Gamma-ray Burst 120911A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 11 Sep 12 07:08:59 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     533268,   Seg_Num: 0
GRB_RA:          357.961d {+23h 51m 51s} (J2000),
                 358.119d {+23h 52m 28s} (current),
                 357.343d {+23h 49m 22s} (1950)
GRB_DEC:         +63.099d {+63d 05' 55"} (J2000),
                 +63.169d {+63d 10' 10"} (current),
                 +62.821d {+62d 49' 14"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4460 [cnts]    Image_Peak=232 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   138     E_range: 15-50 keV
BKG_INTEN:       27580 [cnts]
BKG_TIME:        25702.36 SOD {07:08:22.36} UT
BKG_DUR:         8 [sec]
GRB_DATE:        16181 TJD;   255 DOY;   12/09/11
GRB_TIME:        25713.75 SOD {07:08:33.75} UT
GRB_PHI:          99.86 [deg]
GRB_THETA:        34.06 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     20.78 [sigma]
IMAGE_SIGNIF:    11.79 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +1  +0  +1 +37  +0 
SUN_POSTN:       169.84d {+11h 19m 22s}   +4.37d {+04d 22' 17"}
SUN_DIST:        112.17 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      110.44d {+07h 21m 46s}  +18.16d {+18d 09' 46"}
MOON_DIST:        83.38 [deg]
MOON_ILLUM:      25 [%]
GAL_COORDS:      116.25,  1.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       36.94, 55.55 [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 = 5.52,19.00 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=369040116).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 11 Sep 12 07:13:56 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     9085451,   Seg_Num: 6
GRB_RA:          357.961d {+23h 51m 51s} (J2000),
                 358.119d {+23h 52m 28s} (current),
                 357.343d {+23h 49m 22s} (1950)
GRB_DEC:         +63.099d {+63d 05' 55"} (J2000),
                 +63.169d {+63d 10' 10"} (current),
                 +62.821d {+62d 49' 14"} (1950)
GRB_DATE:        16181 TJD;   255 DOY;   12/09/11
GRB_TIME:        25713.75 SOD {07:08:33.75} UT
TRIGGER_INDEX:   138
GRB_PHI:          99.86 [deg]
GRB_THETA:        34.06 [deg]
DELTA_TIME:      12193.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    0.00 [sigma]
LC_URL:          sw00533268000msb.lc
SUN_POSTN:       169.85d {+11h 19m 23s}   +4.37d {+04d 22' 12"}
SUN_DIST:        112.17 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      110.48d {+07h 21m 56s}  +18.15d {+18d 09' 16"}
MOON_DIST:        83.41 [deg]
MOON_ILLUM:      25 [%]
GAL_COORDS:      116.25,  1.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       36.94, 55.55 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        WARNING: No BAT_Position TDRSS message was received for this trigger_number!  
COMMENTS:           
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 = 5.52,19.00 [deg].
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 11 Sep 12 07:08:55 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     369040116
GRB_RA:          354.880d {+23h 39m 31s} (J2000),
                 355.031d {+23h 40m 07s} (current),
                 354.290d {+23h 37m 10s} (1950)
GRB_DEC:         +62.490d {+62d 29' 24"} (J2000),
                 +62.560d {+62d 33' 37"} (current),
                 +62.213d {+62d 12' 46"} (1950)
GRB_ERROR:       6.83 [deg radius, statistical only]
DATA_SIGNIF:     9.20 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        16181 TJD;   255 DOY;   12/09/11
GRB_TIME:        25713.99 SOD {07:08:33.99} UT
GRB_PHI:         220.00 [deg]
GRB_THETA:        13.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4143 (Gnd S/W Version number)
SUN_POSTN:       169.84d {+11h 19m 22s}   +4.37d {+04d 22' 17"}
SUN_DIST:        112.95 [deg]   Sun_angle= 11.7 [hr] (West of Sun)
MOON_POSTN:      110.44d {+07h 21m 45s}  +18.16d {+18d 09' 46"}
MOON_DIST:        84.91 [deg]
MOON_ILLUM:      25 [%]
GAL_COORDS:      114.73,  0.77 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       34.40, 56.11 [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/FERMI NOTICE
NOTICE_DATE:     Tue 11 Sep 12 07:08:53 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     369040116
GRB_RA:          336.933d {+22h 27m 44s} (J2000),
                 337.045d {+22h 28m 11s} (current),
                 336.495d {+22h 25m 59s} (1950)
GRB_DEC:         +61.567d {+61d 34' 00"} (J2000),
                 +61.632d {+61d 37' 54"} (current),
                 +61.311d {+61d 18' 40"} (1950)
GRB_ERROR:       19.70 [deg radius, statistical plus systematic]
GRB_INTEN:       124 [cnts/sec]
DATA_SIGNIF:     5.40 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        16181 TJD;   255 DOY;   12/09/11
GRB_TIME:        25713.99 SOD {07:08:33.99} UT
GRB_PHI:         180.00 [deg]
GRB_THETA:        10.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      1.83
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      75%  GRB
2nd_MOST_LIKELY:  12%  Generic SGR
DETECTORS:       0,0,0, 0,0,0, 1,1,0, 0,0,0, 0,0,
SUN_POSTN:       169.84d {+11h 19m 22s}   +4.37d {+04d 22' 17"}
SUN_DIST:        113.26 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:      110.44d {+07h 21m 45s}  +18.16d {+18d 09' 46"}
MOON_DIST:        92.06 [deg]
MOON_ILLUM:      25 [%]
GAL_COORDS:      106.68,  3.32 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       22.18, 61.76 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 256.80,23.27 [deg].

GCN Circular #13744
J. K. Cannizzo (NASA/UMBC), V. D'Elia (ASDC), P. A. Evans (U Leicester), C. Guidorzi (U Ferrara), C. B. Markwardt (NASA/GSFC), A. Maselli (INAF-IASFPA), K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU) and E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team:
At 07:08:33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120911A (trigger=533268). Swift could not immediately slew due to the Earth limb constraint. The BAT on-board calculated location is RA, Dec 357.961, +63.099 which is
```
   RA(J2000) = 23h 51m 51s
   Dec(J2000) = +63d 05' 55"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of at least 30 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~1 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+51.6 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.nasa.gov). 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 #13745
W. Rujopakarn (Steward), T. Guver (Sabanci U), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 120911A (Swift trigger 533268; Cannizzo et al., GCN 13744), producing images beginning 9.2 s after the GCN notice time. An automated response took the first image at 07:09:04.2 UT, 30.4 s after the burst, under fair conditions. We took 10 5-sec, 10 20-sec and 40 60-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; however, we are limited as the field is somewhat crowded. Individual images have limiting magnitudes ranging from 15.5-16.6; we set the following specific limits.
```
start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
07:09:04.2   07:09:09.2         5     15.5           30.4       N
07:09:04.2   07:10:46.4        50     16.9           30.4       Y
```

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 11 Sep 12 08:06:59 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     533268,   Seg_Num: 0
POINT_RA:        357.928d {+23h 51m 43s} (J2000)
POINT_DEC:       +63.108d {+63d 06' 30"} (J2000)
POINT_ROLL:      8.696d
IMG_START_DATE:  16181 TJD;   255 DOY;   12/09/11
IMG_START_TIME:  29036.57 SOD {08:03:56.57} UT,   3322.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.708
N_STARS:         190
X_OFFSET:        497 [pixels]
Y_OFFSET:        691 [pixels]
X_MAX:           1456 [pixels]
Y_MAX:           1650 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00533268000msufc3322.fits
SUN_POSTN:       169.88d {+11h 19m 31s}   +4.36d {+04d 21' 22"}
SUN_DIST:        112.18 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      110.96d {+07h 23m 50s}  +18.06d {+18d 03' 53"}
MOON_DIST:        83.68 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      116.24,  1.02 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       36.93, 55.57 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 11 Sep 12 08:08:20 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     533268,   Seg_Num: 0
POINT_RA:        357.928d {+23h 51m 43s} (J2000)
POINT_DEC:       +63.108d {+63d 06' 30"} (J2000)
ROLL:            8.696d
IMG_START_DATE:  16181 TJD;   255 DOY;   12/09/11
IMG_START_TIME:  29036.57 SOD {08:03:56.57} UT,   3322.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     369043446
X_OFFSET:        816 [pixels]
Y_OFFSET:        1010 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       976
Y_GRB_POS:       1170
BINNING_INDEX:   1
IM_URL:          sw00533268000msuni3332.fits
SUN_POSTN:       169.88d {+11h 19m 31s}   +4.36d {+04d 21' 21"}
SUN_DIST:        112.18 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      110.97d {+07h 23m 53s}  +18.06d {+18d 03' 45"}
MOON_DIST:        83.69 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      116.24,  1.02 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       36.93, 55.57 [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:     Tue 11 Sep 12 08:08:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     533268,   Seg_Num: 0
POINT_RA:        357.928d {+23h 51m 43s} (J2000)
POINT_DEC:       +63.108d {+63d 06' 30"} (J2000)
POINT_ROLL:      8.696d
IMG_START_DATE:  16181 TJD;   255 DOY;   12/09/11
IMG_START_TIME:  29036.57 SOD {08:03:56.57} UT,   3322.8 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.708
N_STARS:         190
X_OFFSET:        497 [pixels]
Y_OFFSET:        691 [pixels]
X_MAX:           1456 [pixels]
Y_MAX:           1650 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw00533268000msufc3322.fits
SUN_POSTN:       169.88d {+11h 19m 31s}   +4.36d {+04d 21' 21"}
SUN_DIST:        112.18 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      110.97d {+07h 23m 52s}  +18.06d {+18d 03' 46"}
MOON_DIST:        83.69 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      116.24,  1.02 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       36.93, 55.57 [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:     Tue 11 Sep 12 08:08:31 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     533268,   Seg_Num: 0
POINT_RA:        357.928d {+23h 51m 43s} (J2000)
POINT_DEC:       +63.108d {+63d 06' 30"} (J2000)
ROLL:            8.696d
IMG_START_DATE:  16181 TJD;   255 DOY;   12/09/11
IMG_START_TIME:  29036.57 SOD {08:03:56.57} UT,   3322.8 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     369043446
X_OFFSET:        816 [pixels]
Y_OFFSET:        1010 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       976
Y_GRB_POS:       1170
BINNING_INDEX:   1
IM_URL:          sw00533268000msuni3332.fits
SUN_POSTN:       169.88d {+11h 19m 31s}   +4.36d {+04d 21' 20"}
SUN_DIST:        112.18 [deg]   Sun_angle= 11.5 [hr] (West of Sun)
MOON_POSTN:      110.97d {+07h 23m 53s}  +18.06d {+18d 03' 44"}
MOON_DIST:        83.69 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      116.24,  1.02 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       36.93, 55.57 [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:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 11 Sep 12 08:14:09 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     533268,   Seg_Num: 0
GRB_RA:          357.9815d {+23h 51m 55.55s} (J2000),
                 358.1394d {+23h 52m 33.46s} (current),
                 357.3631d {+23h 49m 27.15s} (1950)
GRB_DEC:         +63.0983d {+63d 05' 53.8"} (J2000),
                 +63.1689d {+63d 10' 08.1"} (current),
                 +62.8201d {+62d 49' 12.4"} (1950)
GRB_ERROR:       4.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  16181 TJD;   255 DOY;   12/09/11
IMG_START_TIME:  29047.00 SOD {08:04:07.00} UT,   3333.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       169.88d {+11h 19m 32s}   +4.35d {+04d 21' 15"}
SUN_DIST:        112.19 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      111.02d {+07h 24m 05s}  +18.05d {+18d 03' 09"}
MOON_DIST:        83.70 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      116.26,  1.00 [deg] galactic lon,lat of the burst
ECL_COORDS:       36.95, 55.54 [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.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 2.8% < P(seren) < 6.6%.

GCN Circular #13746
S. Campana (INAF-OAB), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU) and G. Tagliaferri (INAF-OAB) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 120911A at 08:04:07.0 UT, 3333.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 357.98152, 63.09831 which is equivalent to:
```
   RA(J2000)  = 23h 51m 55.56s
   Dec(J2000) = +63d 05' 53.9"
```
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This location is 33 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. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 6.66 x 10^21 cm^-2 (Kalberla et al. 2005).
GCN Circular #13747
C. Guidorzi (U. Ferrara), A. Gomboc (U. Ljubljana), F. Virgili (LJMU) on behalf of a large collaboration report:
The 2-m Faulkes Telescope North automatically began observing GRB 120911A (Cannizzo et al. GCN Circ. 13744) on September 11 2012, 08:17:24 UT corresponding to ~70 minutes post burst trigger with BVRi' filters. Within the XRT error circle (Campana et al. GCN Circ. 13746), we don't see any uncatalogued object down to the following limits:
```
Mid time from       Exposure        Filter       Limit
GRB (hr)            (s)
----------------------------------------------------------
1.37                240             R > 20.9
1.45                220             i' > 21.2
----------------------------------------------------------
```
We note the presence of a faint, uncatalogued object in the i' band, lying at 5.8" from the XRT centroid, with a magnitude of i=21.0 +- 0.2 (calibrated against USNOB1 nearby stars) at the following position:
```
RA(J2000) =  23:51:56.06
Dec(J2000)= +63:05:49.2
```
with an error of 0.6". Presently we cannot make any statement about its temporal behaviour.
GCN Circular #13748
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 2099 s of XRT Photon Counting mode data and 5 UVOT images for GRB 120911A, 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 = 357.97897, +63.09874 which is equivalent to:
```
RA (J2000): 23h 51m 54.95s
Dec (J2000): +63d 05' 55.5"
```
with an uncertainty of 1.8 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 #13749
S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. K. Cannizzo (NASA/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+863 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120911A (trigger #533268) (Cannizzo, et al., GCN Circ. 13744). The BAT ground-calculated position is RA, Dec = 357.966, 63.090 deg, which is
```
   RA(J2000)  =  23h 51m 51.9s 
   Dec(J2000) = +63d 05' 25.6" 
```
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 23%.
The mask-weighted light curve shows two barely overlapping peaks starting at ~T-4 sec, peaking at ~T+1 and ~T+17 sec, and ending at ~T+50 sec. T90 (15-350 keV) is 17.8 +- 3.9 sec (estimated error including systematics).
The time-averaged spectrum from T-1.84 to T+24.10 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.71 +- 0.16. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band is 2.7 +- 0.3 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/533268/BA/
GCN Circular #13750
K.L. Page (U. Leicester) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift-XRT team:
We have analysed 7.2 ks of XRT data for GRB 120911A (Cannizzo et al. GCN Circ. 13744), from 3.3 ks to 17.3 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN. Circ 13748).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.31 (+0.22, -0.21).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+/-0.4). The best-fitting absorption column is 8.4 (+3.4, -1.8) x 10^21 cm^-2, consistent with the Galactic value of 6.7 x 10^21 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.4 x 10^-11 (1.0 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     8.4 (+3.4, -1.8) x 10^21 cm^-2
Galactic foreground: 6.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.0 (+/-0.4)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00533268.
This circular is an official product of the Swift-XRT team.
GCN Circular #13751
N. P. M. Kuin (MSSL-UCL) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120911A 3323 s after the BAT trigger (Cannizzo et al., GCN Circ. 13744). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 13748) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3323         3473          147         >20.5
white             3323        11009         1229         >21.6
v                 3479        15918         1278         >19.9
b                 4300        10097         1160         >21.5
u                 4095         5730          393         >20.4
w1                3890         5526          393         >20.0
m2                3684         5320          393         >21.1
w2                4710        11585          757         >20.9
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.12 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #13752
Weikang Zheng and Carl Akerlof (Umich), report on behalf of the ROTSE collaboration:
We analyzed Fermi/LAT data of GRB 120911A (Cannizzo et al., GCN 13744) as a follow-up of routine search in Swift trigger catalogs in our LAT data processing pipeline using both the matched filter technique (Akerlof et al. 2010, ApJ, 725, L15; 2011 ApJ, 726, 22; 2012, arXiv:1205.3066; Zheng et al. 2012, ApJ 745,72; ApJ, 756, 64) and likelihood method. We do NOT detect high energy photon emission from both methods.
A standard data selection method is applied when extracting the LAT photon data with energy E > 100 MeV, and a duration of T0 - T0+47.5s after the trigger. A zenith angle cut of <105 degree is applied to all photons.
The burst location of GRB 120911A was only ~14 degrees from the LAT boresight, almost in the center of the LAT field of view, and the zenith angle was about 40 degrees at trigger time. Using the likelihood method, we estimated the upper limit in LAT energy range (0.1 - 10 GeV) is 1.1e-05 (photons cm^-2 s^-1) by assuming a spectral index of -2.2. The pipeline result of GRB 120911A is given in the following link: http://www.rotse.net/LAT/SwiftTriggers/369040116/
GCN Circular #13753
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 120911A (Cannizzo et al., GCNC 13744) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2012-09-11 13:46:32 UT, (~6.6 h after the burst). We did not find any new point source within the enhanced XRT circle (Beardmore et al., GCNC 13748) in all the three bands.
Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration.
```
T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic
------------------------------------------------------
0.31808    14:46:35    5940.0   >20.6  >19.8  >19.2
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
GCN Circular #13754
David Gruber (MPE) reports on behalf of the Fermi GBM Team:
"At 07:08:33.99 UT on 11 September 2012, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 120911A (trigger 369040116 / 120911298). which was also detected by the Swift/BAT (Cannizzo et al. 2012, GCN 13744).
The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 11 degrees.
The GBM light curve consists of two pulses with a duration (T90) of about 22 s (50-300 keV). The time-averaged spectrum from T0-4.6 s to T0+22.0 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.36 +/- 0.26 and the cutoff energy, parameterized as Epeak, is 64.2 +/- 5.1 keV
The event fluence (10-1000 keV) in this time interval is (2.34 +/- 0.04)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.38 s in the 10-1000 keV band is 4.31 +/- 0.27 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #13759
L. Elenin (KIAM), A. Volnova (SAI MSU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 120911A (Cannizzo et al., GCN 13744) with 0.45-m telescope of ISON-NM observatory starting on Sep. 11 (UT) 07:10:42, i.e ~130 s after burst trigger. We took several unfiltered images of 30 s and 60 s exposures. Within enhanced XRT afterglow position (Beardmore et al., GCN 13748) we do not detect any new object. A preliminary photometry of single and co-added frames is based on the USNO-B1.0 (R2) nearby stars is following:
```
  T0+,          Exposure,  OT,         UL (3 sigma)
  mid, d         (s)

 0.0017          30             n/d           18.4
 0.0028        5x30             n/d           19.1
 0.0175       60x30             n/d           20.2
 0.0590       30x120            n/d           20.6
```
GCN Circular #13760
V. Rumyantsev, N.Pit' (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 120911A (Cannizzo et al., GCN 13744) with AZT-11 telescope of CrAO observatory starting on Sep. 11 (UT) 21:10:38. We took several images in R-filter of 180 s exposure. Within enhanced XRT afterglow position (Beardmore et al., GCN 13748) we do not detect any new object. A preliminary photometry of co-added frame is based on the USNO-B1.0 (R2) nearby stars is following:
```
T0+,        Filter   Exposure,   OT,         UL (3 sigma)
mid, d                 (s)

0.6130     R        20x180       n/d          20.9 
```
GCN Report 393.1
GCN_Report 393.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_393_1.pdf by J.K. Cannizzo at NASA/UMBC titled: "Swift Observations of GRB 120911A"
GCN Circular #18183
Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng, Alexei V. Filippenko (UC Berkeley), and S. Bradley Cenko (GSFC) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRBs 120422A (Troja et al., GCN 13243), 120724A (D'Avanzo et al., GCN 13510), 120803B (Racusin et al. GCN 13566), 120911A (Cannizzo et al., GCN 13744), and 120923A (Yershov et al., GCN 13796) at 510 s, 202 s, 196 s, 147 s, and 236 s after the burst, respectively. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. We do not detect any new sources within the XRT error circles. We estimate the following upper limits (magnitudes) in clear-band images for each GRB calibrated to USNO B1.0:
```
GRB       Start-Time  Coadd-Images  Mid-time   Upper-Limit (3 sigma)
120422A   510 s        20 s x 6           758 s              20.6
120724A   202 s        20 s x 10         647 s              20.7
120803B   196 s        20 s x 10         644 s              21.7
120911A   147 s        20 s x 6          501 s               20.9
120923A   236 s        20 s x 6          563 s               21.0
```

Back to JG's homepage

Jochen Greiner, last update: 20-Aug-2015 [Disclaimer]