GRB 101117B

C. W. Wolf (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. Campana (INAF-OAB), N. Gehrels (NASA/GSFC), D. Grupe (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), W.B Landsman (GSFC),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC) and
P. T. O'Brien (U Leicester) report on behalf of the Swift Team:

At 19:13:23 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 101117B (trigger=438675).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is RA, Dec 172.909, -72.662 which is 
   RA(J2000) = 11h 31m 38s
   Dec(J2000) = -72d 39' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a two-spike
structure with a duration of about 6 sec.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 19:14:40.9 UT, 77.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 173.00251, -72.66317 which
is equivalent to:
   RA(J2000)  = 11h 32m 0.60s
   Dec(J2000) = -72d 39' 47.4"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 100 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 (1.33 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 2.2
(+2.09/-1.81) x 10^21 cm^-2 (90% confidence). 

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' x 2.7' sub-image covers 100%  of the XRT error circle.  The
estimated 3-sigma upper limit is white > 20.4 mag.  No correction has
been made for the expected Galactic extinction corresponding to a 
reddening of E_{B-V} =  0.38 mag.  Photometry is on the UVOT
photometry system of Poole et al. (2008). 

Burst Advocate for this burst is C. W. Wolf (cwolf AT astro.psu.edu). 
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.)

Stephen Holland (CRESST/USRA/GSFC) reports,
on behalf of the UVOT Team

     The Swift/UVOT source list has an uncatalogued source at the location of
the XRT afterglow (Wolf et al. 2010, GCNC 1141).  Preliminary photometry
indicates an approximate white magnitude of 18.2.

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

Using 1061 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 101117B, 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 = 173.00136, -72.66293 which is equivalent
to:

RA (J2000): 11h 32m 0.33s
Dec (J2000): -72d 39' 46.5"

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.

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), J. Tueller (GSFC),
T. N. Ukwatta (GWU), C. W. Wolf (PSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 101117B (trigger #438675)
(Wolf, et al., GCN Circ. 11411
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 ).  The BAT ground-calculated position is
RA, Dec = 172.991, -72.651 deg which is 
   RA(J2000)  =  11h 31m 57.8s 
   Dec(J2000) = -72d 39' 04.7" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.
 
The mask-weighted light curve shows two overlapping peaks starting
at ~T-0.2 sec, peaking at ~T+1.0 sec, and roughly exponentially decaying
out to ~T+40 sec.  There is possible emission (at the 2-sigma c.l.)
from around T+150 to T+220 sec.  T90 (15-350 keV) is 5.2 +- 1.8 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-0.1 to T+8.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.50 +- 0.09.  The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.74 sec in the 15-150 keV band
is 4.5 +- 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/438675/BA/

This burst was called the "B" burst to avoid possible confusion with the
earlier published XRF 101117A event by the MAXI team (GCN Circ 11410
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 ).

C. A. Wolf (PSU) and D. Grupe (PSU) report on behalf of the Swift-XRT team:

We have analyzed 15.7 ks of XRT data for GRB 101117B (Wolf et al. GCN Circ.
11411
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 ), from 86 s to 63.0 ks after the BAT trigger. The data are entirely
in Photon Counting (PC) mode.

The light curve can be modeled with an initial power-law decay with an
index of alpha=0.76 (+0.08, -0.09), followed by a break at T+1239 s to an
alpha of 1.26 (+0.10, -0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.23 (+/-0.11). The best-fitting
absorption column is 3.18 (+/-0.43) x 10^21 cm^-2, in excess of the
Galactic value of 1.33 x 10^21 cm^-2 (Kalberla et al. 2005). The
counts-to-observed (unabsorbed) 0.3-10 keV flux conversion factor deduced
from this spectrum is 5.7 x 10^-11 (10.5 x 10^-11) erg cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of 1.26,
the count rate at T+24 hours will be 2.19 x 10^-3 count s^-1, corresponding
to an observed (unabsorbed) 0.3-10 keV flux of 1.25 x 10^-13 (2.30 x
10^-13) erg cm^-2 s^-1. The count rate at T+48 hours will be 0.89 x 10^-3
count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of
5.07 x 10^-14 (9.35 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00438675.

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

S. T. Holland (CRESST/GSFC/USRA) and
C. W. Wolf (PSU)
report on the behalf of the Swift UVOT team:

      The Swift/UVOT observed the field of GRB 101117B starting 63 s
after the BAT trigger (Wolf, et al., 2010, GCN Circ. 11411
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 ).  Settled
observations started at 82 s.  We detect the optical afterglow
(Holland, 2010, GCN Circ. 11412
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 ) in the U, B, and white filters.  The
refined UVOT position is


     RA (J2000)  11:32:00.54  =  173.00225 (deg)
    Dec (J2000) -72:39:45.9   =  -72.66275 (deg)

with an estimated uncertainty of 0.43 arcsec (radius, 90% confidence,
statistical + systematic).  This is 1.16 arcsec northwest of the
UVOT-enhanced XRT position (Goad, et al., 2010, GCN Circ. 11413
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 ).

     Preliminary magnitudes, and 3-sigma upper limits for detecting a
source in the finding charts and in the co-added images, are

Filter      T_start   T_stop    Exp(s)      Mag   Err
-----------------------------------------------------------
white (fc)       82      232       147     17.81 0.08 
    u (fc)      295      545       246     18.68 0.15

    v           626      646        20    >17.9
    b           551      571        20     18.22 0.27
    u           700     1325        59    >19.1
 uvw1           675     1300        78    >19.3
 uvm2           825     1275        58    >18.7   
 uvw2           601     1051        58    >19.0
white           575      595        20     19.20 0.34
-----------------------------------------------------------

     The quoted magnitudes and upper limits have not been corrected
for the expected Galactic extinction along the line of sight
corresponding to a reddening of E_{B-V} = 0.38 mag (Schlegel, et al.,
1998, ApJS, 500, 525).  All photometry is on the UVOT photometry
system described in Poole et al. (2008, MNRAS, 383, 627).

     The non-detection in the UVOT uvw1 filter, and the observed UVOT
spectral energy distribution at 600 s, is consistent with GRB 101117B
having a redshift of approximately z <= 3, although we can not rule
out the non-detection in the ultraviolet being due to extinction in
the host galaxy.  The white light curve exhibits a power-law decay
with an index of alpha = -0.8 +/- 0.1 between 82 and 6005 s after the
BAT trigger.

J. Elliott, R. Filgas, J. Greiner, P. Schady and T. Kruehler (all MPE
Garching) report
on behalf of the GROND team:

We observed the field of GRB 101117B (Swift trigger 438675; Wolf et al.,
GCN #11411
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla
Observatory (Chile).

Observations started at 05:15 UT on November 19, 34 hours after the GRB
trigger, and have total exposure of 6003 s in g'r'i'z' and  4800 s in JHK.
They were performed at an average seeing of 2.0" and at an average airmass
of 1.8.

We do not detect a source within the UVOT error circle reported by Holland
& Wolf (GCN #11420
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 ) down to the following 3 sigma upper limits (all in
AB):

g' > 23.7

r' > 23.8

i' > 23.5

z' > 23.3

J > 21.7,

H > 21.2 and

K > 20.4

The given limits are derived based on calibrating the images against GROND
zeropoints and 2MASS field stars and are not corrected for the Galactic
foreground extinction corresponding to a reddening of E_(B-V)= 0.38 in the
direction of the burst (Schlegel et al. 1998).