Gamma-ray Burst 081226

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:03:53 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     251946218
GRB_RA:           90.383d {+06h 01m 32s} (J2000),
                  90.413d {+06h 01m 39s} (current),
                  90.216d {+06h 00m 52s} (1950)
GRB_DEC:         -59.517d {-59d 30' 59"} (J2000),
                 -59.517d {-59d 31' 00"} (current),
                 -59.515d {-59d 30' 54"} (1950)
GRB_ERROR:       15.15 [deg radius, statistical plus systematic]
GRB_INTEN:       411 [cnts/sec]
DATA_SIGNIF:     7.10 [sigma]
INTEG_TIME:      0.256 [sec]
GRB_DATE:        14826 TJD;   361 DOY;   08/12/26
GRB_TIME:        3817.53 SOD {01:03:37.53} UT
GRB_PHI:          94.00 [deg]
GRB_THETA:       105.00 [deg]
DATA_TIME_SCALE: 0.2560 [sec]
HARD_RATIO:      0.38
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   2%  Distant Particles
DETECTORS:       0,0,1, 0,0,0, 0,0,0, 0,1,0, 0,0,
SUN_POSTN:       275.04d {+18h 20m 10s}  -23.36d {-23d 21' 23"}
SUN_DIST:         97.04 [deg]   Sun_angle= -11.7 [hr] (East of Sun)
MOON_POSTN:      257.34d {+17h 09m 21s}  -26.97d {-26d 58' 28"}
MOON_DIST:        92.84 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      268.29,-29.37 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       91.59,-82.95 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 236.78,-25.57 [deg].

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:03:56 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     338177,   Seg_Num: 0
GRB_RA:          120.527d {+08h 02m 06s} (J2000),
                 120.529d {+08h 02m 07s} (current),
                 120.509d {+08h 02m 02s} (1950)
GRB_DEC:         -69.006d {-69d 00' 20"} (J2000),
                 -69.031d {-69d 01' 51"} (current),
                 -68.864d {-68d 51' 51"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1286 [cnts]    Image_Peak=84 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   481     E_range: 50-350 keV
BKG_INTEN:       22761 [cnts]
BKG_TIME:        3804.63 SOD {01:03:24.63} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14826 TJD;   361 DOY;   08/12/26
GRB_TIME:        3817.37 SOD {01:03:37.37} UT
GRB_PHI:         -159.15 [deg]
GRB_THETA:        47.28 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.97 [sigma]
IMAGE_SIGNIF:    7.60 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +3  +6  +0  +0  -7  +0 
SUN_POSTN:       275.04d {+18h 20m 10s}  -23.36d {-23d 21' 23"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.34d {+17h 09m 21s}  -26.97d {-26d 58' 28"}
MOON_DIST:        78.99 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      205.86,-78.33 [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 = 355.84,8.45 [deg].

red DSS finding chart ps-file

GCN NOTICE

 
TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 26 Dec 08 01:04:16 UT
NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
TRIGGER_NUM:    5393,   Sub_Num: 0
GRB_INTEN:      9.64 [sigma]
GRB_TIME:       3818.04 SOD {01:03:38.04} UT
GRB_DATE:       14826 TJD;   361 DOY;   08/12/26
COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.
COMMENTS:
ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2008-12-26T01-03-37.8210-26069-00007-0.lc

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:04:27 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     251946218
GRB_RA:          120.370d {+08h 01m 29s} (J2000),
                 120.386d {+08h 01m 33s} (current),
                 120.277d {+08h 01m 06s} (1950)
GRB_DEC:         -66.360d {-66d 21' 35"} (J2000),
                 -66.385d {-66d 23' 06"} (current),
                 -66.219d {-66d 13' 09"} (1950)
GRB_ERROR:       12.40 [deg radius, statistical only]
DATA_SIGNIF:     10.20 [sigma]
DATA_INTERVAL:   0.256 [sec]
GRB_DATE:        14826 TJD;   361 DOY;   08/12/26
GRB_TIME:        3817.53 SOD {01:03:37.53} UT
GRB_PHI:          82.00 [deg]
GRB_THETA:       115.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   1 (Gnd S/W Version number)
SUN_POSTN:       275.04d {+18h 20m 10s}  -23.36d {-23d 21' 23"}
SUN_DIST:         88.23 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.34d {+17h 09m 22s}  -26.97d {-26d 58' 29"}
MOON_DIST:        81.10 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      279.21,-18.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      193.05,-77.99 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:05:18 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     338177,   Seg_Num: 0
POINT_RA:        120.525d {+08h 02m 06s} (J2000)
POINT_DEC:       -69.003d {-69d 00' 09"} (J2000)
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3911.95 SOD {01:05:11.95} UT,   94.6 [sec] since BAT Trigger Time
COUNTS:          4    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:07:47 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     338177,   Seg_Num: 0
GRB_RA:          120.527d {+08h 02m 06s} (J2000),
                 120.529d {+08h 02m 07s} (current),
                 120.509d {+08h 02m 02s} (1950)
GRB_DEC:         -69.006d {-69d 00' 20"} (J2000),
                 -69.031d {-69d 01' 51"} (current),
                 -68.864d {-68d 51' 51"} (1950)
GRB_DATE:        14826 TJD;   361 DOY;   08/12/26
GRB_TIME:        3817.37 SOD {01:03:37.37} UT
TRIGGER_INDEX:   481
GRB_PHI:         -159.15 [deg]
GRB_THETA:        47.28 [deg]
DELTA_TIME:      6.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.97 [sigma]
IMAGE_SIGNIF:    7.60 [sigma]
LC_URL:          sw00338177000msb.lc
SUN_POSTN:       275.04d {+18h 20m 11s}  -23.36d {-23d 21' 23"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.37d {+17h 09m 30s}  -26.98d {-26d 58' 32"}
MOON_DIST:        78.99 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      205.86,-78.33 [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 = 355.84,8.45 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:10:14 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     338177,   Seg_Num: 0
GRB_RA:          120.5005d {+08h 02m 00.12s} (J2000),
                 120.5031d {+08h 02m 00.74s} (current),
                 120.4836d {+08h 01m 56.06s} (1950)
GRB_DEC:         -69.0299d {-69d 01' 47.6"} (J2000),
                 -69.0553d {-69d 03' 19.0"} (current),
                 -68.8886d {-68d 53' 19.0"} (1950)
GRB_ERROR:       4.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3926.00 SOD {01:05:26.00} UT,   108.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       275.05d {+18h 20m 11s}  -23.36d {-23d 21' 23"}
SUN_DIST:         85.76 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.40d {+17h 09m 35s}  -26.98d {-26d 58' 34"}
MOON_DIST:        78.98 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.76,-19.22 [deg] galactic lon,lat of the burst
ECL_COORDS:      205.98,-78.34 [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 #8729
O. Godet (U Leicester), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), E. A. Hoversten (PSU), J. A. Kennea (PSU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 01:03:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081226 (trigger=338177). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 120.527, -69.006 which is
```
   RA(J2000) = 08h 02m 06s
   Dec(J2000) = -69d 00' 20"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a short hard burst structure with a duration of about 0.5 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 01:05:11.9 UT, 94.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 120.50054, -69.02994 which is equivalent to:
```
   RA(J2000)  = 08h 02m 0.13s
   Dec(J2000) = -69d 01' 47.8"
```
with an uncertainty of 4.5 arcseconds (radius, 90% containment). This location is 92 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 1.19e+21 cm^-2 (Kalberla et al. 2005).
The UVOT data has not yet been received so it is not possible to comment on the UV/optical nature of the burst at this time. There is a 7th magnitude source nearby which will complicate UVOT observations.
Burst Advocate for this burst is O. Godet (og19 AT star.le.ac.uk). 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:     Fri 26 Dec 08 01:26:30 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     338177,   Seg_Num: 0
POINT_RA:        120.516d {+08h 02m 04s} (J2000)
POINT_DEC:       -69.003d {-69d 00' 08"} (J2000)
POINT_ROLL:      156.682d
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3973.05 SOD {01:06:13.05} UT,   155.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.577
N_STARS:         183
X_OFFSET:        255 [pixels]
Y_OFFSET:        286 [pixels]
X_MAX:           1694 [pixels]
Y_MAX:           1725 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00338177000msufc0155.fits
SUN_POSTN:       275.06d {+18h 20m 14s}  -23.36d {-23d 21' 21"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.55d {+17h 10m 11s}  -26.98d {-26d 58' 48"}
MOON_DIST:        79.03 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.21 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      205.85,-78.34 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:27:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     338177,   Seg_Num: 0
POINT_RA:        120.516d {+08h 02m 04s} (J2000)
POINT_DEC:       -69.003d {-69d 00' 08"} (J2000)
POINT_ROLL:      156.682d
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3973.05 SOD {01:06:13.05} UT,   155.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.577
N_STARS:         183
X_OFFSET:        255 [pixels]
Y_OFFSET:        286 [pixels]
X_MAX:           1694 [pixels]
Y_MAX:           1725 [pixels]
DET_THRESH:      7
PHOTO_THRESH:    3
SL_URL:          sw00338177000msufc0155.fits
SUN_POSTN:       275.06d {+18h 20m 14s}  -23.36d {-23d 21' 21"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.55d {+17h 10m 12s}  -26.98d {-26d 58' 49"}
MOON_DIST:        79.03 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.21 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      205.85,-78.34 [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:     Fri 26 Dec 08 01:27:37 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     338177,   Seg_Num: 0
POINT_RA:        120.516d {+08h 02m 04s} (J2000)
POINT_DEC:       -69.003d {-69d 00' 08"} (J2000)
ROLL:            156.682d
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3973.05 SOD {01:06:13.05} UT,   155.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     251946376
X_OFFSET:        814 [pixels]
Y_OFFSET:        845 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       974
Y_GRB_POS:       1005
BINNING_INDEX:   1
IM_URL:          sw00338177000msuni0155.fits
SUN_POSTN:       275.06d {+18h 20m 14s}  -23.36d {-23d 21' 21"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.56d {+17h 10m 13s}  -26.98d {-26d 58' 49"}
MOON_DIST:        79.03 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.21 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      205.85,-78.34 [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:     Fri 26 Dec 08 01:27:22 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     338177,   Seg_Num: 0
GRB_RA:          120.4990d {+08h 02m 00.24s} (J2000),
                 120.5016d {+08h 02m 00.38s} (current),
                 120.4821d {+08h 01m 55.71s} (1950)
GRB_DEC:         -69.0305d {-69d 01' 49.8"} (J2000),
                 -69.0559d {-69d 03' 21.1"} (current),
                 -68.8892d {-68d 53' 21.2"} (1950)
GRB_ERROR:       3.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3926.00 SOD {01:05:26.00} UT,   108.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       275.06d {+18h 20m 14s}  -23.36d {-23d 21' 21"}
SUN_DIST:         85.76 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.55d {+17h 10m 13s}  -26.98d {-26d 58' 49"}
MOON_DIST:        79.02 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.76,-19.22 [deg] galactic lon,lat of the burst
ECL_COORDS:      205.98,-78.34 [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

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 26 Dec 08 01:28:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     338177,   Seg_Num: 0
POINT_RA:        120.516d {+08h 02m 04s} (J2000)
POINT_DEC:       -69.003d {-69d 00' 08"} (J2000)
ROLL:            156.682d
IMG_START_DATE:  14826 TJD;   361 DOY;   08/12/26
IMG_START_TIME:  3973.05 SOD {01:06:13.05} UT,   155.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     251946376
X_OFFSET:        814 [pixels]
Y_OFFSET:        845 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       974
Y_GRB_POS:       1005
BINNING_INDEX:   1
IM_URL:          sw00338177000msuni0155.fits
SUN_POSTN:       275.06d {+18h 20m 14s}  -23.36d {-23d 21' 21"}
SUN_DIST:         85.78 [deg]   Sun_angle= 10.3 [hr] (West of Sun)
MOON_POSTN:      257.56d {+17h 10m 15s}  -26.98d {-26d 58' 50"}
MOON_DIST:        79.04 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      281.74,-19.21 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      205.85,-78.34 [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_sources_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #8730
B. E. Schaefer (Louisiana State), E.S. Rykoff (UCSB), F. Yuan (U Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 081226 (Swift trigger 338177; Godet, GCN 8729), producing images beginning 8.8 s after the GCN notice time. An automated response took the first image at 01:04:02.8 UT, 25.4 s after the burst, under excellent conditions. We took 10 5-sec, 20 20-sec exposures. These unfiltered images are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the 3-sigma Swift/BAT error circle or the XRT error circle, for both single images and coadding into sets of 10; the field is not crowded. Individual images have limiting magnitudes ranging from 16.8-17.4; we set the following specific limits.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
01:04:02.8   01:04:07.8         5     17.0           25.4       N
01:04:02.9   01:05:19.0        76     17.8           25.5       Y
```
GCN Circular #8731
GRB 081226: GROND afterglow candidate
P. Afonso, T. Kruehler (both MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile),started observations of the field of GRB 081226 (Godet et al. 2008, GCN #8729) in g'r'i'z'JHK at 01:14 UTC, 11 min after the burst. We detect a faint optical source in the XRT error circle (Godet et al. 2008, GCN #8729) at:
```
RA(J2000): 08:01:59.92
DEC(J2000): -69:01:47.4 
```
with uncertainties of 0.5".
At a midtime of 01:57 UTC, we measure a rough preliminary r' band magnitude of 24.3 calibrated with the GROND zeropoint.
No statement about variability can be made at this point. Observations are ongoing.
GCN Circular #8732
E. Berger (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report:
"We imaged the error circle of GRB 081226 (GCN 8729) with GMOS on the Gemini-S telescope starting on 2008 Dec 26.04 UT. In a single 300 sec r-band image we detect the object located by GROND within the XRT error circle (GCN 8731). In addition, we find a second, fainter source within the error circle at (J2000):
```
	RA = 08:02:00.44
	DEC = -69:01:48.9
```
with an uncertainty of about 0.5" in each coordinate. Additional observations are on-going to determine if either of these two sources is fading."
GCN Circular #8733
E. Berger (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report:
"We obtained spectroscopic observations of the possible afterglow of GRB 081226 (GCNs 8731, 8732) with GMOS on the Gemini-South telescope using the R400 grating with a central wavelength of 6000A for a total of 2400 sec. We detect smooth continuum emission but no obvious absorption or emission features in the wavelength range 4000-8000A. Further analysis is on-going."
GCN Circular #8735
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), O. Godet (U Leicester) C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from recent telemetry downlinks, we report further analysis of BAT GRB 081226A (trigger #338177) (Godet, et al., GCN Circ. 8729). The BAT ground-calculated position is RA, Dec = 120.478, -69.014 deg, which is
```
   RA(J2000)  =  08h 01m 54.6s 
   Dec(J2000) = -69d 00' 48.6" 
```
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 32%.
The mask-weighted light curve shows a single spike starting at T+0.0 and ending at T+0.4 sec. T90 (15-350 keV) is 0.4 +- 0.1 sec (estimated error including systematics).
The time-averaged spectrum from T-0.1 to T+0.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.36 +- 0.29. The fluence in the 15-150 keV band is 9.9 +- 1.8 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band is 2.4 +- 0.4 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/338177/BA/
GCN Circular #8736
E. Berger, A. M. Soderberg (Harvard), A. Cucchiara, and D. B. Fox (Penn State) report:
"We re-observed the error circle of GRB 081226 (GCN 8729) with GMOS on the Gemini-South telescope on 2008 Dec 26.349 UT (7.31 hours post burst). A comparison to our first epoch of imaging, taken on 2008 Dec 26.112 UT (1.62 hours post burst; GCN 8732), reveals that neither of the two objects within the XRT error circle (GCN 8732) have varied in brightness. This is confirmed using digital image subtraction with the ISIS package."
GCN Circular #8737
E. A. Hoversten (PSU) and O. Godet (U Leicester) report on behalf of the Swift UVOT team:
The Swift/UVOT began settled observations of the field of GRB 08226A 156s after the BAT trigger (Godet et al., GCN 8729). We do not detect any source at the Swift XRT position. The white filter observation was skipped due to a 7th magnitude star in the field. The UVOT upper limits are around 20th magnitude so the non-detections do not conflict with the possible optical afterglow detections in GCN 8731 and GCN 8732 at 24th magnitude. UVOT magnitude 3-sigma upper limits are reported in the following table:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
v          461      2276     233         > 19.24
b          410      2226     228         > 20.13
u          155      2051     833         > 20.87
uvw1       510      2176     213         > 19.71
uvm2       486      2151     213         > 19.51
uvw2       436      2252     233         > 19.83
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.16 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #8738
O. Godet (U Leicester) on behalf the Swift-XRT team:
The Swift-XRT started observing the field of GRB 081226 (trigger number 338177, Godet et al., GCN Circ. 8729) at 2008-12-26 01:05:11.9 UT, 94.5 seconds after the trigger. Using 11.6 ks of photon counting (PC) mode data, the best XRT position is located at RA, Dec 120.50152, -69.02924 which is equivalent to:
```
RA(J2000) = 08h 02m 00.36s
Dec(J2000) = -46d 01' 45.2"
```
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This location is 2.8 arcseconds from the XRT position given in Godet et al. (GCN Circ. 8729). It is also consistent with the position of the possible optical counterpart reported by Afonso et al. (GCN Circ. 8731).
The X-ray light curve presently spans 11.6 ks of PC mode data from T+109 s to T+42 ks. Due to poor statistics, it is difficult to properly model the light-curve, which shows a decay (with a slope around 1.8) possibly followed by a flattening at later time.
The PC X-ray spectrum from the same interval can be well fit by an absorbed power-law with a photon index of 2.60 +1.61/-0.98 and a column density of (6.4 +8.8/-4.6) x 10^21 cm^-2 (the Galactic value is 1.19 x 10^21 cm^-2 in the direction of the burst - Kalberla et al. 2005). The observed 0.4-10.0 keV flux is (1.8 +0.8/-1.3) x 10^-13 erg cm^-2 s^-1 which corresponds to an unabsorbed flux of (4.7 +1.4/-2.5) x 10^-13 erg cm^-2 s^-1.
No more Swift observations are planned for this burst.
This is an official product of the Swift-XRT team.
GCN Circular #8785
Chryssa Kouveliotou (NASA/MSFC), Valerie Connaughton (UAHuntsville) report on behalf of the Fermi GBM Team:
"At 01:03:37.53 UT on 26 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081226 (trigger 251946218, trigcat 081226044), which was also detected by the SWIFT-BAT (Godet et al. 2008, GCN 8729). The on-ground calculated location, using the GBM trigger data, is RA = 119.01, DEC = -73.8 (J2000 degrees, equivalent to 07 h 56.04 m, -73 d 48'), with an uncertainty of 13.2 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 110 degrees.
The GBM light curve is a single pulse with a duration (T90) of about 1.7 s (20-775 keV). The time-averaged spectrum from T0-0.215 s to T0+0.233 s is best fit by a simple power law function with index 1.17 +/- 0.08 (chi squared 188 for 228 d.o.f.).
The event fluence (50-300 keV) in this time interval is (2.1 +/- 0.1)E-7 erg/cm^2. The 0.256-sec peak photon flux measured starting from T0-0.151 s in the 50-300 keV band is 3.2 +/- 0.1 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #8952
Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope National Facility), Steven Tingay (Curtin Institute of Radio Astronomy), Chris Phillips (Australia Telescope National Facility), Gregory Taylor (University of New Mexico), Mark Wieringa (Australia Telescope National Facility) and Ralph Martin (Perth Observatory) report:
We observed the GROND position of the GRB081226a afterglow (GCN 8731) at 4.800 and 4.928 GHz with the Australia Telescope Compact Array (ATCA) between 01:00:00 UT and 22:00:00 UT on February 21/22, 2009.
We did not detect a radio source at the position of the GRB081226a (GCN 8731). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the GRB optical afterglow position found out to be 0.115 +/- 0.180 mJy/beam (1-sigma).
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 4.800 & 4.928 GHz combined image at:
http://cira.ivec.org/dokuwiki/doku.php/grb/grb081226a/grb081226a_field_image
1206.1806from 11 Jun 12
A. Nicuesa Guelbenzu et al.: Multi-color observations of short GRB afterglows: 20 events observed between 2007 and 2010
H. Hartmann, A. Kuepcue Yoldas, S. McBreen, M. Nardini, F. Olivares E., A. Rau, S. Schmidl, P. Schady, V. Sudilovsky, A. C. Updike, A. Yoldas We report on follow-up observations of 20 short-duration gamma-ray bursts performed in g'r'i'z'JHKs with the seven-channel imager GROND between mid-2007 and the end of 2010. This is one of the most comprehensive data sets on GRB afterglow observations of short bursts published so far. In three cases GROND was on target within less than 10 min after the trigger, leading to the discovery of the afterglow of GRB 081226A and its faint underlying host galaxy. In addition, GROND was able to image the optical afterglow and follow the light-curve evolution in further five cases, GRBs 090305, 090426, 090510, 090927, and 100117A. In all other cases optical/NIR upper limits can be provided on the afterglow magnitudes.

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Jochen Greiner, last update: 11-Jun-2012 [Disclaimer]