GRB 071117

T. N. Ukwatta (GSFC/GWU), W. H. Baumgartner (GSFC/UMBC),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC),
C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), D. M. Palmer (LANL),
P. Romano (Univ. Bicocca & INAF-OAB) and D. E. Vanden Berk (PSU)
report on behalf of the Swift Team:

At 14:50:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071117 (trigger=296805).  Swift did not slew immediately 
to the burst due to an Earth constraint.  The BAT on-board calculated 
location is RA, Dec 335.020, -63.441 which is 
   RA(J2000) = 22h 20m 05s
   Dec(J2000) = -63d 26' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single FRED
peak with a duration of about 5 sec.  The peak count rate
was ~16000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Because of an Earth limb constraint, the spacecraft did not slew promptly
to the BAT position, and so there are no immediate XRT data products
to analyze.  NFI observations are expected at T+43 minutes, when it comes
out of constraint. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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.)

D. E. Vanden Berk (PSU) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift UVOT Team:

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 2852 seconds after the BAT trigger. No
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 18.5 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 extinction of E(B-V) = 0.024.

P. Romano, C. Guidorzi (Univ. Bicocca & INAF-OAB), A. Moretti (OAB)
and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift XRT Team:

Using prompt downlinked data (482.4 s), we find an X-ray
source located at RA, Dec 335.0437, -63.4424 which is
   RA(J2000)  = 22 20 10.49
   Dec(J2000) = -63 26 32.6
with an uncertainty of 4.2 arcsec (radius, 90% containment).
This is 37.2 arcseconds from the BAT position (Ukwatta et al., GCN Circ. 7098
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 ).
Further analysis will be reported in a subsequent circular.

This circular is an official product of the Swift XRT Team.

H. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-119 to T+183 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 071117 (trigger #296805)
(Ukwatta, et al., GCN Circ. 7098
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 ).  The BAT ground-calculated position is
RA, Dec = 335.026, -63.442 deg which is 
   RA(J2000)  =  22h 20m 06.3s 
   Dec(J2000) = -63d 26' 31" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.
 
The mask-weighted light curve shows a single FRED-like peak starting
at ~T-0.5 sec, peaking at ~T+0.5 sec, and decaying away out to ~T+15 sec.
T90 (15-350 keV) is 6.6 +- 1.8 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.4 to T+13.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.57 +- 0.06.  The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.02 sec in the 15-150 keV band
is 11.3 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

C. Guidorzi, P. Romano (Univ. Bicocca & INAF-OAB),
A. Moretti (INAF-OAB) and T.N. Ukwatta (GSFC/GWU),
report on behalf of the Swift-XRT team:

Swift XRT observed the GRB 071117 (trigger=296805, Ukwatta et al., GCN
Circ. 7098
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 ) beginning 2.8 ks after the BAT trigger.
In 4.4 ks of Photon Counting mode data spanning 2.8-14.7 ks after
the trigger the position of the X-ray afterglow is
RA,Dec =335.04579,-63.44278 degrees, which corresponds to

RA(J2000) =  22 20 10.99
Dec(J2000)= -63 26 34.0

with error circle of radius 3.8 arcsec (90%, including
boresight uncertainties). This lies 3.6 arcsec from the previous
XRT position (Romano et al., GCN Circ. 7100
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 ) and 32 arcsec from
the BAT refined position (Krimm et al., GCN Circ 7102
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 ).

The X-ray light curve can be fit by a power law from
T+2.8ks to T+14.7ks, with a decay index of 0.8 +/- 0.2.

The Photon Counting spectrum can modelled with an absorbed power-law, with
a photon index of 2.2 +0.4/-0.3 and a total absorbing column of NH = (2.3
+0.9/-0.8) e21 cm-2. The Galactic value is 2.3e20 cm-2 in the direction
of the burst. The 0.3-10 keV observed (unabsorbed) flux during this time
is 3.0e-12 (5.0e-12) erg cm-2 s-1. Uncertainties are given at 90% 
confidence.

Assuming the source continues to decay with the same rate,
we predict an XRT count rate of 1.3e-2 counts/s at T+24 hours, which
corresponds to an observed 0.3-10keV flux of 7.8e-13 ergs cm-2 s-1.

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

E. Berger (Princeton/OCIW) and S. Gonzalez (LCO) report:

"We observed the XRT error circle of GRB 071117 (GCNs 7102
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 ,7103
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 ) with the 
Swope 40-inch telescope at LCO starting on 2007 Nov. 18.07 UT (10.8 hours 
after the burst).  In a single 300 sec exposure we do not detect any 
source within the XRT error circle to a limit of i>21 mag."

J. S. Bloom (UC Berkeley), on behalf of the Gemini GRB collaboration,  
reports:

"Imaging observations of the field of GRB 071117 (Ukwatta et al., GCN  
7098
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 ) were autonomously queued for Gemini South as part of the  
program GS-2007B-Q-2  (PI = H.-W. Chen). Starting at 2007 Nov 18  
00h24m UT, we obtained 5 x 180 sec images in r-band. Within the  
revised XRT error circle (Guidorzi et al. GCN 7103
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 ) we find one  
source (s1) at position:

   s1:   ra=  22:20:10.63  dec = -63:26:33.7  (J2000)

The uncertainty is 350 mas in each coordinate (relative to USNO  
B1.0). This source, s1, is roughly R=23.3 mag at the time of  
observation (based upon the USNO B.10 catalog magnitude of the source  
at 22:20:13.33 -63:26:32.9).  There is another source straddling the  
90% error circle, embedded in an apparent faint extension to the  
southeast at:

   s2:   ra= 22:20:10.42  dec = -63:26:35.5 (J2000)

Further observations will be required to determine if either of these  
sources are variable."

A finder may be obtained at:
  http://lyra.berkeley.edu/~jbloom/grb071117-gemini-ep1.ps.gz

This message may be cited.

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 071117 detected by SWIFT
(trigger 296805) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 9.5h after the GRB trigger
(GRB occured during daytime). The elevation of the field
decreased from from 54 degrees above horizon and weather
conditions were excellents.

We co-added series of exposures taken in VRI filters
from t_trig+9.5h to t_trig+11.3h. There is no OT detected in
V and R bands. A source is detected in the I-band
close to the limiting magnitude I~20 at a position
compatible with XRT (Romano et al. GCNC 7100) and
s1,s2 sources of Bloom (GCNC 7105). Due to the spatial
sampling of TAROT (3.3arcsec/pixel) and to the very low
signal to noise ratio we cannot discriminate
between s1 and s2.

The source is also present in I-band in series
11.6-13.3 h and also in the series 13.7-15.8 h but
the actual processing does not allow to say if the
brightness decreases or not.

If we consider the I-band source TAROT is the same as the
s1 source of Bloom (R=23.3), the corresponding (R-I)~3
is very high. The galactic extinction in R band is only 0.06
magnitude (estimated from D. Schlegel et al. 1998).
As a consequence, we estimate that GRB 071117 is a good
high redshift candidate (z>4.5).

This message may be cited.

J. S. Bloom (UC Berkeley), on behalf of the Gemini GRB collaboration,  
reports:

"Starting at 2007 Nov 19 00h19m, deep r-band observations of the  
field of GRB 071117 (Ukwatta et al., GCN 7098
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 ) were obtained with  
Gemini (see Bloom, GCN 7105
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  for information about the first epoch).  
Image differencing reveals that source s2 (just outside the formal  
XRT error circle) is fading, and is the likely optical afterglow of  
the GRB. To reiterate the position:

   s2:   ra= 22:20:10.42  dec = -63:26:35.5 (J2000)

The uncertainty is 350 mas in each coordinate (relative to USNO  
B1.0). Further is analysis is ongoing."

A finder may be obtained at:
   http://lyra.berkeley.edu/~jbloom/grb071117-diff.pdf

We thank the expert Gemini staff for carrying out this ToO.

This message may be cited.

S. R. Oates (MSSL-UCL) and T. N. Ukwatta (GSFC/GWU) report on behalf of 
the Swift/UVOT team:

The Swift/UVOT observed the field of GRB 071117 (Ukwatta et al., GCN 7098
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 )
48 minutes after the BAT trigger, once the Earth had come out of observing
constraint. No new source is found in any of the UVOT observations in
either single or co-added exposures at the position of s2 reported by
Bloom et al. (GCN 7110
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 ) or within the XRT error circle (Guidorzi et al., 
GCN 7103
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 ).

The following 3-sigma upper limits were determined at the position
of the Gemini detection (RA=22:20:10.42, DEC=-63:26:35.5, J2000 ):

Filter  Tstart   Tend    Exp       Magnitude
          (s)     (s)     (s)      (3-sigma UL)
-------------------------------------------------
v      2960     44497   1608        >21.2
white  2852     62512   1812        >22.9
b      3779     61600   3125        >22.5
u      3574     56599   3075        >22.2
uvw1   3369     55834   4154        >22.4
uvm2   3164     32613   2368        >21.8
uvw2   4190     62783   2227        >22.1
-------------------------------------------------
The values quoted above are not corrected for the expected Galactic 
extinction corresponding to a reddening of E(B-V) =
0.024 mag in the direction of the GRB (Schlegel et al. 1998).

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
P. Oleynik, M. Ulanov and T. Cline on behalf of the Konus-Wind and
Konus-A teams report:

The GRB 071117 (Swift-BAT trigger #296805:
Ukwatta et al., GCN 7098
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 ; Krimm et al., GCN 7102
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 ) triggered
Konus-Wind at T0=53404.535 s UT (14:50:04.535).
This burst also triggered Konus-A at T0=53408.587 s UT (14:50:08.587).

The Konus-Wind light curve shows a single FRED-like pulse with a 
duration of ~5 s.
As observed by Konus-Wind the burst
had a fluence of 5.84(-2.40, +0.30)x10^-6 erg/cm2,
and a 64-ms peak flux measured from T0+0.160 s
of 6.66(-2.95, +1.13)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).
The burst shows strong hard-to-soft spectral evolution.

The time-integrated spectrum of the burst
(from T0 to T0+8.448 s) is well fitted (in the 20 keV - 1 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
with alpha = 1.53(-0.16, +0.15)
and Ep = 278 (-79, +236) keV (chi2 = 37.5/52 dof).

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB071117_T53404/

C. Guidorzi, P. Romano (Univ. Bicocca & INAF-OAB),
A. Moretti (INAF-OAB) and T.N. Ukwatta (GSFC/GWU),
report on behalf of the Swift-XRT team:

We recalculated the XRT refined position of GRB 071117
(trigger=296805, Ukwatta et al., GCN Circ. 7098
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 )
by excluding the first orbit data, which were affected
by the presence of a dead pixel column.
In 8.3 ks of Photon Counting mode data spanning 8.7-28 ks after
the trigger the position of the X-ray afterglow is
RA,Dec =335.04336,-63.44278 degrees, which corresponds to

RA(J2000) =  22 20 10.41
Dec(J2000)= -63 26 34.0

with error circle of radius 3.8 arcsec (90%, including
boresight uncertainties). The optical afterglow reported by
Bloom et al. (GCN Circ. 7110
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 ) now lies 1.5" away from the new
XRT centroid.

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

P. Jakobsson (Univ. Hertfordshire), J.P.U. Fynbo, D. Malesani 
(DARK/NBI), N.R. Tanvir (Univ. Leicester), B. Milvang-Jensen (DARK/NBI), 
A.O. Jaunsen (Univ. Oslo), P.M. Vreeswijk, J. Hjorth (DARK/NBI), report 
on behalf of a larger collaboration:

We observed the field of GRB 071117 (Ukwatta et al., GCN 7098
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 ) with the 
ESO VLT, starting on 2007 Nov 18.005 UT (9.28 hr after the GRB). We 
clearly detect the two sources indicated by Bloom (GCNs 7105
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 , 7110
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 ), 
including the afterglow s2. Source s1 appears extended in our images, 
while source s2 is indeed pointlike (seeing 0.85"). A faint nebulosity 
is apparent surrounding both objects.

A VLT spectrum was obtained with the FORS1 instrument starting on 2007 
Nov 18.03 UT, placing both sources on the slit. Three exposures of 30 
min each were secured. The afterglow spectrum shows a faint, blue 
continuum between 3700 to 9000 A, and a weak emission line is apparent 
at 8688 A. Interpreting this as [OII], we infer a redshift of z=1.331, 
which we consider as the likely redshift of the GRB. Interpreting the 
observed line as [OIII] or Halpha, we would expect to detect [OII] at 
6466 or 4934 A, respectively, which we do not see. A more conservative 
upper limit to the GRB redshift comes from the nondetection of any 
dropout in the blue down to 3800 A, which implies z < 2.1.

The spectrum of s1 is very red, with no significant flux below 5000 A. A 
plot of the 2D spectrum and a finding chart showing the afterglow and 
the various XRT error circles is posted at:

https://grbtoo.dark-cosmology.dk/public/gcn-pages/grb-071117/

We acknowledge excellent support from the ESO observing staff, in 
particular Stephane Brillant and Emanuela Pompei.