Gamma-ray Burst 150716A

(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 16 Jul 15 07:06:58 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     649157,   Seg_Num: 0
GRB_RA:          278.466d {+18h 33m 52s} (J2000),
                 278.685d {+18h 34m 44s} (current),
                 277.762d {+18h 31m 03s} (1950)
GRB_DEC:         -13.017d {-13d 01' 00"} (J2000),
                 -13.004d {-13d 00' 14"} (current),
                 -13.056d {-13d 03' 22"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4610 [cnts]    Image_Peak=190 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       29177 [cnts]
BKG_TIME:        25585.14 SOD {07:06:25.14} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17219 TJD;   197 DOY;   15/07/16
GRB_TIME:        25603.06 SOD {07:06:43.06} UT
GRB_PHI:          56.31 [deg]
GRB_THETA:        13.03 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.49 [sigma]
IMAGE_SIGNIF:    7.13 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +1 +94  +0 
SUN_POSTN:       115.32d {+07h 41m 16s}  +21.40d {+21d 23' 54"}
SUN_DIST:        162.05 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.23d {+07h 48m 55s}  +16.41d {+16d 24' 36"}
MOON_DIST:       161.75 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.36, -2.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      278.38, 10.18 [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 = 262.38,-16.77 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:08:37 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     649157,   Seg_Num: 0
GRB_RA:          278.4873d {+18h 33m 56.95s} (J2000),
                 278.7061d {+18h 34m 49.45s} (current),
                 277.7832d {+18h 31m 07.95s} (1950)
GRB_DEC:         -12.9787d {-12d 58' 43.3"} (J2000),
                 -12.9658d {-12d 57' 56.7"} (current),
                 -13.0181d {-13d 01' 05.1"} (1950)
GRB_ERROR:       5.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.36e-09 [erg/cm2/sec]
GRB_SIGNIF:      6.78 [sigma]
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25681.23 SOD {07:08:01.23} UT,   78.2 [sec] since BAT Trigger Time
TAM[0-3]:        327.67 237.24 261.62 243.67
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:       115.32d {+07h 41m 16s}  +21.40d {+21d 23' 54"}
SUN_DIST:        162.05 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.24d {+07h 48m 58s}  +16.41d {+16d 24' 28"}
MOON_DIST:       161.75 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.40, -2.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      278.40, 10.21 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 2.59 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:08:46 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     649157,   Seg_Num: 0
GRB_RA:          278.4873d {+18h 33m 56.9s} (J2000),
                 278.7061d {+18h 34m 49.4s} (current),
                 277.7832d {+18h 31m 07.9s} (1950)
GRB_DEC:         -12.9787d {-12d 58' 43.3"} (J2000),
                 -12.9658d {-12d 57' 56.7"} (current),
                 -13.0181d {-13d 01' 05.1"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       46 [cnts]
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25681.23 SOD {07:08:01.23} UT,   78.2 [sec] since BAT Trigger Time
CENTROID_X:      283.08,  raw= 283  [pixels]
CENTROID_Y:      239.96,  raw= 240  [pixels]
ROLL:            299.84 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -136.33
GRB_POS_XRT_Z:   -52.36
IMAGE_URL:       sw00649157000msxps_rw.img
SUN_POSTN:       115.32d {+07h 41m 16s}  +21.40d {+21d 23' 54"}
SUN_DIST:        162.05 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.24d {+07h 48m 59s}  +16.41d {+16d 24' 28"}
MOON_DIST:       161.75 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.40, -2.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      278.40, 10.21 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:08:59 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     649157,   Seg_Num: 0
GRB_RA:          278.4873d {+18h 33m 56.9s} (J2000),
                 278.7061d {+18h 34m 49.4s} (current),
                 277.7832d {+18h 31m 07.9s} (1950)
GRB_DEC:         -12.9787d {-12d 58' 43.3"} (J2000),
                 -12.9658d {-12d 57' 56.7"} (current),
                 -13.0181d {-13d 01' 05.1"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       46 [cnts]
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25681.23 SOD {07:08:01.23} UT,   78.2 [sec] since BAT Trigger Time
CENTROID_X:      283.08,  raw= 283  [pixels]
CENTROID_Y:      239.96,  raw= 240  [pixels]
ROLL:            299.84 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -136.33
GRB_POS_XRT_Z:   -52.36
IMAGE_URL:       sw00649157000msxps_rw.img
SUN_POSTN:       115.32d {+07h 41m 16s}  +21.40d {+21d 23' 53"}
SUN_DIST:        162.05 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.25d {+07h 48m 59s}  +16.41d {+16d 24' 27"}
MOON_DIST:       161.75 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.40, -2.08 [deg] galactic lon,lat of the burst
ECL_COORDS:      278.40, 10.21 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:10:48 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     649157,   Seg_Num: 0
GRB_RA:          278.466d {+18h 33m 52s} (J2000),
                 278.685d {+18h 34m 44s} (current),
                 277.762d {+18h 31m 03s} (1950)
GRB_DEC:         -13.017d {-13d 01' 00"} (J2000),
                 -13.004d {-13d 00' 14"} (current),
                 -13.056d {-13d 03' 22"} (1950)
GRB_DATE:        17219 TJD;   197 DOY;   15/07/16
GRB_TIME:        25603.06 SOD {07:06:43.06} UT
TRIGGER_INDEX:   146
GRB_PHI:          56.31 [deg]
GRB_THETA:        13.03 [deg]
DELTA_TIME:      -31.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.49 [sigma]
IMAGE_SIGNIF:    7.13 [sigma]
LC_URL:          sw00649157000msb.lc
SUN_POSTN:       115.32d {+07h 41m 17s}  +21.40d {+21d 23' 53"}
SUN_DIST:        162.05 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.26d {+07h 49m 03s}  +16.41d {+16d 24' 18"}
MOON_DIST:       161.72 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.36, -2.08 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      278.38, 10.18 [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 = 262.38,-16.77 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:11:58 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     649157,   Seg_Num: 0
POINT_RA:        278.481d {+18h 33m 56s} (J2000)
POINT_DEC:       -13.019d {-13d 01' 07"} (J2000)
POINT_ROLL:      299.839d
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25689.22 SOD {07:08:09.22} UT,   86.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.467
N_STARS:         190
X_OFFSET:        544 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1503 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00649157000msufc0086.fits
SUN_POSTN:       115.32d {+07h 41m 17s}  +21.40d {+21d 23' 52"}
SUN_DIST:        162.06 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.27d {+07h 49m 06s}  +16.40d {+16d 24' 13"}
MOON_DIST:       161.72 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.37, -2.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      278.39, 10.17 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 16 Jul 15 07:12:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     649157,   Seg_Num: 0
POINT_RA:        278.481d {+18h 33m 56s} (J2000)
POINT_DEC:       -13.019d {-13d 01' 07"} (J2000)
POINT_ROLL:      299.839d
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25689.22 SOD {07:08:09.22} UT,   86.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.467
N_STARS:         190
X_OFFSET:        544 [pixels]
Y_OFFSET:        488 [pixels]
X_MAX:           1503 [pixels]
Y_MAX:           1447 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw00649157000msufc0086.fits
SUN_POSTN:       115.32d {+07h 41m 17s}  +21.40d {+21d 23' 52"}
SUN_DIST:        162.06 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.28d {+07h 49m 07s}  +16.40d {+16d 24' 11"}
MOON_DIST:       161.72 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.37, -2.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      278.39, 10.17 [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:     Thu 16 Jul 15 07:14:06 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     649157,   Seg_Num: 0
POINT_RA:        278.481d {+18h 33m 56s} (J2000)
POINT_DEC:       -13.019d {-13d 01' 07"} (J2000)
ROLL:            299.839d
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25689.22 SOD {07:08:09.22} UT,   86.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     458723304
X_OFFSET:        1020 [pixels]
Y_OFFSET:        1074 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1180
Y_GRB_POS:       1234
BINNING_INDEX:   1
IM_URL:          sw00649157000msuni0101.fits
SUN_POSTN:       115.32d {+07h 41m 17s}  +21.40d {+21d 23' 51"}
SUN_DIST:        162.06 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.29d {+07h 49m 10s}  +16.40d {+16d 24' 03"}
MOON_DIST:       161.71 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.37, -2.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      278.39, 10.17 [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:     Thu 16 Jul 15 07:14:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     649157,   Seg_Num: 0
POINT_RA:        278.481d {+18h 33m 56s} (J2000)
POINT_DEC:       -13.019d {-13d 01' 07"} (J2000)
ROLL:            299.839d
IMG_START_DATE:  17219 TJD;   197 DOY;   15/07/16
IMG_START_TIME:  25689.22 SOD {07:08:09.22} UT,   86.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     458723304
X_OFFSET:        1020 [pixels]
Y_OFFSET:        1074 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1180
Y_GRB_POS:       1234
BINNING_INDEX:   1
IM_URL:          sw00649157000msuni0101.fits
SUN_POSTN:       115.32d {+07h 41m 17s}  +21.40d {+21d 23' 51"}
SUN_DIST:        162.06 [deg]   Sun_angle= -10.9 [hr] (East of Sun)
MOON_POSTN:      117.29d {+07h 49m 11s}  +16.40d {+16d 24' 02"}
MOON_DIST:       161.71 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:       19.37, -2.09 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      278.39, 10.17 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #18027
D. Kocevski (NASA/GSFC/ORAU), A. Y. Lien (GSFC/UMBC), A. Maselli (INAF-IASFPA), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the Swift Team:
At 07:06:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150716A (trigger=649157). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 278.466, -13.017 which is
```
   RA(J2000) = 18h 33m 52s
   Dec(J2000) = -13d 01' 00"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~5 sec after the trigger.
The XRT began observing the field at 07:08:01.2 UT, 78.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 278.4873, -12.9787 which is equivalent to:
```
   RA(J2000)  = +18h 33m 56.95s
   Dec(J2000) = -12d 58' 43.3"
```
with an uncertainty of 5.3 arcseconds (radius, 90% containment). This location is 156 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.
The initial flux in the 2.5 s image was 1.36e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of 127 seconds with the White filter starting 86 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 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 0.00% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain extinction expected.
Burst Advocate for this burst is D. Kocevski (dankocevski 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 Circular #18028
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara=20 (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico=20 Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report:
We observed the field of GRB 150716A (Kocevski et al., GCN 18027) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on=20 Sierra San Pedro M=E1rtir from 2015/07 16.30 to 2015/07 16.45 UTC (0.06 to 3.61 hours after the BAT trigger), obtaining a total of 2.21 hours exposure in the r and i bands.
The field is crowded. Nevertheless, we detect a candidate optical afterglow within but close to the edge of the unenhanced Swift-XRT error circle at 18:33:57.20 -12:58:40.1 (J2000, =B10.5"). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections:
```
  r	20.34 =B1 0.02
  i	19.23 =B1 0.02
```
At the moment, we have no information on fading, but further observations are planned.
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=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #18029
S. B. Cenko (NASA/GSFC) and D. A. Perley (DARK) report on behalf of a larger collaboration:
We have imaged the location of the X-ray afterglow of GRB 150716A (Kocevski et al., GCN 18027) with the automated Palomar 60 inch telescope. Observations were obtained in the r, i, and z filters beginning at 07:11 UT (~ 4 minutes after the Swift trigger time) and ending at 8:18 UT. Within the XRT error circle, we detect a large number of sources, one of which shows marginal evidence for fading:
```
  RA: 18:33:57.13
  Dec: -12:58:46.3
```
By comparison with the nearby USNO-B1 catalog star 0770-0591035 (I2 magnitude = 17.66), we measure the following magnitudes for this source:
```
UT          Magnitude
----------------------------------
07:11      21.48 +/- 0.22
08:17      > 22.15 
```
The source reported by RATIR (Watson et al, GCN 18028) is clearly detected in our images, but a) does not appear to fade, and b) is outside the revised XRT error circle.
We thank Alan Watson and Nat Butler for sharing the RATIR images with us.
GCN Circular #18030
B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and D. Kocevski report on behalf of the Swift-XRT team:
We have analysed 3.6 ks of XRT data for GRB 150716A (Kocevski et al. GCN Circ. 18027), from 66 s to 22.7 ks after the BAT trigger. The data comprise 126 s in Windowed Timing (WT) mode (the first 11 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The refined XRT position is RA, Dec = 278.4879, -12.9802 which is equivalent to:
```
RA (J2000): 18 33 57.10
Dec(J2000): -12 58 48.9
```
with an uncertainty of 4.1 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.67 (+0.08, -0.06).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.67 (+0.25, -0.23). The best-fitting absorption column is 1.35 (+0.24, -0.22) x 10^22 cm^-2, in excess of the Galactic value of 7.0 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 3.6 x 10^-11 (1.4 x 10^-10) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Total column:	     1.35 (+0.24, -0.22) x 10^22 cm^-2
Galactic foreground: 7.0 x 10^21 cm^-2
Excess significance: 4.8 sigma
Photon index:	     2.67 (+0.25, -0.23)
```
If the light curve continues to decay with a power-law decay index of 1.67, the count rate at T+24 hours will be 2.4 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.8 x 10^-15 (3.5 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/00649157.
This circular is an official product of the Swift-XRT team.
GCN Circular #18032
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos=E9 A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes=FAs Gonz=E1lez (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report:
We observed the field of GRB 150716A (Kocevski et al., GCN 18027) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron=F3mico Nacional on=20 Sierra San Pedro M=E1rtir from 2015/07 17.16 to 2015/07 17.46 UTC (20.69 to 27.82 hours after the BAT trigger), obtaining a total of 4.31 hours exposure in the r and i bands.
In these observations, the source reported by Watson et al. (GCN 18028) is detected with
```
r 20.43 =B1 0.02
i 19.89 =B1 0.02
```
These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB.
While these formal errors would suggest a slight fading compared to the=20 first night, in a crowded field such as this one, the real errors in the=20 photometry are likely to be much larger than these formal errors of 0.02=20 mag. We feel that there is no strong evidence for fading. Also, as noted=20 by Cenko & Perley (GCN 18029), this source is significantly outside the=20 enhanced XRT error region reported by Sbarufatti et al. (GCN 18030). We=20 therefore conclude that it is not the afterglow.
We see no evidence for the source reported by Cenko & Perley (GCN 18029) in any of our images. However, this is not unexpected, since our images have significantly worse image quality than theirs.
We thank the staff of the Observatorio Astron=F3mico Nacional in San Pedro M=E1rtir.
GCN Circular #18033
S. J. LaPorte (PSU) and D. Kocevski (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 150716A 86 s after the BAT trigger (Kocevski et al., GCN Circ. 18027). No optical afterglow consistent with the enhanced XRT position (Sbarufatti et al. GCN Circ. 18030) 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)          86          213          125         >19.8
white            11701        12468          747         >21.11
v                 5994         6193          196         >18.62
b                 5378        22713         1512         >20.86
u                 6608         6721          111         >19.17
uvw1              6404         6603          196         >19.38
uvm2              6198         6398          196         >19.38
uvw2              5789         5989          196         >19.61
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.43 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18034
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), D. Kocevski (NASA/GSFC/ORAU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), 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-61 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150716A (trigger #649157) (Kocevski, et al., GCN Circ. 18027). The BAT ground-calculated position is RA, Dec = 278.481, -12.978 deg which is
```
   RA(J2000)  =  18h 33m 55.4s
   Dec(J2000) = -12d 58' 40.8"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%.
BAT light curve shows a single peak starting around T+5 sec and ending around T+60 sec. T90 (15-350 keV) is 44 +- 6 sec (estimated error including systematics).
The time-averaged spectrum from T-4.19 to T+50.02 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.10. The fluence in the 15-150 keV band is 1.5 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+9.69 sec in the 15-150 keV band is 0.8 +- 0.1 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/649157/BA/
GCN Circular #18036
Xianggao Wang (UC Berkeley, GXU, UNLV), WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, responded to Swift GRB 150716A (Kocevski et al., GCN 18027) starting at 07:10:08 UT, 195 s after the burst. Observations were performed with an automatic sequence in the clear (roughly R), V, and I filters, and the exposure time was 20 s per image. After combining 6 x 20 s clear-band images, we do not detect the optical source reported by Cenko et al. (GCN 18029), nor any other new source within the XRT error circle (Sbarufatti et al., GCN 18030). The upper limit is estimated to be about 20.9 mag at a mean time of 443 s after the trigger, calibrated to USNO B1.0.

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Jochen Greiner, last update: 20-Jul-2015 [Disclaimer]