GRB 111129A

J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
S. Campana (INAF-OAB), P. A. Evans (U Leicester),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), O. M. Littlejohns (U Leicester),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), M. C. Stroh (PSU), C. A. Swenson (PSU),
E. Troja (NASA/GSFC/ORAU) and B.-B. Zhang (PSU) report on behalf of
the Swift Team:

At 16:18:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 111129A (trigger=508712).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 307.441, -52.724, which is 
   RA(J2000)  =  20h 29m 46s
   Dec(J2000) = -52d 43' 26"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a few weak peaks
with a total duration of about 20 sec.  The peak count rate
was ~800 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 16:19:46.5 UT, 92.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 307.43460, -52.71300 which is
equivalent to:
   RA(J2000)  = 20h 29m 44.30s
   Dec(J2000) = -52d 42' 46.8"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 42 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 3.24
x 10^20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 95 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	20:29:44.15 = 307.43395
  DEC(J2000) = -52:42:46.5  = -52.71291
with a 90%-confidence error radius of about 0.64 arc sec. This position is 1.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.06 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.04. 

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.)

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

Using 809 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 111129A, 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 = 307.43385, -52.71297 which is equivalent
to:

RA (J2000): 20h 29m 44.12s
Dec (J2000): -52d 42' 46.7"

with an uncertainty of 1.9 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.

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 111129A (trigger #508712)
(Racusin, et al., GCN Circ. 12600
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 ).  The BAT ground-calculated position is
RA, Dec = 307.415, -52.722 deg, which is 
   RA(J2000)  =  20h 29m 39.5s 
   Dec(J2000) = -52d 43' 20.9" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 61%.
 
The mask-weighted light curve shows two slightly overlapping peaks
starting at ~T-7 sec, peaking at ~T-5 and T+1 sec, and ending at ~T+10 sec.
T90 (15-350 keV) is 7.6 +- 1.4 sec (estimated error including systematics).
 
The time-averaged spectrum from T-6.29 to T+2.88 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.56 +- 0.38.  The fluence in the 15-150 keV band is 1.8 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.41 sec in the 15-150 keV band
is 0.9 +- 0.2 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/508712/BA/

J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), P.
D'Avanzo (INAF-OAB), V. D'Elia (ASDC), V. Mangano (INAF-IASFPA) and
J.L. Racusin report on behalf of the Swift-XRT team:

We have analysed 9.2 ks of XRT data for GRB 111129A (Racusin  et al.
GCN Circ. 12600
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 ), from 77 s to 34.7 ks after the  BAT trigger. The data
comprise 26 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 Osborne et
al. (GCN. Circ 12601).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.57 (+0.16, -0.17), followed by a break at T+3006 s to
an alpha of 1.19 (+0.12, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.93 (+/-0.08). The
best-fitting absorption column is  1.72 (+0.40, -0.24) x 10^21 cm^-2,
in excess of the Galactic value of 3.2 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.0 x 10^-11 (5.4 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.72 (+0.40, -0.24) x 10^21 cm^-2
Galactic foreground: 3.2 x 10^20 cm^-2
Excess significance: 11.6 sigma
Photon index:	     1.93 (+/-0.08)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00508712.

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

A. Rossi, A. Nicuesa Guelbenzu (all Tautenburg)
and J. Greiner (MPE) report on behalf of the GROND team:

We observed the field of GRB 111129A (Racusin, GCN 12600
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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 on La Silla.

Observations started at 00:30 UT on November 30, about 8.2 hr after the 
burst,
and continued for about 2 hrs. They were performed at an average seeing of 1
arcsec and an average airmass of 1.8.

We detect the afterglow discovered by Racusin et al. (GCN 12600
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 ) in the
optical/NIR. At a mean time of November 30, 01:31 UT
(9.25 hours after the trigger)
with exporures times of 24.3 minutes in griz and 20 min in JHK,
we measure the following preliminary magnitudes (AB system):

   g' = 22.9  +/- 0.1,
   r' = 22.3  +/- 0.1,
   i' = 21.8  +/- 0.1,
   z  = 21.3  +/- 0.1,
   J  = 20.5  +/- 0.2,
   H  = 19.8  +/- 0.2,
   K  = 19.1  +/- 0.3

Optical data are calibrated against GROND zeropoints and
NIR against 2MASS field stars.

A. A. Breeveld (MSSL-UCL) 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 111129A
96 s after the BAT trigger (Racusin et al., GCN Circ. 12600
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 ).
A source consistent with the XRT position (Osborne et al., GCN Circ. 
12601
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 ) is detected in the initial UVOT exposures in the white and u 
filters. The source had already faded by the time the other filters were 
used.

The preliminary UVOT position is:
     RA  (J2000) =  20:29:44.15 = 307.43396 (deg.)
     Dec (J2000) = -52:42:46.5  = -52.71293 (deg.)
with an estimated uncertainty of 0.54 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               96          245          147         19.11 � 0.1
white              534          726           39        >20.32
v                  584        12305          524        >19.9
b                  509        16631         1223        >21.3
u                  254          503          246         19.10 � 0.16
w1                 633        22753         1296        >21.2
m2                 608         6008          413        >20.4
w2                 559        12186         1120        >21.5

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.04 in the direction of the 
burst (Schlegel et al. 1998).