Gamma-ray Burst 090418

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:07:55 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.334d {+17h 57m 20s} (J2000),
                 269.419d {+17h 57m 40s} (current),
                 268.877d {+17h 55m 30s} (1950)
GRB_DEC:         +33.409d {+33d 24' 31"} (J2000),
                 +33.408d {+33d 24' 29"} (current),
                 +33.413d {+33d 24' 47"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4549 [cnts]    Image_Peak=163 [image_cnts]
TRIGGER_DUR:     1.024 [sec]
TRIGGER_INDEX:   149     E_range: 25-100 keV
BKG_INTEN:       27616 [cnts]
BKG_TIME:        40043.33 SOD {11:07:23.33} UT
BKG_DUR:         8 [sec]
GRB_DATE:        14939 TJD;   108 DOY;   09/04/18
GRB_TIME:        40060.22 SOD {11:07:40.22} UT
GRB_PHI:           1.77 [deg]
GRB_THETA:        46.32 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.94 [sigma]
IMAGE_SIGNIF:    8.16 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -2  +0  +0 +26  +0
SUN_POSTN:        26.53d {+01h 46m 07s}  +10.96d {+10d 57' 29"}
SUN_DIST:        105.59 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.55d {+20h 42m 13s}  -17.99d {-17d 59' 39"}
MOON_DIST:        64.67 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.23, 25.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      268.98, 56.85 [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 = 281.99,14.75 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:        GCN/SIMBAD_NED NOTICE
NOTICE_DATE:  Sat Apr 18 11:08:02 UTC 2009
NOTICE_TYPE:  Swift-BAT Position search
TRIGGER_NUM:  349510
RA:           269.3337 (J2000)
DEC:          33.4087 (J2000)

SIMBAD search for BAT_RA,Dec=269.3337,33.4087,radius=10.0arcmin

Num   RA         Dec                    Name                        Type  Num_Pub  Distance

 1 269.35129458  33.40083778                   HD 163948                *   5  
    1.00
 2 269.35129458  33.40083778                   HD 163948                *   5  
    1.00
 3 269.28245042  33.33299611              TYC 2612-413-1               IR   0  
    5.22
 4 269.40639917  33.47747111             TYC 2612-1139-1               IR   0 
   5.50
 5 269.21983917  33.29748306              TYC 2612-713-1               IR   0  
    8.78

NED search for BAT_RA,Dec=269.3337,33.4087,radius=10.0arcmin

Num    RA           Dec       Name                           Type      Distance

Num    RA           Dec       Name                           Type      Distance

 1   269.299458    33.514972  2MASX J17571188+3330541       , IrS      6.60
 2   269.340167    33.293833  NVSS J175721+331737           , RadioS   6.90
 3   269.450917    33.503417  NVSS J175748+333012           , RadioS   8.20
 4   269.513208    33.429694  NVSS J175803+332546           , RadioS   9.10
 5   269.284750    33.255028  2MASX J17570831+3315180       , IrS      9.50
 6   269.160833    33.325889  NVSS J175638+331933           , RadioS   10.00

GCN NOTICE

TITLE:          GCN/INTEGRAL NOTICE
NOTICE_DATE:    Sat 18 Apr 09 11:08:21 UT
NOTICE_TYPE:    INTEGRAL SPI ACS Trigger
TRIGGER_NUM:    5504,   Sub_Num: 0
GRB_INTEN:      9.35 [sigma]
GRB_TIME:       40058.96 SOD {11:07:38.96} UT
GRB_DATE:       14939 TJD;   108 DOY;   09/04/18
COMMENTS:       INTEGRAL SPI_ACS GRB Trigger.
COMMENTS:
+ftp://isdcarc.unige.ch/arc/FTP/ibas/spiacs/2009-04-18T11-07-38.7471-22473-00007-0.lc

GCN NOTICE

TITLE:        GCN/SIMBAD_NED NOTICE
NOTICE_DATE:  Sat Apr 18 11:17:04 UTC 2009
NOTICE_TYPE:  Swift-XRT Position search
TRIGGER_NUM:  349510
RA:           269.3117 (J2000)
DEC:          33.4051 (J2000)

SIMBAD search for XRT_RA,Dec=269.3117,33.4051,radius=1.0arcmin

Num   RA         Dec                    Name                        Type  Num_Pub  Distance



NED search for XRT_RA,Dec=269.3117,33.4051,radius=1.0arcmin

Num    RA           Dec       Name                           Type      Distance

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:09:55 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.3109d {+17h 57m 14.6s} (J2000),
                 269.3959d {+17h 57m 35.0s} (current),
                 268.8540d {+17h 55m 24.9s} (1950)
GRB_DEC:         +33.4039d {+33d 24' 14.0"} (J2000),
                 +33.4033d {+33d 24' 11.9"} (current),
                 +33.4084d {+33d 24' 30.0"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       36 [cnts]
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40156.32 SOD {11:09:16.32} UT,   96.1 [sec] since BAT Trigger Time
CENTROID_X:      315.91,  raw= 316  [pixels]
CENTROID_Y:      303.53,  raw= 304  [pixels]
ROLL:            65.07 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   13.05
GRB_POS_XRT_Z:   32.08
IMAGE_URL:       sw00349510000msxps_rw.img
SUN_POSTN:        26.53d {+01h 46m 07s}  +10.96d {+10d 57' 31"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.57d {+20h 42m 17s}  -17.99d {-17d 59' 19"}
MOON_DIST:        64.68 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.21, 25.16 [deg] galactic lon,lat of the burst
ECL_COORDS:      268.95, 56.84 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:10:03 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.3109d {+17h 57m 14.6s} (J2000),
                 269.3959d {+17h 57m 35.0s} (current),
                 268.8540d {+17h 55m 24.9s} (1950)
GRB_DEC:         +33.4039d {+33d 24' 14.0"} (J2000),
                 +33.4033d {+33d 24' 11.9"} (current),
                 +33.4084d {+33d 24' 30.0"} (1950)
GRB_ERROR:       5.4 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       36 [cnts]
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40156.32 SOD {11:09:16.32} UT,   96.1 [sec] since BAT Trigger Time
CENTROID_X:      315.91,  raw= 316  [pixels]
CENTROID_Y:      303.53,  raw= 304  [pixels]
ROLL:            65.07 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   13.05
GRB_POS_XRT_Z:   32.08
IMAGE_URL:       sw00349510000msxps_rw.img
SUN_POSTN:        26.53d {+01h 46m 07s}  +10.96d {+10d 57' 31"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.57d {+20h 42m 17s}  -17.99d {-17d 59' 17"}
MOON_DIST:        64.68 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.21, 25.16 [deg] galactic lon,lat of the burst
ECL_COORDS:      268.95, 56.84 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:09:46 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.3109d {+17h 57m 14.61s} (J2000),
                 269.3959d {+17h 57m 35.00s} (current),
                 268.8540d {+17h 55m 24.95s} (1950)
GRB_DEC:         +33.4039d {+33d 24' 14.0"} (J2000),
                 +33.4033d {+33d 24' 11.9"} (current),
                 +33.4084d {+33d 24' 30.0"} (1950)
GRB_ERROR:       5.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.05e-09 [erg/cm2/sec]
GRB_SIGNIF:      6.00 [sigma]
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40156.32 SOD {11:09:16.32} UT,   96.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.70 237.23 261.54 243.48
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        26.53d {+01h 46m 07s}  +10.96d {+10d 57' 31"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.57d {+20h 42m 17s}  -17.99d {-17d 59' 20"}
MOON_DIST:        64.68 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.21, 25.16 [deg] galactic lon,lat of the burst
ECL_COORDS:      268.95, 56.84 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.
COMMENTS:        The XRT position is 1.18 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:11:15 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.334d {+17h 57m 20s} (J2000),
                 269.419d {+17h 57m 40s} (current),
                 268.877d {+17h 55m 30s} (1950)
GRB_DEC:         +33.409d {+33d 24' 31"} (J2000),
                 +33.408d {+33d 24' 29"} (current),
                 +33.413d {+33d 24' 47"} (1950)
GRB_DATE:        14939 TJD;   108 DOY;   09/04/18
GRB_TIME:        40060.22 SOD {11:07:40.22} UT
TRIGGER_INDEX:   149
GRB_PHI:           1.77 [deg]
GRB_THETA:        46.32 [deg]
DELTA_TIME:      71.00 [sec]
TRIGGER_DUR:     1.024 [sec]
SOLN_STATUS:     0x3
RATE_SIGNIF:     16.94 [sigma]
IMAGE_SIGNIF:    8.16 [sigma]
LC_URL:          sw00349510000msb.lc
SUN_POSTN:        26.53d {+01h 46m 07s}  +10.96d {+10d 57' 32"}
SUN_DIST:        105.59 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.58d {+20h 42m 20s}  -17.98d {-17d 59' 05"}
MOON_DIST:        64.68 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.23, 25.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      268.98, 56.85 [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 = 281.99,14.75 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:16:58 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     349510,   Seg_Num: 0
GRB_RA:          269.3117d {+17h 57m 14.80s} (J2000),
                 269.3967d {+17h 57m 35.20s} (current),
                 268.8548d {+17h 55m 25.14s} (1950)
GRB_DEC:         +33.4051d {+33d 24' 18.3"} (J2000),
                 +33.4045d {+33d 24' 16.2"} (current),
                 +33.4096d {+33d 24' 34.3"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40283.00 SOD {11:11:23.00} UT,   222.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 37"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.63d {+20h 42m 31s}  -17.97d {-17d 58' 06"}
MOON_DIST:        64.70 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.16 [deg] galactic lon,lat of the burst
ECL_COORDS:      268.95, 56.84 [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.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:15:06 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.407d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.068d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40220.33 SOD {11:10:20.33} UT,   160.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.428
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           2047 [pixels]
Y_MAX:           2047 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00349510000msufc0160.fits
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 35"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.61d {+20h 42m 27s}  -17.97d {-17d 58' 25"}
MOON_DIST:        64.69 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:26:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.406d {+33d 24' 23"} (J2000)
ROLL:            65.069d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40920.19 SOD {11:22:00.19} UT,   860.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     261746524
X_OFFSET:        742 [pixels]
Y_OFFSET:        894 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       902
Y_GRB_POS:       1054
BINNING_INDEX:   1
IM_URL:          sw00349510000msuni0864.fits
SUN_POSTN:        26.54d {+01h 46m 10s}  +10.96d {+10d 57' 46"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.71d {+20h 42m 50s}  -17.94d {-17d 56' 26"}
MOON_DIST:        64.72 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [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:     Sat 18 Apr 09 11:15:06 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.407d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.068d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40220.33 SOD {11:10:20.33} UT,   160.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.428
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           2047 [pixels]
Y_MAX:           2047 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00349510000msufc0160.fits
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 35"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.61d {+20h 42m 27s}  -17.97d {-17d 58' 25"}
MOON_DIST:        64.69 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:16:29 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.407d {+33d 24' 23"} (J2000)
ROLL:            65.068d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40220.33 SOD {11:10:20.33} UT,   160.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     261745825
X_OFFSET:        743 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       903
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00349510000msuni0165.fits
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 37"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.63d {+20h 42m 30s}  -17.97d {-17d 58' 11"}
MOON_DIST:        64.70 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [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:     Sat 18 Apr 09 11:26:17 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.406d {+33d 24' 23"} (J2000)
ROLL:            65.069d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40920.19 SOD {11:22:00.19} UT,   860.0 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     261746524
X_OFFSET:        742 [pixels]
Y_OFFSET:        894 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       902
Y_GRB_POS:       1054
BINNING_INDEX:   1
IM_URL:          sw00349510000msuni0864.fits
SUN_POSTN:        26.54d {+01h 46m 10s}  +10.96d {+10d 57' 45"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.71d {+20h 42m 49s}  -17.94d {-17d 56' 31"}
MOON_DIST:        64.72 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [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 Circular #9148
R. Chornock, S. B. Cenko, W. Li, and A. V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team:
The Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory automatically slewed to the position of GRB 090418 and discovered a new new point source not present in the DSS at coordinates (J2000): 17:57:15.17 +33:24:21.1 at an unfiltered magnitude of approximately 15.8 at UT=11:10:57. Further observations are in progress.
GCN Circular #9149
V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), P.A. Curran (MSSL-UCL), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. Mao (INAF-OAB), P. T. O'Brien (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Perri (ASDC), B. A. Rowlinson (U Leicester), B. Sbarufatti (INAF-IASFPA), G. Tagliaferri (INAF-OAB), T. N. Ukwatta (GSFC/GWU), L. Vetere (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:
At 11:07:40 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090418 (trigger=349510). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 269.334, +33.409 which is
```
   RA(J2000)  =  17h 57m 20s
   Dec(J2000) = +33d 24' 31"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two main peaks with a duration of about 70 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~45 sec after the trigger.
The XRT began observing the field at 11:09:16.3 UT, 96.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 269.3129, 33.4055 which is equivalent to:
```
   RA(J2000)  = 17h 57m 15.09s
   Dec(J2000) = +33d 24' 19.9"
```
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 64 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 consistent with the Galactic value of 3.55e+20 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 1.05e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 250 seconds with the u filter starting 859 seconds after the BAT trigger. An afterglow candidate has been found in the initial data products at
```
    RA(J2000) =  17:57:15.1 = 269.31458
   Dec(J2000) = +33:24:21   = +33.40583
```
with an estimated uncertainty of 1.0 arcsec (radius, 90% confidence, statistical + systematic). This is 1.1 arcsec from the XRT position. The estimated magnitude is u = 17.3 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04.
Burst Advocate for this burst is V. Mangano (vanessa AT ifc.inaf.it). 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 #9150
F. Yuan (U Mich), B. E. Schaefer (Louisiana State), W. Rujopakarn (Steward), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 090418 (Swift trigger 349510; Mangano et al, GCN 9149) in twilight. The first image was at 11:07:59.2 UT, 19.0 s after the burst (4.2 s after the GCN notice time). The unfiltered images are calibrated relative to USNO B1.0. We detect the optical counterpart at the KAIT and UVOT position (Chornock et al. GCN 9148; Mangano et al, GCN 9149) at the following magnitude and limit:
```
start UT            end UT       mag      magerr    mlim(of image)
-------------------------------------------------------------------------------
11:07:59.2     11:09:06.3     15.9       0.1         17.0
11:09:19.6     11:14:02.1     15.9       0.1         16.8
11:14:11.3     11:25:31.5      -          -          16.7
```

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:24:59 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.406d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.069d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40920.19 SOD {11:22:00.19} UT,   860.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.784
N_STARS:         171
X_OFFSET:        183 [pixels]
Y_OFFSET:        335 [pixels]
X_MAX:           1622 [pixels]
Y_MAX:           1774 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00349510000msufc0859.fits
SUN_POSTN:        26.54d {+01h 46m 09s}  +10.96d {+10d 57' 44"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.70d {+20h 42m 47s}  -17.95d {-17d 56' 44"}
MOON_DIST:        64.72 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:25:42 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.406d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.069d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40920.19 SOD {11:22:00.19} UT,   860.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.784
N_STARS:         171
X_OFFSET:        183 [pixels]
Y_OFFSET:        335 [pixels]
X_MAX:           1622 [pixels]
Y_MAX:           1774 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00349510000msufc0859.fits
SUN_POSTN:        26.54d {+01h 46m 09s}  +10.96d {+10d 57' 45"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.70d {+20h 42m 48s}  -17.94d {-17d 56' 37"}
MOON_DIST:        64.72 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [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:     Sat 18 Apr 09 11:16:10 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.407d {+33d 24' 23"} (J2000)
ROLL:            65.068d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40220.33 SOD {11:10:20.33} UT,   160.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     261745825
X_OFFSET:        743 [pixels]
Y_OFFSET:        895 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       903
Y_GRB_POS:       1055
BINNING_INDEX:   1
IM_URL:          sw00349510000msuni0165.fits
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 36"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.62d {+20h 42m 29s}  -17.97d {-17d 58' 14"}
MOON_DIST:        64.70 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [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 Circular #9151
R. Chornock, S. B. Cenko, C. V. Griffith, M. E. Kislak, I. K. W. Kleiser, and A. V. Filippenko (UC Berkeley) report:
We obtained optical spectra of the afterglow of GRB 090418 (Chornock et al., GCN 9148; Mangano et al., GCN 9149; Yuan et al., GCN 9150) using the Kast spectrograph on the Lick 3-meter telescope. Our first 900s exposure, starting at 11:21:16 UT (only 816s after the burst trigger) reveals a smooth continuum extending to the blue limit of our spectra (3450 Angs). Superposed on the continuum are absorption lines of C IV, Mg II, Fe II, Al II, and Mg I at z=1.608, which we suggest is the redshift of this burst. Further analysis is ongoing.
GCN Circular #9152
B. E. Cobb and J. S. Bloom (UC Berkeley) report:
We observed the optical afterglow of GRB 090418 (Mangano et al., GCN 9149) with the 1.3-m Peters Automated Infrared Imaging Telescope (PAIRITEL) beginning at 2009-04-18 11:34 UT, 26 minutes after the Swift Trigger. We detect the afterglow (Chornock et al., GCN 9148; Yuan et al., GCN 9150) in 651 sec mosaics of 7.8 sec simultaneous individual exposures in the J, H, and Ks filters. Preliminary photometry for the afterglow in these mosaics, with midtime 2009-04-18 11:43 UT (35 minutes post-burst), yields J = 17.7 +- 0.4, H = 17.5 +- 0.4, and Ks = 16.1 +- 0.4 (all magnitudes given in the Vega system), calibrated to the 2MASS system.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:15:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.407d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.068d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40220.33 SOD {11:10:20.33} UT,   160.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.428
N_STARS:         190
X_OFFSET:        0 [pixels]
Y_OFFSET:        0 [pixels]
X_MAX:           2047 [pixels]
Y_MAX:           2047 [pixels]
DET_THRESH:      6
PHOTO_THRESH:    2
SL_URL:          sw00349510000msufc0160.fits
SUN_POSTN:        26.53d {+01h 46m 08s}  +10.96d {+10d 57' 36"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.62d {+20h 42m 29s}  -17.97d {-17d 58' 17"}
MOON_DIST:        64.69 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #9154
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 2594 s of XRT Photon Counting mode data and 5 UVOT images for GRB 090418, 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 = 269.31329, +33.40607 which is equivalent to:
```
RA (J2000): 17h 57m 15.19s
Dec (J2000): +33d 24' 21.8"
```
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, arXiv:0812.3662).
This circular was automatically generated, and is an official product of the Swift-XRT team.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 18 Apr 09 11:24:59 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     349510,   Seg_Num: 0
POINT_RA:        269.320d {+17h 57m 17s} (J2000)
POINT_DEC:       +33.406d {+33d 24' 23"} (J2000)
POINT_ROLL:      65.069d
IMG_START_DATE:  14939 TJD;   108 DOY;   09/04/18
IMG_START_TIME:  40920.19 SOD {11:22:00.19} UT,   860.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.784
N_STARS:         171
X_OFFSET:        183 [pixels]
Y_OFFSET:        335 [pixels]
X_MAX:           1622 [pixels]
Y_MAX:           1774 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw00349510000msufc0859.fits
SUN_POSTN:        26.54d {+01h 46m 09s}  +10.96d {+10d 57' 44"}
SUN_DIST:        105.61 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      310.70d {+20h 42m 47s}  -17.95d {-17d 56' 44"}
MOON_DIST:        64.72 [deg]
MOON_ILLUM:      42 [%]
GAL_COORDS:       59.22, 25.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      268.96, 56.84 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #9157
E. E. Fenimore (LANL), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), V. Mangano (INAF-IASFPA), 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+705 sec from recent telemetry downlinks, we report further analysis of BAT GRB 090418 (trigger #349510) (Mangano, et al., GCN Circ. 9149). The BAT ground-calculated position is RA, Dec = 269.320, 33.407 deg, which is
```
   RA(J2000)  =  17h 57m 16.8s 
   Dec(J2000) = +33d 24' 24.4" 
```
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment). The partial coding was 31%.
The mask-weighted light curve shows two clusters of peaks. The first starts at ~T-8 sec, peaks at ~T+1 sec, and reaches a minimum at T+15 sec. The second cluster peaks at around T+40 sec and returns to background at ~T+70 sec. T90 (15-350 keV) is 56 +- 5 sec (estimated error including systematics).
The time-averaged spectrum from T-8.5 to T+61.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.48 +- 0.07. The fluence in the 15-150 keV band is 4.6 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band is 1.9 +- 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/349510/BA/
GCN Circular #9162
F. Yuan (U Mich) report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 090418A (Swift trigger 349510; Mangano et al, GCN 9149) 19.0 s after the burst, during the gamma-ray emission, and detected the optical counterpart (Yuan et al, GCN 9150). We took 10 5-sec, 10 20-sec and 26 60-sec useful exposures before sunrise. Further analysis of single images revealed an initially rising lightcurve with two subsequent peaks at ~40s (~15.6 mag) and ~130s (~15.4 mag) before the OT dropped below our detection limit.
GCN Circular #9163
Mangano V., Sbarufatti B. (INAF-IASFPA) report on behalf of the Swift XRT Team:
We have analysed the first four orbits of Swift-XRT data obtained from GRB 090418 (trigger 349510; Mangano, et al., GCN Circ. 9149), comprising 116 s taken in Windowed Timing (WT) mode, from T+102 s to T+218 s, and a total exposure of 8.5 ks in Photon Counting (PC) mode from T+219 s to the end of the observation at T+18 ks.
The best position of the X-ray afterglow is the UVOT enhanced XRT position given in Goad, et al., GCN Circ. 9154, that is RA, Dec = 269.31329, +33.40607 which is equivalent to:
```
RA (J2000): 17h 57m 15.19s
Dec (J2000): +33d 24' 21.8"
```
with an uncertainty of 1.7 arcsec (radius, 90% confidence).
The 0.3-10 keV X-ray light curve is well fitted by a doubly broken pawer law, with a initial decay slope alpha1=1.7+/-0.1, a first breal at about T+245 s, an intermediate decay slope alpha2=0.35 -0.1+0.06, a second break at about T+2 ks and a final decay slope alpha3=1.39+/-0.06 If decaying at this rate, the afterglow will reach a count-rate of 6.1E-3 counts/s at T+48h.
The average WT spectrum (corresponding to the initial steep decay phase) is best fitted by an absorbed power-law model, with photon index 2.0+/-0.2, and intrinsic NH=(6+/-3)E21 cm-2 (at the redshift z=1.608, Chornock, et al., GCN circ. 9151) in excess with respect to the galactic absorption value of 3.6E20 cm-2 (Kalberla et al. 2005). The average observed(unabsorbed) flux in the 0.3-10 keV band is 3.5(4.6)E-10 ergs cm-2 s-1. The average PC spectrum of the first orbit (covering the intermediate slowly decaying phase) is well fitted by an absorbed power-law model, with photon index 2.1+/-0.1, intrinsic NH=(1.2+/0.3)E22 cm-2 and average observed(unabsorbed) flux in the 0.3-10 keV band of 1.5(2.2)E-10 ergs cm-2 s-1. Finally, the average PC spectrum from T+4.2 ks to T+18 ks (orbits 2-4) is well fitted by an absorbed power-law model, with photon index 2.0+/-0.1, intrinsic NH=(1.1+/0.2)E22 cm-2 and average observed(unabsorbed) flux in the 0.3-10 keV band of 1.3(1.8)E-11 ergs cm-2 s-1. The average count-rate to observed(unabsorbed) flux conversion factor is 4.5(6.5)E-11. All quoted errors are at 90% confidence level.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00349510.
This circular is an official product of the Swift-XRT team.
GCN Circular #9166
Poonam Chandra (RMC) and Dale A. Frail (NRAO) report on behalf of a larger collaboration:
"We used the Very Large Array to observe the field of view toward the GRB 090418 (GCN 9149) at a frequency of 8.46 GHz on 2009 Apr.19.46 UT. We observed the radio afterglow of the GRB at a position J2000 RA 17:57:15.156, Dec 33:24:20.78 which is 0.39" away from the KAIT optical afterglow position reported by Chornock et al. (GCN 9148). The GRB radio afterglow flux density is 219+/-44 uJy.
The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc."
GCN Circular #9168
D. Kuroda, M. Yoshida, M. Isogai, K. Yanagisawa, Y. Shimizu, S. Nagayama, H. Toda, M. Isogai (NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 090417B (Mangano et al. GCN 9149) with optical three color (g', Rc and Ic) CCD cameras attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory and the 1m telescope of Ishigaki-Jima Observatory.
We started the observation at 13:26:42 UT, 8342s after the burst at Okayama. We could not find a new source at the position of the afterglow (Chornock et al. GCN 9148; Mangano et al. GCN 9149; Goad et al. GCN 9154). 3-sigma upper limits to our observations are the following. We used GSC2.3 catalog for flux calibration.
```
Okayama MITSuME observation
 Mid-UT     Td(day)         EXP-T          g'     Rc     Ic
-------------------------------------------------------------
13:56:41    0.11736    2940s (49x60s)     >19.2  >19.1  >19.0
16:27:25    0.22204    5880s (98x60s)     >20.5  >20.3  >20.1
-------------------------------------------------------------

Ishigaki-Jima 1m telescope observation
 Mid-UT     Td(day)         EXP-T          g'     Rc     Ic
-------------------------------------------------------------
14:48:36    0.15342    3000s (10x300s)    >20.6  >20.9  >19.9
-------------------------------------------------------------
```
GCN Circular #9170
M. Yoshida on behalf of the MITSuME collaboration:
I made a typo in GCN 9168. We observed "GRB 090418 (Mangano et al. GCN 9149)" instead of "GRB 090417B". I apologize for my carelessness.
GCN Circular #9175
S. T. Holland (CRESST/GSFC/USRA) and V. Mangano (INAF-IASFPA) report on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 090418A starting 84 s after the BAT trigger (Mangano, et al. 2009, GCN Circ. 9149). Settled exposures started at T+160 s. The refined UVOT position for the optical afterglow is
```
       RA (J2000) =  17:57:15.17  =  269.31321 (deg)
      Dec (J2000) = +33:24:21.1   =  +33.40585 (deg)
```
with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence, statistical + systematic). Preliminary 3-sigma magnitudes and upper limits are
```
Filter   T_start   T_stop   Exp(s)      Mag  Err
-------------------------------------------------------------
u (fc)       160      410      246    17.31 0.09

v            466      485       19    17.31 0.24
b            415      435       19    18.22 0.25
u            539      559       19    18.55 0.39
uvw1         515      835       19   >18.1        3-sigma UL
uvm2         490      510       19   >17.6        3-sigma UL
uvw2         441      461       19   >18.1        3-sigma UL


uvw1         515   11,831     1337    20.82 0.26
          114,115  131,895     2064   >22.0        3-sigma UL
uvm2         490   18,413     2109   >21.8        3-sigma UL
uvw2         441   16,709     1357   >21.8        3-sigma UL
-------------------------------------------------------------
```
The quoted magnitudes have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.04 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627).
The detection in the uvw1 filter, combined with the lack of a detection in the uvm2 filter, is consistent with this source having a redshift of z = 1.608 (Charnock, et al., 2009, GCN Circ. 9151).
GCN Circular #9179
E. Pavlenko, V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the error box of Swift GRB 090418A in series of BVRI exposures on Apr. 18 with Shajn telescope of CrAO. We detect the afterglow (Chornock et al., GCN 9148, Mangano et al., GCN 9149) in all filters in stacked images. Astrometry of the afterglow is RA(J2000): 17 57 15.17 Dec(J2000): +33 24 21.14 with uncertainty of 0.3 arcsec is fully compatible with reported one in GCNs 9148, 9149.
Preliminary photometry of combined images is based on USNO-B1.0 1234-0288651 star RA=17:57:13.29 Dec=+33:25:00.6 is following:
```
T0+     Filter, Exposure, mag.,     err.
(d)             (s)
0.5484   B       36x60     23.30  +/- 0.20
0.5484   R       17x60     22.23  +/- 0.14
0.5491   I       17x60     22.40  +/- 0.24
```
We note, that OT is ~4" North-West of bright galaxy which is also visible in POSS2. Taking the redshift z=1.608 of the GRB source (Chornock et al., GCN 9151) and the scale of ~8.6 kpc/" at that redshift it is unlikely that the galaxy is related with OT.
A finding chart the combined image in I can be found at http://grb.rssi.ru/GRB090418A/GRB090418_I_ZTSh_090418.gif
GCN Circular #9183
S. T. Holland (CRESST/GSFC/USRA) reports on the behalf of the Swift UVOT team:
Swift/UVOT observed the POSS2 galaxy (Pavlenko, et al., 2009, GCNC 9179) located approximately 4 arcsec northwest of the afterglow of GRB 090418A (Mangano, et al.,2009, GCNC 9149). We obtain the following preliminary magnitudes and 1-sigma errors for this galaxy.
```
Filter  Exposure      Mag  Err  Sigma
-------------------------------------
v           6163     21.0  0.2    5.5
b           4361     22.2  0.5    2.3
u           6057     21.3  0.2    5.6
uvw1        6178     21.6  0.2    4.7
uvm2        2109     21.5  0.4    2.9
uvw2        1357     21.3  0.3    3.4
-------------------------------------
```
Exposure is the total exposure time in seconds. The quoted magnitudes have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.04 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).
The detection of the galaxy in the uvw2 filter suggests that the galaxy has a redshift of less than approximately 1.3. The redshift of the afterglow is at least z = 1.608 (Chornock, et al., 2009, GCNC 9151). Therefore, we conclude that this galaxy is unlikely to be the host galaxy of GRB 090418A, in agreement with Pavlenko, et al. (2009, GCNC 9179).
GCN Circular #9190
I. Bikmaev, R.Zhuchkov, N. Sakhibullin (KSU/AST), I. Khamitov, Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI)
report:
The optical afterglow of GRB 090418A (Chornock et al., GCN 9148, Mangano et al., GCN 9149) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) under moderate transparences. We obtained series of 600s exposures in BVRc filters, centered at April 18, 23:40 UT, i.e. 0.52 days after the burst.
The afterglow is clearly seen at combined R image, and marginally detected at combined B,V frames.
Using the same calibration star USNO-B1.0 1234-0288651 as Pavlenko et al. (GCN 9179), we estimate the following magnitudes of OT:
```
Filter, Exposure, mag.,     err.
         (s)
B       3x600     23.5    limit
V       3x600     22.7    limit
R       4x600     22.1    +/- 0.1
```
We made also series of 3x900 sec exposures in Rc filter centered on April 20, 23:00, i.e. 2.5 days after the burst. The afterglow was not detected on the combined frame with a limit R=23.3 mag
RTT150 finding chart (Rc) can be found at:
http://hea.iki.rssi.ru/grb/090418a/indexeng.html
GCN Circular #9196
V. Pal'shin, S. Golenetskii, R.Aptekar, E. Mazets, D. Frederiks, and T. Cline on behalf of the Konus-Wind team,
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), and T. Ukwatta (GWU) on behalf of the Swift-BAT team, report:
We performed the Konus-Wind and the Swift/BAT joint spectral analysis of GRB 090418A (Swift/BAT trigger #349510: Mangano et al., GCN Circ. 9149, Fenimore et al. GCN Circ. 9157). Since the Konus-Wind observed this GRB in the waiting mode, we only have 3 channel spectral data for the Konus-Wind which cover the energy range from 20 keV to 1.2 MeV. Therefore, the joint spectral analysis of the Konus-Wind and the Swift/BAT data enables to derive the broad-band spectral parameters of this burst.
The time interval of the spectral data for each instrument is chosen from T0(BAT)-6.7 to T0(BAT)+58.1 sec where T0(BAT) is the trigger time of BAT at 11:07:40.2 UTC. The energy ranges which we used in the joint spectral analysis are 20-1200 keV and 14-150 keV for the Konus-Wind and the Swift/BAT respectively. The spectral data of two instruments are fitted with the spectral model multiplied by the constant factor to take into account the systematic effective area uncertainties in the response matrices of each instrument.
The spectrum is well fitted with a power-law with exponential cutoff model: dN/dE ~ E^{alpha}*exp(-(2+alpha)*E/Epeak). The constant factors of each instrument agree within 20%. No systematic residual from the best fit model is seen in the spectral data of each instrument. The best fit spectral parameters are: alpha = -1.30 +/- 0.09 and Epeak = 610(-164, +530) keV (chi2/dof = 37.0/57). The best fit spectral parameters for the GRB (Band) model fixing beta = -2.5 are: alpha = -1.30 +/- 0.09, and Epeak = 601(-215, +554) keV (chi2/dof = 37.1/57). The energy fluence in the 15-1200 keV band calculated by a power-law with exponential cutoff model for this 64.8 sec interval is (1.79 +/- 0.21)x10^-5 erg/cm2.
All the quoted errors are at the 90% confidence level.
Assuming z = 1.6 (Chornock et al., GCN Circ. 9151) and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release is E_iso ~2x10^53 erg in 1 keV to 10 MeV at the GRB rest frame extrapolating the best Band function fit fixing beta = -2.5.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB090418A/
GCN Circular #9199
Brajesh Kumar, Rupak Roy, Brijesh Kumar and S. B. Pandey (ARIES, NainiTal, India, on behalf of larger Indian GRB collaboration).
We have imaged the field of swift GRB 090418A (GCN 9149) with the 104 cm Sampurnanand Optical telescope at ARIES Nainital on 18th April 2009 at 19.815 hrs UT. We do not detect any afterglow candidate in our co-added R_c and I_c band images (exp time 1400sec in each band) within the error circle of XRT (GCN 9163). The Photometry of the co-added frames put a 3 sigma upper limit of R ~ 20.64 and I ~ 19.65 mag in comparison to the nearby USNO - B1 stars.
GCN Circular #9211
A. Henden (AAVSO), J. Gross (SRO), B. Denny (DC-3), D. Terrell (SwRI), and W. Cooney (SRO) report:
We obtained photometry of the GRB090418A afterglow reported by Chornock et al. (GCN 9148) using the Sonoita Research Observatory (SRO) 35cm telescope in southern Arizona, utilizing an automatic VOevent trigger. The Rc-band exposures began about 2 minutes after the burst and continued until twilight. Ten 60-second and five 180-second exposures were acquired.
Astrometry of the afterglow from several images and using UCAC as the reference catalog yields coordinates: 17:57:15.151 +33:24:20.93 J2000 (+/- 50mas)
Photometry, assuming that the star at
17:57:42.53 +33:25:47.2
has an R magnitude of 13.12
```
UT(mid)  delT  exp  Rc      err
11.1728   162  60  15.802  0.044
11.1919   231  60  16.185  0.048
11.2111   300  60  16.500  0.043
11.2303   369  60  16.818  0.058
11.2494   438  60  17.019  0.066
11.2686   507  60  17.249  0.067
11.2878   576  60  17.440  0.063
11.3069   645  60  17.605  0.105
11.3261   714  60  17.680  0.089
11.3450   782  60  17.855  0.115
11.3958   965 180  18.007  0.104
11.6522  1888 180  18.778  0.129
11.7067  2084 180  18.919  0.138
11.7592  2273 180  18.960  0.142
11.8114  2461 180  18.891  0.196
```
Where delT is the time in seconds from the burst (Mangano et al., GCN 9149), and the exposure is in seconds. The optical afterglow candidate is in the filter reflection halo from HD163948, a 6.9mag star about 2arcmin distant, so the last few magnitudes may have a systematic bias.
We note that this field was not calibrated by SDSS through DR6. We will perform a BVRI calibration over the next few nights.
GCN Circular #9293
A. Henden (AAVSO), J. Gross (SRO), B. Denny (DC-3), D. Terrell (SwRI), and W. Cooney (SRO) report:
We have performed an all-sky calibration of the field for the GRB090418A afterglow reported by Chornock, et al. (GCN 9148) using the Sonoita Research Observatory (SRO) 35cm telescope in southern Arizona. Two photometric nights were used for the calibration, with multiple Landolt fields observed during each night along with an extinction star for the calibration. The calibration file has a limiting magnitude around V=18, with good standards brighter than V=16. The file is available at ftp://ftp.aavso.org/public/calib/grb/grb090418a.dat
We estimate the external zeropoint error of this calibration to be about 0.02mag. In particular, the star used by Henden, et al. (GCN 9211) as a comparison star:
17:57:42.53 +33:25:47.2 J2000
has an R magnitude of 12.82, so all of the photometry in GCN 9211 should be adjusted 0.30mag brighter.
Our system is available for any other bright UBVRI calibrations (4 The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network,
GCN Circular #9329
V. Rumyantsev, E. Pavlenko(CrAO), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the afterglow of the Swift GRB 090418A (Mangano et al., GCN 9149) in I-filter on Apr. 20 (UT) 02:34:12 - 04:08:27 and in R-filter on Apr. 20 (UT) 21:03:05 - 22:49:20 with Shajn telescope of CrAO. We clearly detect afterglow in both epochs in stacked images. Preliminary photometry of Apr. 20 as well a photometry in V-filter of Apr. 18 observations (Pavlenko et al. GCN 9179) is following:
```
T0+     Filter, Exposure, mag.,     err.  UL Seeing
(d)             (s)

0.5476  V       17x60     22.3 +/- 0.2  23.2  1.9"
2.4507  R       70x60     22.8 +/- 0.1  24.4  1.9"
```
Due to worse seeing (2.4") on Apr. 20 (UT) 02:34:12 - 04:08:27 the afterglow is evidently contaminated with nearby galaxy and photometry will be reported later. The photometry of Apr. 20 (UT) 21:03:05 - 22:49:20 also should be treated with caution due to possible contamination.
GCN Report 217.1
GCN_Report 217.1 has been posted: http://gcn.gsfc.nasa.gov/reports/report_217_1.pdf by V. Mangano at INAF IASF Pa titled: "Final Results on Swift GRB 090418A"

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