Gamma-ray Burst 170906C

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 06 Sep 17 07:26:34 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     770981,   Seg_Num: 0
GRB_RA:          128.704d {+08h 34m 49s} (J2000),
                 129.149d {+08h 36m 36s} (current),
                 127.431d {+08h 29m 44s} (1950)
GRB_DEC:         +70.782d {+70d 46' 54"} (J2000),
                 +70.720d {+70d 43' 11"} (current),
                 +70.953d {+70d 57' 12"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3676 [cnts]    Image_Peak=235 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   148     E_range: 25-100 keV
BKG_INTEN:       20040 [cnts]
BKG_TIME:        26764.35 SOD {07:26:04.35} UT
BKG_DUR:         8 [sec]
GRB_DATE:        18002 TJD;   249 DOY;   17/09/06
GRB_TIME:        26777.60 SOD {07:26:17.60} UT
GRB_PHI:         -30.69 [deg]
GRB_THETA:        45.37 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.11 [sigma]
IMAGE_SIGNIF:    11.09 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +1  +0  +0 -36  +0 
SUN_POSTN:       165.17d {+11h 00m 41s}   +6.33d {+06d 19' 51"}
SUN_DIST:         68.31 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.05d {+23h 04m 12s}   -7.79d {-07d 47' 35"}
MOON_DIST:       112.93 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.85, 33.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      108.61, 49.83 [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 = 186.49,-1.44 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 06 Sep 17 07:29:43 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     770981,   Seg_Num: 0
GRB_RA:          128.704d {+08h 34m 49s} (J2000),
                 129.149d {+08h 36m 36s} (current),
                 127.431d {+08h 29m 44s} (1950)
GRB_DEC:         +70.782d {+70d 46' 54"} (J2000),
                 +70.720d {+70d 43' 11"} (current),
                 +70.953d {+70d 57' 12"} (1950)
GRB_DATE:        18002 TJD;   249 DOY;   17/09/06
GRB_TIME:        26777.60 SOD {07:26:17.60} UT
TRIGGER_INDEX:   148
GRB_PHI:         -30.69 [deg]
GRB_THETA:        45.37 [deg]
DELTA_TIME:      -44.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     21.11 [sigma]
IMAGE_SIGNIF:    11.09 [sigma]
LC_URL:          sw00770981000msb.lc
SUN_POSTN:       165.17d {+11h 00m 41s}   +6.33d {+06d 19' 49"}
SUN_DIST:         68.32 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.08d {+23h 04m 19s}   -7.78d {-07d 47' 03"}
MOON_DIST:       112.91 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.85, 33.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      108.61, 49.83 [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 = 186.49,-1.44 [deg].

GCN Circular #21826
M. H. Siegel (PSU), S. D. Barthelmy (GSFC), P. A. Evans (U Leicester), C. Gronwall (PSU), K. L. Page (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Swift Team:
At 07:26:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 170906C (trigger=770981). Swift did not slew due to an observing constraint. The BAT on-board calculated location is RA, Dec 128.704, +70.782, which is
```
   RA(J2000)  =  08h 34m 49s
   Dec(J2000) = +70d 46' 54"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple overlapping peaks with a total duration of about 30 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~6 sec after the trigger.
Due to an observing constraint, Swift will not slew until T0+18.9 minutes. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is M. H. Siegel (siegel 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:     Wed 06 Sep 17 08:00:12 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     770981,   Seg_Num: 0
POINT_RA:        128.813d {+08h 35m 15s} (J2000)
POINT_DEC:       +70.824d {+70d 49' 27"} (J2000)
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28069.67 SOD {07:47:49.67} UT,   1292.1 [sec] since BAT Trigger Time
COUNTS:          3    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:     Wed 06 Sep 17 08:01:42 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     770981,   Seg_Num: 0
POINT_RA:        128.812d {+08h 35m 15s} (J2000)
POINT_DEC:       +70.824d {+70d 49' 28"} (J2000)
POINT_ROLL:      140.651d
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28073.96 SOD {07:47:53.96} UT,   1296.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.740
N_STARS:         43
X_OFFSET:        747 [pixels]
Y_OFFSET:        871 [pixels]
X_MAX:           1706 [pixels]
Y_MAX:           1830 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00770981000msufc1296.fits
SUN_POSTN:       165.19d {+11h 00m 46s}   +6.32d {+06d 19' 19"}
SUN_DIST:         68.34 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.36d {+23h 05m 27s}   -7.69d {-07d 41' 40"}
MOON_DIST:       112.76 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.79, 33.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      108.63, 49.89 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Wed 06 Sep 17 08:01:59 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     770981,   Seg_Num: 0
POINT_RA:        128.812d {+08h 35m 15s} (J2000)
POINT_DEC:       +70.824d {+70d 49' 28"} (J2000)
POINT_ROLL:      140.651d
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28073.96 SOD {07:47:53.96} UT,   1296.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.740
N_STARS:         43
X_OFFSET:        747 [pixels]
Y_OFFSET:        871 [pixels]
X_MAX:           1706 [pixels]
Y_MAX:           1830 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw00770981000msufc1296.fits
SUN_POSTN:       165.19d {+11h 00m 46s}   +6.32d {+06d 19' 18"}
SUN_DIST:         68.34 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.36d {+23h 05m 27s}   -7.69d {-07d 41' 38"}
MOON_DIST:       112.76 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.79, 33.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      108.63, 49.89 [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:     Wed 06 Sep 17 08:02:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     770981,   Seg_Num: 0
POINT_RA:        128.812d {+08h 35m 15s} (J2000)
POINT_DEC:       +70.824d {+70d 49' 28"} (J2000)
ROLL:            140.651d
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28073.96 SOD {07:47:53.96} UT,   1296.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     526376893
X_OFFSET:        1066 [pixels]
Y_OFFSET:        1190 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1226
Y_GRB_POS:       1350
BINNING_INDEX:   1
IM_URL:          sw00770981000msuni1316.fits
SUN_POSTN:       165.19d {+11h 00m 46s}   +6.32d {+06d 19' 18"}
SUN_DIST:         68.34 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.37d {+23h 05m 29s}   -7.69d {-07d 41' 28"}
MOON_DIST:       112.75 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.79, 33.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      108.63, 49.89 [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:     Wed 06 Sep 17 08:03:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     770981,   Seg_Num: 0
POINT_RA:        128.812d {+08h 35m 15s} (J2000)
POINT_DEC:       +70.824d {+70d 49' 28"} (J2000)
ROLL:            140.651d
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28073.96 SOD {07:47:53.96} UT,   1296.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     526376893
X_OFFSET:        1066 [pixels]
Y_OFFSET:        1190 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1226
Y_GRB_POS:       1350
BINNING_INDEX:   1
IM_URL:          sw00770981000msuni1316.fits
SUN_POSTN:       165.19d {+11h 00m 46s}   +6.32d {+06d 19' 17"}
SUN_DIST:         68.34 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.37d {+23h 05m 30s}   -7.69d {-07d 41' 26"}
MOON_DIST:       112.75 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.79, 33.96 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      108.63, 49.89 [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:     Wed 06 Sep 17 08:03:37 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     770981,   Seg_Num: 0
GRB_RA:          128.6498d {+08h 34m 35.95s} (J2000),
                 129.0962d {+08h 36m 23.08s} (current),
                 127.3760d {+08h 29m 30.23s} (1950)
GRB_DEC:         +70.8119d {+70d 48' 42.8"} (J2000),
                 +70.7501d {+70d 45' 00.4"} (current),
                 +70.9834d {+70d 59' 00.1"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18002 TJD;   249 DOY;   17/09/06
IMG_START_TIME:  28100.00 SOD {07:48:20.00} UT,   1322.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       165.19d {+11h 00m 46s}   +6.32d {+06d 19' 17"}
SUN_DIST:         68.36 [deg]   Sun_angle= 2.4 [hr] (West of Sun)
MOON_POSTN:      346.38d {+23h 05m 31s}   -7.69d {-07d 41' 21"}
MOON_DIST:       112.72 [deg]
MOON_ILLUM:      100 [%]
GAL_COORDS:      143.82, 33.91 [deg] galactic lon,lat of the burst
ECL_COORDS:      108.57, 49.85 [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 Circular #21828
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB) and G. Cusumano (INAF-IASF PA) report on behalf of the Swift-XRT team:
The XRT began observing the field of GRB 170906C at 07:47:49.6 UT, 1292.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 128.65022, 70.81211 which is equivalent to:
```
   RA(J2000)  = 08h 34m 36.05s
   Dec(J2000) = +70d 48' 43.6"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 125 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 (3.30 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.1 (+0.39/-0.34) x 10^22 cm^-2 (90% confidence).
GCN Circular #21831
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1795 s of XRT Photon Counting mode data and 2 UVOT images for GRB 170906C, 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 = 128.65367, +70.81162 which is equivalent to:
```
RA (J2000): 08h 34m 36.88s
Dec (J2000): +70d 48' 41.8"
```
with an uncertainty of 1.8 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 #21832
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 170906C (trigger #770981) (Siegel, et al., GCN Circ. 21826). The BAT ground-calculated position is RA, Dec = 128.659, 70.805 deg, which is
```
   RA(J2000)  =  08h 34m 38.1s
   Dec(J2000) = +70d 48' 16.7"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 32%.
The mask-weighted light curve shows multiple overlapping peaks starting at ~T-40 sec, peaking at ~T+7 sec, and returning to baseline at ~T+100 sec. T90 (15-350 keV) is 48.4 +- 4.7 sec (estimated error including systematics).
The time-averaged spectrum from T-35.21 to T+39.22 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.30 +- 0.22, and Epeak of 104.8 +- 43.0 keV (chi squared 47.9 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 8.8 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+6.18 sec in the 15-150 keV band is 7.2 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.67 +- 0.05 (chi squared 56.9 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/770981/BA/
GCN Circular #21834
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), D.N. Burrows (PSU), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB) and M.H. Siegel report on behalf of the Swift-XRT team:
We have analysed 6.5 ks of XRT data for GRB 170906C (Siegel et al. GCN Circ. 21826), from 1.3 ks to 20.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 21831).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.65 (+0.07, -0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.69 (+0.21, -0.20). The best-fitting absorption column is 9.4 (+1.4, -1.3) x 10^21 cm^-2, in excess of the Galactic value of 3.3 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 3.4 x 10^-11 (1.2 x 10^-10) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     9.4 (+1.4, -1.3) x 10^21 cm^-2
Galactic foreground: 3.3 x 10^20 cm^-2
Excess significance: 11.3 sigma
Photon index:	     2.69 (+0.21, -0.20)
```
If the light curve continues to decay with a power-law decay index of 0.65, the count rate at T+24 hours will be 0.027 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.1 x 10^-13 (3.2 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00770981.
This circular is an official product of the Swift-XRT team.
GCN Circular #21835
M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 170906C 1296 s after the BAT trigger (Siegel et al., GCN Circ. 21826). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 21828) 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          1296         1446          147         >21.6
white             1296         2585          284         >21.4
v                 1578         2635          136         >19.4
b                 1504         2913          333         >19.9
u                 1479         2708          156         >20.6
w1                1454         2684          156         >19.9
m2                2467         2487           19         >17.8
w2                2591         2611           19         >19.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #21837
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Carlos Rom=E1n-Z=FA=F1iga (UNAM), and William H. Lee (UNAM) report:
We observed the field of the GRB 170906C (Siegel et al., GCN Circ. 21826) with the COATLI 50-cm telescope and interim CCD imager (Watson et al. 2016, Proc. SPIE, 9908, 50) at the Observatorio Astron=F3mico Nacional on the Sierra de San Pedro M=E1rtir from 2017-09-06 08:17 to 12:11 obtaining a total of 2.93 hours of observation in the clear w filter.
We do not detect a source within the enhanced XRT error region reported by Evans et al. (GCN Circ. 21831). Calibrating with respect to the USNO-B1 catalog, we estimate a 3-sigma upper limit of:
w > 21.7
This magnitude is in the AB system and is not corrected for Galactic extinction in the direction of the GRB.
We thank the COATLI technical team (Fernando =C1ngeles, Oscar Chapa, Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosal=EDa Langarica, Fernando Quir=F3s, and Carlos Tejada) and the staff of the Observatorio Astron=F3mico Nacional.
GCN Circular #21843
L. Izzo, A. de Ugarte Postigo, D.A. Kann (IAA-CSIC/HETH) report on behalf of a larger collaboration:
We observed the field of GRB 170906C (Siegel et al., GCN 21826) with the T24 (Plane Wave CDK 0.61m) of the iTelescope.Net (http://www.itelescope.net) located at Auberry, CA. A set of 3 images of 300 s each were taken in the I filter, starting at 10:30:39 UT, ~ 2.9 hours after the GRB trigger.
We do not detect any source inside the XRT refined error region (Evans et al., GCN 21831) and estimate a 3-sigma upper limit of I > 19.0
GCN Circular #21857
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 170906C (Swift-BAT trigger #770981: Siegel et al., GCN 21826; Lien et al., GCN 21832) triggered Konus-Wind at T0=3D26780.985 s UT (07:26:20.985).
The burst light curve shows a single pulse started at ~T0-40.8 s with a total duration of ~65.8 s. The emission is seen up to ~4 MeV.
As observed by Konus-Wind, the burst had a fluence of=A0 1.60(-0.19,+0.28)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+0.354 s, of 2.77(-0.73,+0.74)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 4 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with=A0 alpha =3D -1.06(-0.18,+0.19), and Ep =3D 154(-19,+26) keV (chi2 =3D 64/72 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.56 (chi2 =3D 64/71 dof).
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170906_T26780/
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #21949
K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
The AMI Large Array robotically triggered on the Swift alert for GRB 170906C (Siegel et al., GCN 21826) as part of the 4pisky program. Our observation at 15 GHz on 2017 Sep 06.55 (UT) does not reveal any radio source at the XRT location (Evans et al., GCN 21831), with a 3sigma upper limit of 156 uJy. Further follow up observations have not been possible due to telescope maintenance.
We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.

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