Gamma-ray Burst 131226A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 26 Dec 13 05:47:56 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     582123,   Seg_Num: 0
GRB_RA:          301.307d {+20h 05m 14s} (J2000),
                 301.629d {+20h 06m 31s} (current),
                 300.153d {+20h 00m 37s} (1950)
GRB_DEC:         -64.962d {-64d 57' 43"} (J2000),
                 -64.922d {-64d 55' 17"} (current),
                 -65.104d {-65d 06' 15"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1481 [cnts]    Image_Peak=206 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   65     E_range: 15-50 keV
BKG_INTEN:       23388 [cnts]
BKG_TIME:        20844.56 SOD {05:47:24.56} UT
BKG_DUR:         8 [sec]
GRB_DATE:        16652 TJD;   360 DOY;   13/12/26
GRB_TIME:        20859.66 SOD {05:47:39.66} UT
GRB_PHI:         -92.35 [deg]
GRB_THETA:        25.64 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.42 [sigma]
IMAGE_SIGNIF:    14.93 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +1  +4 -100  +0 -70  +0 
SUN_POSTN:       275.02d {+18h 20m 06s}  -23.36d {-23d 21' 23"}
SUN_DIST:         45.01 [deg]   Sun_angle= -1.8 [hr] (East of Sun)
MOON_POSTN:      190.60d {+12h 42m 25s}   -6.68d {-06d 41' 02"}
MOON_DIST:        92.61 [deg]
MOON_ILLUM:      43 [%]
GAL_COORDS:      331.24,-32.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      287.63,-43.43 [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 = 116.44,-12.86 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 26 Dec 13 05:51:23 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     582123,   Seg_Num: 0
GRB_RA:          301.307d {+20h 05m 14s} (J2000),
                 301.629d {+20h 06m 31s} (current),
                 300.153d {+20h 00m 37s} (1950)
GRB_DEC:         -64.962d {-64d 57' 43"} (J2000),
                 -64.922d {-64d 55' 17"} (current),
                 -65.104d {-65d 06' 15"} (1950)
GRB_DATE:        16652 TJD;   360 DOY;   13/12/26
GRB_TIME:        20859.66 SOD {05:47:39.66} UT
TRIGGER_INDEX:   65
GRB_PHI:         -92.35 [deg]
GRB_THETA:        25.64 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.42 [sigma]
IMAGE_SIGNIF:    14.93 [sigma]
LC_URL:          sw00582123000msb.lc
SUN_POSTN:       275.03d {+18h 20m 06s}  -23.36d {-23d 21' 22"}
SUN_DIST:         45.01 [deg]   Sun_angle= -1.8 [hr] (East of Sun)
MOON_POSTN:      190.63d {+12h 42m 32s}   -6.69d {-06d 41' 37"}
MOON_DIST:        92.59 [deg]
MOON_ILLUM:      43 [%]
GAL_COORDS:      331.24,-32.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      287.63,-43.43 [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 = 116.44,-12.86 [deg].

GCN Circular #15612
S. R. Oates (UCL-MSSL), H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 05:47:39 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 131226A (trigger=582123). The BAT on-board calculated location is RA, Dec 301.307, -64.962 which is
```
   RA(J2000) = 20h 05m 14s
   Dec(J2000) = -64d 57' 43"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 10 sec. The peak count rate was ~15000 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 2014 January 27. There will thus be no XRT or UVOT data for this trigger.
Burst Advocate for this burst is S. R. Oates (samantha.oates AT ucl.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 #15613
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/UMBC), C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL), T. Sakamoto (AGU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+481 sec from the recent telemetry downlink, we report further analysis of BAT GRB 131226A (trigger #582123) (Oates, et al., GCN Circ. 15612). The BAT ground-calculated position is RA, Dec = 301.309, -64.943 deg which is
```
    RA(J2000)  =  20h 05m 14.2s
    Dec(J2000) = -64d 56' 35.2"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 56%.
The mask-weighted light curve shows a very complex structure with more than a dozen peaks covering the time period from T-0.5 sec to T+8.5 sec and peaking at T+1 sec. This is followed by lower-level extended emission out to ~T+180 sec. T90 (15-350 keV) is 7.20 +- 0.16 sec (estimated error including systematics).
The time-averaged spectrum from T-0.26 to T+8.42 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.38 +- 0.04. The fluence in the 15-150 keV band is 4.0 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+1.11 sec in the 15-150 keV band is 10.4 +- 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/582123/BA/
GCN Circular #15619
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 131226A (Swift-BAT trigger 582123: Oates, et al., GCN 15612; Stamatikos, et al. GCN 15613) triggered Konus-Wind at T0=20858.013 s UT (05:47:38.013).
The burst light curve shows a multi-peaked structure with a total duration of ~7 s.
As observed by Konus-Wind, the burst had a fluence of 1.01(-0.07,+0.08)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+2.704 s, of (5.0 +/- 1.0)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum (measured from T0 to T0+8.448 s) is well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with alpha = -0.90(-0.12,+0.13), and Ep = 264(-17,+20) keV (chi2 = 65.6/60 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.5.
All the quoted values are preliminary.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB131226_T20858/

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Jochen Greiner, last update: 27-Dec-2013 [Disclaimer]