Gamma-ray Burst 081226B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 26 Dec 08 12:13:29 UT
NOTICE_TYPE:    INTEGRAL Wakeup
TRIGGER_NUM:    5394,   Sub_Num: 0
GRB_RA:          25.4643d {+01h 41m 51s} (J2000),
                 25.5560d {+01h 42m 13s} (current),
                 24.9534d {+01h 39m 49s} (1950)
GRB_DEC:        -47.4253d {-47d 25' 30"} (J2000),
                -47.3801d {-47d 22' 47"} (current),
                -47.6771d {-47d 40' 37"} (1950)
GRB_ERROR:      3.13 [arcmin, radius, statistical only]
GRB_INTEN:      9.08 [sigma]
GRB_TIME:       43993.27 SOD {12:13:13.27} UT
GRB_DATE:       14826 TJD;   361 DOY;   08/12/26
SC_RA:           31.41 [deg] (J2000)
SC_DEC:         -54.14 [deg] (J2000)
SUN_POSTN:      275.56d {+18h 22m 14s}  -23.34d {-23d 20' 21"}
SUN_DIST:        85.47 [deg]   Sun_angle= -7.3 [hr] (East of Sun)
MOON_POSTN:     263.53d {+17h 34m 07s}  -27.01d {-27d 00' 31"}
MOON_DIST:       89.18 [deg]
GAL_COORDS:     280.31,-67.43 [deg] galactic lon,lat of the burst
ECL_COORDS:     357.56,-52.31 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 26 Dec 08 12:13:31 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     251986391
GRB_RA:           49.367d {+03h 17m 28s} (J2000),
                  49.442d {+03h 17m 46s} (current),
                  48.946d {+03h 15m 47s} (1950)
GRB_DEC:         -46.183d {-46d 10' 59"} (J2000),
                 -46.151d {-46d 09' 02"} (current),
                 -46.365d {-46d 21' 54"} (1950)
GRB_ERROR:       18.48 [deg radius, statistical plus systematic]
GRB_INTEN:       425 [cnts/sec]
DATA_SIGNIF:     9.80 [sigma]
INTEG_TIME:      0.256 [sec]
GRB_DATE:        14826 TJD;   361 DOY;   08/12/26
GRB_TIME:        43990.71 SOD {12:13:10.71} UT
GRB_PHI:         176.00 [deg]
GRB_THETA:        35.00 [deg]
DATA_TIME_SCALE: 0.2560 [sec]
HARD_RATIO:      0.41
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      52%  Distant Particles
2nd_MOST_LIKELY:  45%  GRB
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       275.56d {+18h 22m 14s}  -23.34d {-23d 20' 21"}
SUN_DIST:         98.93 [deg]   Sun_angle= -8.9 [hr] (East of Sun)
MOON_POSTN:      263.53d {+17h 34m 07s}  -27.01d {-27d 00' 31"}
MOON_DIST:       100.58 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      256.25,-55.52 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       23.39,-60.58 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 70.58,-25.38 [deg].

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 26 Dec 08 12:16:27 UT
NOTICE_TYPE:    INTEGRAL Refined
TRIGGER_NUM:    5394,   Sub_Num: 1
GRB_RA:          25.4773d {+01h 41m 55s} (J2000),
                 25.5690d {+01h 42m 17s} (current),
                 24.9665d {+01h 39m 52s} (1950)
GRB_DEC:        -47.4287d {-47d 25' 42"} (J2000),
                -47.3836d {-47d 23' 00"} (current),
                -47.6806d {-47d 40' 49"} (1950)
GRB_ERROR:      2.92 [arcmin, radius, statistical only]
GRB_INTEN:      11.50 [sigma]
GRB_TIME:       43999.20 SOD {12:13:19.20} UT
GRB_DATE:       14826 TJD;   361 DOY;   08/12/26
SC_RA:           31.41 [deg] (J2000)
SC_DEC:         -54.14 [deg] (J2000)
SUN_POSTN:      275.56d {+18h 22m 14s}  -23.34d {-23d 20' 20"}
SUN_DIST:        85.48 [deg]   Sun_angle= -7.3 [hr] (East of Sun)
MOON_POSTN:     263.55d {+17h 34m 13s}  -27.01d {-27d 00' 29"}
MOON_DIST:       89.18 [deg]
GAL_COORDS:     280.30,-67.42 [deg] galactic lon,lat of the burst
ECL_COORDS:     357.57,-52.32 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       Possibly real GRB event

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Fri 26 Dec 08 13:57:17 UT
NOTICE_TYPE:    INTEGRAL Offline
TRIGGER_NUM:    5394,   Sub_Num: 2
GRB_RA:          25.4949d {+01h 41m 59s} (J2000),
                 25.5866d {+01h 42m 21s} (current),
                 24.9843d {+01h 39m 56s} (1950)
GRB_DEC:        -47.4389d {-47d 26' 19"} (J2000),
                -47.3938d {-47d 23' 37"} (current),
                -47.6908d {-47d 41' 26"} (1950)
GRB_ERROR:      2.50 [arcmin, radius, statistical only]
GRB_INTEN:      11.50 [sigma]
GRB_TIME:       43999.20 SOD {12:13:19.20} UT
GRB_DATE:       14826 TJD;   361 DOY;   08/12/26
SC_RA:           31.41 [deg] (J2000)
SC_DEC:         -54.14 [deg] (J2000)
SUN_POSTN:      275.64d {+18h 22m 33s}  -23.34d {-23d 20' 10"}
SUN_DIST:        85.44 [deg]   Sun_angle= -7.3 [hr] (East of Sun)
MOON_POSTN:     264.49d {+17h 37m 57s}  -26.99d {-26d 59' 23"}
MOON_DIST:       88.71 [deg]
GAL_COORDS:     280.28,-67.41 [deg] galactic lon,lat of the burst
ECL_COORDS:     357.57,-52.33 [deg] ecliptic lon,lat of the burst
COMMENTS:       INTEGRAL GRB Coordinates.  
COMMENTS:       REFINED_COORDINATES_AFTER_OFFLINE_ANALYSIS

GCN Circular #8734
S.Mereghetti, A.Paizis (IASF-Milano), D.Gotz (CEA-Saclay), M.Turler, V.Beckmann, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report:
A short hard GRB consisting of a single peak with duration of about 0.7 s has been detected by IBAS in IBIS/ISGRI data at 12:13:11 UT on December 26th.
The refined coordinates (J2000) are:
```
RA = 25.495 [degrees]
DEC= -47.439 [degrees]
```
with an uncertainty of 2.5 arcmin (90% c.l.).
A preliminary analysis gives a peak flux in the 20-200 keV range of about 3 ph/cmq/s (0.2 s integration time) and a fluence over the same energy range of about 10e-7 erg/cmq.
A plot of the light curve will be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html This message can be cited.
GCN Circular #8740
P.A. Evans (U. Leicester) and E.A. Hoversten (PSU) report on behalf of the Swift team:
Swift observed the field of GRB 081226B (Mereghetti et al. GCN Circ 8734) for 8 ks, beginning 9.6 ks after the INTEGRAL trigger. The XRT data (all in Photon Counting mode) contain no source in the INTEGRAL error circle. A 3-sigma upper limit is 0.001 counts/sec which is 5.6e-14 erg cm^-2 s^-1 for a typical GRB spectrum.
Given the absence of an XRT position, the UVOT images were compared to archival images from the Digitized Sky Survey. No candidate afterglow was found in the INTEGRAL error circle. UVOT magnitude 3-sigma upper limits are reported in the following table:
```
Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
WHITE     9744     22737    1414        > 22.24
v         9621     27619    1940        > 20.48
b         9720     21824    1414        > 21.06
u         9694     16082     352        > 20.34
uvw1     10019     15877     313        > 20.20
uvm2     15472     28224     787        > 20.75
uvw2     10812     23271     932        > 21.27
```
The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.01 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
This circular is an official product of the Swift XRT and UVOT teams.
GCN Circular #8751
E. Bissaldi (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team:
"At 12:13:10.71 UT on 26 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081226B (trigger 251986391 / 081226509), which was also detected by INTEGRAL (Mereghetti et al. 2008, GCN 8734) The GBM on-ground location is consistent with the INTEGRAL position.
The angle from the Fermi LAT boresight is 22 degrees.
The GBM light curve consists of a single pulse with a duration (T90) of about 0.35 s (8-1000 keV). The time-averaged spectrum from T0-0.08 s to T0+0.12 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.51 +/- 0.17 and the cutoff energy, parameterized as Epeak, is 530 +/- 110 keV (chi squared 300 for 324 d.o.f.). A Band function fits the spectrum equally well with Epeak = 300 +/- 110 keV, alpha = -0.2 +/- 0.3 and beta = -1.82 +/- 0.23 (chi squared 292 for 323 d.o.f.).
The event fluence (8-1000 keV) in this time interval for the power law function with exponential cutoff is (6.1 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.01 s in the 8-1000 keV band is 17.7 +/- 1.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #8953
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 INTEGRAL-IBAS position of the GRB081226b (GCN 8734) 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 GRB081226b (GCN 8734). The data at 4.800 and 4.928 GHz were merged and the radio flux density at the GRB position found out to be -0.176 +/- 0.196 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/grb081226b/grb081226b_field_image

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Jochen Greiner, last update: 09-Mar-2009 [Disclaimer]