GRB 131117A

M. J. Page (UCL-MSSL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
F. E. Marshall (NASA/GSFC), C. J. Mountford (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL) and C. A. Swenson (PSU)
report on behalf of the Swift Team:

At 00:34:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131117A (trigger=577968).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 332.339, -31.722 which is 
   RA(J2000) = 22h 09m 21s
   Dec(J2000) = -31d 43' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 20 sec.  The peak count rate
was ~1750 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 00:35:10.8 UT, 66.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 332.33119, -31.76055 which
is equivalent to:
   RA(J2000)  = 22h 09m 19.49s
   Dec(J2000) = -31d 45' 38.0"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 140 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 consistent with the Galactic value of 1.41
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 69 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 none of
the XRT error circle. 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 0.02. 

Burst Advocate for this burst is M. J. Page (m.page AT ucl.ac.uk). 
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.)

A.Trotter, D. Reichart, J. Haislip, N. Frank, A. LaCluyze, J. Moore, T. 
Berger, H. T. Cromartie, R. Egger, A. Foster, K. Ivarsen, M. Maples, M. 
Nysewander, and J. A. Crain report:

Skynet observed the Swift/XRT localization of GRB 131117A (Page et al., 
GCN 15490
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 , Swift trigger 577968) with four 14" telescopes of the PROMPT 
array at Cerro Tololo, Chile, beginning 91s after the trigger, 
simultaneously in the BVRI bands. We detect a fading optical source in 
V, R and I bands at:
RA 22:09:19.3
Dec -31:45:44.4 (J2000.0)
which is within the error circle reported by the Swift XRT.  The 
afterglow fades from R~17.2 at t=1.5min to R~19.7 at t=24min.

Photometry is calibrated to six APASS-DR7 stars in the field, and has 
not been corrected for Galactic foreground extinction.

A preliminary light curve is at: http://skynet.unc.edu/grb/grb131117a.png

Skynet observations are ongoing.

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

Using 599 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 131117A, 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 = 332.33113, -31.76237 which is equivalent
to:

RA (J2000): 22h 09m 19.47s
Dec (J2000): -31d 45' 44.5"

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.

GRB 131117A: GROND confirmation of the afterglow and  photo-z.

M. Tanga (MPE Garching), S. Schmidl, S. Klose (both TLS Tautenburg), K.
Varela (MPE Garching) and J.Greiner (MPE Garching) report on behalf of the
GROND team:

We observed the field of GRB 131117A (Swift trigger 577968, Page et al.,
GCN 15490
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on November 17, 2013, at 00:36:34 UT, 150 s after the
GRB trigger. They were performed at an average seeing of 1".0 and at an
average airmass of 1.2 .

We detect the fading afterglow discovered by Trotter et al. (GCN 15491
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 ).

Based on a total exposure time of 460 s in g'r'i'z' and 480 s in JHK, at a
midtime of 0.80 hrs after the burst, we measure the following preliminary
AB magnitudes:

g' = 20.9 +/- 0.1,
r' = 19.6 +/- 0.1,
i' = 19.1 +/- 0.1,
z' = 19.0 +/- 0.1,
J =  19.0 +/- 0.1,
H =  18.9 +/- 0.1 and
K =  18.7 +/- 0.3.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
reddening of E(B-V) = 0.02 mag in the direction of the burst (Schlegel et
al. 1998).

On the basis of the preliminary analysis we estimate the photometric
redshift to be z = 4.18 +/-0.16.

O. E. Hartoog (U. Amsterdam), D. Xu (DARK/NBI), D. Malesani (DARK/NBI),
N. R. Tanvir (U. Leicester), J. P. U. Fynbo (DARK/NBI), L. Kaper (U. Amsterdam)
and V. D'Elia (ASI/ASDC) report:

We observed the afterglow of GRB 131117A (Page et al. GCN 15490
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 ,
Trotter et al. GCN 15491
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 , Tanga et al. GCN 15493
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 ) with the VLT
X-shooter spectrograph covering a spectral range 3200A to 18000A.
Poor conditions meant that observations could not start until 01:42 UT,
68 minutes post-burst.

The continuum level is faint, but we see a strong break corresponding
to Ly-alpha at a redshift of z=4.042.  This is supported by the detection
of absorption lines corresponding to SiII 1259/1260, SiIV 1393/1402
and SiII 1526.  There is also a clear Ly-a forest blueward of the break.
We therefore propose this as the redshift of the GRB, noting it
is consistent with the photometric redshift of Tanga et al. (GCN15493
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 ).

We thank the staff at Paranal, particularly Christophe Martayan,
for their support in obtaining these observations.

V. Mangano (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U.
Leicester), P.A. Evans (U. Leicester), V. D'Elia (ASDC), A. Maselli 
(INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU), D.N. Burrows
(PSU) and M.J. Page report on behalf of the Swift-XRT team:

We have analysed 7.2 ks of XRT data for GRB 131117A (Page  et al. GCN
Circ. 15490
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 ),  from 51 s to 34.0 ks after the  BAT trigger. The data
comprise 82 s in Windowed Timing (WT) mode (the first 8 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 15492).

The late-time light curve (from T0+4.1 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.88 (+0.23, -0.20).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 3.03 (+0.31, -0.28). The
best-fitting absorption column is  2.0 (+0.6, -0.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.4 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.27 (+0.28, -0.26)
and a best-fitting absorption column of 5.9 (+5.2, -4.5) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.2 x 10^-11 (4.0 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     5.9 (+5.2, -4.5) x 10^20 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.27 (+0.28, -0.26)

If the light curve continues to decay with a power-law decay index of
0.88, the count rate at T+24 hours will be 4.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x
10^-13 (1.7 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/00577968.

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

A. A. Breeveld (UCL-MSSL) and M. J. Page (UCL-MSSL) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131117A 
70s after the BAT trigger (Page et al., GCN Circ. 15490
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 ).
A fading source consistent with the afterglow position found by Trotter 
et al. (GCN Circ. 15491
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 ) is found in the white filter only. This is 
consistent with the redshift of z=4.042 given by Hartoog et al. (GCN 
Circ. 15494
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 ).

The preliminary UVOT position is:
     RA  (J2000) =  22:09:19.36 = 332.33067 (deg.)
     Dec (J2000) = -31:45:44.3  = -31.76231 (deg.)
with an estimated uncertainty of 0.64 arc sec. (radius, 90% confidence).

Preliminary detections and 3-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               70          219          147         20.13 � 0.17
v                  611         5157          216        >20.0
b                  537         4542          216        >20.6
u                  282         4336          442        >20.7
w1                 660         5567          216        >20.4
m2                 636         5362          216        >20.0
w2                 587         4952          216        >20.5

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.02 in the direction of the 
burst (Schlegel et al. 1998).

Klotz A., Turpin D. (IRAP-CNRS-OMP), Gendre B.,
Boer M., Siellez K., Dereli H., Bardho O. (UNS-CNRS-OCA),
Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 131117 detected by SWIFT
(trigger 577968) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 40s after the GRB trigger
(14s after the notice). The elevation of the field decreased from
71 degrees above horizon and weather conditions
were good.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We detect the OT discovered by Trotter et al. (GCNC 15491)
and confirmed by Tanga et al. (GCNC 15493). The OT is seen
at a constant level considering the 2 sigma error of +/- 0.5
mag.

t0+40s to t0+46s  R=17.0 +/-0.5
t0+46s to t0+52s  R=17.0 +/-0.5
t0+52s to t0+58s  R=17.0 +/-0.5
t0+58s to t0+64s  R=17.0 +/-0.5
t0+64s to t0+70s  R=17.0 +/-0.5
t0+70s to t0+76s  R=17.0 +/-0.5
t0+76s to t0+82s  R=17.0 +/-0.5
t0+82s to t0+88s  R=17.0 +/-0.5
t0+88s to t0+94s  R=17.0 +/-0.5
t0+94s to t0+100s R=17.0 +/-0.5

Then series of image acquired in tracking mode
shows the decay of the OT:

t0+113s to t0+173s   R=17.2  +/-0.1
t0+194s to t0+464s   R=18.8  +/-0.2
t0+630s to t0+1080s  R=19.0  +/-0.2
t0+1472s to t0+2192s R=19.1  +/-0.2
t0+2524s to t0+4324s Rlim=20.0

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/UMBC),
C. B. Markwardt (GSFC), M. J. Page (UCL-MSSL) D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU) (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 131117A (trigger #577968)
(Page, et al., GCN Circ. 15490
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 ).  The BAT ground-calculated position is
RA, Dec = 332.354, -31.761 deg which is
  RA(J2000)  =  22h 09m 25.0s
  Dec(J2000) = -31d 45' 38.8"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.

The mask-weighted light curve shows a single peak structure starts at ~T-1 sec
and ends at ~T+12 sec. T90 (15-350 keV) is 11.00 +- 3.16 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.00 to T+12.00 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.40 +- 1.41,
and Epeak of 44.0 +- 7.4 keV (chi squared 45.16 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.5 +- 0.4 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+0.00 sec in the 15-150 keV band is
0.7 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.79 +- 0.18 (chi squared 58.98 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/577968/BA/