Gamma-ray Burst 081228

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:17:59 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     338338,   Seg_Num: 0
GRB_RA:           39.467d {+02h 37m 52s} (J2000),
                  39.602d {+02h 38m 24s} (current),
                  38.722d {+02h 34m 53s} (1950)
GRB_DEC:         +30.843d {+30d 50' 33"} (J2000),
                 +30.881d {+30d 52' 52"} (current),
                 +30.626d {+30d 37' 35"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4493 [cnts]    Image_Peak=194 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   137     E_range: 15-50 keV
BKG_INTEN:       29617 [cnts]
BKG_TIME:        4644.63 SOD {01:17:24.63} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14828 TJD;   363 DOY;   08/12/28
GRB_TIME:        4660.75 SOD {01:17:40.75} UT
GRB_PHI:           4.69 [deg]
GRB_THETA:        25.91 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.67 [sigma]
IMAGE_SIGNIF:    7.61 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +2  +0  +0 +62  +0 
SUN_POSTN:       277.27d {+18h 29m 05s}  -23.27d {-23d 16' 09"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.2 [hr] (East of Sun)
MOON_POSTN:      283.88d {+18h 55m 30s}  -25.21d {-25d 12' 47"}
MOON_DIST:       123.76 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       46.75, 14.67 [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 = 358.39,0.58 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:19:05 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.466d {+02h 37m 52s} (J2000)
POINT_DEC:       +30.841d {+30d 50' 26"} (J2000)
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4738.74 SOD {01:18:58.74} UT,   78.0 [sec] since BAT Trigger Time
COUNTS:          2    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:     Sun 28 Dec 08 01:20:18 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.467d {+02h 37m 52s} (J2000)
POINT_DEC:       +30.840d {+30d 50' 26"} (J2000)
POINT_ROLL:      263.520d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4742.67 SOD {01:19:02.67} UT,   81.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.738
N_STARS:         28
X_OFFSET:        485 [pixels]
Y_OFFSET:        585 [pixels]
X_MAX:           1444 [pixels]
Y_MAX:           1544 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00338338000msufc0081.fits
SUN_POSTN:       277.27d {+18h 29m 05s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      283.90d {+18h 55m 35s}  -25.21d {-25d 12' 35"}
MOON_DIST:       123.74 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.75, 14.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:20:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.467d {+02h 37m 52s} (J2000)
POINT_DEC:       +30.840d {+30d 50' 26"} (J2000)
POINT_ROLL:      263.520d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4742.67 SOD {01:19:02.67} UT,   81.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.738
N_STARS:         28
X_OFFSET:        485 [pixels]
Y_OFFSET:        585 [pixels]
X_MAX:           1444 [pixels]
Y_MAX:           1544 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    3
SL_URL:          sw00338338000msufc0081.fits
SUN_POSTN:       277.27d {+18h 29m 05s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      283.90d {+18h 55m 36s}  -25.21d {-25d 12' 33"}
MOON_DIST:       123.73 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.75, 14.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:21:37 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.467d {+02h 37m 52s} (J2000)
POINT_DEC:       +30.840d {+30d 50' 26"} (J2000)
ROLL:            263.520d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4742.67 SOD {01:19:02.67} UT,   81.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     252119946
X_OFFSET:        804 [pixels]
Y_OFFSET:        904 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       964
Y_GRB_POS:       1064
BINNING_INDEX:   1
IM_URL:          sw00338338000msuni0081.fits
SUN_POSTN:       277.27d {+18h 29m 05s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      283.91d {+18h 55m 38s}  -25.21d {-25d 12' 29"}
MOON_DIST:       123.73 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.75, 14.67 [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 28 Dec 08 01:22:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.467d {+02h 37m 52s} (J2000)
POINT_DEC:       +30.840d {+30d 50' 26"} (J2000)
ROLL:            263.520d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4742.67 SOD {01:19:02.67} UT,   81.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     252119946
X_OFFSET:        804 [pixels]
Y_OFFSET:        904 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       964
Y_GRB_POS:       1064
BINNING_INDEX:   1
IM_URL:          sw00338338000msuni0081.fits
SUN_POSTN:       277.27d {+18h 29m 05s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      283.91d {+18h 55m 39s}  -25.21d {-25d 12' 26"}
MOON_DIST:       123.72 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.75, 14.67 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:24:02 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     338338,   Seg_Num: 0
GRB_RA:           39.4604d {+02h 37m 50.49s} (J2000),
                  39.5946d {+02h 38m 22.71s} (current),
                  38.7155d {+02h 34m 51.71s} (1950)
GRB_DEC:         +30.8539d {+30d 51' 14.0"} (J2000),
                 +30.8925d {+30d 53' 33.0"} (current),
                 +30.6378d {+30d 38' 16.1"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  4749.00 SOD {01:19:09.00} UT,   88.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       277.27d {+18h 29m 06s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.63 [deg]   Sun_angle= -8.2 [hr] (East of Sun)
MOON_POSTN:      283.93d {+18h 55m 43s}  -25.20d {-25d 12' 16"}
MOON_DIST:       123.70 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.42,-26.70 [deg] galactic lon,lat of the burst
ECL_COORDS:       46.75, 14.68 [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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 01:26:04 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     7842322,   Seg_Num: 194
GRB_RA:           39.467d {+02h 37m 52s} (J2000),
                  39.602d {+02h 38m 24s} (current),
                  38.722d {+02h 34m 53s} (1950)
GRB_DEC:         +30.843d {+30d 50' 33"} (J2000),
                 +30.881d {+30d 52' 52"} (current),
                 +30.626d {+30d 37' 35"} (1950)
GRB_DATE:        14828 TJD;   363 DOY;   08/12/28
GRB_TIME:        4660.75 SOD {01:17:40.75} UT
TRIGGER_INDEX:   137
GRB_PHI:           4.69 [deg]
GRB_THETA:        25.91 [deg]
DELTA_TIME:      7797.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.67 [sigma]
IMAGE_SIGNIF:    7.61 [sigma]
LC_URL:          sw00338338000msb.lc
SUN_POSTN:       277.28d {+18h 29m 06s}  -23.27d {-23d 16' 08"}
SUN_DIST:        128.64 [deg]   Sun_angle= -8.2 [hr] (East of Sun)
MOON_POSTN:      283.95d {+18h 55m 48s}  -25.20d {-25d 12' 05"}
MOON_DIST:       123.69 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.43,-26.71 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       46.75, 14.67 [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 = 358.39,0.58 [deg].  
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN Circular #8742
K. L. Page (U Leicester), W. H. Baumgartner (GSFC/UMBC), P. J. Brown (PSU), D. N. Burrows (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:
At 01:17:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081228 (trigger=338338). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 39.467, +30.843 which is
```
   RA(J2000) = 02h 37m 52s
   Dec(J2000) = +30d 50' 33"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak with a duration of about 2.5 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0.5 sec after the trigger.
The XRT began observing the field at 01:18:58.7 UT, 78.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 39.46043, 30.85393 which is equivalent to:
```
   RA(J2000)  = 02h 37m 50.50s
   Dec(J2000) = +30d 51' 14.1"
```
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 44 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 8.8e+20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 37 seconds with the White filter starting 82 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 25% of the BAT 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 BAT 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 0.16.
Burst Advocate for this burst is K. L. Page (kpa 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 Circular #8743
Klotz, A. (CESR-OMP), Gendre, B. (OAMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:
We imaged the field of GRB 081228 detected by SWIFT (trigger 338338) with the TAROT robotic telescope (D=25cm) located at the Calern observatory, France.
The observations started 24.7s after the GRB trigger (6.1s after the notice). The elevation of the field decreased from 24 degrees above horizon and weather conditions were good.
The first image is trailed with a duration of 60.0s (see the description in Klotz et al., 2006, A&A 451, L39). We do not detect any OT in the XRT error box (Page et al. GCNC 8742) with a limiting magnitude of: t0+24.7s to t0+84.7s : R > 16.9
The second image is 30.0s exposure in tracking mode: t0+91.8s to t0+121.8s : R > 17.4
We co-added a series of exposures: t0+91.8s to t0+384.6s : R > 18.4
Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=148.4290 lat=-26.7069 and the galactic extinction in R band is 0.4 magnitude estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 02:24:36 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.438d {+02h 37m 45s} (J2000)
POINT_DEC:       +30.827d {+30d 49' 37"} (J2000)
POINT_ROLL:      263.521d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  7982.71 SOD {02:13:02.71} UT,   3322.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.338
N_STARS:         21
X_OFFSET:        357 [pixels]
Y_OFFSET:        743 [pixels]
X_MAX:           1316 [pixels]
Y_MAX:           1702 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00338338000msufc3321.fits
SUN_POSTN:       277.32d {+18h 29m 17s}  -23.27d {-23d 16' 00"}
SUN_DIST:        128.57 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      284.47d {+18h 57m 54s}  -25.12d {-25d 06' 57"}
MOON_DIST:       123.19 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.41,-26.73 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.72, 14.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 02:24:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.438d {+02h 37m 45s} (J2000)
POINT_DEC:       +30.827d {+30d 49' 37"} (J2000)
POINT_ROLL:      263.521d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  7982.71 SOD {02:13:02.71} UT,   3322.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.338
N_STARS:         21
X_OFFSET:        357 [pixels]
Y_OFFSET:        743 [pixels]
X_MAX:           1316 [pixels]
Y_MAX:           1702 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw00338338000msufc3321.fits
SUN_POSTN:       277.32d {+18h 29m 17s}  -23.27d {-23d 16' 00"}
SUN_DIST:        128.57 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      284.48d {+18h 57m 55s}  -25.12d {-25d 06' 55"}
MOON_DIST:       123.19 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.41,-26.73 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.72, 14.67 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 28 Dec 08 02:25:56 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.438d {+02h 37m 45s} (J2000)
POINT_DEC:       +30.827d {+30d 49' 37"} (J2000)
ROLL:            263.521d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  7982.71 SOD {02:13:02.71} UT,   3322.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     252123186
X_OFFSET:        676 [pixels]
Y_OFFSET:        1062 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       836
Y_GRB_POS:       1222
BINNING_INDEX:   1
IM_URL:          sw00338338000msuni3321.fits
SUN_POSTN:       277.32d {+18h 29m 17s}  -23.27d {-23d 16' 00"}
SUN_DIST:        128.57 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      284.49d {+18h 57m 57s}  -25.11d {-25d 06' 50"}
MOON_DIST:       123.18 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.41,-26.73 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.72, 14.67 [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 28 Dec 08 02:26:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     338338,   Seg_Num: 0
POINT_RA:         39.438d {+02h 37m 45s} (J2000)
POINT_DEC:       +30.827d {+30d 49' 37"} (J2000)
ROLL:            263.521d
IMG_START_DATE:  14828 TJD;   363 DOY;   08/12/28
IMG_START_TIME:  7982.71 SOD {02:13:02.71} UT,   3322.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     252123186
X_OFFSET:        676 [pixels]
Y_OFFSET:        1062 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       836
Y_GRB_POS:       1222
BINNING_INDEX:   1
IM_URL:          sw00338338000msuni3321.fits
SUN_POSTN:       277.32d {+18h 29m 17s}  -23.27d {-23d 16' 00"}
SUN_DIST:        128.57 [deg]   Sun_angle= -8.1 [hr] (East of Sun)
MOON_POSTN:      284.49d {+18h 57m 57s}  -25.11d {-25d 06' 48"}
MOON_DIST:       123.18 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      148.41,-26.73 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       46.72, 14.67 [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 #8744
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 27 s of XRT Photon Counting mode data and 1 UVOT images for GRB 081228, 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 = 39.4616, +30.8526 which is equivalent to:
```
RA (J2000): 02h 37m 50.77s
Dec (J2000): +30d 51' 09.5"
```
with an uncertainty of 2.9 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method.
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #8745
GRB 081228: detection by GROND
P. Afonso (MPE), S. Klose (Tautenburg), T. Kruehler, (MPE), J. Greiner (MPE), A. Updike (Clemson University), A. Kupcu-Yoldas(ESO), A. Yoldas (MPE), and G. Szokoly (Eotvos Univ. Budapest) 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) imaged the field of GRB 081228 (Swift trigger 338338, Page et al., GCN #8742) simultaneously in g'r'i'z'JHK.
Inside the enhanced XRT error circle (position, RA (J2000): 02h 37m 50.77s Dec (J2000): +30d 51' 09.5"), reported by Goad et alia, GCN #8744, we detect an object in the g'r'i'z' bands, but not in JHK.
Observations started at 01h26 UT, 9 min after the burst.
We used 4 images of 375 s exposure in g'r'i'z' and 120 images of 10s exposure in JHK. The images midtimes for g'r'i'z' and JHK are respectively 02h23m59s and 02h24m20s UT, or 1h6m19s and 1h6m40s after the burst.
Observations were done at high air mass and seeing bigger than 1''.
The object is detected in the g'r'i'z' bands, implying a redshift smaller than 3.5. The detection is fainter in the g' band.
Preliminary VEGA magnitudes calibrated against USNO-B field stars and upper limits are as follows:
```
g' = 23.73 +/- 0.11
r' = 21.98 +/- 0.04
i' = 21.42 +/- 0.06
z' = 21.80 +/- 0.08
J > 19.6
H > 18.4
K > 17.6
```
No correction for galactic extinction was done.
GCN Circular #8746
K.L. Page & P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
We have analysed the first 4.6 ks of XRT data obtained for GRB 081228 (Page et al., GCN Circ. 8742), all of which was collected in Photon Counting mode. We have further refined the position given by Goad et al. in GCN Circ. 8744, and now find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) of
```
RA (J2000):   02 37 50.89
Dec (J2000): +30 51 09.1
```
with an uncertainty of 2.2 arcsec (radius, 90% confidence).
The data can be fitted with a single power-law with a decay of alpha = 1.4 +/- 0.1, although there is some evidence for a flattening after about 8 ks.
The spectrum of the first orbit of data can be modelled with a power-law of photon index Gamma = 1.5 +/- 0.4, absorbed by the Galactic column in this direction of 8.8x10^20 cm^-2. The upper limit on the total absorbing column is 4.7x10^21 cm^-2. The observed (unabsorbed) flux over this time (86-117 s after the trigger) is 1.23x10^-10 (1.38x10^-10) erg cm^-2 s^-1, corresponding to a counts to observed flux conversion of 5.1x10^-11 erg cm^-2 count^-1.
Taking into account the possible flattening of the decay at later times, the count rate at 24 hours is predicted to be between 4.5x10^-3 and 2.7x10^-4 count s^-1 (observed flux between 2.3x10^-13 and 1.4x10^-14 erg cm^-2 s^-1).
This circular is an official product of the Swift-XRT team.
GCN Circular #8747
W. Landsman (GSFC) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 081228 82s after the BAT trigger (Page et al., GCN 8742). The exposure time was limited by observing constraints until about 1 hour after the trigger. We do not detect any source at the refined Swift XRT position (Page & Evans GCN 8746). UVOT magnitude 3-sigma upper limits in a 5" aperture are reported in the following table:
```
Filter   T_start     Exp(s)  Mag (3-sigma upper limit)
------------------------------------------------------
white       82         37      > 20.0
white     4679        137      > 20.7
v         3653        197      > 19.3
b         4473        197      > 20.3
u         4268        197      > 20.0
uvw1      4063        197      > 20.0
uvm2      3858        197      > 20.0
uvw2      9102        886      > 20.9
```
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 #8749
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), K. McLean (GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), 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-239 to T+963 sec from the recent telemetry downlink, we report further analysis of Swift GRB 081228 (trigger #338338) (Page, et al., GCN Circ. 8742). The BAT ground-calculated position is RA, Dec = 39.477, 30.833 deg which is
```
  RA(J2000)  =  02h 37m 54.4s
  Dec(J2000) = +30d 49' 57.3"
```
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%.
The mask-weighted light curve begins with a possible faint soft 20-second precursor beginning at T-180 sec. The main emission consists of a single peak beginning at T-0.5 sec and lasting ~2.5 seconds. T90 (15-350 keV) is 3.0 +- 1.4 sec (estimated error including systematics). An observing constraint caused the Swift spacecraft to slew away from the burst location at ~T+250 seconds, so no information about the burst is available after ~T+300 sec, when the burst was no longer in the field of view.
The time-averaged spectrum from T-0.1 to T+2.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.10 +- 0.31. The fluence in the 15-150 keV band is 8.9 +- 1.8 x 10-8 erg/cm2. The 1-sec peak photon flux measured from T+0.87 sec in the 15-150 keV band is 0.6 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
With a duration longer than 2 s and a soft spectrum, this burst is likely to be in the "long" category.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/338338/BA/
GCN Circular #8752
P. Afonso, T. Kruehler, J. Greiner (all MPE), and S. Klose (Tautenburg) report on behalf of the GROND team:
We report on further analysis of the GROND data of the optical afterglow candidate of GRB 081228 (Swift trigger 338338, Page et al., GCN #8742).
The optical/NIR source inside the XRT errorcircle, previously reported in GCN #8745 by P. Afonso et al., is found to be clearly variable. The position of the afterglow is:
```
RA(J2000): 02:37:50.94
DEC(J2000): +30:51:10.5
```
with uncertainties of 0.5" in each coordinate.
Preliminary photometry yields the following r' band magnitudes, uncorrected for Galactic foreground reddening:
```
T_mid[s]  Exp[s] Mag     MagErr
-------------------------------
449       35     19.81   0.04
667       35     20.25   0.04
872       35     20.59   0.06
1380      115    21.21   0.05
1581      115    21.34   0.05
3308      375    22.09   0.08
```
The quoted error is statistical only. There is an additional systematic error in the absolute calibration using the GROND zeropoint which is expected to be in the 0.2 mag range. As the GROND photometric system is based on the SDSS in g'r'i'z' these values are AB magnitudes.
The complete light curve obtained during the first night post burst can be reasonably well described with a power law of index 1.1 +- 0.2.
A broad band SED from g' to K was constructed using data obtained simultaneously at a midtime of 1500 s after the trigger. After correcting for a Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.16 (Schlegel et al. 1998), the r' to K band SED is well described with a power law of spectral index beta = 0.85 +- 0.15.
We tentatively associate the large, foreground extinction corrected g'-r' color of around 1.4 mag with Ly-alpha absorption in the host at a redshift of 3.8 +- 0.4. This photometric redshift estimate has been obtained using hyperZ (Bolzonella et al. 2000). We caution, however, that this might be subject to changes due to a future improved calibration.
GCN Report 188.1
GCN_Report 188.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_188_1.pdf by K.L. Page at U. Leicester titled: "Final Swift observations of GRB 081228"
1011.1205 from 5 Nov 10
T. Kr�hler et al.: Photometric redshifts for GRB afterglows from GROND and Swift/UVOT
We present a framework to obtain photometric redshifts (photo-zs) for gamma-ray burst afterglows. Using multi-band photometry from GROND and Swift/UVOT, photo-zs are derived for five GRBs for which spectroscopic redshifts are not available. We use UV/optical/NIR data and synthetic photometry based on afterglow observations and theory to derive the photometric redshifts of GRBs and their accuracy. Taking into account the afterglow synchrotron emission properties, we investigate the application of photometry to derive redshifts in a theoretical range between z~1 and z~12. The measurement of photo-zs for GRB afterglows provides a quick, robust and reliable determination of the distance scale to the burst, particularly in those cases where spectroscopic observations in the optical/NIR range cannot be obtained. Given a sufficiently bright and mildly reddened afterglow, the relative photo-z accuracy is better than 10% between z=1.5 and z~7 and better than 5% between z=2 and z=6. We detail the approach on 5 sources without spectroscopic redshifts observed with UVOT on-board Swift and/or GROND. The distance scale to those same afterglows is measured to be $z=4.31^{+0.14}_{-0.15}$ for GRB 080825B, $z=2.13^{+0.14}_{-0.20}$ for GRB 080906, $z=3.44^{+0.15}_{-0.32}$ for GRB 081228, $z=2.03^{+0.16}_{-0.14}$ for GRB 081230 and $z=1.28^{+0.16}_{-0.15}$ for GRB 090530. Combining the response from UVOT with ground-based observatories and in particular GROND operating in the optical/NIR wavelength regime, reliable photo-zs can be obtained from z ~ 1.0 out to z ~ 10, and possibly even at higher redshifts in some favorable cases, provided that these GRBs exist, are localized quickly, have sufficiently bright afterglows and are not heavily obscured.

Back to JG's homepage

Jochen Greiner, last update: 05-Nov-2010 [Disclaimer]