given in Evens et al. (GCN Circular 9950). This location is 24.8" from the BAT on-board calculated location (Grupe et al., GCN Circular 9945), inside the BAT error circle, and 0.5" from the UVOT position given in Gronwall & Grupe (GCN Circular 9946).
Based on the Photon Counting mode (pc) mode data of the first orbit with an exposure time of 1421s we extracted a spectrum which can be fitted with a single absorbed power law model with Gamma = 1.64+/-0.49 and an absorption column density consistent with the Galactic value of 2.92 x 10^20 cm^-2 (Kalberla et al. 2005).
The light curve can be modelled with a single power-law decay with an index of alpha=1.76+2.05/-0.96. If the afterglow continues to decay with this slope the predicted count rate 24 hours after the trigger is 2.5e-4 counts s^-1 or 1.3e-14 ergs s^-1 cm^-2.
This circular is an official product of the Swift-XRT team.

GCN Circular #9954
N.P.M. Kuin (MSSL-UCL) and D. Grupe (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began a delayed observing the field of GRB 090927 2121s after the trigger due to an observing constraint (Grupe, GCN Circ. 9945). We detect a fading optical afterglow in white, v,b, and u filters at the position reported by UVOT (Gronwall et al., GCN Circ. 9946).
Preliminary magnitudes are reported below.

Filter   T_start(s) T_stop(s) Exposure(s) Magnitude
===================================================
white(FC)    2141    2291    147.4    19.13 +/- 0.09
white        2372    2920    235.6    19.40 +/- 0.09
v            2121    2617     48.6    19.0  +/- 0.37
v            3131    3331    196.6    19.37 +/- 0.25
b            2348    2542     38.9    19.50 +/- 0.31
b            2696    2716     19.5    19.09 +/- 0.34
u            2323    2517     38.9    18.77 +/- 0.26
u            2671    2691     19.5   >18.89
uvw1         2299    3576     92.8   >19.63
uvm2         2446    3536    235.6   >19.89
uvw2         2397    2592     38.9   >18.84
====================================================

The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.03 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 #9955
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (GWU) (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 090927 (trigger #370846) (Grupe, et al., GCN Circ. 9945). The BAT ground-calculated position is RA, Dec = 343.929, -70.973 deg which is
```
    RA(J2000)  =  22h 55m 42.9s
    Dec(J2000) = -70d 58' 24.2"
```
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 55%.
The mask-weighted light curve shows a single irregular peak with an overall roughly FRED shape. T90 (15-350 keV) is 2.2 +- 0.4 sec (estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+2.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.80 +- 0.20. The fluence in the 15-150 keV band is 2.0 +- 0.3 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.01 sec in the 15-150 keV band is 2.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The classification of this burst as short or long is not clear. The burst appears to have significant lag between energy bands, and moreover is not particularly hard. We expect to perform a more quantitative lag analysis and report the results in an additional circular.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/370846/BA/
GCN Circular #9956
A. Klotz, T.P. Vaalsta, Liang Yan, and J. Zadko report on behalf of the Zadko Telescope Team.
A. Klotz (CESR, OHP), T.P. Vaalsta, Liang Yan, J. Zadko, H. Miao, J. Moore, K. Frost, D. Coward, A. Imerito, D. Blair, R. Burman, P. Luckas, S. Gordon, A. Fletcher, A. Ahmet, (University of Western Australia) M. Todd, M. Zadnik (Curtin University) M. Boer, M. Laas (OHP), P. Thierry (Airbus)
The 1.0m F/4 Zadko telescope started imaging the field of GRB 090927 (trigger=370846, Grupe et al., GCN 9945) 110 minutes after the Swift trigger. A fading source was found within the XRT error circle (GCN 9946, Gronwall et al.). The field was observed for 50 minutes using a preliminary version of a robotic observation mode.
Preliminary photometry of unfiltered images taken with an iKon DW436BV camera show the following initial magnitudes of the optical afterglow:
```
tmid(min) Exp. Time  R Magnitude
-------------------------------------
110           42s    >16
126          540s     19.8 +/- 0.5
158          360s     20.0 +/- 0.5
```
The fading seems to have low decay which is encouraging to perform spectrocopy in the next hours.
GCN Circular #9958
Andrew J. Levan (Univ. Warwick), Johan P.U. Fynbo (DARK/NBI), Jens Hjorth (DARK/NBI), Daniele Malesani (DARK/NBI), Paolo D'Avanzo (INAF/OABr), Valerio D'Elia (INAF/OAR), report on behalf of a larger collaboration:
We observed the afterglow of GRB 090927 (Grupe et al., GCN 9945; Gronwall et al., GCN 9946), possibly short (Stamatikos et al., GCN 9955). Using FORS2 on the Very Large Telescope, we have obtained 3x30 min spectra (300V grism) of the optical afterglow (Gronwall & Grupe, GCN 9946; Klotz et al., GCN 9956). Observations started on Sep 27.11 UT, about 16.5 hr after the burst. The afterglow had a magnitude R ~ 21.7 as measured from the acquisition images.
The obtained spectrum shows Mg II and Fe II absorption lines corresponding to z = 1.37. There is no evidence for higher redshift systems or a Lyman-alpha and hence z = 1.37 is the likely redshift of GRB 090927.
We acknowledge excellent support from the ESO observing staff, in particular Yuri Beletsky and Stephane Brillant.
GCN Circular #9960
Z. Cano, A. Melandri, C. Mundell, D. Bersier, R.J. Smith, I. A. Steele, S. Kobayashi, C.J. Mottram (Liverpool JMU), A. Gomboc (U. Ljubljana) report, on behalf of the Liverpool GRB group:
The Faulkes Telescope South (Australia) observed the field of GRB 090927 (Swift trigger=370846, Grupe et al., GCN 9945) on 2009 September 27 and 28.
The afterglow candidate reported by Gronwell & Grupe (GCN 9946) is clearly visible and fading at position:
```
RA(J2000):   22 55 53.42
Dec(J2000): -70 58 49.54
```
with the following magnitudes calibrated wrt USNO-B1 objects in the field:
```
I = 19.4 +/- 0.1  @ 3.66 hrs
I = 21.3 +/- 0.2  @ 27.23 hrs

R = 19.9 +/- 0.1 @ 4.21 hrs
```
Observations are on-going, but we derive preliminary decay rates using the above FTS measurements and the R-band magnitude reported by Levan et al. (GCN 9958) to be: alpha_I=0.9+/-0.2, alpha_R=1.2+/-0.2.
GCN Circular #9974
D. Gruber (MPE), E. Bissaldi (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team:
"At 10:07:17.21 UT on 27 September 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090927 (trigger 275738839 / 090927422), which was also detected by the Swift-BAT (Grupe al. 2009, GCN 9945). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 85 degrees.
The GBM light curve consists of one weak pulse with a duration of about 2 seconds. The time-averaged spectrum from T0-0.256 s to T0+0.896 s is adequately fit by a simple power law function with index -1.47 +/- 0.06 (C-stat 330 for 239 d.o.f.).
The event fluence (8-1000 keV) in this time interval is (6.1 +/- 0.5)E-07 erg/cm^2. The 128-msec peak photon flux measured starting from T0-0.128 s in the 8-1000 keV band is 7.2 +/- 0.9 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #10021
Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope National Facility), Dale A. Frail (National Radio Astronomy Observatory), Steven Tingay (Curtin Institute of Radio Astronomy), Jean-Pierre Macquart (Curtin Institute of Radio Astronomy) report:
We observed the enhanced Swift-XRT position of the GRB090927 (GCN 9950) at 5.5 GHz with the Australia Telescope Compact Array (ATCA) between 05:00:00 UT and 10:00:00 UT on October 01, 2009. The ATCA was in its most compact configuration giving a synthesized beam of 126 x 76 arcsec.
We did not detect a radio source at the XRT position of the GRB090926a (GCN 9950). The radio flux density at the GRB position found out to be 0.036 = 0.172 mJy/beam.
No further observations are planned.
The Australia Telescope Compact Array (/ Parkes telescope / Mopra telescope / Long Baseline Array) is part of the Australia Telescope which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.
See the GRB field image at:=20
http://cira.ivec.org/dokuwiki/doku.php/grb/grb090927_field_image
GCN Report 252.1
GCN_Report 252.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_252_1.pdf by D. Grupe at PSU titled: "Final Results on Swift GRB 090927"

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Jochen Greiner, last update: 19-Oct-2009 [Disclaimer]