Gamma-ray Burst 150907B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 07 Sep 15 23:26:45 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     654803,   Seg_Num: 0
GRB_RA:          255.219d {+17h 00m 53s} (J2000),
                 255.592d {+17h 02m 22s} (current),
                 254.033d {+16h 56m 08s} (1950)
GRB_DEC:         -63.819d {-63d 49' 07"} (J2000),
                 -63.841d {-63d 50' 26"} (current),
                 -63.745d {-63d 44' 41"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3599 [cnts]    Image_Peak=143 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   148     E_range: 25-100 keV
BKG_INTEN:       23409 [cnts]
BKG_TIME:        84368.89 SOD {23:26:08.89} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17272 TJD;   250 DOY;   15/09/07
GRB_TIME:        84387.77 SOD {23:26:27.77} UT
GRB_PHI:         -56.66 [deg]
GRB_THETA:        32.52 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.13 [sigma]
IMAGE_SIGNIF:    7.04 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  -3  +0  +0  +8  +0 
SUN_POSTN:       166.21d {+11h 04m 49s}   +5.90d {+05d 54' 03"}
SUN_DIST:         95.02 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      106.65d {+07h 06m 35s}  +17.37d {+17d 22' 17"}
MOON_DIST:       128.93 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      326.59,-13.12 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      261.45,-40.82 [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 = 8.78,1.83 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 07 Sep 15 23:30:36 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     654803,   Seg_Num: 0
GRB_RA:          255.219d {+17h 00m 53s} (J2000),
                 255.592d {+17h 02m 22s} (current),
                 254.033d {+16h 56m 08s} (1950)
GRB_DEC:         -63.819d {-63d 49' 07"} (J2000),
                 -63.841d {-63d 50' 26"} (current),
                 -63.745d {-63d 44' 41"} (1950)
GRB_DATE:        17272 TJD;   250 DOY;   15/09/07
GRB_TIME:        84387.77 SOD {23:26:27.77} UT
TRIGGER_INDEX:   148
GRB_PHI:         -56.66 [deg]
GRB_THETA:        32.52 [deg]
DELTA_TIME:      32.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.13 [sigma]
IMAGE_SIGNIF:    7.04 [sigma]
LC_URL:          sw00654803000msb.lc
SUN_POSTN:       166.21d {+11h 04m 50s}   +5.90d {+05d 53' 59"}
SUN_DIST:         95.02 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      106.68d {+07h 06m 44s}  +17.37d {+17d 22' 06"}
MOON_DIST:       128.92 [deg]
MOON_ILLUM:      24 [%]
GAL_COORDS:      326.59,-13.12 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      261.45,-40.82 [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 = 8.78,1.83 [deg].  
COMMENTS:        The 2nd packet (of 3) was missing in the lightcurve data stream.

GCN Circular #18249
T. G. R. Roegiers (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 23:26:27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150907B (trigger=654803). Swift could not slew immediately to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 255.219, -63.819 which is
```
   RA(J2000) = 17h 00m 53s
   Dec(J2000) = -63d 49' 07"    
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Only partial BAT lightcurve data is available, but the light curve shows a complex structure at least 10 seconds long. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+49.0 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is T. G. R. Roegiers (troegiers AT swift.psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 08 Sep 15 00:16:43 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     654803,   Seg_Num: 0
POINT_RA:        255.164d {+17h 00m 39s} (J2000)
POINT_DEC:       -63.829d {-63d 49' 44"} (J2000)
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  997.81 SOD {00:16:37.81} UT,   3010.0 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    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:     Tue 08 Sep 15 00:22:08 UT
NOTICE_TYPE:     Swift-UVOT Source List 
TRIGGER_NUM:     654803,   Seg_Num: 0   
POINT_RA:        255.164d {+17h 00m 39s} (J2000)
POINT_DEC:       -63.829d {-63d 49' 44"} (J2000)
POINT_ROLL:      273.604d 
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  1001.34 SOD {00:16:41.34} UT,   3013.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.639
N_STARS:         190 
X_OFFSET:        351 [pixels]
Y_OFFSET:        717 [pixels]
X_MAX:           1310 [pixels]
Y_MAX:           1676 [pixels]
DET_THRESH:      24
PHOTO_THRESH:    15
SL_URL:          sw00654803000msufc3013.fits
SUN_POSTN:       166.24d {+11h 04m 58s}   +5.89d {+05d 53' 11"}
SUN_DIST:         94.97 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      107.15d {+07h 08m 36s}  +17.33d {+17d 19' 36"}
MOON_DIST:       128.73 [deg] 
MOON_ILLUM:      24 [%] 
GAL_COORDS:      326.57,-13.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      261.42,-40.83 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

 
TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 08 Sep 15 00:22:44 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     654803,   Seg_Num: 0 
POINT_RA:        255.164d {+17h 00m 39s} (J2000)
POINT_DEC:       -63.829d {-63d 49' 44"} (J2000)
POINT_ROLL:      273.604d 
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  1001.34 SOD {00:16:41.34} UT,   3013.6 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.639
N_STARS:         190 
X_OFFSET:        351 [pixels]
Y_OFFSET:        717 [pixels]
X_MAX:           1310 [pixels]
Y_MAX:           1676 [pixels]
DET_THRESH:      24
PHOTO_THRESH:    15
SL_URL:          sw00654803000msufc3013.fits
SUN_POSTN:       166.24d {+11h 04m 58s}   +5.89d {+05d 53' 10"}
SUN_DIST:         94.97 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      107.16d {+07h 08m 37s}  +17.33d {+17d 19' 35"}
MOON_DIST:       128.73 [deg] 
MOON_ILLUM:      24 [%] 
GAL_COORDS:      326.57,-13.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      261.42,-40.83 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.
COMMENTS:        All 4 attachments are included.

GCN NOTICE

  
TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 08 Sep 15 00:23:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     654803,   Seg_Num: 0
POINT_RA:        255.164d {+17h 00m 39s} (J2000)
POINT_DEC:       -63.829d {-63d 49' 44"} (J2000)
ROLL:            273.604d
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  1001.34 SOD {00:16:41.34} UT,   3013.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     463364216
X_OFFSET:        670 [pixels]
Y_OFFSET:        1036 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       830 
Y_GRB_POS:       1196
BINNING_INDEX:   1
IM_URL:          sw00654803000msuni3029.fits
SUN_POSTN:       166.24d {+11h 04m 58s}   +5.89d {+05d 53' 09"}
SUN_DIST:         94.97 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      107.17d {+07h 08m 40s}  +17.33d {+17d 19' 32"}
MOON_DIST:       128.72 [deg] 
MOON_ILLUM:      24 [%] 
GAL_COORDS:      326.57,-13.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      261.42,-40.83 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image. 
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.        
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

  
TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 08 Sep 15 00:24:05 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     654803,   Seg_Num: 0 
POINT_RA:        255.164d {+17h 00m 39s} (J2000)
POINT_DEC:       -63.829d {-63d 49' 44"} (J2000)
ROLL:            273.604d
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  1001.34 SOD {00:16:41.34} UT,   3013.6 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     463364216
X_OFFSET:        670 [pixels]
Y_OFFSET:        1036 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       830 
Y_GRB_POS:       1196
BINNING_INDEX:   1
IM_URL:          sw00654803000msuni3029.fits
SUN_POSTN:       166.24d {+11h 04m 58s}   +5.89d {+05d 53' 09"}
SUN_DIST:         94.97 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      107.17d {+07h 08m 40s}  +17.33d {+17d 19' 31"}
MOON_DIST:       128.72 [deg] 
MOON_ILLUM:      24 [%] 
GAL_COORDS:      326.57,-13.11 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      261.42,-40.83 [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:     Tue 08 Sep 15 00:26:33 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     654803,   Seg_Num: 0
GRB_RA:          255.3080d {+17h 01m 13.91s} (J2000),
                 255.6807d {+17h 02m 43.37s} (current),
                 254.1229d {+16h 56m 29.50s} (1950)
GRB_DEC:         -63.7859d {-63d 47' 09.2"} (J2000),
                 -63.8078d {-63d 48' 27.9"} (current),
                 -63.7125d {-63d 42' 45.0"} (1950)
GRB_ERROR:       4.0 [arcsec radius, statistical plus systematic, 90% containment]    
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17273 TJD;   251 DOY;   15/09/08
IMG_START_TIME:  1073.00 SOD {00:17:53.00} UT,   3085.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       166.24d {+11h 04m 58s}   +5.89d {+05d 53' 07"}
SUN_DIST:         95.03 [deg]   Sun_angle= -6.0 [hr] (East of Sun)
MOON_POSTN:      107.19d {+07h 08m 46s}  +17.32d {+17d 19' 23"}
MOON_DIST:       128.79 [deg] 
MOON_ILLUM:      24 [%] 
GAL_COORDS:      326.64,-13.13 [deg] galactic lon,lat of the burst
ECL_COORDS:      261.49,-40.78 [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 1.1% < P(seren) < 2.8%.

GCN Circular #18251
J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), G. Cusumano (INAF-IASF PA), M. Perri (ASDC) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 150907B at 00:16:37.8 UT, 3010.0 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 255.30809, -63.78591 which is equivalent to:
```
   RA(J2000)  = 17h 01m 13.94s
   Dec(J2000) = -63d 47' 09.3"
```
with an uncertainty of 4.0 arcseconds (radius, 90% containment). This location is 185 arcseconds from the BAT onboard position, outside 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 1.52 x 10^21 cm^-2 (Willingale et al. 2013).
GCN Circular #18252
P. Wiseman, C. Delvaux and J. Greiner (all MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 150907B (Swift trigger 654803; Roegiers et al., GCN #18249) 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 02:03 UT on 08/09/2015, 2.63 hours after the GRB trigger. They were performed at an average seeing of 2.5" and an average airmass of 2.0.
We do not detect a source within the Swift-XRT error circle reported by Osborne et al. (GCN #18251) down to limits of:
g' > 24.5 mag,
r' > 23.9 mag,
i' > 23.3 mag,
z' > 23.2 mag,
J > 21.1 mag,
H > 20.6 mag, and
K > 19.2 mag.
We note a source at the eastern edge of the Swift-XRT error circle, at a position:
RA = 255.3110 Dec = -63.7860, or 17h 01m 14.64s -64d 47' 09.6".
This source does not seem to be fading, and with a non GRB-like SED, and matches to the known source S7FP064671 from The Guide Star Catalogue, Version 2.3.2 (Lasker B., Lattanzi M.G., McLean B.J., et al. Astron. J. 136, 735 (2008)).
The given 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)= 0.1432 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18253
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 3059 s of XRT Photon Counting mode data and 4 UVOT images for GRB 150907B, 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 = 255.30407, -63.78510 which is equivalent to:
```
RA (J2000): 17h 01m 12.98s
Dec (J2000): -63d 47' 06.4"
```
with an uncertainty of 1.9 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 #18254
D.Buckley, S. Potter, M.Kotze South African Astronomical Observatory
V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, I.Gorbunov Lomonosov Moscow State University, Sternberg Astronomical Institute
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
A. Tlatov, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory
K.Ivanov, O.Gres, N.M.Budnev, S.Yazev, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich Blagoveschensk Educational State University, Blagoveschensk
V.Krushinski, I.Zalozhnih Ural Federal University, Kourovka
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Carlos Lopez, Claudio Mallamaci and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA)
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in SAAO was pointed to the Swift Alert (Roegiers et al., GCN 18249) GRB150907B 25 sec after notice time and 40 sec after trigger time at 2015-09-07 23:27:10 UT. On our first (10s exposure) set we haven`t found optical transient within SWIFT error-box (ra=17 00 51 dec=-63 49 07 r=0.050000). The next images limit without OT:

  Id     	Coord             Pro.type Time,UT Exp.time  Lim Filt. Tube

110113	16h 59m 04.1s -63d 41m 01s  Alert  23:27:10  10	    15.5  P  EAST
110114	17h 00m 00.1s -63d 42m 55s  Alert  23:27:10  10     15.7  P  WEST
110115	16h 59m 47.7s -63d 42m 57s  Alert  23:27:34  10     15.4  P  WEST
110116	16h 59m 22.0s -63d 41m 10s  Alert  23:27:34  10     15.2  P  EAST
110117	16h 59m 47.5s -63d 42m 57s  Alert  23:27:56  20	    15.9  P  WEST
110118	16h 59m 21.8s -63d 41m 10s  Alert  23:27:56  20	    15.7  P  EAST
110119	16h 59m 21.6s -63d 41m 09s  Alert  23:28:27  20	    15.9  P  EAST
110120	16h 59m 47.4s -63d 42m 56s  Alert  23:28:27  20	    16.1  P  WEST
110121	16h 59m 21.6s -63d 41m 09s  Alert  23:28:58  30	    13.2  P  EAST
110122	16h 59m 47.4s -63d 42m 56s  Alert  23:28:58  30     13.5  P  WEST
110123	17h 00m 00.1s -63d 42m 55s SumAlert23:27:10  40	    16.3  P  WEST
110124	16h 59m 21.4s -63d 41m 08s  Alert  23:29:39  40	    15.1  P  EAST
110125	16h 59m 47.1s -63d 42m 55s  Alert  23:29:39  40	    15.5  P  WEST
110126	16h 59m 04.1s -63d 41m 01s SumAlert23:27:10  40	    16.1  P  EAST
110127	16h 59m 47.1s -63d 42m 55s  Alert  23:30:30  50	    15.9  P  WEST
110128	16h 59m 21.3s -63d 41m 08s  Alert  23:30:30  50	    15.5  P  EAST
110129	16h 59m 47.4s -63d 42m 56s SumAlert23:28:27  90     15.9  P  WEST
110130	16h 59m 21.2s -63d 41m 08s  Alert  23:31:31  60	    14.8  P  EAST
110131	16h 59m 47.1s -63d 42m 56s  Alert  23:31:31  60	    15.4  P  WEST
110132	16h 59m 21.6s -63d 41m 09s SumAlert23:28:27  110    16.1  P  EAST

There was a short time between rain and clouds. Then the clouds returned.
The message may be cited.

GCN Circular #18256
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. G. R. Roegiers (PSU), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlinks, we report further analysis of BAT GRB 150907B (trigger #654803) (Roegiers, et al., GCN Circ. 18249). The BAT ground-calculated position is RA, Dec = 255.265, -63.798 deg, which is
```
   RA(J2000)  =  17h 01m 03.5s 
   Dec(J2000) = -63d 47' 51.6" 
```
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%.
The mask-weighted light curve shows a Fred-like starting at ~T-1 sec, peaking at ~T+1 sec, and ending around T+100 sec. T90 (15-350 keV) is 62.0 +- 11.1 sec (estimated error including systematics).
The time-averaged spectrum from T-1.48 to T+64.53 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.17 +- 1.03, and Epeak of 67.4 +- 29.7 keV (chi squared 53.2 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+0.59 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.47 +- 0.18 (chi squared 59.8 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/654803/BA/
GCN Circular #18260
B. Sbarufatti (INAF-OAB/PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU) and T. G. R. Roegiers (PSU) report on behalf of the Swift-XRT team:
We have analysed 7.9 ks of XRT data for GRB 150907B (Roegiers et al. GCN Circ. 18249), from 3.0 ks to 32.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 18253).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.61 (+0.37, -0.28).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.02 (+0.28, -0.35). The best-fitting absorption column is 4.4 (+7.7, -1.8) x 10^21 cm^-2, in excess of the Galactic value of 1.5 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 4.1 x 10^-11 (6.7 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.4 (+7.7, -1.8) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 2.6 sigma
Photon index:	     2.02 (+0.28, -0.35)
```
If the light curve continues to decay with a power-law decay index of 1.61, the count rate at T+24 hours will be 3.4 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.4 x 10^-14 (2.3 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/00654803.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 08-Sep-2015 [Disclaimer]