Gamma-ray Burst 110420A

(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:     Wed 20 Apr 11 11:02:41 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.165d {+00h 08m 40s} (J2000),
                   2.308d {+00h 09m 14s} (current),
                   1.532d {+00h 06m 08s} (1950)
GRB_DEC:         -37.855d {-37d 51' 17"} (J2000),
                 -37.792d {-37d 47' 31"} (current),
                 -38.133d {-38d 07' 59"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4272 [cnts]    Image_Peak=155 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   144     E_range: 15-50 keV
BKG_INTEN:       28976 [cnts]
BKG_TIME:        39729.12 SOD {11:02:09.12} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15671 TJD;   110 DOY;   11/04/20
GRB_TIME:        39744.03 SOD {11:02:24.03} UT
GRB_PHI:         -34.11 [deg]
GRB_THETA:        50.19 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.64 [sigma]
IMAGE_SIGNIF:    7.93 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -2  +0  +0 -57  +0 
SUN_POSTN:        27.94d {+01h 51m 45s}  +11.48d {+11d 28' 50"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.11d {+16h 00m 26s}  -22.62d {-22d 37' 16"}
MOON_DIST:        98.80 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.23,-76.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      344.64,-35.09 [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 = 324.28,20.03 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:04:29 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.1609d {+00h 08m 38.61s} (J2000),
                   2.3038d {+00h 09m 12.90s} (current),
                   1.5274d {+00h 06m 06.57s} (1950)
GRB_DEC:         -37.8876d {-37d 53' 15.3"} (J2000),
                 -37.8247d {-37d 49' 29.0"} (current),
                 -38.1659d {-38d 09' 57.0"} (1950)
GRB_ERROR:       5.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       8.02e-10 [erg/cm2/sec]
GRB_SIGNIF:      6.63 [sigma]
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39831.63 SOD {11:03:51.63} UT,   87.6 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.22 261.42 243.67
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        27.94d {+01h 51m 45s}  +11.48d {+11d 28' 51"}
SUN_DIST:         54.84 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.13d {+16h 00m 30s}  -22.62d {-22d 37' 24"}
MOON_DIST:        98.76 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.14,-75.98 [deg] galactic lon,lat of the burst
ECL_COORDS:      344.62,-35.12 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.96 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:04:39 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.1609d {+00h 08m 38.6s} (J2000),
                   2.3038d {+00h 09m 12.9s} (current),
                   1.5274d {+00h 06m 06.5s} (1950)
GRB_DEC:         -37.8876d {-37d 53' 15.3"} (J2000),
                 -37.8247d {-37d 49' 29.0"} (current),
                 -38.1659d {-38d 09' 57.0"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       44 [cnts]
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39831.63 SOD {11:03:51.63} UT,   87.6 [sec] since BAT Trigger Time
CENTROID_X:      349.53,  raw= 350  [pixels]
CENTROID_Y:      292.38,  raw= 292  [pixels]
ROLL:            31.38 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -13.24
GRB_POS_XRT_Z:   111.34
IMAGE_URL:       sw00451757000msxps_rw.img
SUN_POSTN:        27.94d {+01h 51m 45s}  +11.48d {+11d 28' 51"}
SUN_DIST:         54.84 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.13d {+16h 00m 31s}  -22.62d {-22d 37' 24"}
MOON_DIST:        98.76 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.14,-75.98 [deg] galactic lon,lat of the burst
ECL_COORDS:      344.62,-35.12 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:04:45 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.1609d {+00h 08m 38.6s} (J2000),
                   2.3038d {+00h 09m 12.9s} (current),
                   1.5274d {+00h 06m 06.5s} (1950)
GRB_DEC:         -37.8876d {-37d 53' 15.3"} (J2000),
                 -37.8247d {-37d 49' 29.0"} (current),
                 -38.1659d {-38d 09' 57.0"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       44 [cnts]
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39831.63 SOD {11:03:51.63} UT,   87.6 [sec] since BAT Trigger Time
CENTROID_X:      349.53,  raw= 350  [pixels]
CENTROID_Y:      292.38,  raw= 292  [pixels]
ROLL:            31.38 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -13.24
GRB_POS_XRT_Z:   111.34
IMAGE_URL:       sw00451757000msxps_rw.img
SUN_POSTN:        27.94d {+01h 51m 45s}  +11.48d {+11d 28' 51"}
SUN_DIST:         54.84 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.13d {+16h 00m 31s}  -22.62d {-22d 37' 25"}
MOON_DIST:        98.76 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.14,-75.98 [deg] galactic lon,lat of the burst
ECL_COORDS:      344.62,-35.12 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:06:05 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.165d {+00h 08m 40s} (J2000),
                   2.308d {+00h 09m 14s} (current),
                   1.532d {+00h 06m 08s} (1950)
GRB_DEC:         -37.855d {-37d 51' 17"} (J2000),
                 -37.792d {-37d 47' 31"} (current),
                 -38.133d {-38d 07' 59"} (1950)
GRB_DATE:        15671 TJD;   110 DOY;   11/04/20
GRB_TIME:        39744.03 SOD {11:02:24.03} UT
TRIGGER_INDEX:   144
GRB_PHI:         -34.11 [deg]
GRB_THETA:        50.19 [deg]
DELTA_TIME:      -50.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.64 [sigma]
IMAGE_SIGNIF:    7.93 [sigma]
LC_URL:          sw00451757000msb.lc
SUN_POSTN:        27.94d {+01h 51m 45s}  +11.48d {+11d 28' 52"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.14d {+16h 00m 35s}  -22.63d {-22d 37' 31"}
MOON_DIST:        98.78 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.23,-76.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      344.64,-35.09 [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 = 324.28,20.03 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:07:43 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.178d {+00h 08m 43s} (J2000)
POINT_DEC:       -37.859d {-37d 51' 30"} (J2000)
POINT_ROLL:      31.379d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39841.41 SOD {11:04:01.41} UT,   97.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.993
N_STARS:         14
X_OFFSET:        440 [pixels]
Y_OFFSET:        504 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1463 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00451757000msufc0097.fits
SUN_POSTN:        27.94d {+01h 51m 46s}  +11.48d {+11d 28' 54"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.16d {+16h 00m 39s}  -22.63d {-22d 37' 38"}
MOON_DIST:        98.77 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.18,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:08:15 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.178d {+00h 08m 43s} (J2000)
POINT_DEC:       -37.859d {-37d 51' 30"} (J2000)
POINT_ROLL:      31.379d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39841.41 SOD {11:04:01.41} UT,   97.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.993
N_STARS:         14
X_OFFSET:        440 [pixels]
Y_OFFSET:        504 [pixels]
X_MAX:           1399 [pixels]
Y_MAX:           1463 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00451757000msufc0097.fits
SUN_POSTN:        27.94d {+01h 51m 46s}  +11.48d {+11d 28' 54"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.17d {+16h 00m 40s}  -22.63d {-22d 37' 40"}
MOON_DIST:        98.76 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.18,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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:     Wed 20 Apr 11 11:09:46 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.178d {+00h 08m 43s} (J2000)
POINT_DEC:       -37.859d {-37d 51' 30"} (J2000)
ROLL:            31.379d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39841.41 SOD {11:04:01.41} UT,   97.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     324990248
X_OFFSET:        626 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       786
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0104.fits
SUN_POSTN:        27.94d {+01h 51m 46s}  +11.48d {+11d 28' 56"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.18d {+16h 00m 44s}  -22.63d {-22d 37' 46"}
MOON_DIST:        98.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.18,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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:     Wed 20 Apr 11 11:10:04 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.178d {+00h 08m 43s} (J2000)
POINT_DEC:       -37.859d {-37d 51' 30"} (J2000)
ROLL:            31.379d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39841.41 SOD {11:04:01.41} UT,   97.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     324990248
X_OFFSET:        626 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       786
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0104.fits
SUN_POSTN:        27.94d {+01h 51m 46s}  +11.48d {+11d 28' 56"}
SUN_DIST:         54.81 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.19d {+16h 00m 45s}  -22.63d {-22d 37' 48"}
MOON_DIST:        98.75 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.18,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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:     Wed 20 Apr 11 11:11:41 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.1636d {+00h 08m 39.26s} (J2000),
                   2.3065d {+00h 09m 13.55s} (current),
                   1.5301d {+00h 06m 07.22s} (1950)
GRB_DEC:         -37.8866d {-37d 53' 11.7"} (J2000),
                 -37.8237d {-37d 49' 25.4"} (current),
                 -38.1649d {-38d 09' 53.4"} (1950)
GRB_ERROR:       0.8 [arcsec radius, statistical only]
GRB_MAG:         17.77 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39846.00 SOD {11:04:06.00} UT,   102.0 [sec] since BAT Trigger Time
SUN_POSTN:        27.94d {+01h 51m 46s}  +11.48d {+11d 28' 57"}
SUN_DIST:         54.84 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.20d {+16h 00m 49s}  -22.63d {-22d 37' 55"}
MOON_DIST:        98.71 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.14,-75.98 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      344.62,-35.12 [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 8.3 arcsec from the XRT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:15:59 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
POINT_ROLL:      31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40053.42 SOD {11:07:33.42} UT,   309.4 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.654
N_STARS:         10
X_OFFSET:        306 [pixels]
Y_OFFSET:        689 [pixels]
X_MAX:           1265 [pixels]
Y_MAX:           1648 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00451757000msufc0309.fits
SUN_POSTN:        27.95d {+01h 51m 47s}  +11.48d {+11d 29' 01"}
SUN_DIST:         54.82 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.25d {+16h 01m 00s}  -22.64d {-22d 38' 13"}
MOON_DIST:        98.70 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:16:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
POINT_ROLL:      31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40053.42 SOD {11:07:33.42} UT,   309.4 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.654
N_STARS:         10
X_OFFSET:        306 [pixels]
Y_OFFSET:        689 [pixels]
X_MAX:           1265 [pixels]
Y_MAX:           1648 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00451757000msufc0309.fits
SUN_POSTN:        27.95d {+01h 51m 47s}  +11.48d {+11d 29' 01"}
SUN_DIST:         54.82 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.25d {+16h 01m 01s}  -22.64d {-22d 38' 14"}
MOON_DIST:        98.70 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #11941
V. Mangano (INAF-IASFPA), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), S. Campana (INAF-OAB), J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester), J. M. Gelbord (PSU), B. Gendre (ASDC), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), P. T. O\'Brien (U Leicester), C. Pagani (U Leicester), P. Romano (INAF-IASFPA), A. Rowlinson (U Leicester), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team:
At 11:02:24 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 110420A (trigger=451757). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 2.165, -37.855 which is
```
   RA(J2000) = 00h 08m 40s
   Dec(J2000) = -37d 51' 17"
```
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 20 sec. The peak count rate was 4000 counts/sec (15-350 keV), at 10 sec after the trigger.
The XRT began observing the field at 11:03:51.6 UT, 87.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 2.16337, -37.88696 which is equivalent to:
```
    RA(J2000)  = 00h 08m 39.21s
    Dec(J2000) = -37d 53' 13.1"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 115 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.26 x 10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.8 (+2.08/-1.84) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 8.02e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 97 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =	00:08:39.27 =	2.16364
  DEC(J2000) = -37:53:12.0  = -37.88667
```
with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.77 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01.
Burst Advocate for this burst is V. Mangano (vanessa AT ifc.inaf.it). 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:     Wed 20 Apr 11 11:18:34 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
ROLL:            31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40053.42 SOD {11:07:33.42} UT,   309.4 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     324990460
X_OFFSET:        626 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       786
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0316.fits
SUN_POSTN:        27.95d {+01h 51m 47s}  +11.48d {+11d 29' 03"}
SUN_DIST:         54.82 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.28d {+16h 01m 07s}  -22.64d {-22d 38' 24"}
MOON_DIST:        98.68 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:18:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
ROLL:            31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40053.42 SOD {11:07:33.42} UT,   309.4 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     324990460
X_OFFSET:        626 [pixels]
Y_OFFSET:        1009 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       786
Y_GRB_POS:       1169
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0316.fits
SUN_POSTN:        27.95d {+01h 51m 47s}  +11.48d {+11d 29' 04"}
SUN_DIST:         54.82 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.28d {+16h 01m 08s}  -22.64d {-22d 38' 26"}
MOON_DIST:        98.68 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:26:23 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     451757,   Seg_Num: 0
GRB_RA:            2.1633d {+00h 08m 39.19s} (J2000),
                   2.3062d {+00h 09m 13.47s} (current),
                   1.5298d {+00h 06m 07.15s} (1950)
GRB_DEC:         -37.8864d {-37d 53' 11.0"} (J2000),
                 -37.8235d {-37d 49' 24.7"} (current),
                 -38.1647d {-38d 09' 52.7"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  39901.00 SOD {11:05:01.00} UT,   157.0 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        27.95d {+01h 51m 48s}  +11.49d {+11d 29' 10"}
SUN_DIST:         54.85 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.36d {+16h 01m 27s}  -22.65d {-22d 38' 57"}
MOON_DIST:        98.60 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.14,-75.98 [deg] galactic lon,lat of the burst
ECL_COORDS:      344.62,-35.12 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:38:21 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
POINT_ROLL:      31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40606.15 SOD {11:16:46.15} UT,   862.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.130
N_STARS:         22
X_OFFSET:        66 [pixels]
Y_OFFSET:        449 [pixels]
X_MAX:           1505 [pixels]
Y_MAX:           1888 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    13
SL_URL:          sw00451757000msufc0862.fits
SUN_POSTN:        27.96d {+01h 51m 50s}  +11.49d {+11d 29' 20"}
SUN_DIST:         54.83 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.49d {+16h 01m 58s}  -22.66d {-22d 39' 48"}
MOON_DIST:        98.53 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 20 Apr 11 11:38:37 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
POINT_ROLL:      31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40606.15 SOD {11:16:46.15} UT,   862.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.130
N_STARS:         22
X_OFFSET:        66 [pixels]
Y_OFFSET:        449 [pixels]
X_MAX:           1505 [pixels]
Y_MAX:           1888 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    13
SL_URL:          sw00451757000msufc0862.fits
SUN_POSTN:        27.96d {+01h 51m 50s}  +11.49d {+11d 29' 20"}
SUN_DIST:         54.83 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.49d {+16h 01m 59s}  -22.66d {-22d 39' 49"}
MOON_DIST:        98.53 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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:     Wed 20 Apr 11 11:39:51 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
ROLL:            31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40606.15 SOD {11:16:46.15} UT,   862.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     324991013
X_OFFSET:        625 [pixels]
Y_OFFSET:        1008 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       785
Y_GRB_POS:       1168
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0869.fits
SUN_POSTN:        27.96d {+01h 51m 51s}  +11.49d {+11d 29' 21"}
SUN_DIST:         54.83 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.51d {+16h 02m 02s}  -22.67d {-22d 39' 54"}
MOON_DIST:        98.52 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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:     Wed 20 Apr 11 11:40:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     451757,   Seg_Num: 0
POINT_RA:          2.175d {+00h 08m 42s} (J2000)
POINT_DEC:       -37.860d {-37d 51' 34"} (J2000)
ROLL:            31.383d
IMG_START_DATE:  15671 TJD;   110 DOY;   11/04/20
IMG_START_TIME:  40606.15 SOD {11:16:46.15} UT,   862.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     324991013
X_OFFSET:        625 [pixels]
Y_OFFSET:        1008 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       785
Y_GRB_POS:       1168
BINNING_INDEX:   1
IM_URL:          sw00451757000msuni0869.fits
SUN_POSTN:        27.96d {+01h 51m 51s}  +11.49d {+11d 29' 22"}
SUN_DIST:         54.83 [deg]   Sun_angle= 1.7 [hr] (West of Sun)
MOON_POSTN:      240.51d {+16h 02m 02s}  -22.67d {-22d 39' 55"}
MOON_DIST:        98.52 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:      340.19,-76.01 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      344.65,-35.10 [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 #11942
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 1599 s of XRT Photon Counting mode data and 2 UVOT images for GRB 110420A, 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 = 2.16355, -37.88627 which is equivalent to:
```
RA (J2000): 00h 08m 39.25s
Dec (J2000): -37d 53' 10.6"
```
with an uncertainty of 1.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #11943
V. Mangano (INAF-IASFPA) and B. Sbarufatti (INAF OAB/INAF-IASFPA) report on behalf of the Swift-XRT team:
We have analysed 1.9 ks of XRT data for GRB 110420A (Mangano et al. GCN Circ. 11941), from 77 s to 17.0 ks after the BAT trigger. The data comprise 57 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 11942).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.87 (+0.31, -0.29). At T+181 s the decay flattens to an alpha of 0.23 (+0.08, -0.09) before breaking again at T+11.0 ks to a final decay with index alpha=3.9 (+1.8, -2.1).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 4.2 (+0.5, -0.4). The best-fitting absorption column is 1.9 (+0.6, -0.5) x 10^21 cm^-2, in excess of the Galactic value of 1.3 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.37 (+0.16, -0.15) and a best-fitting absorption column of 2.1 (+/-0.4) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (6.4 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.1 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: 8.8 sigma
Photon index:	     2.37 (+0.16, -0.15)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00451757.
This circular is an official product of the Swift-XRT team.
GCN Circular #11945
GRB 110420A: Swift-BAT refined analysis
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), 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 recent telemetry downlinks, we report further analysis of BAT GRB 110420A (trigger #451757) (Mangano, et al., GCN Circ. 11941). The BAT ground-calculated position is RA, Dec = 2.164, -37.877 deg which is
```
   RA(J2000)  =  00h 08m 39.3s 
   Dec(J2000) = -37d 52' 35.5" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%.
The mask-weighted light curve shows a single peak with some structure starting at ~T-15 sec, peaking at ~T+8 sec, and ending at ~T+35 sec. T90 (15-350 keV) is 11.8 +- 0.9 sec (estimated error including systematics).
The time-averaged spectrum from T-0.1 to T+16.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.30 +- 0.07. The fluence in the 15-150 keV band is 5.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+8.04 sec in the 15-150 keV band is 14.0 +- 0.9 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/451757/BA/
GCN Circular #11948
S. R. Oates (MSSL-UCL) & V. Mangano (INAF-IASFPA) report on behalf of the Swift-UVOT team
The Swift/UVOT began settled observations of the field of GRB 110420A 97s after the trigger (Mangano et al., GCN Circ. 11941). We detect a source at a refined position of RA(J2000), DEC(J2000)= 2.16363deg,-37.88664deg. This is equivalent to:
```
    RA (J2000)  00:08:39.27
   Dec (J2000) -37:53:11.9
```
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). This is consistent with the position of the X-ray afterglow (Beardmore et al., GCN Circ. 11942). The afterglow is detected in all filters providing a photometric redshift limit of z~<1.6.
Preliminary magnitudes using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the finding chart (FC) and summed exposures at the location of the optical afterglow are:
```
Filter  T_start(s)  T_stop(s)   Exp(s)       Mag
#####################################################
wh (FC)     97         247       147     17.81 +/- 0.05
wh	    761        781       19       18.10 +/- 0.17
u (FC)      309        559      246      17.46 +/- 0.07
u           712        732       19       17.96 +/- 0.36
v           811        831       19       18.20 +/- 0.67
b	    737        757       19       18.04 +/- 0.28
uvw1	    688        707       19       17.08 +/- 0.24
uvm2	    663        683       19       17.73 +/- 0.41
uvw2        614        634       19       17.91 +/- 0.35
#####################################################
```
The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #11951
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long soft GRB 110420A (Swift-BAT trigger #451757: Mangano et al., GCN 11941; Krimm et al., GCN 11945) triggered Konus-Wind at T0(KW)=39750.543 s UT (11:02:30.543).
The burst light curve shows a single pulse started at ~T0(KW)-9 s with a duration of ~18 s.
As observed by Konus-Wind the burst had a fluence of 6.54(-0.53, +0.64)x10^-6 erg/cm2, and a 256-ms peak flux measured from T0-0.320 s of (1.11 +/- 0.17)x10^-6 erg/cm2/s (both in the 20 - 500 keV energy range).
The time-integrated spectrum of the burst (from T0 to T0+8.448 s) is well fitted (in the 20 - 500 keV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.71(-0.26, +0.31), and Ep = 43(-18, +17) keV (chi2 = 31.1/39 dof). Fitting by GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.61 (chi2 = 31.1/38 dof).
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB110420_T39750/
GCN Circular #11954
P. Afonso, J. Elliott, and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 110420A (Swift trigger 451757; Mangano et al., GCN #11941) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile).
Observations started at 09:34 UT on April 21, 22.5 hours after the GRB trigger. They were performed at an average seeing of 1.8'' and at an average airmass of 2.3.
We confirm the detection of the single point source reported by Oates et al. (GCN #11948).
Based on the first 142-s exposures in r', we estimate a preliminary magnitude (AB system) of
r' = 20.6 +/- 0.1 mag.
In combination with the early UVOT detection, this would imply a decay slope of 0.85 between 700 s and 22.5 hours.
Given magnitudes are calibrated against GROND zeropoints and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.014 mag in the direction of the burst (Schlegel et al. 1998).
GCN Report 361.1
GCN_Report 361.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_361_1.pdf by V. Mangano at INAF IASF Pa titled: "Final Swift Observations of GRB 110420A"

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Jochen Greiner, last update: 21-Apr-2011 [Disclaimer]