GRB 160917A

J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), J. A. Kennea (PSU),
D. Malesani (DARK/NBI and DTU Space), F. E. Marshall (NASA/GSFC),
B. Mingo (U Leicester), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Swift Team:

At 11:30:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160917A (trigger=712505).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 295.671, +46.399 which is 
   RA(J2000)  =  19h 42m 41s
   Dec(J2000) = +46d 23' 56"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows several overlapping peaks
with a total duration of about 25 sec.  The peak count rate
was ~2300 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:31:52.9 UT, 93.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 295.66805, 46.40321 which
is equivalent to:
   RA(J2000)  = 19h 42m 40.33s
   Dec(J2000) = +46d 24' 11.6"
with an uncertainty of 4.2 arcseconds (radius, 90% containment). This
location is 16 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 7.72e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 125 seconds with the White
filter  starting 99 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.  Results from the list of
sources  generated on-board are not available at this time. No
correction has been made  for the expected extinction corresponding to
E(B-V) of 0.16. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin AT 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.)

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

Using 77 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 160917A, 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 = 295.66637, +46.40368 which is equivalent
to:

RA (J2000): 19h 42m 39.93s
Dec (J2000): +46d 24' 13.2"

with an uncertainty of 2.5 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.

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), Z. Cano (IAA-CSIC) & F. Aceituno
(IAA-CSIC) report on behalf of a larger collaboration:

We observed the field of GRB 160917A (Racusin et al.; GCN Circ. 19926
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 ) with
the 1.5-m OSN telescope in Granada, Spain.  We began observing at 19:08:34
UT (7.64 hours after the GRB onset), and obtained 14x300s images in
I-band.  In our coadded image, we find no new source in the refined XRT
error circle (Evans et al; GCN Circ. 19927
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 ) down to a a 3-sigma limit of
I(Vega) = 22.6.  The calibration was performed using a nearby star in the
USNO B1 catalog, and the upper limit corresponds to an isolated point
source in our co-added image.

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 160917A (Racusin et al. GCN 19926
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 ) with 
  AZT-33IK telescope of Sayan observatory (Mondy) starting on Sep., 17 
(UT) 14:30:30. We obtained several images in R-filter. We detected the 
optical source within enhanced XRT error circle (Evans et al., GCN 
19927
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 ) in coordinates (J2000) 19 42 39.81 +46 24 12.1 with 
uncertainities of 0.4 arcsec in both coordinates. Preliminary photometry 
  of the afterglow is following

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

2016-09-17  14:30:30   0.14601    R     120*30 20.60 +/- 0.20  22.9

Photometry is based on nearby USNO-B1.0 stars
ID             RA           Dec        R2

1 1363-0324591 19:42:38.95 +46:23:53.8 16.62
2 1364-0326339 19:42:40.68 +46:24:37.0 17.40
3 1363-0324630 19:42:42.78 +46:23:28.7 17.05

We suggest the source as optical afterglow of GRB 160917A.

The finding chart can be found at 
http://grb.rssi.ru/GRB160917A/160917A_Mondy_fc.png

S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai
(INAF-IASFPA), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M. McCauley
(PSU) and J.L. Racusin report on behalf of the Swift-XRT team:

We have analysed 6.2 ks of XRT data for GRB 160917A (Racusin et al. GCN
Circ. 19926
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 ), from 80 s to 17.4 ks after the  BAT trigger. The data
comprise 43 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 Evans et
al. (GCN Circ. 19927
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.243 (+0.030, -0.029).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.81 (+0.22, -0.21). The
best-fitting absorption column is  2.8 (+1.1, -0.9) x 10^21 cm^-2, in
excess of the Galactic value of 1.7 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 (5.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.8 (+1.1, -0.9) x 10^21 cm^-2
Galactic foreground: 1.7 x 10^21 cm^-2
Excess significance: 2.0 sigma
Photon index:	     1.81 (+0.22, -0.21)

If the light curve continues to decay with a power-law decay index of
1.243, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.5 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/00712505.

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

N. P. M. Kuin (UCL-MSSL) and J. L. Racusin (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 160917A
100 s after the BAT trigger (Racusin et al., GCN Circ. 19926
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 ). The
refined XRT position (Evans et al. GCN Circ. 19927
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 ) is close to a
bright star. However, a faint GRB candidate has been found at an
offset of 6.5 arcsec to the south east from the bright star in the
u exposures.
The UVOT candidate position is: RA, Dec = 295.66687, 46.40368 (J2000)
which is :
RA = 19:42:40.049
Dec = +46:24:13.25
with an estimated accuracy of 1.5 arcsec.

Preliminary detections 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              100          224          123          >21.01
b                 4222         4422          100          >20.64
u                 4017         5545          146           20.47 +- 0.36
v                 3402         5038          200          >19.77
uvw1              3812         5448          200          >20.16
uvm2              3606         5242          100          >19.97
uvw2              4633         4833          200          >19.70

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.16 in the direction of the burst
(Schlegel et al. 1998).

P Veres (UAH), A von Kienlin (MPE) and C Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 11:30:19.286 UT on 17 September 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160917A (trigger 495804623 / 160917479).
which was also detected by the Swift/BAT
��� ���
(Racusin et al., GCN 19926
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 ).
��� ���
The GBM on-ground location is consistent with the Swift position.


The angle from the Fermi LAT boresight at the GBM trigger time is 46
degrees.


The GBM light curve consists of a single peak
with a duration (T90) of about 47 s (50-300 keV).
The time-averaged spectrum from T0 to T0+14.1 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.00 +/- 0.05 and
the cutoff energy, parameterized as Epeak, is 1604 +/- 357 keV.


The event fluence (10-1000 keV) in this time interval is
(7.2 +/- 0.3)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0 in the 10-1000 keV band
is 5.1 +/- 0.2 ph/s/cm^2.

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

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 160917A (Racusin, et al., GCN 19926
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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 18.12 to 2016/09 18.36 UTC (15.39 to
21.08 hours after the BAT trigger), obtaining a total of 3.72 hours
exposure in the r and i bands and 1.63 hours exposure in the Z, Y, J, and H
bands.

For a source within the Swift-XRT error circle (Evans et al., GCN 19927
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 ),
in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following
upper limits (3-sigma):

  r > 24.31
  i > 24.28
  Z > 23.20
  Y > 22.90
  J > 22.57
  H > 22.20

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.

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC),  J. R. Cummings (CPI),
N. Gehrels (GSFC), 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-60 to T+243 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 160917A (trigger #712505)
(Racusin, et al., GCN Circ. 19926
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 ).  The BAT ground-calculated position is
RA, Dec = 295.652, 46.400 deg which is
   RA(J2000)  =  19h 42m 36.4s
   Dec(J2000) = +46d 23' 59.3"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows an initial bright peak about 1 second
long with
some structure on finer time scales, and variable emission for another 30
seconds. Another weak peak occurs from T+50 to T+90 seconds. T90 (15-350
keV) is 16 +- 2 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.34 to T+15.31 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
0.89 +- 0.15.  The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-06
erg/cm2.
The 1-sec peak photon flux measured from T-0.01 sec in the 15-150 keV band
is 2.2 +- 0.3 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/712505/BA/

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 160917A (Racusin et al. GCN 19926
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 ) with 
  AZT-33IK telescope of Sayan observatory (Mondy) starting on Sep., 18 
(UT) 15:25:21. We obtained several images in R-filter. We do not detect 
the optical source reported as afterglow candidate (Volnova et al. GCN 
19929
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 ; Kuin  et al. GCN  19931
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 ). Preliminary photometry of the field is 
following

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

2016-09-18  15:25:21   1.18522    R     60*60  n/d    22.0

Photometry is based on nearby USNO-B1.0 stars used in GCN circ. 19929
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 .
In comparison with our previous observation (Volnova et al. GCN 19929
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 ) 
the source is not visible  up to 22.0 mag. The source faded between two 
epochs on at least  1.4 magnitudes and it is most probably the afterglow 
of GRB 160917A. Our observation is compatible with more deep RATIR 
observation in r-filter (Butler et al. GCN 19933
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 ).

V. Bhalerao (IUCAA), V. Kumar (IUCAA), D. Bhattacharya (IUCAA), A. R. Rao (TIFR), S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:

Analysis of Astrosat data showed the CZTI detection of GRB160917A (Swift BAT detection: S.Barthelmy et al., GCN Circ. 19926
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 ).

The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak at 11:30:25.0 UT, 6 seconds after Swift Trigger at 11:30:19.0 UT. The peak count rate was 116.0 counts/sec above the background (four quadrants summed together), with a total of 1008.0 counts. The local mean background count rate was 327.0 counts/sec. Using cumulative rates, we measure a T90 of 21 sec.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb . CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

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 
160917A (Racusin et al., GCN 19926
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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 17.65, Sep 20.87, and 
Sep 24.87 (UT) do not reveal any radio source at the XRT location (Evans 
et al., GCN 19927
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 ), with 3sigma upper limits of 150 uJy, 84 uJy, and 90 
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/.

N.L.Dzhioeva,V.V.Bogomolov, S.I.Svertilov,
A.M.Amelushkin, V.O.Barinova, M.I.Panasyuk, A.V.Bogomolov, A.F.Iyudin, 
V.V.Kalegaev, D.Nguen,  V.L. Petrov, I.V.Yashin, P.S.Kazarian
Physics Department, Skobel`tsyn Institute of Nuclear Physics, Moscow State

V. Lipunov, E.S. Gorbovskoy, N.Tyurina, D.Kuvshinov
Lomonosov Moscow State University, Sternberg Astronomical Institute

I. Park, J. Lee, S. Jeong
Department of Physics, Sungkyunkwan University, Seobu-ro, Jangangu, Suwonsi, 
Korea

At 11:30:20 UT on 17 Sep 2016, the Lomonosov BDRG  Gamma-ray Burst
Monitor  (http://lomonosov.sinp.msu.ru/en/scientific-equipment-2/bdrg )
triggered GRB 160917A (J. L. Racusin, GCN 19962
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 ).
GRB 160917A has several peaks LC, total duration 25s,
the energy range 70-1000 keV.
More information will be available at:
http://lomonosov.sinp.msu.ru/category/results/observation-gamma-ray-bursts
This Notice was ground-generated.
The message may be cited.