Gamma-ray Burst 150818A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:36:53 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     652603,   Seg_Num: 0
GRB_RA:          230.446d {+15h 21m 47s} (J2000),
                 230.478d {+15h 21m 55s} (current),
                 230.348d {+15h 21m 24s} (1950)
GRB_DEC:         +68.342d {+68d 20' 32"} (J2000),
                 +68.287d {+68d 17' 13"} (current),
                 +68.520d {+68d 31' 11"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4128 [cnts]    Image_Peak=174 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   139     E_range: 15-50 keV
BKG_INTEN:       26537 [cnts]
BKG_TIME:        41776.98 SOD {11:36:16.98} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17252 TJD;   230 DOY;   15/08/18
GRB_TIME:        41792.92 SOD {11:36:32.92} UT
GRB_PHI:         -149.52 [deg]
GRB_THETA:        43.90 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.92 [sigma]
IMAGE_SIGNIF:    8.04 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  -2  +0  +0 -25  +0 
SUN_POSTN:       147.50d {+09h 50m 00s}  +13.11d {+13d 06' 42"}
SUN_DIST:         75.24 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.16d {+12h 28m 39s}   -2.41d {-02d 24' 36"}
MOON_DIST:        76.71 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.96, 43.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      155.19, 74.99 [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 = 156.98,2.64 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:38:32 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     652603,   Seg_Num: 0
GRB_RA:          230.3621d {+15h 21m 26.90s} (J2000),
                 230.3938d {+15h 21m 34.50s} (current),
                 230.2636d {+15h 21m 03.26s} (1950)
GRB_DEC:         +68.3446d {+68d 20' 40.5"} (J2000),
                 +68.2891d {+68d 17' 20.8"} (current),
                 +68.5224d {+68d 31' 20.6"} (1950)
GRB_ERROR:       6.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.59e-08 [erg/cm2/sec]
GRB_SIGNIF:      6.00 [sigma]
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41877.37 SOD {11:37:57.37} UT,   84.5 [sec] since BAT Trigger Time
TAM[0-3]:        327.67 237.15 261.66 243.73
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       147.50d {+09h 50m 00s}  +13.11d {+13d 06' 40"}
SUN_DIST:         75.21 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.18d {+12h 28m 42s}   -2.41d {-02d 24' 51"}
MOON_DIST:        76.69 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.99, 43.18 [deg] galactic lon,lat of the burst
ECL_COORDS:      155.16, 74.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.86 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:38:48 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     652603,   Seg_Num: 0
GRB_RA:          230.3621d {+15h 21m 26.9s} (J2000),
                 230.3938d {+15h 21m 34.5s} (current),
                 230.2636d {+15h 21m 03.2s} (1950)
GRB_DEC:         +68.3446d {+68d 20' 40.5"} (J2000),
                 +68.2891d {+68d 17' 20.8"} (current),
                 +68.5224d {+68d 31' 20.6"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       36 [cnts]
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41877.37 SOD {11:37:57.37} UT,   84.5 [sec] since BAT Trigger Time
CENTROID_X:      226.05,  raw= 226  [pixels]
CENTROID_Y:      288.55,  raw= 289  [pixels]
ROLL:            268.42 [deg]
GAIN:            1
MODE:            2, Short Image mode
WAVEFORM:        134
EXPO_TIME:       0.10 [sec]
GRB_POS_XRT_Y:   -21.79
GRB_POS_XRT_Z:   -186.79
IMAGE_URL:       sw00652603000msxps_rw.img
SUN_POSTN:       147.50d {+09h 50m 00s}  +13.11d {+13d 06' 40"}
SUN_DIST:         75.21 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.18d {+12h 28m 43s}   -2.42d {-02d 24' 54"}
MOON_DIST:        76.69 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.99, 43.18 [deg] galactic lon,lat of the burst
ECL_COORDS:      155.16, 74.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:38:59 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     652603,   Seg_Num: 0
GRB_RA:          230.3621d {+15h 21m 26.9s} (J2000),
                 230.3938d {+15h 21m 34.5s} (current),
                 230.2636d {+15h 21m 03.2s} (1950)
GRB_DEC:         +68.3446d {+68d 20' 40.5"} (J2000),
                 +68.2891d {+68d 17' 20.8"} (current),
                 +68.5224d {+68d 31' 20.6"} (1950)
GRB_ERROR:       5.8 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       36 [cnts]
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41877.37 SOD {11:37:57.37} UT,   84.5 [sec] since BAT Trigger Time
CENTROID_X:      226.05,  raw= 226  [pixels]
CENTROID_Y:      288.55,  raw= 289  [pixels]
ROLL:            268.42 [deg]
GAIN:            1
MODE:            2, Short Image mode
WAVEFORM:        134
EXPO_TIME:       0.10 [sec]
GRB_POS_XRT_Y:   -21.79
GRB_POS_XRT_Z:   -186.79
IMAGE_URL:       sw00652603000msxps_rw.img
SUN_POSTN:       147.50d {+09h 50m 00s}  +13.11d {+13d 06' 40"}
SUN_DIST:         75.21 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.18d {+12h 28m 43s}   -2.42d {-02d 24' 56"}
MOON_DIST:        76.69 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.99, 43.18 [deg] galactic lon,lat of the burst
ECL_COORDS:      155.16, 74.96 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:39:34 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.499d {+15h 22m 00s} (J2000)
POINT_DEC:       +68.337d {+68d 20' 14"} (J2000)
POINT_ROLL:      268.412d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41887.02 SOD {11:38:07.02} UT,   94.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.232
N_STARS:         23
X_OFFSET:        624 [pixels]
Y_OFFSET:        496 [pixels]
X_MAX:           1583 [pixels]
Y_MAX:           1455 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00652603000msufc0094.fits
SUN_POSTN:       147.50d {+09h 50m 01s}  +13.11d {+13d 06' 40"}
SUN_DIST:         75.26 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.18d {+12h 28m 44s}   -2.42d {-02d 25' 01"}
MOON_DIST:        76.72 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.93, 43.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.23, 75.01 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:40:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.499d {+15h 22m 00s} (J2000)
POINT_DEC:       +68.337d {+68d 20' 14"} (J2000)
POINT_ROLL:      268.412d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41887.02 SOD {11:38:07.02} UT,   94.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        0.232
N_STARS:         23
X_OFFSET:        624 [pixels]
Y_OFFSET:        496 [pixels]
X_MAX:           1583 [pixels]
Y_MAX:           1455 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00652603000msufc0094.fits
SUN_POSTN:       147.50d {+09h 50m 01s}  +13.11d {+13d 06' 39"}
SUN_DIST:         75.26 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.19d {+12h 28m 45s}   -2.42d {-02d 25' 07"}
MOON_DIST:        76.72 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.93, 43.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.23, 75.01 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 11:40:28 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.499d {+15h 22m 00s} (J2000)
POINT_DEC:       +68.337d {+68d 20' 14"} (J2000)
ROLL:            268.412d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41887.02 SOD {11:38:07.02} UT,   94.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461590702
X_OFFSET:        1146 [pixels]
Y_OFFSET:        733 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1306
Y_GRB_POS:       893
BINNING_INDEX:   1
IM_URL:          sw00652603000msuni0110.fits
SUN_POSTN:       147.50d {+09h 50m 01s}  +13.11d {+13d 06' 39"}
SUN_DIST:         75.26 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.19d {+12h 28m 46s}   -2.42d {-02d 25' 09"}
MOON_DIST:        76.72 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.93, 43.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.23, 75.01 [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:     Tue 18 Aug 15 11:40:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.499d {+15h 22m 00s} (J2000)
POINT_DEC:       +68.337d {+68d 20' 14"} (J2000)
ROLL:            268.412d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  41887.02 SOD {11:38:07.02} UT,   94.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461590702
X_OFFSET:        1146 [pixels]
Y_OFFSET:        733 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1306
Y_GRB_POS:       893
BINNING_INDEX:   1
IM_URL:          sw00652603000msuni0110.fits
SUN_POSTN:       147.50d {+09h 50m 01s}  +13.11d {+13d 06' 39"}
SUN_DIST:         75.26 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.19d {+12h 28m 46s}   -2.42d {-02d 25' 11"}
MOON_DIST:        76.72 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.93, 43.15 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.23, 75.01 [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:     Tue 18 Aug 15 11:41:04 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     652603,   Seg_Num: 0
GRB_RA:          230.446d {+15h 21m 47s} (J2000),
                 230.478d {+15h 21m 55s} (current),
                 230.348d {+15h 21m 24s} (1950)
GRB_DEC:         +68.342d {+68d 20' 32"} (J2000),
                 +68.287d {+68d 17' 13"} (current),
                 +68.520d {+68d 31' 11"} (1950)
GRB_DATE:        17252 TJD;   230 DOY;   15/08/18
GRB_TIME:        41792.92 SOD {11:36:32.92} UT
TRIGGER_INDEX:   139
GRB_PHI:         -149.52 [deg]
GRB_THETA:        43.90 [deg]
DELTA_TIME:      7.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     12.92 [sigma]
IMAGE_SIGNIF:    8.04 [sigma]
LC_URL:          sw00652603000msb.lc
SUN_POSTN:       147.50d {+09h 50m 01s}  +13.11d {+13d 06' 38"}
SUN_DIST:         75.24 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.20d {+12h 28m 47s}   -2.42d {-02d 25' 15"}
MOON_DIST:        76.71 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.96, 43.16 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      155.19, 74.99 [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 = 156.98,2.64 [deg].

GCN Circular #18152
V. D'Elia (ASDC), A. A. Breeveld (UCL-MSSL), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), L. Izzo (URoma/ICRA), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:
At 11:36:32 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150818A (trigger=652603). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 230.446, +68.342 which is
```
   RA(J2000) = 15h 21m 47s
   Dec(J2000) = +68d 20' 32"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 50 sec. The peak count rate was ~1990 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:37:57.3 UT, 84.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 230.3621, 68.3446 which is equivalent to:
```
   RA(J2000)  = +15h 21m 26.90s
   Dec(J2000) = +68d 20' 40.6"
```
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This location is 111 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 28 seconds with the White filter starting 94 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image processing failed because of no aspect solution is available. Results from the list of sources generated on-board are not available at this time.
Burst Advocate for this burst is V. D'Elia (delia AT asdc.asi.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 12:38:01 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.526d {+15h 22m 06s} (J2000)
POINT_DEC:       +68.349d {+68d 20' 56"} (J2000)
POINT_ROLL:      268.488d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  45207.81 SOD {12:33:27.81} UT,   3414.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.631
N_STARS:         22
X_OFFSET:        836 [pixels]
Y_OFFSET:        319 [pixels]
X_MAX:           1795 [pixels]
Y_MAX:           1278 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00652603000msufc3414.fits
SUN_POSTN:       147.54d {+09h 50m 10s}  +13.10d {+13d 05' 52"}
SUN_DIST:         75.27 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.64d {+12h 30m 34s}   -2.57d {-02d 33' 57"}
MOON_DIST:        76.76 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.94, 43.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.19, 75.03 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 12:38:30 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.526d {+15h 22m 06s} (J2000)
POINT_DEC:       +68.349d {+68d 20' 56"} (J2000)
POINT_ROLL:      268.488d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  45207.81 SOD {12:33:27.81} UT,   3414.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.631
N_STARS:         22
X_OFFSET:        836 [pixels]
Y_OFFSET:        319 [pixels]
X_MAX:           1795 [pixels]
Y_MAX:           1278 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00652603000msufc3414.fits
SUN_POSTN:       147.54d {+09h 50m 10s}  +13.10d {+13d 05' 52"}
SUN_DIST:         75.27 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.64d {+12h 30m 35s}   -2.57d {-02d 34' 01"}
MOON_DIST:        76.76 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.94, 43.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.19, 75.03 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 12:39:42 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.526d {+15h 22m 06s} (J2000)
POINT_DEC:       +68.349d {+68d 20' 56"} (J2000)
ROLL:            268.488d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  45207.81 SOD {12:33:27.81} UT,   3414.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461594022
X_OFFSET:        1155 [pixels]
Y_OFFSET:        638 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1315
Y_GRB_POS:       798
BINNING_INDEX:   1
IM_URL:          sw00652603000msuni3430.fits
SUN_POSTN:       147.54d {+09h 50m 10s}  +13.10d {+13d 05' 51"}
SUN_DIST:         75.27 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.65d {+12h 30m 37s}   -2.57d {-02d 34' 12"}
MOON_DIST:        76.76 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.94, 43.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.19, 75.03 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 18 Aug 15 12:40:00 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     652603,   Seg_Num: 0
POINT_RA:        230.526d {+15h 22m 06s} (J2000)
POINT_DEC:       +68.349d {+68d 20' 56"} (J2000)
ROLL:            268.488d
IMG_START_DATE:  17252 TJD;   230 DOY;   15/08/18
IMG_START_TIME:  45207.81 SOD {12:33:27.81} UT,   3414.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     461594022
X_OFFSET:        1155 [pixels]
Y_OFFSET:        638 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1315
Y_GRB_POS:       798
BINNING_INDEX:   1
IM_URL:          sw00652603000msuni3430.fits
SUN_POSTN:       147.54d {+09h 50m 10s}  +13.10d {+13d 05' 51"}
SUN_DIST:         75.27 [deg]   Sun_angle= -5.5 [hr] (East of Sun)
MOON_POSTN:      187.66d {+12h 30m 37s}   -2.57d {-02d 34' 15"}
MOON_DIST:        76.76 [deg]
MOON_ILLUM:      13 [%]
GAL_COORDS:      104.94, 43.14 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      155.19, 75.03 [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 Circular #18154
XMM-Newton will observe GRB 150818A at location (RA=15h 21m 26.9s, DEC=68d 20' 40.5", J2000), starting at 18:15:45 UT, on August 18, 2015, for an exposure of 22400 seconds.
GCN Circular #18155
F. E. Marshall (NASA/GSFC) and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team:
UVOT took a finding chart exposure of 28 seconds with the White filter starting 94 seconds after the BAT trigger on GRB 150818A. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at
```
  RA(J2000)  =  15:21:25.48 = 230.35616
  DEC(J2000) =  68:20:34.0  = 68.34278
```
with a 90%-confidence error radius of about 1.0 arc sec. This position is 10 arcseconds from the center of the XRT error circle (D'Elia et al. GCN Circ. 18152). The estimated magnitude is 19.5 with a 1-sigma error of about 0.2. No correction has been made for extinction.
GCN Circular #18157
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), V. D'Elia (ASDC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlinks, we report further analysis of BAT GRB 150818A (trigger #652603) (D'Elia, et al., GCN Circ. 18152). The BAT ground-calculated position is RA, Dec = 230.340, 68.342 deg, which is
```
   RA(J2000)  =  15h 21m 21.7s 
   Dec(J2000) = +68d 20' 31.5" 
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 36%.
The mask-weighted light curves shows two overlapping peaks starting at ~T-25 sec, peaking at ~T+1 sec, and ending at ~T+180 sec. T90 (15-350 keV) is 123.3 +- 31.3 sec (estimated error including systematics).
The time-averaged spectrum from T-11.18 to T+165.12 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.96 +- 0.09. The fluence in the 15-150 keV band is 4.1 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.88 sec in the 15-150 keV band is 2.4 +- 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/652603/BA/
GCN Circular #18159
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 2975 s of XRT Photon Counting mode data and 7 UVOT images for GRB 150818A, 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 = 230.35595, +68.34204 which is equivalent to:
```
RA (J2000): 15h 21m 25.43s
Dec (J2000): +68d 20' 31.4"
```
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 #18161
L. M. McCauley (PSU), L. M. Z. Hagen (PSU), and V. D'Elia (ASDC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150818A 94 s after the BAT trigger (D'Elia et al., GCN Circ. 18152). A source consistent with the XRT position (Beardmore et al. GCN Circ. 18159) is detected in the initial UVOT exposures.
The preliminary UVOT position is:

    RA  (J2000) =  15:21:25.43 = 230.35594 (deg.)
    Dec (J2000) = +68:20:33.0  =  68.34251 (deg.)

with an estimated uncertainty of 0.66 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white_fc            94          121           27         19.39+-0.25
white             3414         4790          344         19.92+-0.17
white            10222        10826          590         19.68+-0.07
v                 3572         5201          393        >19.36
b                 4385         4585          196        >20.16
b                 5821        10217          927         20.56+-0.33
u                 4180         4379          196        >19.66
u                 5616         5816          196         19.63+-0.25
uvw1              3976         4175          195         18.78+-0.20
uvw1              5411         5611          196         18.95+-0.20
uvm2              3776         3976          192         18.81+-0.23
uvm2              5206         5406          196         18.89+-0.24
uvw2              4796         4996          196         18.90+-0.19

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).

GCN Circular #18162
P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), A. D'ai (INAF-IASFPA), A. Maselli (INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester) and V. D'Elia report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 150818A (D'Elia et al. GCN Circ. 18152), from 74 s to 21.7 ks after the BAT trigger. The data comprise 34 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 18159).
The late-time light curve (from T0+3.5 ks) can be modelled with a power-law decay with a decay index of alpha=.
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.59 (+0.11, -0.10). The best-fitting absorption column is 2.33 (+0.28, -0.27) x 10^21 cm^-2, in excess of the Galactic value of 2.5 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.96 (+0.30, -0.27) and a best-fitting absorption column of 7.6 (+7.6, -5.1) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.6 (+7.6, -5.1) x 10^20 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.96 (+0.30, -0.27)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00652603.
This circular is an official product of the Swift-XRT team.
GCN Circular #18164
S. Schulze (PUC, MAS), J. P. U. Fynbo (DARK, NBI), T. Kruehler (MPE), D. Malesani, (DARK/NBI), I. V. Rasmussen, J. L. Marcher, L. L. Thomson (NBI), A. Djupvik (NOT), B. Milvang-Jensen (DARK/NBI) and P. Jakobsson (U Iceland) report on behalf a larger collaboration:
We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 180 s and a 3x300 s image in R band. Observations started at 21:34 UT on August 18 (i.e. 9.62 hr after the burst).
We clearly detect the source reported in Marshall et al. (GCN 18155) and McCauley et al. (GCN 18161). We measure R=20.86 +/- 0.08 mag calibrated against several USNO stars. This value is not corrected for foreground extinction.
Given the lack of evidence for variability (McCauley et al., GCN 18161), the association of this object with GRB 150818A remains unclear.
GCN Circular #18166
P.A. Evans (U, Leicester) reports on behalf of the Swift-XRT team:
Due to a computer error, the light curve decay index was missing in GCN 18162.
At the present time, we have analysed 7.6 ks of XRT data for GRB 150818A (D'Elia et al. GCN Circ. 18152), from 74 s to 44.1 ks after the BAT trigger.
The XRT light curve can be modelled as a broken power-law, with an initial decay index of 2.36 (+0.08, -0.06), a break at T0 + 3600 (+/-500) s, and a subsequent shallow decay of 0.66 (+0.16, -0.15).
If the decay continues at alpha=0.66, the predicted count-rate at T0+24 hrs is 8.9e-3 ct/sec, which corresponds to an observed (unabsorbed) 0.3-10 keV flux of 2.97e-13 (3.56e-13) erg/cm^2/s.
This circular is an official product of the Swift-XRT team.
GCN Circular #18171
T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, Y. Yano, S. Kurita, Y.Ono, S.Harita,Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 150818A (V. D'Elia et al. GCN Circular #18152) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-08-18 11:54:53 UT (~18 min after the burst). We did not find any new point source within XRT circle in all three bands.
We obtained following limits for the magnitudes.
```
T0+[sec]      MID-UT      T-EXP[sec]         g'           Rc           Ic
---------------------------------------------------------------------------------------
  1101     11:59:46          540           >19.4      >19.4     > 18.5
---------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration
```
GCN Circular #18174
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ), K. Yanagisawa (OAO, NAOJ), S.Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME and OISTER collaboration:
We observed the field of GRB 150818A (D'Elia et al., GCNC 18152) with the optical three color (g', Rc and Ic) CCD camera attached to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory.
The observation started on 2015-08-18 13:09:10 UT (~1.5h after the burst). We could not detect the previously reported afterglow (Marshall and D'Elia, GCNC 18155; McCauley et al., GCNC 18161; Schulze et al., GCNC 18164) in all the three bands.
Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration.
```
#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc     Ic
-----------------------------------------------------
0.11943    14:28:30    6180.0   >19.4  >19.7  >19.5
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
GCN Circular #18175
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of Swift GRB 150818A (D'Elia et al., GCNC 18152) with AZT-33IK telescope of Sayan observatory (Mondy) starting on Aug., 18 (UT) 15:07:42. We obtained several images in R-filter of 120 s exposure. The source previously mentioned (McCauley et al., GCN 18161; Schulze et al., GCN 18164) is clearly visible. Coordinates of the source are (J2000) 15:21:25.56 +68:20:32.0 with uncertainty of 0.3 arcsec in both coordinates. Preliminary photometry of the source is following
```
Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-18 15:07:42   0.16843  R        31*120  20.25 0.08
```
Photometry is based on USNO-B1.0 stars:
```
USNO-B.1_id  R2
1583-0162302 16.65
1583-0162268 17.48
1583-0162214 16.71
1583-0162248 19.43
```
We can suggest the source as shallow fading afterglow because the source is significantly faded between our observations (R=20.25+/-0.08 at 4 hrs after burst trigger) and NOT observations at 9.62 hrs (Schulze et al., GCN 18164).
GCN Circular #18177
R. Sanchez-Ramirez (UPV/EHU, IAA-CSIC), J. Gorosabel (+, UPV/EHU, IAA-CSIC), D. Perez-Ramirez (+, Univ. de Jaen), S. Jeong (IAA-CSIC, SKKU), A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), F. J. Aceituno, R. Cunniffe, P. Ferrero, Y. Hu, S. R. Oates, J. C. Tello, B.-B. Zhang (IAA-CSIC), M. Jelinek (ASU-CAS), S. Guziy (Nikolaev Univ.), V. Sokolov (SAO-RAS), J.M. Castro Ceron (ESAC), J. Cepa (IAC), A. Garcia (GRANTECAN) and R. Scarpa (IAC, GRANTECAN), report:
Following the detection of GRB 150818A by Swift/BAT (D Elia et al. 2015, GCNC 18152), we have obtained an optical spectrum (2 x 900s) with the 10.4m GTC telescope (+OSIRIS) in La Palma (Spain), starting on Aug 18, 22:05 UT (i.e. 10.5 hr postburst), covering the 3700-7800 A wavelength range. The slit included the position of the proposed optical afterglow (Marshall and D Elia, GCNC 18155; Schulze et al., GCNC 18164; Mazaeva et al. GCNC 18175).
At the position of the optical afterglow, we see no obvious absorption features with the continuum extending from 3700 to 7800 A. However we clearly detect emission lines of [OII] 3727A, H-beta and [OIII] 4960A,5008A, all at a common redshift z =3D 0.282. Indeed a diffuse object seems to be adjacent (within 1=94 to the west) to the optical afterglow in the acquisition image (under 0=94.7 seeing), which could be the host galaxy at the above mentioned redshift.
Further spectroscopy and monitoring at all wavelengths is encouraged to search for the emergence of the underlying supernova component in the next weeks.
GCN Circular #18179
S. Schulze (PUC, MAS), J. P. U. Fynbo, D. Malesani (DARK/NBI), R. Tuma, S. Dinh, M. Homann, M. Munoz (NBI) and P. Jakobsson (U. Iceland) report on behalf a larger collaboration:
We observed the field of GRB 150818A (D'Elia et al., GCN 18152) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained a 300-s image in R band. Observations started at 21:03 UT on August 19 (i.e. 1.39 days after the burst).
We clearly detect the source reported in Marshall et al. (GCN 18155), McCauley et al. (GCN 18161), Schulze et al. (GCN 18164) and Mazaeva et al. (GCN 18175). We measure R=21.18 +/- 0.05 calibrated against several USNO stars. The optical transient faded by 0.3 mag compared to Schulze et al. (GCN 18164) in agreement with Mazaeva et al. (GCN 18175) who also found evidence for a shallow decay. Sanchez-Ramirez (GCN) hinted that the host is possibly detected in GTC image. A significant host contribution would explain the shallow decay.
GCN Circular #18182
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We continue observations of the of Swift GRB 150818A (D'Elia et al., GCNC 18152) with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images in R-filter starting on Aug., 19 (UT) 15:33:10. The optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) is clearly visible. Preliminary photometry of the optical transient is following
```
Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-19  15:33:10   1.18517  R        30*120  21.0 0.1
```
Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN 18175)
GCN Circular #18189
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We continue observations of the of Swift GRB 150818A (D'Elia et al., GCNC 18152) with AZT-33IK telescope of Sayan observatory (Mondy). We obtained several images in R-filter starting on Aug., 20 (UT) 16:54:32. The optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) is clearly visible. Preliminary photometry of the optical transient is following
```
Date       UT start   t-T0     Filter   Exp.    OT    Err.
                       (mid, days)       (s)

2015-08-20 16:54:32   2.23334  R        15*120  21.15 0.09
```
Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN 18175).
The continued shallow decay mentioned in Schulze et al. (GCN 18179) indeed can be explained by underlying host galaxy (Sanchez-Ramirez et al., GCN 18177).
GCN Circular #18198
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 150818A (Swift-BAT trigger #652603: D'Elia, et al., GCN Circ. 18152; Palmer, et al., GCN Circ. 18157) was detected by Konus-Wind in the waiting mode.
The burst light curve shows a single pulse with a total duration of about 47 s.
As observed by Konus-Wind, the burst had a fluence of 5.3(-0.6,+0.7)x10^-6 erg/cm2 and a 2.944-s peak flux, measured from ~T0(BAT)-3.3 s, of 1.8(-0.3,+0.4)x10^-7 erg/cm2/s (both in the 20 - 1000 keV energy range).
Modeling the K-W 3-channel time-integrated spectrum (from T0(BAT)-6.2 s to T0(BAT)+40.9 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.4(-0.2,+0.6) and Ep = 100 (-18,+29) keV.
The K-W light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB150818A/
Assuming the redshift z=0.282 (Sanchez-Ramirez, et al., GCN 18177) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~1.0x10^51 erg, the peak luminosity L_iso is ~3.6x10^49 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~128 keV.
All the quoted errors are at 1 sigma confidence level. All the quoted values are preliminary.
GCN Circular #18205
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We continue observations of the Swift GRB 150818A (D'Elia et al., GCN 18152) with AZT-33IK telescope of Sayan observatory (Mondy). We imaged optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) in R-filter on Aug., 21, 22, 23, and 26. The optical transient is clearly visible in each epochs. Preliminary light curve of the optical transient can be found in
http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png
(Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN 18175).
One can suggest that steady re-brightening of the optical transient is related to a Supernova associated with nearby GRB 150818A (z = 0.282, Sanchez-Ramirez et al., GCN 18177). We encourage observation for spectroscopic SN-confirmation.
GCN Circular #18213
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), Z. Cano (U. Iceland), D. A. Perley (DARK/NBI), S. Schulze (PUC, MAS), D. Xu (NAOC/CAS), R. Sanchez-Ramirez (IAA-CSIC), D. Malesani (DARK/NBI), G. Lombardi (GRANTECAN, IAC, ULL), and A. Garcia (GRANTECAN), R. Scarpa (GRANTECAN) report on behalf of a larger collaboration:
We observed the counterpart of GRB 150818A (D'Elia et al. GCN 18152; Marshall et al. GCN 18155; McCauley et al. GCN 18161; Mazaeva et al. GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et al. GCN 18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) with the 10.4 m GTC telescope (+OSIRIS) on the 29th August 2015 (11.4 days after the burst). The observation consisted of 3x900 s spectroscopy using the R1000B grism (3700-7800 AA coverage with a resolution of ~1000) plus g-, r- and i-band imaging. We detect a point-like source at the location of the afterglow superposed on top of an extended source.
The combined spectrum shows broad features typical of a broad-lined Type Ic SN near maximum light, thus confirming the detection of a rising supernova proposed by Mazaeva et al. (GCN 18205). The spectrum also shows narrow emission features of [OII], [OIII] and H-beta at z=0.282 (Sanchez-Ramirez et al. GCN 18177).
GCN Circular #18244
E. Mazaeva (IKI), A. Moskvitin (SAO RAS), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We are continuing observations the field of Swift GRB 150818A (D'Elia et al., GCNC 18152) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory and Zeiss-1000, 1-m telescope of SAO RAS. The optical transient (Marshall et al. GCN 18155; McCauley et al. GCN 18161; Mazaeva et al. GCN 18175; Sanchez-Ramirez et al. GCN 18177; Mazaeva et al. GCN 18182, GCN 18189, GCN 18205; Schulze et al. GCN 18179) is clearly visible on combined images in each epochs. The updated light curve of Supernova (de Ugarte Postigo et al. GCN 18213; Mazaeva et al. GCN 18205) + host galaxy (Sanchez-Ramirez et al., GCN 18177; de Ugarte Postigo et al. GCN 18213) can be found in
http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png
The evident maximum of SN brightness (in Rc-filter) was on ~ Sep. 1-2, and the brightness of SN+host galaxy was R ~ 21.1 +/- 0.1 on Sep. 6 (UT) 18:00. We are grateful to V.P. Goranskiy for assistance in SAO RAS observations.

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