GRB 160912A

K. P. Mooley, 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 
160912A (Cannizzo et al., GCN 19912
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 ) as part of the 4pisky program, and 
subsequent follow up observations were obtained up to 10 days 
post-burst. Our observations at 15 GHz on 2016 Sep 12.72, Sep 13.81, and 
Sep 18.87 (UT) do not reveal any radio source at the XRT location 
(Beardmore et al., GCN 19915
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 ), with 3sigma upper limits of 147 uJy, 258 
uJy, and 102 uJy respectively.

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/.

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. K. Cannizzo (NASA/UMBC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
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-239 to T+959 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160912A (trigger #711914)
(Cannizzo, et al., GCN Circ. 19912
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 ).  The BAT ground-calculated position is
RA, Dec = 301.595, 57.585 deg which is
  RA(J2000)  =  20h 06m 22.7s
  Dec(J2000) = +57d 35' 04.8"
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows some weak emissions that starts at ~ T-33 s,
and a FRED-like pulse from ~T+140 s to ~T+200 s. We do not have much
information of the burst emission afterwards due to some large gaps in the data
after ~T+320 s.

The time-averaged spectrum using the available data from T-33 to T+211 sec is best fit
by a simple power-law model.  The power law index of the time-averaged spectrum is
1.43 +- 0.11.  The fluence in the 15-150 keV band is 3.7 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+148.56 sec in the 15-150 keV band
is 1.6 +- 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/711914/BA/

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora
Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos�� A.
de Diego (UNAM), Leonid Georgiev (UNAM), Jes��s Gonz��lez (UNAM), Carlos
Rom��n-Z����iga (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 160912A (Cannizzo et al., GCN 19912
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 ) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional on
Sierra San Pedro M��rtir from 2016/09 13.14 to 2016/09 13.24 UTC (11.20 to
13.52 hours after the BAT trigger), obtaining a total of 1.76 hours
exposure in the r and i bands and 0.74 hours exposure in the Z, Y, J, and H
bands.

We detect the optical afterglow reported by Tanvir et al. (GCN 19918
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 ).  In
comparison with the USNO-B1 and 2MASS catalogs, we obtain the following
detections and (3-sigma) upper limits:

r = 23.05 +/- 0.10
i = 22.73 +/- 0.13
Z = 22.62 +/- 0.31
Y = 22.13 +/- 0.29
J > 21.91
H > 21.72

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��mico Nacional in San Pedro
M��rtir.

F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160912A
138 s after the BAT trigger (Cannizzo et al., GCN Circ. 19912
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 ).
There is a weak detection of a source consistent with the XRT position
(Beardmore et al., GCN Circ. 19915
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 ) and the optical afterglow
positions (Tanvir and Levan, GCN Circ. 19918
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 ; Mazaeva et al., GCN Circ. 19919
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 )
in the initial UVOT exposures. There is little evidence for
variability.

The preliminary UVOT position is:
   RA  (J2000) =  20:05:59.74  = 301.49893 (deg.)
   Dec (J2000) =  +57:33:56.0  =  57.56555 (deg.)
with an estimated uncertainty of 1.0 arcsec. (radius, 90% confidence).

Preliminary detections and 2-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              138         8135          883         22.03 +/- 0.27
v                  626         7110          411         20.60 +/- 0.44
b                  552         7931          584        >22.14
u                  296         7726          814        >21.92
w1                 675         7520          588        >21.25
m2                 650         7314          391        >20.75
w2                 602         8215          484        >21.05

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.20 in the direction of the burst
(Schlegel et al. 1998).

A. Volnova (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP), E. Mazaeva 
(IKI), I. Korobtsev (ISTP)  report on behalf of larger GRB follow-up 
collaboration:

We observed the field of the GRB 160912A (Cannizzo et al.
GCN 19912
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 ) with  AZT-33IK telescope of Sayan observatory (Mondy) 
starting on Sep., 12 (UT) 18:14:25. We obtained several images in 
R-filter. We  clearly detected optical afterglow (Tanvir et al., GCN 
1991
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 ). Coordinates of the afterglow are (J2000)   20 05 59.64
+57 33 55.2 with uncertainty of 0.4 arcsec in both coordinates. The 
afterglow is 5 arcsec from nearby star (USNO-B1.0 1475-0371357 (J2000) 
RA = 20:06:00.32 Dec = +57:33:57.0 R2 = 18.21) and within enhanced XRT 
position (Beardmore et al. GCN 19915
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 ). Preliminary photometry  of the 
afterglow is following

Date        UT start   t-T0      Filter Exp.   OT        UL (3 sigma)
                        (mid, days)       (s)

2016-09-12  18:14:25   0.10883    R     30*120 22.57 +/-0.08  23.5

Photometry is based on nearby USNO-B1.0 stars
ID             RA           Dec        R2
2 1475-0371275 20:05:49.83 +57:33:12.9 17.09
3 1475-0371352 20:05:59.47 +57:32:43.8 17.46
4 1475-0371174 20:05:41.08 +57:33:00.0 17.43
5 1475-0371504 20:06:16.57 +57:32:46.8 17.62

The finding chart can be found at 
http://grb.rssi.ru/GRB160912A/GRB160912A_160912_AZT33IK_fc.png

N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick),
report on behalf of a larger collaboration:

We observed the field of Swift GRB 160912A (Cannizzo et al.
GCN 19912
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 ) with the 2m Liverpool Telescope on La Palma
with the IO:O camera.

Images were obtained in the r and i filters at two epochs,
each exposure being 25 mins in total. Within the revised
X-ray error circle (Beardmore et al. GCN 19915
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 ) we find a
point source with the following provisional magnitudes 
and start times relative to the BAT trigger time:

epoch1 dt=17053s i=22.10+/-0.15
epoch1 dt=18664s r=22.77+/-0.20
epoch2 dt=29285s i=22.57+/-0.17
epoch2 dt=30897s r=23.11+/-0.21

Given the evidence for fading, we conclude this is likely
the optical afterglow of the GRB.

The J2000 position of the source is 20:05:59.68 +57:33:54.9
to an accuracy of about 0.5".

L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),
B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri
(INAF-OAB) and J.K. Cannizzo report on behalf of the Swift-XRT team:

We have analysed 8.0 ks of XRT data for GRB 160912A (Cannizzo et al.
GCN Circ. 19912
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 ), from 119 s to 36.9 ks after the  BAT trigger. The
data comprise 776 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
Beardmore et al. (GCN Circ. 19915
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 ).

The late-time light curve (from T0+5.8 ks) can be modelled with a
power-law decay with a decay index of alpha=.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.63 (+/-0.04). The
best-fitting absorption column is  2.80 (+/-0.20) x 10^21 cm^-2, in
excess of the Galactic value of 2.4 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.81 (+0.11, -0.10)
and a best-fitting absorption column of 3.0 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.2 x 10^-11 (5.6 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.0 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 2.4 x 10^21 cm^-2
Excess significance: 2.1 sigma
Photon index:	     1.81 (+0.11, -0.10)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00711914.

This circular is an official product of the Swift-XRT team.

R. Hamburg (UAH)
reports on behalf of the Fermi GBM Team:

"At 16:10:11.39 UT on 12 September 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160912A (trigger 495389415 / 160912674).

This burst was also detected by the Swift BAT approximately
150 s after the Swift trigger time and reported as an x-ray flare
approximately 89 arcseconds from the BAT onboard position
(Cannizzo et al. 2016, GCN 19912
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 ). At the time of the Swift trigger,
the source was occulted by the Earth for Fermi.
The GBM on-ground location is consistent with the Swift position.

The GBM light curve consists of multiple peaks
with a duration (T90) of about 48 s (10-1000 keV).
The time-averaged spectrum from T0-4 s to T0+42 s is
best fit by a simple power law function with index -1.48 +/- 0.03.

The event fluence (10-1000 keV) in this time interval is
(6.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.4 s in the 10-1000 keV band
is 1.6 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1795 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160912A, 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 = 301.49915, +57.56557 which is equivalent
to:

RA (J2000): 20h 05m 59.80s
Dec (J2000): +57d 33' 56.0"

with an uncertainty of 1.7 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.

J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU), A. D'Ai (INAF-IASFPA),
V. D'Elia (ASDC), S. W. K Emery (UCL-MSSL), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
B. Mingo (U Leicester), K. L. Page (U Leicester) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 16:07:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160912A (trigger=711914).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 301.518, +57.543, which is 
   RA(J2000)  =  20h 06m 04s
   Dec(J2000) = +57d 32' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, the BAT light curve
does not show anything significant over the trigger window.  However, at ~T+150 sec
there is a flare in the light curve (~1300 cnts/sec). 

The XRT began observing the field at 16:09:57.0 UT, 134.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 301.4981,
57.5655 which is equivalent to:
   RA(J2000)  = 20h 05m 59.56s
   Dec(J2000) = +57d 33' 55.8"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 89 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 note the presence in the XRT raw light curve of a large X-ray flare 
coincident with the BAT flare mentioned above. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.35
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 137 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. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.20. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.nasa.gov). 
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.)