Gamma-ray Burst 091031

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 31 Oct 09 12:00:44 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     278683230
GRB_RA:           71.217d {+04h 44m 52s} (J2000),
                  71.265d {+04h 45m 04s} (current),
                  70.971d {+04h 43m 53s} (1950)
GRB_DEC:         -56.233d {-56d 13' 59"} (J2000),
                 -56.216d {-56d 12' 56"} (current),
                 -56.324d {-56d 19' 24"} (1950)
GRB_ERROR:       10.73 [deg radius, statistical plus systematic]
GRB_INTEN:       131 [cnts/sec]
DATA_SIGNIF:     8.70 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         120.00 [deg]
GRB_THETA:        25.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.62
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:        103.57 [deg]   Sun_angle= 9.6 [hr] (West of Sun)
MOON_POSTN:        6.94d {+00h 27m 46s}   +8.26d {+08d 15' 22"}
MOON_DIST:        83.16 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      264.99,-39.69 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       40.36,-76.42 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 182.90,-24.88 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 31 Oct 09 12:00:56 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      57
TRIGGER_NUM:     278683230
GRB_RA:           76.033d {+05h 04m 08s} (J2000),
                  76.053d {+05h 04m 13s} (current),
                  75.932d {+05h 03m 44s} (1950)
GRB_DEC:         -63.367d {-63d 21' 59"} (J2000),
                 -63.353d {-63d 21' 11"} (current),
                 -63.434d {-63d 26' 02"} (1950)
GRB_ERROR:       5.62 [deg radius, statistical plus systematic]
GRB_INTEN:       378 [cnts/sec]
DATA_SIGNIF:     24.10 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         105.00 [deg]
GRB_THETA:        20.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.68
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      96%  GRB
2nd_MOST_LIKELY:   3%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:         96.43 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:        6.95d {+00h 27m 47s}   +8.26d {+08d 15' 24"}
MOON_DIST:        88.29 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      273.30,-35.99 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       21.93,-83.30 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 182.90,-24.88 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 31 Oct 09 12:01:15 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      71
TRIGGER_NUM:     278683230
GRB_RA:           71.980d {+04h 47m 55s} (J2000),
                  72.013d {+04h 48m 03s} (current),
                  71.812d {+04h 47m 15s} (1950)
GRB_DEC:         -60.710d {-60d 42' 35"} (J2000),
                 -60.693d {-60d 41' 34"} (current),
                 -60.797d {-60d 47' 46"} (1950)
GRB_ERROR:       1.12 [deg radius, statistical only]
DATA_SIGNIF:     37.20 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         114.00 [deg]
GRB_THETA:        21.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:         99.70 [deg]   Sun_angle= 9.6 [hr] (West of Sun)
MOON_POSTN:        6.95d {+00h 27m 47s}   +8.26d {+08d 15' 29"}
MOON_DIST:        85.47 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      270.54,-38.40 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       27.84,-80.15 [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:     Sat 31 Oct 09 12:01:05 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      69
TRIGGER_NUM:     278683230
GRB_RA:           76.267d {+05h 05m 04s} (J2000),
                  76.287d {+05h 05m 09s} (current),
                  76.165d {+05h 04m 40s} (1950)
GRB_DEC:         -63.317d {-63d 18' 59"} (J2000),
                 -63.304d {-63d 18' 12"} (current),
                 -63.383d {-63d 22' 58"} (1950)
GRB_ERROR:       5.55 [deg radius, statistical plus systematic]
GRB_INTEN:       391 [cnts/sec]
DATA_SIGNIF:     34.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         105.00 [deg]
GRB_THETA:        20.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.77
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   2%  Generic Transient
DETECTORS:       0,0,0, 0,0,0, 1,0,0, 1,0,0, 0,0,
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:         96.41 [deg]   Sun_angle= 9.3 [hr] (West of Sun)
MOON_POSTN:        6.95d {+00h 27m 47s}   +8.26d {+08d 15' 26"}
MOON_DIST:        88.36 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      273.22,-35.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       22.80,-83.36 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 182.90,-24.88 [deg].

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 31 Oct 09 12:01:03 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      56
TRIGGER_NUM:     278683230
GRB_RA:           75.010d {+05h 00m 02s} (J2000),
                  75.041d {+05h 00m 10s} (current),
                  74.851d {+04h 59m 24s} (1950)
GRB_DEC:         -60.810d {-60d 48' 35"} (J2000),
                 -60.796d {-60d 47' 44"} (current),
                 -60.882d {-60d 52' 56"} (1950)
GRB_ERROR:       1.99 [deg radius, statistical only]
DATA_SIGNIF:     17.70 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         110.00 [deg]
GRB_THETA:        22.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:         98.73 [deg]   Sun_angle= 9.4 [hr] (West of Sun)
MOON_POSTN:        6.95d {+00h 27m 47s}   +8.26d {+08d 15' 26"}
MOON_DIST:        86.86 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      270.29,-36.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       33.96,-81.25 [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:     Sat 31 Oct 09 12:01:08 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      68
TRIGGER_NUM:     278683230
GRB_RA:           70.700d {+04h 42m 48s} (J2000),
                  70.731d {+04h 42m 55s} (current),
                  70.546d {+04h 42m 11s} (1950)
GRB_DEC:         -61.580d {-61d 34' 47"} (J2000),
                 -61.562d {-61d 33' 42"} (current),
                 -61.672d {-61d 40' 20"} (1950)
GRB_ERROR:       1.01 [deg radius, statistical only]
DATA_SIGNIF:     32.80 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        15135 TJD;   304 DOY;   09/10/31
GRB_TIME:        43228.85 SOD {12:00:28.85} UT
GRB_PHI:         114.00 [deg]
GRB_THETA:        20.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   413 (Gnd S/W Version number)
SUN_POSTN:       215.82d {+14h 23m 18s}  -14.24d {-14d 14' 15"}
SUN_DIST:         99.34 [deg]   Sun_angle= 9.7 [hr] (West of Sun)
MOON_POSTN:        6.95d {+00h 27m 47s}   +8.26d {+08d 15' 27"}
MOON_DIST:        85.30 [deg]
MOON_ILLUM:      94 [%]
GAL_COORDS:      271.81,-38.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       21.60,-80.26 [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 Circular #10115
S. McBreen (UCD/MPE) and V. Chaplin (UAH) report on behalf of the Fermi GBM Team:
"At 12:00:28.85 UT on 31 October 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 091031 (trigger 278683230 / 091031500).
The on-ground calculated location, using the GBM trigger data, is RA = 70.6, DEC = -59.1 (J2000 degrees, equivalent to 04 h 42 m, -59 d 06 '), with an uncertainty of 1 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 22 degrees.
The GBM light curve consists of a number of pulses with sub-structure and has a duration (T90) of about 35 s (8-1000 keV). The time-averaged spectrum from T0-0.003 s to T0+36.609 s is best fit by a Band function with Epeak = 503.10 (+47.30/-46.60) keV, alpha = 0.91 +/- 0.04, and beta = -2.34 (+0.19/-0.31) (CSTAT 674 for 602 d.o.f.).
The event fluence (8-1000 keV) in this time interval is (2.05 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.9 s in the 8-1000 keV band is 7.5 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #10163
F. de Palma (University and INFN Bari), N. Omodei (INFN Pisa), Julie McEnery (NASA/GSFC) and V. Vasileiou (NASA GSFC/UMBC) report on behalf of the Fermi LAT team:
At 12:00:28 (UT) on 31 October 2009 , the Fermi Large Area Telescope (LAT) detected gamma rays from the long GRB 091031, which was triggered and located by the Fermi Gamma-ray Burst Monitor (GBM) (trigger 278683230 / 091031500,GCN 10115). The angle of the GBM best position (RA, Dec= 70.58, -59.08) with respect to the LAT boresight was ~22 degrees at the time of the trigger, which is well inside our field of view.
The Fermi LAT events after the GBM trigger are spatially and temporally correlated with the emission measured by GBM. In the time interval T0-T0+100s using likelihood methods on photons above 100 MeV this burst has a significance of more than 3 sigma; using counting methods the significance is well over 6 sigma in the full energy band (20 MeV - 300 GeV). More than 30 photons above 100 Mev and 2 photons above 1 GeV were observed in the same time interval in an energy dependent ROI centered on the GBM position. The best LAT on-ground localization is found to be (RA, Dec = 71.7, -57.5) with a 90% containment radius of 0.3 deg (statistical; 68% containment radius: 0.2 deg, preliminary systematic error is less than 0.1 deg) which is consistent with the GBM localization.
Further analysis is ongoing.
The point of contact for this burst is Francesco de Palma : francesco.depalma@ba.infn.it
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
This message can be cited.
GCN Circular #10166
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, and D. Svinkin on behalf of Konus-Wind and Konus-RF teams, and T. Cline on behalf of the Konus-Wind team, report:
The long GRB 091031 (Fermi-GBM trigger 278683230/091031500, McBreen and Chaplin, 10115) localized by Fermi-LAT (de Palma et al., GCN 10163) triggered Konus-Wind at T0=3D43232.687s UT (12:00:32.687) and Konus-RF onboard Coronas-Photon s/c at T0=3D43230.291s UT (12:00:30.291).
The burst light curve shows a complex structure with a total duration of ~40 s. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB091031_T43232/
As observed by Konus-Wind the burst had a fluence of (1.94 =B1 0.2)x10-5 erg/cm2, and a 256-ms peak flux measured from T0 + 4.608s of (2.74 =B1 0.35)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range).
The time-integrated spectrum of the burst (from T0 to T0+41.216 s) is well fitted in the 20 keV - 2 MeV range by a power law with exponential cutoff model, for which: alpha =3D 0.93 (-0.08, +0.09), and Epeak =3D 477 (-91, +138) keV, Chi2 =3D 31/58 dof.
Fitting by a GRB (Band) model yiels the same alpha and Epeak values with high energy spectral index beta of -9.4 (<-2.4)
All the quoted values are preliminary. All the quoted errors are at the 90% confidence level.

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Jochen Greiner, last update: 13-Nov-2009 [Disclaimer]