GRB 161117B

E. Troja (NASA/GSFC/UMCP), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC),
P.A. Evans (U Leicester), H. A. Krimm (CRESST/NSF/USRA),
K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 09:49:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161117B (trigger=722642).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 298.855, -67.707 which is 
   RA(J2000) = 19h 55m 25s
   Dec(J2000) = -67d 42' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed am initial weak peak
near the trigger time followed by stronger emission starting about 100
seconds later.  The total duration is about 150 sec.  The peak count rate
was ~4500 counts/sec (15-350 keV), at ~135 sec after the trigger. 

The XRT began observing the field at 09:50:58.0 UT, 74.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
298.8244, -67.7029 which is equivalent to:
   RA(J2000)  = 19h 55m 17.85s
   Dec(J2000) = -67d 42' 10.6"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 44 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 (6.49 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.3
(+2.89/-2.47) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 4.69e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 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
0.10. 

Burst Advocate for this burst is E. Troja (eleonora.troja 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.)

C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), C.G. Mundell 
(U. Bath), A. Gomboc (U. Nova Gorica) on behalf of a large collaboration 
report:

One of the LCO 1-m telescope units in Siding Springs began observing 
Swift GRB 161117B (Troja et al., GCN 20182
Loading...
 
 ) in the SDSS r filter on 
November 17, 10:28:49 UT (39 minutes since the GRB trigger time). We do 
not find any object within the XRT error circle down to the following limit:

Mid time from GRB     Exposure     Filter       Magnitude
(min)                  (s)
----------------------------------------------------------
45                    5x120        SDSS-R       > 21.2
----------------------------------------------------------

Calibration is done against nearby USNOB-1 stars.

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

Using 787 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 161117B, 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 = 298.82508, -67.70256 which is equivalent
to:

RA (J2000): 19h 55m 18.02s
Dec (J2000): -67d 42' 09.2"

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.

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),  J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP), 
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 161117B (trigger #722642)
(Troja, et al., GCN Circ. 20182
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 298.830, -67.681 deg which is 
   RA(J2000)  =  19h 55m 19.1s 
   Dec(J2000) = -67d 40' 51.8" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows a complex structure.  The first set of peaks
begins around T-10 sec, peaks at T+2 and fades by T+10 sec.  The second set 
of peaks begins around T+92 sec, peaks at T+102 sec and fades nearly to 
background by T+115 sec.  This is when the third set of peaks begins to rise,
which peaks at T+T+135 sec and fades by T+160 sec.  All of these peak 
structures have multiple sub-peaks. T90 (15-350 keV) is 152.51 +- 3.37 sec 
(estimated error including systematics).

The time-averaged spectrum from T-8.32 to T+157.44 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.39 +- 0.28, 
and Epeak of 37.5 +- 5.5 keV (chi squared 39.62 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 6.0 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+133.80 sec in the 15-150 keV band is
6.0 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.14 +- 0.06 (chi squared 64.42 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/722642/BA/

F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161117B
84 s after the BAT trigger (Troja et al., GCN Circ. 20182
Loading...
 
 ).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 20186
Loading...
 
 )
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            84          234          147         >21.1
u_FC               296          546          246         >20.3
white               84         1026          334         >21.4
v                  626          820           39         >18.1
b                  552          745           39         >19.6
u                  296          720          265         >20.3
w1                 676          870           39         >18.9
m2                 651          844           39         >19.9
w2                 602         1050           57         >19.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).

V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), T.G.R.
Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Mingo (U.
Leicester), A.P. Beardmore (U. Leicester) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift-XRT team:

We have analysed 5.9 ks of XRT data for GRB 161117B (Troja et al. GCN
Circ. 20182
Loading...
 
 ), from 65 s to 206.7 ks after the  BAT trigger. The data
comprise 178 s in Windowed Timing (WT) mode (the first 7 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 Osborne et
al. (GCN Circ. 20186
Loading...
 
 ).

The light curve shows an initial bright flare that is part of 
the prompt GRB emission. At T+95.1 s the decay can be modelled with 
a power-law of index alpha of 0.43 (+0.09, -0.07) before breaking at
T+101 ks to a final decay with index alpha=6.7 (+1.3, -5.2).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.10 (+/-0.05). The
best-fitting absorption column is  3.8 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 6.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.98 (+0.24, -0.23)
and a best-fitting absorption column of 5.3 (+1.5, -1.3) 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 (6.8 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.3 (+1.5, -1.3) x 10^21 cm^-2
Galactic foreground: 6.5 x 10^20 cm^-2
Excess significance: 5.9 sigma
Photon index:	     1.98 (+0.24, -0.23)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00722642.

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