Gamma-ray Burst 091018

(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 18 Oct 09 20:57:26 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.211d {+02h 08m 51s} (J2000),
                  32.290d {+02h 09m 10s} (current),
                  31.803d {+02h 07m 13s} (1950)
GRB_DEC:         -57.526d {-57d 31' 34"} (J2000),
                 -57.480d {-57d 28' 48"} (current),
                 -57.763d {-57d 45' 44"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2091 [cnts]    Image_Peak=200 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   120     E_range: 15-50 keV
BKG_INTEN:       34137 [cnts]
BKG_TIME:        74882.81 SOD {20:48:02.81} UT
BKG_DUR:         8 [sec]
GRB_DATE:        15122 TJD;   291 DOY;   09/10/18
GRB_TIME:        74899.58 SOD {20:48:19.58} UT
GRB_PHI:         107.05 [deg]
GRB_THETA:        15.92 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.71 [sigma]
IMAGE_SIGNIF:    11.47 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +1  +1  +0  +0 +37  +0 
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 53' 58"}
SUN_DIST:        112.26 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.65d {+13h 58m 37s}  -17.36d {-17d 21' 28"}
MOON_DIST:       105.13 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.04,-56.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      350.87,-62.61 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This Notice was delayed by more than 60 sec past the end of the trigger integration interval;  
COMMENTS:        probably due to it occurring during a Malindi downlink session.  
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 = 17.37,-19.98 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:58:10 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.1845d {+02h 08m 44.2s} (J2000),
                  32.2643d {+02h 09m 03.4s} (current),
                  31.7769d {+02h 07m 06.4s} (1950)
GRB_DEC:         -57.5475d {-57d 32' 50.9"} (J2000),
                 -57.5014d {-57d 30' 04.8"} (current),
                 -57.7836d {-57d 47' 01.1"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       24 [cnts]
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74960.49 SOD {20:49:20.49} UT,   60.9 [sec] since BAT Trigger Time
CENTROID_X:      297.67,  raw= 298  [pixels]
CENTROID_Y:      275.81,  raw= 276  [pixels]
ROLL:            170.97 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -52.30
GRB_POS_XRT_Z:   -10.90
IMAGE_URL:       sw00373172000msxps_rw.img
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 53' 58"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.66d {+13h 58m 38s}  -17.36d {-17d 21' 37"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.08,-56.66 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.82,-62.61 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:58:15 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.1845d {+02h 08m 44.2s} (J2000),
                  32.2643d {+02h 09m 03.4s} (current),
                  31.7769d {+02h 07m 06.4s} (1950)
GRB_DEC:         -57.5475d {-57d 32' 50.9"} (J2000),
                 -57.5014d {-57d 30' 04.8"} (current),
                 -57.7836d {-57d 47' 01.1"} (1950)
GRB_ERROR:       6.5 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       24 [cnts]
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74960.49 SOD {20:49:20.49} UT,   60.9 [sec] since BAT Trigger Time
CENTROID_X:      297.67,  raw= 298  [pixels]
CENTROID_Y:      275.81,  raw= 276  [pixels]
ROLL:            170.97 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -52.30
GRB_POS_XRT_Z:   -10.90
IMAGE_URL:       sw00373172000msxps_rw.img
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 53' 58"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.66d {+13h 58m 39s}  -17.36d {-17d 21' 38"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.08,-56.66 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.82,-62.61 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:58:00 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.1845d {+02h 08m 44.27s} (J2000),
                  32.2643d {+02h 09m 03.43s} (current),
                  31.7769d {+02h 07m 06.46s} (1950)
GRB_DEC:         -57.5475d {-57d 32' 50.9"} (J2000),
                 -57.5014d {-57d 30' 04.8"} (current),
                 -57.7836d {-57d 47' 01.1"} (1950)
GRB_ERROR:       6.6 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       4.40e-10 [erg/cm2/sec]
GRB_SIGNIF:      4.89 [sigma]
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74960.49 SOD {20:49:20.49} UT,   60.9 [sec] since BAT Trigger Time
TAM[0-3]:        327.63 237.23 261.44 243.50
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 53' 58"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.66d {+13h 58m 38s}  -17.36d {-17d 21' 35"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.08,-56.66 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.82,-62.61 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.51 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:59:07 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.211d {+02h 08m 51s} (J2000),
                  32.290d {+02h 09m 10s} (current),
                  31.803d {+02h 07m 13s} (1950)
GRB_DEC:         -57.526d {-57d 31' 34"} (J2000),
                 -57.480d {-57d 28' 48"} (current),
                 -57.763d {-57d 45' 44"} (1950)
GRB_DATE:        15122 TJD;   291 DOY;   09/10/18
GRB_TIME:        74899.58 SOD {20:48:19.58} UT
TRIGGER_INDEX:   120
GRB_PHI:         107.05 [deg]
GRB_THETA:        15.92 [deg]
DELTA_TIME:      -75.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     29.71 [sigma]
IMAGE_SIGNIF:    11.47 [sigma]
LC_URL:          sw00373172000msb.lc
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 00"}
SUN_DIST:        112.25 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.67d {+13h 58m 41s}  -17.36d {-17d 21' 47"}
MOON_DIST:       105.12 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.04,-56.67 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      350.87,-62.61 [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 = 17.37,-19.98 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:59:19 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.211d {+02h 08m 51s} (J2000)
POINT_DEC:       -57.541d {-57d 32' 28"} (J2000)
POINT_ROLL:      170.971d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74968.23 SOD {20:49:28.23} UT,   68.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.579
N_STARS:         41
X_OFFSET:        360 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1319 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0068.fits
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 00"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.67d {+13h 58m 41s}  -17.36d {-17d 21' 50"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.05,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.85,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:59:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.211d {+02h 08m 51s} (J2000)
POINT_DEC:       -57.541d {-57d 32' 28"} (J2000)
POINT_ROLL:      170.971d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74968.23 SOD {20:49:28.23} UT,   68.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.579
N_STARS:         41
X_OFFSET:        360 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1319 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0068.fits
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 00"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.68d {+13h 58m 42s}  -17.37d {-17d 21' 55"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.05,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.85,-62.62 [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 18 Oct 09 21:01:00 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.211d {+02h 08m 51s} (J2000)
POINT_DEC:       -57.541d {-57d 32' 28"} (J2000)
ROLL:            170.971d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74968.23 SOD {20:49:28.23} UT,   68.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277591773
X_OFFSET:        853 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0074.fits
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 01"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.69d {+13h 58m 45s}  -17.37d {-17d 22' 09"}
MOON_DIST:       105.10 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.05,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.85,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:01:18 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.211d {+02h 08m 51s} (J2000)
POINT_DEC:       -57.541d {-57d 32' 28"} (J2000)
ROLL:            170.971d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74968.23 SOD {20:49:28.23} UT,   68.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277591773
X_OFFSET:        853 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0074.fits
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 01"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.69d {+13h 58m 45s}  -17.37d {-17d 22' 12"}
MOON_DIST:       105.10 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.05,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.85,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 20:59:19 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.211d {+02h 08m 51s} (J2000)
POINT_DEC:       -57.541d {-57d 32' 28"} (J2000)
POINT_ROLL:      170.971d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74968.23 SOD {20:49:28.23} UT,   68.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.579
N_STARS:         41
X_OFFSET:        360 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1319 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0068.fits
SUN_POSTN:       203.74d {+13h 34m 58s}   -9.90d {-09d 54' 00"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.67d {+13h 58m 41s}  -17.36d {-17d 21' 50"}
MOON_DIST:       105.11 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.05,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.85,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:05:26 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
ROLL:            170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75180.25 SOD {20:53:00.25} UT,   280.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     277591985
X_OFFSET:        853 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0286.fits
SUN_POSTN:       203.74d {+13h 34m 59s}   -9.90d {-09d 54' 05"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.73d {+13h 58m 55s}  -17.38d {-17d 22' 58"}
MOON_DIST:       105.09 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:05:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
ROLL:            170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75180.25 SOD {20:53:00.25} UT,   280.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     277591985
X_OFFSET:        853 [pixels]
Y_OFFSET:        957 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1013
Y_GRB_POS:       1117
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0286.fits
SUN_POSTN:       203.75d {+13h 34m 59s}   -9.90d {-09d 54' 05"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.73d {+13h 58m 55s}  -17.38d {-17d 23' 02"}
MOON_DIST:       105.09 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:06:16 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.1858d {+02h 08m 44.59s} (J2000),
                  32.2656d {+02h 09m 03.75s} (current),
                  31.7782d {+02h 07m 06.77s} (1950)
GRB_DEC:         -57.5482d {-57d 32' 53.5"} (J2000),
                 -57.5021d {-57d 30' 07.4"} (current),
                 -57.7843d {-57d 47' 03.6"} (1950)
GRB_ERROR:       0.6 [arcsec radius, statistical only]
GRB_MAG:         14.60 +/- 0.14 [mag]
FILTER:          10, White
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  74971.00 SOD {20:49:31.00} UT,   71.4 [sec] since BAT Trigger Time
SUN_POSTN:       203.75d {+13h 34m 59s}   -9.90d {-09d 54' 06"}
SUN_DIST:        112.23 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.74d {+13h 58m 56s}  -17.39d {-17d 23' 08"}
MOON_DIST:       105.08 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:      284.08,-56.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      350.82,-62.61 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The UVOT position is 3.6 arcsec from the XRT position.

GCN Circular #10034
M. Stamatikos (OSU/NASA/GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), W.B Landsman (GSFC), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), M. Perri (ASDC), J. L. Racusin (NASA/GSFC/ORAU) and G. Stratta (ASDC) report on behalf of the Swift Team:
At 20:48:19 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 091018 (trigger=373172). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 32.211, -57.526 which is
```
   RA(J2000) = 02h 08m 51s
   Dec(J2000) = -57d 31` 34``
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single smooth FRED peak a duration of about 10 sec. The peak count rate was ~16000 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 20:49:20.5 UT, 60.9 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 32.18587, -57.54749 which is equivalent to:
```
   RA(J2000)  = 02h 08m 44.61s
   Dec(J2000) = -57d 32' 51.0"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 91 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 in excess of the Galactic value (2.81e+20 cm^-2, Kalberla et al. 2005), with an excess column of 1.4 (+1.00/-0.93) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 4.40e-10 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 68 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7`x2.7` sub-image at
```
  RA(J2000)  =	02:08:44.61 = 32.18588
  DEC(J2000) = -57:32:53.8  = -57.54827
```
with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.8 arc sec. from the center of the XRT error circle. The estimated magnitude is 14.60 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03.
Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT 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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:11:47 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
POINT_ROLL:      170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75759.23 SOD {21:02:39.23} UT,   859.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.583
N_STARS:         119
X_OFFSET:        293 [pixels]
Y_OFFSET:        397 [pixels]
X_MAX:           1732 [pixels]
Y_MAX:           1836 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0859.fits
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 11"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.79d {+13h 59m 09s}  -17.40d {-17d 24' 10"}
MOON_DIST:       105.07 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:11:47 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
POINT_ROLL:      170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75759.23 SOD {21:02:39.23} UT,   859.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.583
N_STARS:         119
X_OFFSET:        293 [pixels]
Y_OFFSET:        397 [pixels]
X_MAX:           1732 [pixels]
Y_MAX:           1836 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0859.fits
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 11"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.79d {+13h 59m 09s}  -17.40d {-17d 24' 10"}
MOON_DIST:       105.07 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 18 Oct 09 21:12:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
POINT_ROLL:      170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75759.23 SOD {21:02:39.23} UT,   859.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.583
N_STARS:         119
X_OFFSET:        293 [pixels]
Y_OFFSET:        397 [pixels]
X_MAX:           1732 [pixels]
Y_MAX:           1836 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00373172000msufc0859.fits
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 11"}
SUN_DIST:        112.24 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.79d {+13h 59m 10s}  -17.40d {-17d 24' 17"}
MOON_DIST:       105.07 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [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 18 Oct 09 21:13:08 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
ROLL:            170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75759.23 SOD {21:02:39.23} UT,   859.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277592564
X_OFFSET:        852 [pixels]
Y_OFFSET:        956 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1012
Y_GRB_POS:       1116
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0865.fits
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 12"}
SUN_DIST:        112.23 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.80d {+13h 59m 12s}  -17.41d {-17d 24' 25"}
MOON_DIST:       105.07 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [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 18 Oct 09 21:13:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     373172,   Seg_Num: 0
POINT_RA:         32.209d {+02h 08m 50s} (J2000)
POINT_DEC:       -57.544d {-57d 32' 37"} (J2000)
ROLL:            170.973d
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75759.23 SOD {21:02:39.23} UT,   859.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     277592564
X_OFFSET:        852 [pixels]
Y_OFFSET:        956 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1012
Y_GRB_POS:       1116
BINNING_INDEX:   1
IM_URL:          sw00373172000msuni0865.fits
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 12"}
SUN_DIST:        112.23 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.80d {+13h 59m 12s}  -17.41d {-17d 24' 28"}
MOON_DIST:       105.07 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.06,-56.66 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      350.84,-62.62 [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:     Sun 18 Oct 09 21:12:55 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     373172,   Seg_Num: 0
GRB_RA:           32.1861d {+02h 08m 44.66s} (J2000),
                  32.2659d {+02h 09m 03.82s} (current),
                  31.7785d {+02h 07m 06.84s} (1950)
GRB_DEC:         -57.5486d {-57d 32' 54.9"} (J2000),
                 -57.5025d {-57d 30' 08.8"} (current),
                 -57.7847d {-57d 47' 05.0"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  15122 TJD;   291 DOY;   09/10/18
IMG_START_TIME:  75052.00 SOD {20:50:52.00} UT,   152.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       203.75d {+13h 35m 00s}   -9.90d {-09d 54' 12"}
SUN_DIST:        112.23 [deg]   Sun_angle= 11.4 [hr] (West of Sun)
MOON_POSTN:      209.80d {+13h 59m 11s}  -17.41d {-17d 24' 22"}
MOON_DIST:       105.06 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      284.08,-56.66 [deg] galactic lon,lat of the burst
ECL_COORDS:      350.82,-62.61 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
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:        This position was enhanced using UVOT field astrometry

GCN Circular #10036
B. E. Schaefer (Louisiana State) and S. B. Pandey (U Mich), report on behalf of the ROTSE collaboration:
ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, responded to GRB 091018 (Swift trigger 373172, Stamatikos et al., GCN 10034). The first image was at 20:57:36.1 UT, 556.6 s after the burst (11.1 s after the GCN notice time). The unfiltered images are calibrated relative to USNO A2.0. We detect a new object, not visible in the DSS (second epoch), with coordinates:
02:08:44.6 -57:32:53.6 (J2000),
with positional uncertainty of 1" or better
```
start UT    	mag     mlim(of image)
----------------------------------
20:57:36.1     15.4     16.4 
```
With this, we confirm the optical afterglow reported in GCN 10034 as a UVOT detection. The source is rapidly fading. A jpeg image is available at http://www.rotse.net/images/gsb373172_3c01_img.jpg Note that the object numbered 14 (in the lower of the two circles) is the candidate in question.
Continuing observations are in progress.
GCN Circular #10037
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1175 s of XRT Photon Counting mode data and 2 UVOT images for GRB 091018, 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 = 32.18588, -57.54825 which is equivalent to:
```
RA (J2000): 02h 08m 44.61s
Dec (J2000): -57d 32' 53.7"
```
with an uncertainty of 1.7 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 #10038
Hsiao-Wen Chen, Jennifer Helsby (UChicago), Stephen Shectman, Ian Thompson, Jeffrey Crane (Carnegie Observatory) report on behalf of a larger collaboration:
"We observed the afterglow of GRB091018 reported by Stamatikos et al. (GCN 10034) and confirmed by Schaefer et al. (GCN10036) using the MagE echellette spectrograph on the Magellan Clay Telescope. The observations started at UT 00:28 on October 19, 2009, ~ 3.5 hours after the inital trigger. We obtained 2x900s exposures. Our preliminary reduction shows that the afterglow spectrum displays strong absorption transitions due to MgII, FeII, MnII at redshift z=0.971, which we tentatively identify as the host redsdhift of the GRB.
Further analysis is underway.
This message may be cited."
GCN Circular #10039
R. Filgas, T. Kruehler, A. Yoldas (all MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching), report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started follow-up observations of GRB 091018 (Stamatikos et al. 2009, GCN 10034) on October 18, at 23:47 UTC (~4 hrs after the burst).
For the afterglow candidate reported by Stamatikos et al. we estimate the following preliminary magnitudes (in the AB system):
```
g'= 19.061 +/- 0.010
r'= 18.853 +/- 0.007
i'= 18.732 +/- 0.013
z'= 18.70  +/- 0.10
J = 18.3   +/- 0.1
H = 18.2   +/- 0.1
K = 17.9   +/- 0.1
```
calibrated against GROND zeropoints.
GCN Circular #10040
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), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 091018 (trigger #373172) (Stamatikos, et al., GCN Circ. 10034). The BAT ground-calculated position is RA, Dec = 32.191, -57.546 deg, which is
```
   RA(J2000)  =  02h 08m 45.9s 
   Dec(J2000) = -57d 32' 45.0" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 84%.
The mask-weighted light curve shows the FRED peak starting at ~T-5 sec, peaking at T+1.1 sec, and ending at ~T+20 sec. T90 (15-350 keV) is 4.4 +- 0.6 sec (estimated error including systematics).
The time-averaged spectrum from T-0.3 to T+7.7 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.77 +- 0.24, and Epeak of 19.2 +18,-11 keV (chi squared 40.01 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.80 sec in the 15-150 keV band is 10.3 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.30 +- 0.06 (chi squared 52.2 for 57 d.o.f.). 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/373172/BA/
GCN Circular #10041
W.B. Landsman (NASA/GSFC) and M. Stamatikos (OSU/NASA/GSFC) report on =20 behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 091018 =20 69s after the BAT trigger (Stamatikos et al., GCN 10034). The =20 afterglow is well-detected in all seven UVOT filters at the position=20 reported by Stamatikos et al. The initial magnitudes are as follows:
```
Filter    T_start(s) Exp(s)      Mag
white         69    147     14.57 =B1 0.012
white        860    147     16.48 =B1 0.018

u            281    246     15.07 =B1 0.017
u           6911    197     18.04 =B1 0.08

v            610     19     16.4 =B1 0.14
b            536     19     16.4 =B1 0.08
uvw1         660     20     15.9 =B1 0.12
uvm2         635     20     15.7 =B1 0.16
uvw2         586     20     16.1 =B1 0.15
```
The detection in the uvw2 filter indicates a redshift less than z = 1.1, consistent with the value of z=3D 0.971 reported by the Magellan group (Chen et al., GCN 10038).
The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) =3D 0.029 in the direction of the burst (Schlegel et al. 1998). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
GCN Circular #10042
A. de Ugarte Postigo (OAB-INAF), P. Goldoni (APC/Univ. Paris 7 and SAp/CEA), C.C. Thoene (OAB-INAF), N. Tanvir (Univ. Leicester), P. Jakobsson (Univ. of Iceland), S.D. Vergani (APC/Univ. Paris 7), H. Flores (Paris Obs.) D. Malesani (DARK/NBI), A. Levan (Univ. Warwick) and J.P.U. Fynbo (DARK/NBI) report on behalf of the X-shooter GRB collaboration:
X-shooter observed the afterglow of GRB 091018 (Stamatikos et al. CGN 10034) starting at 23:58 UT of the 18th Oct 2009. The observation consisted of 4 x 600s exposures, having a mean epoch of October 19.0148 UT, 3.53 hours after the burst. In the spectra we detect the continuum in the complete range from 3000 to 24800 Angstroms. On a preliminary analysis we find several absorption features including AlII (1670), AlIII (1854, 1862), FeII (2260, 2344, 2374, 2382, 2586, 2600) MnII (2576, 2594, 2606), MgII (2797, 2803), MgI (2852), CaII (3934, 3969) at a common redshift of 0.9710 +/- 0.0003, consistent with the observation reported by Chen et al. (GCN 10038). There is also a tentative detection of [OII], [OIII] and H-alpha emission lines from the host galaxy at the same redshift. Further analysis is ongoing.
We thank the ESO observing staff, in particular A. Smette, C. Martayan and C. Cid.
GCN Circular #10043
A. de Ugarte Postigo (INAF-OAB), P. Kubanek (U. Valencia, IAA-CSIC), M. Jelinek, A.J. Castro-Tirado, J. Gorosabel, R. Cunniffe, S. Guziy (IAA-CSIC), B.A. Allen (Vintage Lane Obs.) and P. Yock (Auckland Univ.) report:
We have observed the afterglow of GRB 091018 (Stamatikos et al. CGN 10034) with the 0.6m Yock-Allen telescope (BOOTES-3) located in Blenheim (New Zealand). A combination of 21x30s unfiltered images with mean epoch Oct. 19.625 UT (18.2 hours after the burst) shows the afterglow at a magnitude of R=20.0+/-0.3. The photometry has been obtained using as comparison 5 USNO-B1.0 stars. This magnitude implies a rough decay slope of alpha = 0.7 +/- 0.2 (with F ~ t^(-alpha)) as compared to the values of Filgas et al. (GCN 10039). Further analysis is ongoing.
GCN Circular #10044
Z. Cano (Liverpool JMU), C. Guidorzi (U. Ferrara), D. Bersier, N.R. Clay, S. Kobayashi, A. Melandri, C.G. Mundell, C.J. Mottram, R.J. Smith, I.A. Steele (Liverpool JMU), A. Gomboc (U. Ljubljana), N.R. Tanvir (U. Leicester) on behalf of a larger collaboration report:
The Faulkes Telescope South (Australia) observed the field of GRB 091018 (Swift trigger=373172, Stamatikos et al., GCN 10034) on 2009 October 19.
We clearly detect the afterglow candidate (Schaefer & Pandey, GCN 10036; Chen et al., GCN 10038; Filgas et al., GCN 10039; Landsman & Stamatikos, GCN 10041; A. de Ugarte Postigo et al., GCN 10042 & GCN 10043) in the Ri' filters with the following magnitudes:
```
Filter   mag        merr      T-To (hr)
---------------------------------------
I       19.73      0.06      15.17
I       20.13      0.08      20.95
R       19.67      0.06      15.72
R       20.06      0.08      20.95
```
As calibrated against nearby USNO object 0342-0026807 (R2 = 16.34, I2 = 16.22).
From the images obtained on FTS we derive preliminary decay rates of: alpha_I = 1.1 +/- 0.3 & alpha_R = 1.2 +/- 0.3.
GCN Circular #10045
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, and D. Svinkin on behalf of the Konus-RF team, report:
The soft GRB 091018 (Swift-BAT trigger #373172: Stamatikos et al., GCN 10034, Markwardt et al., GCN 10040) triggered Konus-RF at T0=74900.651 s UT (20:48:20.651).
The burst light curve shows a single pulse with a duration of ~5 s.
As observed by Konus-RF the burst had a fluence of 1.44(-0.16, +0.19)x10^-6 erg/cm2, and a 256-ms peak flux measured from T0-0.280 s of 4.32(-0.94, +0.97)x10^-7 erg/cm2/s (both in the 20 keV - 1 MeV energy range).
The time-integrated spectrum of the burst (from T0-2s to T0+3s) is well fitted (in the 10 keV - 1 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with alpha = -1.53(-0.39, +0.59), and Ep = 28(-16, +10) keV (chi2 = 83.4/94 dof). Fitting by GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.44 (chi2 = 81.7/93 dof).
All the quoted values are preliminary. All the quoted errors are at the 90% confidence level.
Assuming z = 0.971 (Chen et al., GCN 10038) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release E_iso ~3.7x10^51 erg, the peak luminosity (L_iso)_max ~2.2x10^51 erg/s, and Ep_rest ~55 keV.
The Konus-RF light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB091018_T74900/KRF/
GCN Circular #10046
A. LaCluyze, D. Reichart, J. Haislip, K. Ivarsen, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report:
Skynet observed the Swift/BAT localization of GRB 091018 (Stamatikos et al., GCN 10034) with four of the 16" PROMPT telescopes at CTIO beginning 3.0 hours after the the trigger in BVRI.
We detect the afterglow (Stamatikos et al., GCN 10034) in all filters.
Between 3.0 and 12.3 hours after the trigger, the afterglow faded with periods of rebrightening (1) beginning around 5 hours and peaking around 6 hours, and (2) beginning around 8 hours and peaking around 9 hours.
Overall, if fitted with a power law, the afterglow faded with a power-law index of about -0.95 in BVR but only about -0.65 in I. I - R brightened by about 0.45 mag over the course of 12 hours.
At 12.3 hours after the trigger, the afterglow's magnitude was R = 19.82 +0.14 -0.12 (statistical) +/- 0.56 (systematic; calibrated to 115 USNO B1 stars).
Skynet's most recent BVRI light curve, calibrated to USNO B1 and NOMAD stars, can be found here:
http://skynet.unc.edu/grb/grb091018.png
GCN Circular #10047
K. Motohara, M. Konishi, K. Toshikawa, N. Mitani, T. Minezaki, S. Koshida, D. Kato, Y. Yoshii$B!!(B(University of Tokyo), Y. Ita (National Astronomical Observatory of Japan) on behalf of the TAO project team:
We report the NIR imaging observation of GRB 091018 carried out from October 19 2:09 to 2:57 (UTC), using NIR Camera ANIR (Motohara et al. 2008, Proc. SPIE 7014, 70142T) mounted on the 1.0m miniTAO telescope (Sako et al. 2008, Proc. SPIE7012, 70122T) at the University of Tokyo Atacama Observatory on the summit of Co. Chajnantor (5640m altitude) in the northern Chile.
The preliminary magnitudes (AB system) for the afterglow candidate reported by Stamatikos et al. 2009 (GCN 10034) are ;
```
Y  = 18.98 +/- 0.14
J  = 19.40 +/- 0.19
H  = 18.93 +/- 0.17
Ks = 18.22 +/- 0.07
```
which are taken with the MKO filter system.
GCN Circular #10055
G. Stratta (ASDC) reports on behalf of the Swift-XRT team:
The Swift-XRT began observing GRB 091018 (trigger=373172) on 2009-10-18 at 20:49:20.5 UT, 60.9 seconds after the BAT trigger (Stamatikos et al., GCN Circ. 7226). The data have been taken in Windowed Timing (WT) mode from T + 67 s to T + 144 s and in Photon Counting (PC) mode later on.
Enhanced position of the detected, bright X-ray afterglow was given by Osborne et al. (GCN Circ. 10037)
The X-ray light curve from T + 67 s to T + 53.3 ks is well fit by a broken power law model (chi^2 = 115 for 128 degrees of freedom) with a temporal break at tb = T + (500 +/- 100) s and decay indices alpha1 = -0.4 +/- 0.1 and alpha2 = -1.17 +/- 0.03 before and after the break, respectively.
The 0.3-10 keV spectrum from T + 156 s to T + 7.1 ks is well fit by an absorbed power law (reduced chi2 of 1.0, with 50 degrees of freedom). The best fit photon index is 1.9 +/- 0.1, with an hydrogen column density at the burst rest frame (z=0.971, Hsiao-Wen Chen et al. GCN Circ.10038) of NHz = (1.4 +/- 0.8)e21 cm^-2 in addition to the Galactic column along the line of sight, that is NH = 2.8e20 cm^-2 (Kalberla et al. 2005). Errors are given at 90% confidence level. The observed (unabsorbed) flux in the 0.3-10 keV band is 1.5(1.8)e-10 erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular #10061
A. LaCluyze, D. Reichart, J. Haislip, K. Ivarsen, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report:
Skynet has continued to observed the afterglow (Stamatikos et al., GCN 10034) of GRB 091018 (Stamatikos et al., GCN 10034) with four of the 16" PROMPT telescopes at CTIO in BVRI.
After fading with a power-law index of about -0.95 in BVR between 3 and 12 hours after the trigger (LaCluyze et al., GCN 10046), the afterglow faded with a steeper power-law index of about -1.3 in BR between 12 hours and 1.5 days after the trigger, which is consistent with the findings of Cano et al. (GCN 10044).
However, between 1.5 days and 3.4 days after the trigger, the afterglow faded with a shallower power-law index of about -0.9 in R.
The I - R color of the afterglow, which brightened by about 0.45 mag between 3 and 12 hours after the trigger (LaCluyze et al., GCN 10046), has faded by about 0.1 +/- 0.3 mag between 12 hours and 3.4 days after the trigger, which is consistent with no additional color change, but the uncertainty is large.
At 3.4 days after the trigger, the afterglow's magnitude was R = 22.27 +0.28 -0.23 (statistical) +/- 0.56 (systematic; calibrated to 115 USNO B1 stars).
Skynet's most recent BVRI light curve, calibrated to USNO B1 and NOMAD stars, can be found here:
http://skynet.unc.edu/grb/grb091018.png
Continued observations with larger telescopes are encouraged.
GCN Circular #10110
B. E. Cobb (UC Berkeley) reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 091018 (GCN 10034, Stamatikos et al.) over several epochs, starting ~3.9 hours post-burst. For the first epoch, several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIJK and 120s in each of H and V. For later epochs, total summed exposure times amounted to 15 minutes in I and V and 12 minutes in J and K.
At a mid-exposure time of 2009-10-19 00:57 UT (4.1 hrs post-burst), the GRB afterglow (e.g. GCN 10034, Stamatikos et al., GCN 10036, Schaefer et al., GCN 10039, Filgas et al.) is detected with the following magnitudes:
```
B = 19.59 +/- 0.04
V = 19.27 +/- 0.05
R = 18.88 +/- 0.04
I = 18.44 +/- 0.04
J = 18.0 +/- 0.2
H = 17.1 +/- 0.2
K = 16.1 +/- 0.2
```
Between 4.1 hrs and 33.0 hrs post-burst, the GRB afterglow fades with a decay rate of approximately alpha = -1.3 (where afterglow flux is proportional to t^alpha).
```
time
post-burst      I-band magnitude
4.1 hrs         18.44 +/- 0.04
5.5 hrs         18.82 +/- 0.04
8.0 hrs         19.26 +/- 0.04
9.7 hrs         19.49 +/- 0.05
28.6 hrs        21.04 +/- 0.06
33.0 hrs        21.27 +/- 0.08
```
(Optical photometry is calibrated against Landolt standard stars and IR photometry is calibrated against 2MASS stars in the field.)
GCN Circular #10112
A. LaCluyze, D. Reichart, J. Haislip, K. Ivarsen, R. Egger, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report:
Skynet has continued to observed the afterglow (Stamatikos et al., GCN 10034) of GRB 091018 (Stamatikos et al., GCN 10034) with two of the 16" PROMPT telescopes at CTIO in RI (LaCluyze et al., GCNs 10046, 10061).
Between 3.2 and 7.5 days after the trigger, the light curve is consistent with constant emission, which suggests that we are observing the host galaxy.
If so, we measure its brightness to be:
R = 22.30 +/- 0.11 (statistical) +/- 0.56 (systematic; calibrated to 115 USNO B1 stars).
and
I = 21.78 +/- 0.16 (statistical) +/- 0.54 (systematic; calibrated to 67 USNO B1 stars).
1203.4265 from 21 Mar 12
K. Wiersema et al.: Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: Polarisation evolution
[Abridged] A number of phenomena have been observed in GRB afterglows that defy explanation by simple versions of the standard fireball model, leading to a variety of new models. Polarimetry can be a major independent diagnostic of afterglow physics, probing the magnetic field properties and internal structure of the GRB jets. In this paper we present the first high quality multi-night polarimetric light curve of a Swift GRB afterglow, aimed at providing a well calibrated dataset of a typical afterglow to serve as a benchmark system for modelling afterglow polarisation behaviour. In particular, our dataset of the afterglow of GRB 091018 (at redshift z=0.971) comprises optical linear polarimetry (R band, 0.13 - 2.3 days after burst); circular polarimetry (R band) and near-infrared linear polarimetry (Ks band). We add to that high quality optical and near-infrared broadband light curves and spectral energy distributions as well as afterglow spectroscopy. The linear polarisation varies between 0 and 3%, with both long and short time scale variability visible. We find an achromatic break in the afterglow light curve, which corresponds to features in the polarimetric curve. We find that the data can be reproduced by jet break models only if an additional polarised component of unknown nature is present in the polarimetric curve. We probe the ordered magnetic field component in the afterglow through our deep circular polarimetry, finding P_circ < 0.15% (2 sigma), the deepest limit yet for a GRB afterglow, suggesting ordered fields are weak, if at all present. Our simultaneous R and Ks band polarimetry shows that dust induced polarisation in the host galaxy is likely negligible.

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Jochen Greiner, last update: 21-Mar-2012 [Disclaimer]