Gamma-ray Burst 170331A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:41:40 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     744791,   Seg_Num: 0
GRB_RA:          323.782d {+21h 35m 08s} (J2000),
                 324.029d {+21h 36m 07s} (current),
                 323.066d {+21h 32m 16s} (1950)
GRB_DEC:         -24.414d {-24d 24' 48"} (J2000),
                 -24.336d {-24d 20' 09"} (current),
                 -24.637d {-24d 38' 13"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       25885 [cnts]    Image_Peak=323 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   327     E_range: 15-50 keV
BKG_INTEN:       192329 [cnts]
BKG_TIME:        5957.16 SOD {01:39:17.16} UT
BKG_DUR:         64 [sec]
GRB_DATE:        17843 TJD;    90 DOY;   17/03/31
GRB_TIME:        6046.44 SOD {01:40:46.44} UT
GRB_PHI:         -62.74 [deg]
GRB_THETA:        39.65 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     9.43 [sigma]
IMAGE_SIGNIF:    7.93 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +1  -2  +0  +0 -60  +0 
SUN_POSTN:         9.69d {+00h 38m 46s}   +4.17d {+04d 10' 22"}
SUN_DIST:         52.76 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.74d {+03h 18m 57s}  +13.10d {+13d 06' 08"}
MOON_DIST:        91.55 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.00,-46.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      318.15, -9.51 [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 = 60.64,-15.08 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:42:57 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.771d {+21h 35m 05s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 13"} (J2000)
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6170.64 SOD {01:42:50.64} UT,   124.2 [sec] since BAT Trigger Time
COUNTS:          4    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:44:50 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     744791,   Seg_Num: 0
GRB_RA:          323.782d {+21h 35m 08s} (J2000),
                 324.029d {+21h 36m 07s} (current),
                 323.066d {+21h 32m 16s} (1950)
GRB_DEC:         -24.414d {-24d 24' 48"} (J2000),
                 -24.336d {-24d 20' 09"} (current),
                 -24.637d {-24d 38' 13"} (1950)
GRB_DATE:        17843 TJD;    90 DOY;   17/03/31
GRB_TIME:        6046.44 SOD {01:40:46.44} UT
TRIGGER_INDEX:   327
GRB_PHI:         -62.74 [deg]
GRB_THETA:        39.65 [deg]
DELTA_TIME:      32.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     9.43 [sigma]
IMAGE_SIGNIF:    7.93 [sigma]
LC_URL:          sw00744791000msb.lc
SUN_POSTN:         9.69d {+00h 38m 46s}   +4.17d {+04d 10' 25"}
SUN_DIST:         52.76 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.77d {+03h 19m 05s}  +13.11d {+13d 06' 36"}
MOON_DIST:        91.58 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.00,-46.00 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      318.15, -9.51 [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 = 60.64,-15.08 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:46:37 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     744791,   Seg_Num: 0
GRB_RA:          323.7926d {+21h 35m 10.22s} (J2000),
                 324.0391d {+21h 36m 09.39s} (current),
                 323.0765d {+21h 32m 18.36s} (1950)
GRB_DEC:         -24.3860d {-24d 23' 09.5"} (J2000),
                 -24.3084d {-24d 18' 30.2"} (current),
                 -24.6096d {-24d 36' 34.5"} (1950)
GRB_ERROR:       3.7 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6188.00 SOD {01:43:08.00} UT,   141.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:         9.69d {+00h 38m 47s}   +4.17d {+04d 10' 27"}
SUN_DIST:         52.75 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.79d {+03h 19m 09s}  +13.11d {+13d 06' 51"}
MOON_DIST:        91.58 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.04,-46.00 [deg] galactic lon,lat of the burst
ECL_COORDS:      318.17, -9.49 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:47:17 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.771d {+21h 35m 05s} (J2000)
POINT_DEC:       -24.403d {-24d 24' 11"} (J2000)
POINT_ROLL:      63.751d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6173.89 SOD {01:42:53.89} UT,   127.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.073
N_STARS:         37
X_OFFSET:        572 [pixels]
Y_OFFSET:        623 [pixels]
X_MAX:           1531 [pixels]
Y_MAX:           1582 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    12
SL_URL:          sw00744791000msufc0127.fits
SUN_POSTN:         9.69d {+00h 38m 47s}   +4.17d {+04d 10' 28"}
SUN_DIST:         52.77 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.80d {+03h 19m 11s}  +13.12d {+13d 06' 57"}
MOON_DIST:        91.61 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:47:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.771d {+21h 35m 05s} (J2000)
POINT_DEC:       -24.403d {-24d 24' 11"} (J2000)
POINT_ROLL:      63.751d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6173.89 SOD {01:42:53.89} UT,   127.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.073
N_STARS:         37
X_OFFSET:        572 [pixels]
Y_OFFSET:        623 [pixels]
X_MAX:           1531 [pixels]
Y_MAX:           1582 [pixels]
DET_THRESH:      21
PHOTO_THRESH:    12
SL_URL:          sw00744791000msufc0127.fits
SUN_POSTN:         9.69d {+00h 38m 47s}   +4.17d {+04d 10' 28"}
SUN_DIST:         52.77 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.80d {+03h 19m 12s}  +13.12d {+13d 07' 02"}
MOON_DIST:        91.62 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 01:48:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.771d {+21h 35m 05s} (J2000)
POINT_DEC:       -24.403d {-24d 24' 11"} (J2000)
ROLL:            63.751d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6173.89 SOD {01:42:53.89} UT,   127.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     512617392
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0146.fits
SUN_POSTN:         9.70d {+00h 38m 47s}   +4.17d {+04d 10' 29"}
SUN_DIST:         52.77 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.81d {+03h 19m 15s}  +13.12d {+13d 07' 10"}
MOON_DIST:        91.63 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 01:49:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.771d {+21h 35m 05s} (J2000)
POINT_DEC:       -24.403d {-24d 24' 11"} (J2000)
ROLL:            63.751d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6173.89 SOD {01:42:53.89} UT,   127.5 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     512617392
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0146.fits
SUN_POSTN:         9.70d {+00h 38m 47s}   +4.17d {+04d 10' 30"}
SUN_DIST:         52.77 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.81d {+03h 19m 15s}  +13.12d {+13d 07' 12"}
MOON_DIST:        91.63 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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 #20946
A. Melandri (INAF-OAB), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), P. D'Avanzo (INAF-OAB), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:
At 01:40:46 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170331A (trigger=744791). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 323.782, -24.414, which is
```
   RA(J2000)  =  21h 35m 08s
   Dec(J2000) = -24d 24' 48"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a complicated set of overlapping peaks with a total duration of about 25 sec. The peak count rate was ~1400 counts/sec (15-350 keV), at ~5 sec after the trigger.
The XRT began observing the field at 01:42:50.6 UT, 124.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 323.79260, -24.38604 which is equivalent to:
```
   RA(J2000)  = 21h 35m 10.22s
   Dec(J2000) = -24d 23' 09.7"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 105 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.65 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.1 (+3.11/-2.65) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 127 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.05.
Burst Advocate for this burst is A. Melandri (andrea.melandri AT brera.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 NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 01:55:37 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 12"} (J2000)
ROLL:            63.752d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6331.82 SOD {01:45:31.82} UT,   285.4 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     512617550
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0304.fits
SUN_POSTN:         9.70d {+00h 38m 48s}   +4.18d {+04d 10' 36"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.88d {+03h 19m 31s}  +13.14d {+13d 08' 09"}
MOON_DIST:        91.70 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 01:55:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 12"} (J2000)
ROLL:            63.752d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6331.82 SOD {01:45:31.82} UT,   285.4 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     512617550
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0304.fits
SUN_POSTN:         9.70d {+00h 38m 48s}   +4.18d {+04d 10' 36"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.88d {+03h 19m 32s}  +13.14d {+13d 08' 12"}
MOON_DIST:        91.70 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 02:02:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 13"} (J2000)
POINT_ROLL:      63.753d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6909.73 SOD {01:55:09.73} UT,   863.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.367
N_STARS:         69
X_OFFSET:        332 [pixels]
Y_OFFSET:        383 [pixels]
X_MAX:           1771 [pixels]
Y_MAX:           1822 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00744791000msufc0863.fits
SUN_POSTN:         9.70d {+00h 38m 49s}   +4.18d {+04d 10' 43"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.95d {+03h 19m 49s}  +13.15d {+13d 09' 12"}
MOON_DIST:        91.77 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 02:02:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 13"} (J2000)
POINT_ROLL:      63.753d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6909.73 SOD {01:55:09.73} UT,   863.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.367
N_STARS:         69
X_OFFSET:        332 [pixels]
Y_OFFSET:        383 [pixels]
X_MAX:           1771 [pixels]
Y_MAX:           1822 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw00744791000msufc0863.fits
SUN_POSTN:         9.70d {+00h 38m 49s}   +4.18d {+04d 10' 43"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.95d {+03h 19m 49s}  +13.15d {+13d 09' 13"}
MOON_DIST:        91.77 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 02:03:13 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 13"} (J2000)
ROLL:            63.753d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6909.73 SOD {01:55:09.73} UT,   863.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     512618128
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0882.fits
SUN_POSTN:         9.70d {+00h 38m 49s}   +4.18d {+04d 10' 43"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.96d {+03h 19m 50s}  +13.15d {+13d 09' 15"}
MOON_DIST:        91.77 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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:     Fri 31 Mar 17 02:03:36 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     744791,   Seg_Num: 0
GRB_RA:          323.7921d {+21h 35m 10.10s} (J2000),
                 324.0386d {+21h 36m 09.27s} (current),
                 323.0760d {+21h 32m 18.24s} (1950)
GRB_DEC:         -24.3857d {-24d 23' 08.5"} (J2000),
                 -24.3081d {-24d 18' 29.2"} (current),
                 -24.6093d {-24d 36' 33.5"} (1950)
GRB_ERROR:       2.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6188.00 SOD {01:43:08.00} UT,   141.6 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:         9.70d {+00h 38m 49s}   +4.18d {+04d 10' 44"}
SUN_DIST:         52.76 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.96d {+03h 19m 51s}  +13.16d {+13d 09' 19"}
MOON_DIST:        91.75 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.04,-46.00 [deg] galactic lon,lat of the burst
ECL_COORDS:      318.17, -9.49 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 31 Mar 17 02:03:29 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     744791,   Seg_Num: 0
POINT_RA:        323.768d {+21h 35m 04s} (J2000)
POINT_DEC:       -24.404d {-24d 24' 13"} (J2000)
ROLL:            63.753d
IMG_START_DATE:  17843 TJD;    90 DOY;   17/03/31
IMG_START_TIME:  6909.73 SOD {01:55:09.73} UT,   863.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     512618128
X_OFFSET:        891 [pixels]
Y_OFFSET:        942 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1051
Y_GRB_POS:       1102
BINNING_INDEX:   1
IM_URL:          sw00744791000msuni0882.fits
SUN_POSTN:         9.70d {+00h 38m 49s}   +4.18d {+04d 10' 43"}
SUN_DIST:         52.78 [deg]   Sun_angle= 3.0 [hr] (West of Sun)
MOON_POSTN:       49.96d {+03h 19m 50s}  +13.15d {+13d 09' 18"}
MOON_DIST:        91.78 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       25.01,-45.98 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      318.14, -9.50 [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 #20948
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 170331A, we find an enhanced XRT position of the afterglow: RA, Dec: 323.7920, -24.3858 which is equivalent to:
```
   RA (J2000)  = 21 35 10.08
   Dec (J2000) = -24 23 08.9
```
with an uncertainty of 2.1 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/744791.
Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.
GCN Circular #20949
C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc (U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large collaboration report:
We observed Swift GRB 170331A (Melandri et al. GCN 20946) on March 31, 03:21 UT (1.7 hours since the GRB) with two 1-m LCO units in Sutherland (South Africa) with the SDSS i filter. We do not find any object within the prompt enhanced Swift-XRT error circle (Evans GCN 20948) down to i>17.5 mag (with an exposure of 2x120s) as calibrated against USNOB-1 nearby stars.
GCN Circular #20960
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 1885 s of XRT Photon Counting mode data and 1 UVOT images for GRB 170331A, 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 = 323.79186, -24.38626 which is equivalent to:
```
RA (J2000): 21h 35m 10.05s
Dec (J2000): -24d 23' 10.5"
```
with an uncertainty of 1.6 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 #20962
S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Cholden-Brown (PSU) and report on behalf of the Swift-XRT team: report on behalf of the Swift-XRT team:
We have analysed 7.4 ks of XRT data for GRB 170331A, from 127 s to 19.2 ks after the BAT trigger. The data comprise 12 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=0.99 (+0.12, -0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.5 (+/-0.3). The best-fitting absorption column is 5.6 (+1.7, -1.5) x 10^21 cm^-2, in excess of the Galactic value of 4.7 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (7.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.6 (+1.7, -1.5) x 10^21 cm^-2
Galactic foreground: 4.7 x 10^20 cm^-2
Excess significance: 5.8 sigma
Photon index:	     2.5 (+/-0.3)
```
If the light curve continues to decay with a power-law decay index of 0.99, the count rate at T+24 hours will be 1.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.7 x 10^-14 (8.9 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00744791.
This circular is an official product of the Swift-XRT team.
GCN Circular #20965
N. P. M. Kuin (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170331A 128 s after the BAT trigger (Melandri et al., GCN Circ. 20946). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 20960) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           128          278          147         >20.4
u_FC               286          536          246         >19.6
white              128         1532          392         >21.0
v                  616         1753          134         >18.5
b                  542         1680          117         >19.1
u                  286         1655          343         >19.7
w1                 665         1631          117         >19.1
m2                1069         1606           58         >19.4
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #20967
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170331A (trigger #744791) (Melandri et al., GCN Circ. 20946). The BAT ground-calculated position is RA, Dec = 323.778, -24.406 deg which is
```
  RA(J2000)  =  21h 35m 06.8s
  Dec(J2000) = -24d 24' 22.4"
```
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 18%.
The mask-weighted light curve shows a weak pulse that starts at ~T-3 s, peaks at ~T+1 s, and ends at ~T+17 s. T90 (15-350 keV) is 17.57 +- 2.57 sec (estimated error including systematics).
The time-averaged spectrum from T-2.78 to T+17.17 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.37 +- 1.19, and Epeak of 48.2 +- 12.7 keV (chi squared 61.51 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 9.7 +- 1.6 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+0.42 sec in the 15-150 keV band is 1.2 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.86 +- 0.21 (chi squared 68.07 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/744791/BA/

Back to JG's homepage

Jochen Greiner, last update: 01-Apr-2017 [Disclaimer]