Gamma-ray Burst 160121A

(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:     Thu 21 Jan 16 13:51:02 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     671231,   Seg_Num: 0
GRB_RA:          109.079d {+07h 16m 19s} (J2000),
                 109.248d {+07h 17m 00s} (current),
                 108.554d {+07h 14m 13s} (1950)
GRB_DEC:         -23.578d {-23d 34' 40"} (J2000),
                 -23.607d {-23d 36' 25"} (current),
                 -23.488d {-23d 29' 17"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2564 [cnts]    Image_Peak=144 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       16225 [cnts]
BKG_TIME:        49824.27 SOD {13:50:24.27} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17408 TJD;    21 DOY;   16/01/21
GRB_TIME:        49837.71 SOD {13:50:37.71} UT
GRB_PHI:           7.73 [deg]
GRB_THETA:        22.82 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.04 [sigma]
IMAGE_SIGNIF:    7.25 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +1 +69  +0 
SUN_POSTN:       303.17d {+20h 12m 40s}  -19.94d {-19d 56' 39"}
SUN_DIST:        134.38 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.24d {+06h 00m 57s}  +18.38d {+18d 22' 44"}
MOON_DIST:        45.90 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.70, -5.39 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      115.24,-45.36 [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 = 158.07,3.83 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 13:52:24 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.088d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 52"} (J2000)
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49928.75 SOD {13:52:08.75} UT,   91.0 [sec] since BAT Trigger Time
COUNTS:          20    Min_needed= 20
STD_DEV:         35.64   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        3    Max_iter_allowed= 4
ERROR_CODE:      3
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Standard deviation too large.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 13:54:26 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     671231,   Seg_Num: 0
GRB_RA:          109.079d {+07h 16m 19s} (J2000),
                 109.248d {+07h 17m 00s} (current),
                 108.554d {+07h 14m 13s} (1950)
GRB_DEC:         -23.578d {-23d 34' 40"} (J2000),
                 -23.607d {-23d 36' 25"} (current),
                 -23.488d {-23d 29' 17"} (1950)
GRB_DATE:        17408 TJD;    21 DOY;   16/01/21
GRB_TIME:        49837.71 SOD {13:50:37.71} UT
TRIGGER_INDEX:   146
GRB_PHI:           7.73 [deg]
GRB_THETA:        22.82 [deg]
DELTA_TIME:      -63.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     10.04 [sigma]
IMAGE_SIGNIF:    7.25 [sigma]
LC_URL:          sw00671231000msb.lc
SUN_POSTN:       303.17d {+20h 12m 41s}  -19.94d {-19d 56' 37"}
SUN_DIST:        134.38 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.27d {+06h 01m 05s}  +18.38d {+18d 22' 46"}
MOON_DIST:        45.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.70, -5.39 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      115.24,-45.36 [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 = 158.07,3.83 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 13:55:51 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     671231,   Seg_Num: 0
GRB_RA:          109.0892d {+07h 16m 21.40s} (J2000),
                 109.2580d {+07h 17m 01.92s} (current),
                 108.5635d {+07h 14m 15.24s} (1950)
GRB_DEC:         -23.5915d {-23d 35' 29.3"} (J2000),
                 -23.6209d {-23d 37' 15.0"} (current),
                 -23.5017d {-23d 30' 05.9"} (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:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49953.00 SOD {13:52:33.00} UT,   115.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       303.17d {+20h 12m 41s}  -19.94d {-19d 56' 36"}
SUN_DIST:        134.37 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.28d {+06h 01m 08s}  +18.38d {+18d 22' 46"}
MOON_DIST:        45.90 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.72, -5.39 [deg] galactic lon,lat of the burst
ECL_COORDS:      115.25,-45.37 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        There is a bright star (mag=6.32) 11.84 arcmin from the XRT position.  
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:     Thu 21 Jan 16 13:57:42 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
POINT_ROLL:      198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49989.20 SOD {13:53:09.20} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.157
N_STARS:         190
X_OFFSET:        349 [pixels]
Y_OFFSET:        290 [pixels]
X_MAX:           1788 [pixels]
Y_MAX:           1729 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00671231000msufc0151.fits
SUN_POSTN:       303.17d {+20h 12m 41s}  -19.94d {-19d 56' 35"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.30d {+06h 01m 13s}  +18.38d {+18d 22' 47"}
MOON_DIST:        45.87 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        There is a bright star (mag=6.27) 10.10 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 13:58:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
POINT_ROLL:      198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49989.20 SOD {13:53:09.20} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.157
N_STARS:         190
X_OFFSET:        349 [pixels]
Y_OFFSET:        290 [pixels]
X_MAX:           1788 [pixels]
Y_MAX:           1729 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw00671231000msufc0151.fits
SUN_POSTN:       303.17d {+20h 12m 42s}  -19.94d {-19d 56' 35"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.31d {+06h 01m 14s}  +18.38d {+18d 22' 47"}
MOON_DIST:        45.87 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        There is a bright star (mag=6.27) 10.10 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 13:58:24 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     671231,   Seg_Num: 0
GRB_RA:          109.0891d {+07h 16m 21.38s} (J2000),
                 109.2579d {+07h 17m 01.89s} (current),
                 108.5634d {+07h 14m 15.21s} (1950)
GRB_DEC:         -23.5918d {-23d 35' 30.4"} (J2000),
                 -23.6212d {-23d 37' 16.1"} (current),
                 -23.5020d {-23d 30' 07.0"} (1950)
GRB_ERROR:       2.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49953.00 SOD {13:52:33.00} UT,   115.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       303.17d {+20h 12m 42s}  -19.94d {-19d 56' 35"}
SUN_DIST:        134.37 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.31d {+06h 01m 14s}  +18.38d {+18d 22' 47"}
MOON_DIST:        45.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.72, -5.39 [deg] galactic lon,lat of the burst
ECL_COORDS:      115.25,-45.37 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        There is a bright star (mag=6.32) 11.83 arcmin from the XRT position.  
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:     Thu 21 Jan 16 14:01:42 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
ROLL:            198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49989.20 SOD {13:53:09.20} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     475077204
X_OFFSET:        908 [pixels]
Y_OFFSET:        849 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1068
Y_GRB_POS:       1009
BINNING_INDEX:   1
IM_URL:          sw00671231000msuni0167.fits
SUN_POSTN:       303.18d {+20h 12m 42s}  -19.94d {-19d 56' 33"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.34d {+06h 01m 22s}  +18.38d {+18d 22' 48"}
MOON_DIST:        45.86 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [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).  
COMMENTS:        There is a bright star (mag=6.27) 10.10 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 14:01:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
ROLL:            198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  49989.20 SOD {13:53:09.20} UT,   151.5 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     475077204
X_OFFSET:        908 [pixels]
Y_OFFSET:        849 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1068
Y_GRB_POS:       1009
BINNING_INDEX:   1
IM_URL:          sw00671231000msuni0167.fits
SUN_POSTN:       303.18d {+20h 12m 42s}  -19.94d {-19d 56' 33"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.34d {+06h 01m 23s}  +18.38d {+18d 22' 48"}
MOON_DIST:        45.85 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [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.  
COMMENTS:        There is a bright star (mag=6.27) 10.10 arcmin from the BAT position.

GCN Circular #18912
L. M. Z. Hagen (PSU), D. N. Burrows (PSU), P.A. Evans (U Leicester), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), F. E. Marshall (NASA/GSFC), L. M. McCauley (PSU), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:
At 13:50:37 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160121A (trigger=671231). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 109.079, -23.578 which is
```
   RA(J2000) = 07h 16m 19s
   Dec(J2000) = -23d 34' 40"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single FRED- shaped peak with a duration of about 15 sec. The peak count rate was ~1700 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 13:52:08.7 UT, 91.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 109.0890, -23.5920 which is equivalent to:
```
   RA(J2000)  = 07h 16m 21.35s
   Dec(J2000) = -23d 35' 31.3"
```
with an uncertainty of 2.4 arcseconds (radius, 90% containment). This location is 60 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. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.26 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of nominal 250.000 seconds with the U filter starting 151 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.66.
Burst Advocate for this burst is L. M. Z. Hagen (lea.zernow.hagen AT gmail.com). 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:     Thu 21 Jan 16 14:06:38 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
POINT_ROLL:      198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  50697.91 SOD {14:04:57.91} UT,   860.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.294
N_STARS:         190
X_OFFSET:        349 [pixels]
Y_OFFSET:        290 [pixels]
X_MAX:           1788 [pixels]
Y_MAX:           1729 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00671231000msufc0860.fits
SUN_POSTN:       303.18d {+20h 12m 43s}  -19.94d {-19d 56' 30"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.39d {+06h 01m 34s}  +18.38d {+18d 22' 50"}
MOON_DIST:        45.84 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        There is a bright star (mag=6.19) 2.23 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 14:07:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
POINT_ROLL:      198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  50697.91 SOD {14:04:57.91} UT,   860.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.294
N_STARS:         190
X_OFFSET:        349 [pixels]
Y_OFFSET:        290 [pixels]
X_MAX:           1788 [pixels]
Y_MAX:           1729 [pixels]
DET_THRESH:      5
PHOTO_THRESH:    2
SL_URL:          sw00671231000msufc0860.fits
SUN_POSTN:       303.18d {+20h 12m 43s}  -19.94d {-19d 56' 30"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.39d {+06h 01m 35s}  +18.38d {+18d 22' 50"}
MOON_DIST:        45.83 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        There is a bright star (mag=6.19) 2.23 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 14:07:34 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
ROLL:            198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  50697.91 SOD {14:04:57.91} UT,   860.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     475077913
X_OFFSET:        908 [pixels]
Y_OFFSET:        849 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1068
Y_GRB_POS:       1009
BINNING_INDEX:   1
IM_URL:          sw00671231000msuni0876.fits
SUN_POSTN:       303.18d {+20h 12m 43s}  -19.94d {-19d 56' 29"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.40d {+06h 01m 36s}  +18.38d {+18d 22' 50"}
MOON_DIST:        45.83 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [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).  
COMMENTS:        There is a bright star (mag=6.19) 2.23 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 21 Jan 16 14:07:58 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     671231,   Seg_Num: 0
POINT_RA:        109.089d {+07h 16m 21s} (J2000)
POINT_DEC:       -23.565d {-23d 33' 53"} (J2000)
ROLL:            198.640d
IMG_START_DATE:  17408 TJD;    21 DOY;   16/01/21
IMG_START_TIME:  50697.91 SOD {14:04:57.91} UT,   860.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     475077913
X_OFFSET:        908 [pixels]
Y_OFFSET:        849 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1068
Y_GRB_POS:       1009
BINNING_INDEX:   1
IM_URL:          sw00671231000msuni0876.fits
SUN_POSTN:       303.18d {+20h 12m 43s}  -19.94d {-19d 56' 29"}
SUN_DIST:        134.40 [deg]   Sun_angle= -11.1 [hr] (East of Sun)
MOON_POSTN:       90.40d {+06h 01m 37s}  +18.38d {+18d 22' 51"}
MOON_DIST:        45.83 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      236.69, -5.38 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      115.25,-45.35 [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.  
COMMENTS:        There is a bright star (mag=6.19) 2.23 arcmin from the BAT position.

GCN Circular #18913
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk
E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory
D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Blagoveschensk was pointed to the GRB160121A (Hagen et al GCN 18912) 22 sec after notice time and 34 sec after trigger time at 2016-01-21 13:51:15 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT. The 5-sigma upper limit has been about 15.3 mag The message may be cited.
GCN Circular #18917
S. R. Oates, J. C. Tello (IAA-CSIC Granada), P. Tristram (Mt. John Univ. Observatory), I. Bond (Massey Univ.), S. Takahiro (Osaka Univ.), P. Yock (Univ. of Auckland) and A. J. Castro-Tirado (IAA-CSIC & ISA-UMA) report on behalf of a larger collaboration:
We observed the field of GRB 160121A (Hagen et al., GCN 18912) with the 1.8m MOA-II telescope at Mt John University Observatory in New Zealand. A series of 60s exposures were taken with the R-band filter beginning 4.38 min (13:55:0 UT on 21-01-2016) after the Swift trigger 671231.
We detect a single source at the edge of the Swift-XRT error circle (Hagen et al., GCN 18912), which we propose is the afterglow, at coordinates:
```
RA (J2000.0) = 07:16:21.16
Dec (J2000.0) = -23:35:31.6
```
with an error of around 0.5".
In the first exposure, ~292s after the trigger, we measure R ~19.7+\-0.2. The light curve appears to increase slightly in brightness, plateauing around 500s with a magnitude ~19. The light curve begins to decay around 1200s after the trigger.
Magnitudes and upper limits are calibrated against USNO-B1 catalogue and are not corrected for the significant Galactic extinction corresponding to a reddening of E_B-V = 0.53 mag (Schlafly & Finkbeiner 2011).
GCN Circular #18918
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team.
Using 2518 s of XRT Photon Counting mode data and 3 UVOT images for GRB 160121A, 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 = 109.08819, -23.59221 which is equivalent to:
```
RA (J2000): 07h 16m 21.17s
Dec (J2000): -23d 35' 32.0"
```
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 #18919
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), L. M. Z. Hagen (PSU), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), (i.e. the Swift-BAT team):
Using the data set from T-239 to T+340 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160121A (trigger #671231) (Hagen, et al., GCN Circ. 18912). The BAT ground-calculated position is RA, Dec = 109.080, -23.590 deg which is
```
    RA(J2000)  =  07h 16m 19.1s
    Dec(J2000) = -23d 35' 25.5"
```
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%.
The mask-weighted light curve shows a single peak starting at T-4 sec, peaking at T+3 sec and returning to baseline by T+14 sec. T90 (15-350 keV) is 12.0 +- 2.4 sec (estimated error including systematics).
The time-averaged spectrum from T-0.03 to T+14.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.77 +- 0.13. The fluence in the 15-150 keV band is 6.1 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+2.76 sec in the 15-150 keV band is 1.2 +- 0.2 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/671231/BA/
GCN Circular #18920
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of a larger GRB follow-up collaboration:
We observed the field of the Swift GRB 160121A (Hagen et al., GCN 18912) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory starting on Jan. 21 (UT) 16:04:44. We obtained several images in R filter. We detect afterglow (Oates et al., GCN 18917) in a combined image within center of the enhanced Swift-XRT position (Osborne et al., GCN 18918). Preliminary photometry of the afterglow is following
```
Date       UT start    t-T0     Filter  Exp.    OT     Err
                        (mid, days)      (s)

2016-01-21 16:04:44    0.12598  R       29*180  20.26  0.22
```
The photometry is based on nearby USNO-B1.0 stars.
```
USNO-B1.0_id    R2
0664-0122909    16.87
0664-0122918    16.73
0664-0122943    17.72
0664-0123015    18.03
0663-0123485    16.91
```
GCN Circular #18921
C. Delvaux (MPE Garching), S. Schmidl (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 160121A (Swift trigger 671231; Hagen et al., GCN #18912) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 04:09 UT on 22-01-2016, 14.3hrs after the GRB trigger. They were performed at an average seeing of 0.9" and at an average airmass of 1.0.
We clearly detect the afterglow at the position reported by Oates et al. (GCN#18917) and Mazaeva et al. (GCN#18920).
Based on the first 72 min of total exposures in g'r'i'z' and 60 min in JHK, at a midtime of 04:49 UT, we estimate preliminary magnitudes and upper limits (all in AB system) of
```
g' = 22.6 +/- 0.1 mag
r' = 21.2 +/- 0.1 mag,
i' = 21.1 +/- 0.1 mag,
z' = 21.0 +/- 0.1 mag,
J =  19.6 +/- 0.1 mag,
H =  19.3 +/- 0.1 mag,
K > 19.1 mag.
```
The given magnitudes and limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.53 in the direction of the burst (Schlafly and Finkbeiner 2011).
GCN Circular #18922
S. R. Oates (IAA-CSIC/UCL-MSSL) and L. M. Z. Hagen (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 160121A 152 s after the BAT trigger (Hagen et al., GCN Circ. 18912). No optical afterglow consistent with the optical position reported by MOA (Oates et al., GCN Circ. 18917) 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

u_FC               152          401          246         >19.7
v                  435          830           78         >18.6
u                  152          918          356         >19.9
w1                 484          754           58         >18.3
m2                 459          854           78         >18.4
w2                 410          805           78         >18.5
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.53 in the direction of the burst (Schlafly and Finkbeiner 2011).
GCN Circular #18923
P. D'Avanzo (INAF-OAB), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA) and L.M.Z. Hagen report on behalf of the Swift-XRT team:
We have analysed 7.7 ks of XRT data for GRB 160121A (Hagen et al. GCN Circ. 18912), from 75 s to 46.0 ks after the BAT trigger. The data comprise 80 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 Osborne et al. (GCN Circ. 18918).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.9 (+0.8, -0.4). At T+209 s the decay flattens to an alpha of 0.31 (+/-0.07) before breaking again at T+20.7 ks to a final decay with index alpha=2.1 (+1.6, -1.2).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.00 (+0.24, -0.18). The best-fitting absorption column is 5.8 (+1.6, -0.5) x 10^21 cm^-2, consistent with the Galactic value of 5.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10^-11 (7.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.8 (+1.6, -0.5) x 10^21 cm^-2
Galactic foreground: 5.3 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.00 (+0.24, -0.18)
```
If the light curve continues to decay with a power-law decay index of 2.1, the count rate at T+24 hours will be 3.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10^-13 (2.1 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00671231.
This circular is an official product of the Swift-XRT team.
GCN Circular #18924
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=EF=BF=BD A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=EF=BF=BDs Gonz=EF=BF=BDlez (UNAM), Carlos Rom=EF=BF=BDn-Z=EF=BF=BD=EF=BF=BDiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 160121A (Hagen et al., GCN Circular 18912) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=EF=BF=BDmico Nacional on Sierra San Pedro M=EF=BF=BDrtir from 2016/01 22.13 to 2016/01 22.29 UTC (13.28 to 17.14 hours after the BAT trigger), obtaining a total of 2.92 hours exposure in the r, i, and z bands.
We detect a source at 07:16:21.16 -23:35:31.5 J2000 (=EF=BF=BD0.5 arcsec), consistent with the enhanced Swift-XRT position (Osborne et al., GCN Circular 18918). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following magnitudes and 3-sigma upper limits:
```
   r =3D 21.73 =EF=BF=BD 0.13
   i =3D 21.10 =EF=BF=BD 0.08
   z > 19.80
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
Our observations have almost the same midpoint as the GROND observations reported by Delvaux et al. (GCN Circular 18921). The i band observations are consistent, but our r band measurement is surprisingly 0.6 mag fainter than theirs.
We thank the staff of the Observatorio Astron=EF=BF=BDmico Nacional in San Pedro M=EF=BF=BDrtir.
GCN Circular #18925
R. Sanchez-Ramirez, S. R. Oates, J. C. Tello (IAA-CSIC Granada), S. Geier (GRANTECAN), P. Tristam (Mt. John Univ. Observatory) and A. J. Castro-Tirado (IAA-CSIC and ISA-UMA) report on behalf of a larger collaboration:
We observed the field of GRB 160121A (Hagen et al. GCN 18912) with the 10.4m GTC telescope (+OSIRIS) at La Palma. 6x900s spectra were taken at the position of the optical afterglow, detected by the 1.8m MOA (Oates et al. GCNC 18917), starting at 22:30 UT (i.e. 8.7 h post-burst). We identify Mg II and several Fe-II absorption lines at z = 1.960 which we propose to be the host galaxy redshift. An intervening system at z = 1.645 is also detected.
GCN Circular #18933
E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of a larger GRB follow-up collaboration:
We observed the field of the Swift GRB 160121A (Hagen et al., GCN 18912) with Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory starting on Jan. 22 (UT) 16:17:07. We obtained several images in R filter. We do not detect afterglow (Oates et al., GCN 18917; Mazaeva et al., GCN 18920) in a combined image. Preliminary upper limit is following
```
Date       UT start    t-T0     Filter  Exp.    OT     UL (3 sigma)
                        (mid, days)      (s)

2015-01-22 16:17:07    1.13572  R       30*180  n/d    21.2
```
The photometry is based on nearby USNO-B1.0 stars (see GCN 18920).
GCN Circular #18935
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=EF=BF=BD A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=EF=BF=BDs Gonz=EF=BF=BDlez (UNAM), Carlos Rom=EF=BF=BDn-Z=EF=BF=BD=EF=BF=BDiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:
We observed the field of GRB 160121A (Hagen et al., GCN Circular 18912) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=EF=BF=BDmico Nacional on Sierra San Pedro M=EF=BF=BDrtir from 2016/01 24.13 to 2016/01 24.42 UTC (61.29 to 68.12 hours after the BAT trigger), obtaining a total of 4.27 hours exposure in the r, i and z bands.
We no longer detect the source previously reported by Watson et al. (GCN Circular 18924). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper limits:
```
   r > 22.97
   i > 22.94
   z > 20.10
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron=EF=BF=BDmico Nacional in San Pedro M=EF=BF=BDrtir.

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Jochen Greiner, last update: 25-Jan-2016 [Disclaimer]