Gamma-ray Burst 100425A

(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:     Sun 25 Apr 10 02:51:29 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.187d {+19h 56m 45s} (J2000),
                 299.344d {+19h 57m 22s} (current),
                 298.424d {+19h 53m 42s} (1950)
GRB_DEC:         -26.441d {-26d 26' 27"} (J2000),
                 -26.413d {-26d 24' 46"} (current),
                 -26.575d {-26d 34' 30"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       5375 [cnts]    Image_Peak=238 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   139     E_range: 15-50 keV
BKG_INTEN:       35656 [cnts]
BKG_TIME:        10226.26 SOD {02:50:26.26} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15311 TJD;   115 DOY;   10/04/25
GRB_TIME:        10245.07 SOD {02:50:45.07} UT
GRB_PHI:         -83.40 [deg]
GRB_THETA:        28.53 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.24 [sigma]
IMAGE_SIGNIF:    9.39 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +0  +0  +0 +14  +0 
SUN_POSTN:        32.53d {+02h 10m 07s}  +13.12d {+13d 07' 21"}
SUN_DIST:         98.60 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.63d {+11h 14m 32s}   -0.12d {-00d 07' 22"}
MOON_DIST:       125.67 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      296.02, -5.60 [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 = 62.51,20.16 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:52:32 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.1953d {+19h 56m 46.87s} (J2000),
                 299.3523d {+19h 57m 24.55s} (current),
                 298.4332d {+19h 53m 43.95s} (1950)
GRB_DEC:         -26.4318d {-26d 25' 54.4"} (J2000),
                 -26.4037d {-26d 24' 13.4"} (current),
                 -26.5660d {-26d 33' 57.5"} (1950)
GRB_ERROR:       5.0 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       3.11e-09 [erg/cm2/sec]
GRB_SIGNIF:      11.53 [sigma]
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10323.91 SOD {02:52:03.91} UT,   78.8 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.21 261.57 243.37
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        32.53d {+02h 10m 07s}  +13.12d {+13d 07' 22"}
SUN_DIST:         98.59 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.64d {+11h 14m 34s}   -0.13d {-00d 07' 38"}
MOON_DIST:       125.68 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.80,-25.29 [deg] galactic lon,lat of the burst
ECL_COORDS:      296.03, -5.59 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.73 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:52:41 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.1953d {+19h 56m 46.8s} (J2000),
                 299.3523d {+19h 57m 24.5s} (current),
                 298.4332d {+19h 53m 43.9s} (1950)
GRB_DEC:         -26.4318d {-26d 25' 54.4"} (J2000),
                 -26.4037d {-26d 24' 13.4"} (current),
                 -26.5660d {-26d 33' 57.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       133 [cnts]
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10323.91 SOD {02:52:03.91} UT,   78.8 [sec] since BAT Trigger Time
CENTROID_X:      271.29,  raw= 271  [pixels]
CENTROID_Y:      313.00,  raw= 313  [pixels]
ROLL:            79.63 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   35.37
GRB_POS_XRT_Z:   -73.09
IMAGE_URL:       sw00420398000msxps_rw.img
SUN_POSTN:        32.53d {+02h 10m 07s}  +13.12d {+13d 07' 22"}
SUN_DIST:         98.59 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.64d {+11h 14m 35s}   -0.13d {-00d 07' 40"}
MOON_DIST:       125.67 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.80,-25.29 [deg] galactic lon,lat of the burst
ECL_COORDS:      296.03, -5.59 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:52:44 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.1953d {+19h 56m 46.8s} (J2000),
                 299.3523d {+19h 57m 24.5s} (current),
                 298.4332d {+19h 53m 43.9s} (1950)
GRB_DEC:         -26.4318d {-26d 25' 54.4"} (J2000),
                 -26.4037d {-26d 24' 13.4"} (current),
                 -26.5660d {-26d 33' 57.5"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       133 [cnts]
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10323.91 SOD {02:52:03.91} UT,   78.8 [sec] since BAT Trigger Time
CENTROID_X:      271.29,  raw= 271  [pixels]
CENTROID_Y:      313.00,  raw= 313  [pixels]
ROLL:            79.63 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   35.37
GRB_POS_XRT_Z:   -73.09
IMAGE_URL:       sw00420398000msxps_rw.img
SUN_POSTN:        32.53d {+02h 10m 07s}  +13.12d {+13d 07' 22"}
SUN_DIST:         98.59 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.65d {+11h 14m 35s}   -0.13d {-00d 07' 41"}
MOON_DIST:       125.67 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.80,-25.29 [deg] galactic lon,lat of the burst
ECL_COORDS:      296.03, -5.59 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:54:27 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.187d {+19h 56m 45s} (J2000),
                 299.344d {+19h 57m 22s} (current),
                 298.424d {+19h 53m 42s} (1950)
GRB_DEC:         -26.441d {-26d 26' 27"} (J2000),
                 -26.413d {-26d 24' 46"} (current),
                 -26.575d {-26d 34' 30"} (1950)
GRB_DATE:        15311 TJD;   115 DOY;   10/04/25
GRB_TIME:        10245.07 SOD {02:50:45.07} UT
TRIGGER_INDEX:   139
GRB_PHI:         -83.40 [deg]
GRB_THETA:        28.53 [deg]
DELTA_TIME:      39.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.24 [sigma]
IMAGE_SIGNIF:    9.39 [sigma]
LC_URL:          sw00420398000msb.lc
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 24"}
SUN_DIST:         98.60 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.66d {+11h 14m 39s}   -0.14d {-00d 08' 07"}
MOON_DIST:       125.65 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      296.02, -5.60 [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 = 62.51,20.16 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:56:14 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
POINT_ROLL:      79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.931
N_STARS:         106
X_OFFSET:        552 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00420398000msufc0088.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 25"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.68d {+11h 14m 42s}   -0.14d {-00d 08' 34"}
MOON_DIST:       125.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:56:14 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
POINT_ROLL:      79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.931
N_STARS:         106
X_OFFSET:        552 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00420398000msufc0088.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 25"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.68d {+11h 14m 42s}   -0.14d {-00d 08' 34"}
MOON_DIST:       125.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:56:14 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
POINT_ROLL:      79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.931
N_STARS:         106
X_OFFSET:        552 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00420398000msufc0088.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 25"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.68d {+11h 14m 42s}   -0.14d {-00d 08' 34"}
MOON_DIST:       125.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:56:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
POINT_ROLL:      79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.931
N_STARS:         106
X_OFFSET:        552 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1511 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw00420398000msufc0088.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 25"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.68d {+11h 14m 43s}   -0.14d {-00d 08' 38"}
MOON_DIST:       125.62 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_srclist.ps.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 02:58:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
ROLL:            79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293856739
X_OFFSET:        905 [pixels]
Y_OFFSET:        732 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1065
Y_GRB_POS:       892
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0094.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 27"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.70d {+11h 14m 47s}   -0.15d {-00d 09' 06"}
MOON_DIST:       125.60 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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:     Sun 25 Apr 10 02:58:29 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.176d {+19h 56m 42s} (J2000)
POINT_DEC:       -26.445d {-26d 26' 40"} (J2000)
ROLL:            79.630d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10333.37 SOD {02:52:13.37} UT,   88.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293856739
X_OFFSET:        905 [pixels]
Y_OFFSET:        732 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1065
Y_GRB_POS:       892
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0094.fits
SUN_POSTN:        32.53d {+02h 10m 08s}  +13.12d {+13d 07' 27"}
SUN_DIST:         98.61 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.70d {+11h 14m 47s}   -0.15d {-00d 09' 08"}
MOON_DIST:       125.60 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.79,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_image.ps.gz file does not exist; skipping the attachment.

GCN Circular #10673
D. Grupe (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (NASA/UMBC), S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 02:50:45 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100425A (trigger=420398). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 299.187, -26.441 which is
```
   RA(J2000) = 19h 56m 45s
   Dec(J2000) = -26d 26' 27"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed two peaks, one with a duration of about 8 sec at T0 and one of about 6 sec at T+38 sec. The peak count rate was ~500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 02:52:03.9 UT, 78.8 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 299.19593, -26.43039 which is equivalent to:
```
   RA(J2000)  = 19h 56m 47.02s
   Dec(J2000) = -26d 25' 49.4"
```
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 47 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.59e+20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 3.11e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 88 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.15.
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 25 Apr 10 03:04:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.116
N_STARS:         59
X_OFFSET:        585 [pixels]
Y_OFFSET:        412 [pixels]
X_MAX:           1544 [pixels]
Y_MAX:           1371 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00420398000msufc0301.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 32"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.75d {+11h 15m 01s}   -0.18d {-00d 10' 45"}
MOON_DIST:       125.53 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:04:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.116
N_STARS:         59
X_OFFSET:        585 [pixels]
Y_OFFSET:        412 [pixels]
X_MAX:           1544 [pixels]
Y_MAX:           1371 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00420398000msufc0301.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 32"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.75d {+11h 15m 01s}   -0.18d {-00d 10' 45"}
MOON_DIST:       125.53 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:04:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.116
N_STARS:         59
X_OFFSET:        585 [pixels]
Y_OFFSET:        412 [pixels]
X_MAX:           1544 [pixels]
Y_MAX:           1371 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00420398000msufc0301.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 32"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.75d {+11h 15m 01s}   -0.18d {-00d 10' 45"}
MOON_DIST:       125.53 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:05:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.116
N_STARS:         59
X_OFFSET:        585 [pixels]
Y_OFFSET:        412 [pixels]
X_MAX:           1544 [pixels]
Y_MAX:           1371 [pixels]
DET_THRESH:      12
PHOTO_THRESH:    6
SL_URL:          sw00420398000msufc0301.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 32"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.76d {+11h 15m 02s}   -0.18d {-00d 10' 49"}
MOON_DIST:       125.53 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_srclist.ps.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:06:16 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
ROLL:            79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     293856952
X_OFFSET:        905 [pixels]
Y_OFFSET:        732 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1065
Y_GRB_POS:       892
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0307.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 33"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.77d {+11h 15m 04s}   -0.19d {-00d 11' 07"}
MOON_DIST:       125.51 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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:     Sun 25 Apr 10 03:06:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
ROLL:            79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10546.30 SOD {02:55:46.30} UT,   301.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     293856952
X_OFFSET:        905 [pixels]
Y_OFFSET:        732 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1065
Y_GRB_POS:       892
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0307.fits
SUN_POSTN:        32.54d {+02h 10m 09s}  +13.13d {+13d 07' 33"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.77d {+11h 15m 05s}   -0.19d {-00d 11' 09"}
MOON_DIST:       125.51 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_image.ps.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:06:45 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     420398,   Seg_Num: 0
GRB_RA:          299.1965d {+19h 56m 47.16s} (J2000),
                 299.3535d {+19h 57m 24.84s} (current),
                 298.4344d {+19h 53m 44.25s} (1950)
GRB_DEC:         -26.4301d {-26d 25' 48.3"} (J2000),
                 -26.4020d {-26d 24' 07.2"} (current),
                 -26.5643d {-26d 33' 51.4"} (1950)
GRB_ERROR:       3.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  10442.00 SOD {02:54:02.00} UT,   196.9 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        32.54d {+02h 10m 10s}  +13.13d {+13d 07' 34"}
SUN_DIST:         98.60 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.77d {+11h 15m 05s}   -0.19d {-00d 11' 15"}
MOON_DIST:       125.54 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.81,-25.29 [deg] galactic lon,lat of the burst
ECL_COORDS:      296.03, -5.59 [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 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:11:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.342
N_STARS:         190
X_OFFSET:        345 [pixels]
Y_OFFSET:        172 [pixels]
X_MAX:           1784 [pixels]
Y_MAX:           1611 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00420398000msufc0878.fits
SUN_POSTN:        32.54d {+02h 10m 10s}  +13.13d {+13d 07' 38"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.82d {+11h 15m 16s}   -0.21d {-00d 12' 32"}
MOON_DIST:       125.46 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:11:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.342
N_STARS:         190
X_OFFSET:        345 [pixels]
Y_OFFSET:        172 [pixels]
X_MAX:           1784 [pixels]
Y_MAX:           1611 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00420398000msufc0878.fits
SUN_POSTN:        32.54d {+02h 10m 10s}  +13.13d {+13d 07' 38"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.82d {+11h 15m 16s}   -0.21d {-00d 12' 32"}
MOON_DIST:       125.46 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:12:02 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.342
N_STARS:         190
X_OFFSET:        345 [pixels]
Y_OFFSET:        172 [pixels]
X_MAX:           1784 [pixels]
Y_MAX:           1611 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00420398000msufc0878.fits
SUN_POSTN:        32.54d {+02h 10m 10s}  +13.13d {+13d 07' 38"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.82d {+11h 15m 17s}   -0.21d {-00d 12' 35"}
MOON_DIST:       125.46 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_srclist.ps.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:11:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
POINT_ROLL:      79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.342
N_STARS:         190
X_OFFSET:        345 [pixels]
Y_OFFSET:        172 [pixels]
X_MAX:           1784 [pixels]
Y_MAX:           1611 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw00420398000msufc0878.fits
SUN_POSTN:        32.54d {+02h 10m 10s}  +13.13d {+13d 07' 38"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.82d {+11h 15m 16s}   -0.21d {-00d 12' 32"}
MOON_DIST:       125.46 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 25 Apr 10 03:13:30 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
ROLL:            79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293857529
X_OFFSET:        904 [pixels]
Y_OFFSET:        731 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1064
Y_GRB_POS:       891
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0884.fits
SUN_POSTN:        32.54d {+02h 10m 11s}  +13.13d {+13d 07' 39"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.83d {+11h 15m 20s}   -0.22d {-00d 12' 58"}
MOON_DIST:       125.44 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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 25 Apr 10 03:13:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     420398,   Seg_Num: 0
POINT_RA:        299.172d {+19h 56m 41s} (J2000)
POINT_DEC:       -26.446d {-26d 26' 45"} (J2000)
ROLL:            79.634d
IMG_START_DATE:  15311 TJD;   115 DOY;   10/04/25
IMG_START_TIME:  11123.85 SOD {03:05:23.85} UT,   878.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     293857529
X_OFFSET:        904 [pixels]
Y_OFFSET:        731 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1064
Y_GRB_POS:       891
BINNING_INDEX:   1
IM_URL:          sw00420398000msuni0884.fits
SUN_POSTN:        32.54d {+02h 10m 11s}  +13.13d {+13d 07' 39"}
SUN_DIST:         98.62 [deg]   Sun_angle= 6.2 [hr] (West of Sun)
MOON_POSTN:      168.84d {+11h 15m 21s}   -0.22d {-00d 13' 01"}
MOON_DIST:       125.44 [deg]
MOON_ILLUM:      85 [%]
GAL_COORDS:       14.78,-25.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      296.01, -5.60 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.  
COMMENTS:        The uvot_field_image.ps.gz file does not exist; skipping the attachment.

GCN Circular #10680
D. Malesani (DARK/NBI), A. J. Levan (Univ. Warwick), N. R. Tanvir (Univ. Leicester), J. P. U. Fynbo (DARK/NBI), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), report on behalf of a larger collaboration:
We are observing the field of GRB 100425A (Grupe et al., GCN 10673) with the ESO VLT equipped with the X-shooter spectrograph.
In the R-band acquisition image, taken starting around 06:51 UT (approximately 4 hr after the GRB), we detect two sources within the refined XRT error circle (http://www.swift.ac.uk/sper/), at coordinates:
```
A: RA(J2000) = 19:56:47.30, Dec(J2000) = -26:25:49.3
B: RA(J2000) = 19:56:47.13, Dec(J2000) = -26:25:50.1
```
Source A is visible in the DSS, and has a similar magnitude to its archival value. Source B is not readily visible in the DSS and has a magnitude R = 20.55 +- 0.2, which is at the limit of the DSS sensitivity. The large error comes mostly from calibration scatter in comparison with USNO-B1 stars.
In a second image taken starting at 7:44 UT (4.9 hr after the GRB), source B has faded by 0.17 +- 0.08 mag.
Given the consistency of its position with the XRT error circle and the moderate evidence for variability, we propose source B as the optical afterglow of GRB 100425A.
A finding chart from the X-shooter image can be seen at the following URL:
http://www.astro.ku.dk/~malesani/GRB/100425A/GRB100425A_finder.png
Further observations and analysis are ongoing. We acknowledge a particularly helpful and attentive support from the ESO staff in Paranal, especially Jonathan Smoker, Lorena Faundez, Marcelo Olivares and Steffen Mieske.
GCN Circular #10683
F. Olivares, T. Kruehler and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 100425A (Swift trigger 420398; Grupe et al., GCN 10673) 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 05:17 UT on April 25, 2.4 hours after the GRB trigger, and were initially performed through thin cloud coverage.
The optical afterglow candidate reported by Malesani et al. (GCN 10680, source 'B') is found to be clearly variable. Between 2.9 and 5.9 hours after the burst, the source decayed roughly 0.5 mag in the r' band. At a midtime of 08:45 UT we measure the following preliminary magnitudes (all in the AB system) in stacked images with a total integration time of 24 min in g'r'i'z' and 20 min in JHK:
```
g = 21.5 +- 0.2
r = 21.0 +- 0.1
i = 20.8 +- 0.1
z = 20.5 +- 0.1
J = 20.1 +- 0.2
H = 19.9 +- 0.2
K = 19.6 +- 0.2
```
calibrated against the GROND zeropoints and 2MASS field stars, and not corrected for the expected foreground extinction of E(B-V)=0.15 (Schlegel et al. 1998).
GCN Circular #10684
P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), H. Flores (Paris Obs.), D. Malesani (DARK/NBI), A. J. Levan (Univ. Warwick), N. R. Tanvir (Univ. Leicester), J. P. U. Fynbo (DARK/NBI), report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 100425A (Grupe et al., GCN 10673; Malesani et al., GCN 10680; Olivares et al., GCN 10683) with th ESO VLT equipped with the X-shooter spectrograph. Four spectra lasting 10 minutes each were obtained, covering the spectral range 3000-25000 AA, starting on 2010 April 25, at 6:53 UT (4.0 hr after the GRB).
We detect the traces of both objects lying within the XRT error circle. Preliminary inspection of the spectrum of the afterglow reveals several absorption features which we interpret as due to Mg II and Fe II, at a common redshift z = 1.755.
We caution that the data reduction was carried out using archival calibration files. We acknowledge a particularly helpful and attentive support from the ESO staff in Paranal, especially Jonathan Smoker, Lorena Faundez, Manuel Olivares and Steffen Mieske.
GCN Circular #10685
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), 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 recent telemetry downlinks, we report further analysis of BAT GRB 100425A (trigger #420398) (Grupe, et al., GCN Circ. 10673). The BAT ground-calculated position is RA, Dec = 299.161, -26.463 deg, which is
```
   RA(J2000)  =  19h 56m 38.7s 
   Dec(J2000) = -26d 27' 47.8" 
```
The mask-weighted light curve shows three peaks. A first, precursor peak at ~T-45 sec, then the main peak at T-2 sec to ~T+10 sec, and the third peak at T+35 to ~T+65 sec. T90 (15-350 keV) is 37.0 +- 2.4 sec (estimated error including systematics).
The time-averaged spectrum from T-2.1 to T+39.4 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.42 +- 0.32. The fluence in the 15-150 keV band is 4.7 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.27 sec in the 15-150 keV band is 1.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/420398/BA/
GCN Circular #10686
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 5331 s of XRT Photon Counting mode data and 8 UVOT images for GRB 100425A, 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 = 299.19651, -26.43069 which is equivalent to:
```
RA (J2000): 19h 56m 47.16s
Dec (J2000): -26d 25' 50.5"
```
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 #10689
S. R. Oates (MSSL-UCL) and D. Grupe (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 100425A 88s after the BAT trigger (Grupe et al., GCN 10673). We do not detect a new source at the enhanced Swift XRT position (Goad et al. GCN 10686) and at the location of source B detected by the VLT telescope (Malesani et al. GCN 10680) and GROND telescope (Olivares et al. GCN 10683). Photometry is complicated by the prescence of the VLT source A within the source aperture.
The 3-sigma upper limits for the finding chart exposures (FC) and summed images are:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
white (FC)  88      238      147         >19.37
white       88      5778     513         >19.59
u     (FC)  301     551      246         >18.92
u	    301     6796     650         >19.08
v           631     11961    1317        >19.76
b           556     5573     236         >19.71
uvw1        680     6600     432         >19.44
uvm2        4757    12580    997         >20.87
uvw2        606     11048    1318        >21.26
-------------------------------------------------------------
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.15 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10691
D. Grupe (PSU) reports on behalf of the Swift-XRT team:
We have analyzed 14.2 ks of XRT data for GRB 100425A (Grupe et al. GCN Circ. 10673), from 85 s to 81 ks after the BAT trigger. The data consist of 106s in Windowed Timing mode (WT) and 14.1 ks in Photon Counting (PC) mode. The current XRT light curve can be fit by a broken power law model with an initial decay slope of 5.3+/-0.3 with a beak at 330+/-20 s followed by a shallow decay slope of 0.55+/- 0.05. The last data point at 77 ks after the burst suggests a break at about 60ks. However, this is based on one data point. Therefore, a prediction on the future behavior of the X-ray afterglow can not be given at this point.
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 4.00 (+/-0.15). The best-fitting absorption column density is 1.49 (+0.18, -0.17) x 10^22 cm^-2, at a redshift of 1.755 (Goldini et al. GCN Circ 10684), in addition to the Galactic value of 8.6 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.30+/-0.13 and a best-fitting absorption column density consistent with the Galactic value. Based on this spectrum, the counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.77 x 10^-11 (5.17 x 10^-11) erg cm^-2 count^-1.
Swift will continue observing the X-ray afterglow of GRB 100425A over the next few days.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00420398.
This circular is an official product of the Swift-XRT team.
GCN Report 279.1
GCN_Report 279.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_279_1.pdf by D. Grupe at PSU titled: "Final Swift Observations of GRB 100425A"

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Jochen Greiner, last update: 25-Apr-2010 [Disclaimer]