GRB 161129A

D. Kocevski (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), B. Mingo (U Leicester),
K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and
M. H. Siegel (PSU) report on behalf of the Swift Team:

At 07:11:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 161129A (trigger=724438).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 316.193, +32.125 which is 
   RA(J2000)  =  21h 04m 46s
   Dec(J2000) = +32d 07' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
with a duration of about 50 sec.  The peak count rate
was ~4400 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:13:01.8 UT, 82.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 316.22890, 32.13574 which is equivalent
to:
   RA(J2000)  = 21h 04m 54.94s
   Dec(J2000) = +32d 08' 08.7"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 116 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 (2.50 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 2.5
(+2.84/-2.37) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White 
filter  starting 86 seconds after the BAT trigger. No credible 
afterglow candidate has  been found in the initial data products. The 
2.7'x2.7' sub-image does not cover 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 0.21. 

Burst Advocate for this burst is D. Kocevski (dankocevski 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.)

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

Using 2977 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 161129A, 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 = 316.22770, +32.13488 which is equivalent
to:

RA (J2000): 21h 04m 54.65s
Dec (J2000): +32d 08' 05.6"

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.

A. Melandri (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), S.L.
Gibson (U. Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo
(INAF-OAB), V. D'Elia (ASDC) and D. Kocevski report on behalf of the
Swift-XRT team:

We have analysed 7.8 ks of XRT data for GRB 161129A (Kocevski et al.
GCN Circ. 20210
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 ), from 90 s to 17.8 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Beardmore et al. (GCN Circ. 20211
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 ).

The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=2.21 (+0.15, -0.14).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.74 (+0.13, -0.12). The
best-fitting absorption column is  3.2 (+0.7, -0.6) x 10^21 cm^-2, in
excess of the Galactic value of 2.5 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.4 x 10^-11 (5.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.2 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 2.5 x 10^21 cm^-2
Excess significance: 2.0 sigma
Photon index:	     1.74 (+0.13, -0.12)

If the light curve continues to decay with a power-law decay index of
2.21, the count rate at T+24 hours will be 7.1 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x
10^-14 (4.1 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/00724438.

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

V. Sharma, D. Bhattacharya and V. Bhalerao (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed clear detection of GRB161129A (Swift BAT detection: S. Barthelmy et al., GCN Circ. 20210
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 ) in the 40-200 keV energy 
range. The light curve shows multiple peak structure at 07:12:06.0 UT, after 27 secs of the Swift Trigger. The measured peak count rate is 170.205 counts/sec 
above the background in combined data of four quadrants, with a total of 2160.0 counts. The local mean background count rate was 377.79 counts/sec. Using 
cumulative rates, we measure a T90 of 34.06 secs.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb.  CZTI is built by a TIFR-led consortium of institutes
across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

-------------------------
Vidushi
JRF
IUCAA, Pune
E-mail: vidushi@iucaa.in
-------------------------

E. Mazaeva (IKI), I. Reva (Fesenkov Astrophysical Institute), A. Kusakin 
(Fesenkov Astrophysical Institute),  A. Volnova (IKI), A. Pozanenko 
(IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of 161129A  (Kocevski et al., GCN 20210
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 )  with 
Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory. 
We obtained several images in R filter starting on 2016-11-29 (UT) 
12:51:12.  Within enhanced XRT position (Beardmore et al. GCN 20211
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 )  we 
detected  optical source which is absent in USNO-B1.0 but barely visible 
in DSS2 (red). At the moment we can not say anything about the source 
variability. The source might be a superposition of the afterglow and a 
host galaxy.  Preliminary photometry of the source  is following

Date       UT start   t-T0   Filter  Exp.   OT     Err.  UL
                       (mid, days)    (s)

2016-11-29 12:51:12 0.25949  R       13*300 20.60  0.06  22.4

Photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id    R2
1221-0612083 17.30
1221-0612140 19.02

S. Klose and B. Stecklum (both Thueringer Landessternwarte Tautenburg) 
report:

We imaged the field of GRB 161129A (Kocevski et al., GCN 20210
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 ) with the 
Tautenburg Schmidt telescope equipped with the prime focus CCD camera. 
Observations were performed at a midtime of 16:41 UT (November 29).

Inside the enhanced XRT error circle (radius 1.7 arcsec; Beardmore et al., 
GCN 20211
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 ) we find a faint source at coordinates RA, Decl. (J2000) = 
21:04:54.53, 32:08:05.9 (+/- 0.5 arcsec). Using the USNO B2 star at 
coordinates RA, Decl. (J2000) = 21:04:54.65, 32:08:05.6 as a photometric 
reference (Ic = 18.38), we measure for this source a preliminary (Vega) 
magnitude of Ic = 20.3 +/- 0.2 mag.

We note, however, that the DSS2 red shows a faint source at the central 
position of the enhanced XRT error circle at roughly the same coordinates. 
Given that the seeing in our images is about 2 arcsec, and given that our 
images are not substantially deeper than the DSS2 red, we cannot decide 
whether we see this faint source or a faint transient on top of it. In any 
case, at the time of our observations any optical transient was fainter 
than about Ic=20.

N. P. M. Kuin (UCL-MSSL) and D. Kocevski (NASA/GSFC/ORAU) report on
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 161129A
86 s after the BAT trigger (Kocevski et al., GCN Circ. 20210
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 ).
A source consistent with the XRT position (Beardmore et al. GCN Circ.
20211
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 ) is detected in the initial UVOT exposures.

The source is detected in UVOT images at position:
RA =  21h 04m 54.6s (J2000)
Dec = 32d 08' 05.52" (J2000)
with an uncertainty of 0.6" (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               86         6356          400         20.61 +/- 0.20
v                 3858         5493          393        >19.0
b                  554         6314          413        >20.0
u                  298         6109          639        >19.8
w1                4268         5903          393        >19.4
m2                4063         5698          393        >19.6
w2                 604         5288          208        >19.5

There are low-significance signs of the source in all other filters. Though
the source seems to reach peak brightness around 500s the photometric
errors are also consistent with a constant source brightness up to 10ks.

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.21 in the direction of the burst
(Schlegel et al. 1998).

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 161129A (Kocevski et al., GCNC 20210)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2016-11-29 08:54:33 UT (~1.7 h after
the burst). We detected the previously reported source (Mazaeva
et al., GCNC 20215; Klose and Stecklum, GCNC 20216) in Rc and Ic
bands.

Photometric results and three sigma upper limit of the OT are
listed below. We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc  Rc_err  Ic  Ic_err
------------------------------------------------------------------
0.11332    09:54:50    6120.0   >20.2   19.2 0.2    18.6 0.2
------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

O.J. Roberts (UCD), C. Meegan (UAH), and R. Hamburg (UAH)
report on behalf of the Fermi GBM Team:

"At 07:11:39.96 UT on the 29th of November 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 161129A
(trigger 502096303/161129300), which was also detected by
Swift (Kocevski et al., GCN 20210
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 ). The GBM on-ground location
is consistent with the Swift position. The angle from the Fermi
LAT boresight is 87 degrees using the Swift position.

The GBM light curve shows a bright burst, with multiple peaks
over a duration (T90) of about 36 s (50-300 keV).
The time-averaged spectrum from T0+4.8 s to T0+45.7 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.13 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 197 +/- 21 keV.

The event fluence (10-1000 keV) in this time interval is
(8.4 +/- 0.4)E-06  erg/cm^2. The 1-sec peak photon flux measured
starting from T0+26 s in the 10-1000 keV band is 5.6 +/- 0.3 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),

N. Gehrels (GSFC), H. A. Krimm (NSF/USRA),

D. Kocevski (NASA/MSFC), A. Y. Lien (GSFC/UMBC),

C. B. Markwardt (GSFC), J. P. Norris (BSU),

D. M. Palmer (LANL), T. Sakamoto (AGU),

M. Stamatikos (OSU), T. N. Ukwatta (LANL)

(i.e. the Swift-BAT team):


Using the data set from T-239 to T+963 sec from the recent telemetry downlink,

we report further analysis of BAT GRB 161129A (trigger #724438)

(Kocevski, et al., GCN Circ. 20210
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 ).  The BAT ground-calculated position is

RA, Dec = 316.221, 32.137 deg which is

  RA(J2000)  =  21h 04m 53.1s

  Dec(J2000) = +32d 08' 11.9"

with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 69%.


The mask-weighted light curve shows a short spike from ~T0 to ~T+0.2 s,

followed by several overlapping pulses that last until ~T+45 s.

T90 (15-350 keV) is 35.53 +- 2.09 sec (estimated error including systematics).


The time-averaged spectrum from T+0.06 to T+44.58 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 3.6 +- 0.1 x 10^-6 erg/cm2.

The 1-sec peak photon flux measured from T+26.64 sec in the 15-150 keV band

is 3.4 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence

level.


Because the light curve seems to resemble that of a short GRB with

extended emission (Norris et al. 2010), we perform further analysis of the

short spike. Using a 4-ms binned light curve, the lag analysis finds a lag of

4 +/- 3 ms for the 50-100 keV to 15-25 keV band, which is consistent with

that of a short GRB. However, the spectral fit of the short spike

using a simple power-law model gives a power-law index of 1.9 +/- 0.3.

This value is on the softer end of short GRBs, and also softer than all the

initial pulses of those short GRBs with extended emission (Lien et al. 2016).

The power-law index of the spectrum for the rest of the light curve

is 1.53 +/- 0.06, which is harder than the initial spike and thus

unexpected from a short GRB with extended emission.


The results of the batgrbproduct analysis are available at

http://gcn.gsfc.nasa.gov/notices_s/724438/BA/

K. Yanagisawa, D. Kuroda, Y. Shimizu, H. Izumiura (OAO/NAOJ),
M. Yoshida (Hiroshima), K. Ohta(Kyoto), and N. Kawai(Tokyo Tech.)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 161129A (Kocevski et al., GCNC 20210)
in Ks-band with a wide-field NIR camera at Okayama Astrophysical
Observatory (Japan). The camera has an effective aperture of 0.91m.

Observations started from 08:44 UT on 29th November, 93 min after
the BAT trigger, to 09:29 UT. The total exposure of 17.3 min was
successfully obtained.

In our co-add image, we found a faint source at coordinates
   R.A.(J2000) = 21:04:54.59
   DEC (J2000) = +32:08:05.2,
close to the position reported by Beardmore et al.(GCNC 20211),
and Klose & Stecklum (GCNC 20216).

We measured the source magnitude of Ks = 15.95 +/- 0.14 (Vega).
The calibration was made against 2MASS field stars.

T0+[min]    MID-UT     T-EXP[min]    Ks
------------------------------------------------------------
  +115       09:06       17.3         15.95 +/- 0.14 (Vega)
------------------------------------------------------------
T0+ : Elapsed time after the burst [min]
T-EXP: Total Exposure time [min]

E. Mazaeva (IKI),  E. Chornaya (UAFO, ISON), A. Cochergin (UAFO), I. Molotov 
(KIAM), A. Pozanenko (IKI) report on behalf of  larger GRB  follow-up 
collaboration:

We observed the field of  GRB 161129A  (Kocevski et al., GCN 20210
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 ) with 
SANTEL-650 (0.65m)  telescope  of UAFO/ISON-Ussuriysk observatory. We 
obtained several unfiltered images starting on  November 29 (UT) 11:47:34. 
We detected  optical afterglow (Mazaeva et al. GCN 20215
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 ; Klose et al. GCN 
20216
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 ; Kuin et al. GCN 20217
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 ). Preliminary photometry of a combined image is 
following

Date             UT start      t-T0        Filter  Exp.     OT     Err.  UL
                                       (mid, days)         (s)

2016-11-29 10:46:15  0.16055  CR      27*60 19.90  0.08  22.5
2016-11-29 11:19:35  0.18449  CR      30*60 19.95  0.09  22.5


Photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id    R2
1221-0612083 17.30
1221-0612140 19.02

E. Mazaeva (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), A. Volnova
(IKI), I. Korobtsev (ISTP)  report on behalf of larger GRB follow-up
collaboration:

We observed the field of  GRB 161129A  (Kocevski et al., GCN 20210
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 ) with 
  AZT-33IK telescope of Sayan observatory (Mondy) starting on November, 
30 (UT) 11:19:53. We obtained several images in R-filter.
We detected  a source coinsiding with optical afterglow (Mazaeva et al. 
GCN 20215
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 ; Klose et al. GCN 20216
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 ; Kuin et al. GCN 20217
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 ; Kuroda et al. 
GCN 20218
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 ; Yanagisawa et al. GCN 20223
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 ). Preliminary photometry of a 
combined image is following

Date       UT start   t-T0    Filter  Exp.     OT     Err.  UL
                      (mid, days)      (s)

2016-11-30 11:19:53  1.19324  R      29*120    21.60  0.17  22.8

Photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id    R2
1221-0612083 17.30
1221-0612140 19.02

J. C. Sun (IHEP), M. R. Kole (DPNC/UniGe), Y. H. Wang (IHEP),

S. L. Xiong (IHEP),Z. H. Li (IHEP),H. C. Li (IHEP),

Y. Zhao (IHEP), T. Batsch(NCBJ),T. Bernasconi (ISDC/UniGe),

  F. Cadoux (DPNC/UniGe), Y. W. Dong (IHEP),M. Z. Feng

(IHEP), M. Y. Ge (IHEP), W.Hajdas (PSI),Y. Huang (IHEP),

Karol Jedrzejczak (NCBJ), F. J. Lu (IHEP), R. Marcinkowski

(PSI), M. Pohl (DPNC/UniGe),N. Produit (ISDC/UniGe),

A. Rutczynska (NCBJ), D. Rybka (NCBJ),L. M. Song (IHEP),

J. Szabelski (NCBJ), X. Wen (IHEP), B. B. Wu (IHEP),X. Wu

(DPNC/UniGe), H. L. Xiao (PSI), M. Xu (IHEP), J. Zhang

(IHEP),L. Y. Zhang (IHEP), P. Zhang (PSI), S. N. Zhang

(IHEP),Y. J. Zhang (IHEP), A. Zwolinska (NCBJ)

report on behalf of the POLAR team:

At 2016-11-29T07:11:40.00 UT(T0), during a routine

on-ground search of data, POLAR detected the GRB 161129A,

which was also observed by the Swift/BAT (trigger

#724438), Fermi/GBM (trigger 502096303/161129300), and

Astrosat/CZTI (V. Sharma et al., GCN Circ. 20214
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 ). The

detection of this GRB happened on the tail of a big Solar Flare.

The POLAR light curve consists of multiple peaks

with a duration (T90) of 41.5 s measured from T0+3.75 s.

The 500-ms peak flux, measured from T0+27.25 s, is 705.7

cnts/sec. The above measurements are in the preliminary

calculated energy range of about 80 ��� 500 keV.

LC_URL:

http://www.isdc.unige.ch/polar/lc/161129A/lcr.png

The incident angle at T0 in POLAR detector coordinate is:

theta:  42.6   [deg]

phi:    52.3   [deg]

These direction is computed using the best location from

the Swift/BAT, which is (J2000):

RA:   316.221  [deg]

Dec:  32.137   [deg]

Err:  1.8      [arcmin]

The distribution of the GRB signal among its 25 detector

modules is also consistent with this incident geometry.

Preliminary calculations of the MDP show that a

polarimetric measurement of this burst can be attempted.


The analysis results presented above are preliminary. The

calibration work is ongoing.


POLAR is a dedicated Gamma-Ray Burst polarimeter which was

launchedon-board the Chinese space laboratory Tiangong-2

(TG-2) on Sep 15, 2016.The energy detection range of POLAR

is ~ 50-500 keV.More information about POLAR can be found

at _http://polar.ihep.ac.cn/en/_.

Tomoki Morokuma and Yuki Sarugaku (Univ. of Tokyo) report on behalf 
of���the OISTER collaboration:

We observed the field of GRB 161129A (Kocevski et al. GCN 20210
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 ) 
with���the 1.05-m Schmidt telescope and KWFC (Sako et al. 2012, Proc. 
SPIE���8446, 84466L) at Kiso Observatory in Japan. The observations were 
made���in z-band at 2016-11-29 08:15-08:36 (UT; about 1 hour after the 
burst). The flux is calibrated with z-band imaging data for a nearby 
SDSS field taken at almost the same airmass as that of the GRB field.

We do not detect any new source within the XRT error circle or at the 
position with Swift/UVOT and other telescopes' detections (e.g., Kuin et 
al. GCN 20217
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 ) and the upper limits are as follows.

# ------------------------------------------------
# MID-MJD    MID-UT   t_exp  z_lim
# ------------------------------------------------
57721.3442  08:15:36   60.0   16.9
57721.3477  08:20:44  120.0   17.7
57721.3513  08:25:50  180.0   18.3
57721.3542  08:30:08  180.0   18.6
57721.3573  08:34:25  180.0   18.7
# ------------------------------------------------
MID-MJD [day] : MJD in the middle of exposure
MID-UT        : UT in the middle of exposure
t_exp [sec]   : Exposure time
z_lim         : 5-sigma limiting magnitude (AB)

K. E. Heintz (Univ. Iceland and DARK/NBI), D. Malesani (DARK/NBI and DTU 
Space), Z. Cano (IAA-CSIC), A. De Ugarte Postigo (IAA-CSIC and 
DARK/NBI), G. Fedorets (NOT and Univ. Helsinki), R. Tronsgaard Rasmussen 
(NOT), A. A. Djupvik (NOT), I. R. Losada (NOT and Stockholm Univ.), I. 
Svardh (NOT), J. Clasen (NOT), S. Armas Perez (NOT), report on behalf of 
a larger collaboration:

We observed the optical counterpart of GRB 161129A (Kocevski et al., GCN 
20210
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 ; Mazaeva et al., GCN 20215
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 ) with the Nordic Optical Telescope 
(NOT) equipped with the AlFOSC imager. Observations were carried out in 
the R band (3x200 s), with a mid time 2016 Dec 4.83 UT (5.6 days after 
the GRB). Observing conditions were good with a seeing of 0.8".

Two objects are detected within the XRT error region (Beardmore et al. 
2016, GCN Circ. 20211
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 ), at the following coordinates (calibrated against 
the USNO-B1.0 catalog):

source A: RA = 21:04:54.69, Dec = +32:08:04.7
source B: RA = 21:04:54.63, Dec = +32:08:05.9

A finding chart is posted at this URL: 
http://www.astro.ku.dk/~malesani/GRB/161129A/GRB161129A.png

Given their small separation (1.4"), these objects may be blended in 
images with coarser spatial resolution. Source A (with a magnitude R = 
21.6) is consistent in flux and position with the faint smudge visible 
in the DSS red, previously noted by Mazaeva et al. (GCN 20215
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 ) and Klose 
& Stecklum (GCN 20216
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 ).

Source B is extended, and is consistent with the position reported for 
the optical afterglow by Kuin et al. (GCN 20217
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 ) and Kuroda et al. (GCN 
20218
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 ). We propose that source B is (dominated by) the host galaxy of 
GRB 161129A. We further note that the cumulative magnitude of the 
complex (objects A+B) is R ~ 21.2, which is significantly fainter than 
previous reports (e.g. Kuroda et al., GCN 20218
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 ; Mazaeva et al., GCN 
20224
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 ), thus firmly establishing the presence of a fading optical 
afterglow for GRB 161129A. Photometry was computed against the values of 
the two USNO-B1.0 stars as listed by Mazaeva et al. (GCN 20215
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 ).

���Z. Cano (IAA-CSIC), D. Malesani (DARK/NBI and DTU Space), A. de Ugarte
Postigo (IAA-CSIC, DARK/NBI), L. Izzo, C. C. Thoene (IAA-CSIC) and N.
Castro-Rodriguez (GRANTECAN/IAC/Universidad de La Laguna) report:

We observed the field of GRB 161129A (Kocevski et al., GCN Circ. 20210
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 )
with OSIRIS on the 10.4 m GTC telescope on La Palma (Spain).  The
observations started at 19:46:40.9 UT on 05-December-2016 (6.52 days after
the burst), which consisted of 4 x 1200 s spectra using grism R1000B, which
covers the wavelength range 3700-7800 angstroms, with a resolution of
R~1000.

Within the enhanced XRT error region (Beardmore et al. 2016, GCN Circ.
20211
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 ) we note the presence of sources A & B detected by Heintz et al. (GCN
Circ. 20244
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 ).  The spectrum of the extended object (source B) shows a
continuum with a strong emission line that we attribute to the [OII]
3727/3729 doublet at z=0.645, as well as weaker emission lines consistent
with being H-gamma and H-delta at the same redshift. We propose this
star-forming galaxy to be the host of GRB 161129A. The spectrum of source A
displays absorption features of Ca II K and H, Mg I and MgH at z~0,
confirming it is a foreground star and not related to GRB 161129A.

K. P. Mooley (Hintze Fellow, Oxford), T. D. Staley, R. P. Fender 
(Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. 
Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, 
P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)

The AMI Large Array robotically triggered on the Swift alert for GRB 
161129A (Kocevski et al., GCN 20210
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 ) as part of the 4pisky program, and 
subsequent follow up observations were obtained up to 10 days 
post-burst. Our observations at 15 GHz on 2016 Nov 29.50, Nov 30.72, Dec 
02.69 and Dec 06.68 (UT) do not reveal any radio source at the XRT 
location (Beardmore et al., GCN 20211
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 ), with 3sigma upper limits of 120 
uJy, 102 uJy, 90 uJy and 117 uJy respectively.

We thank the AMI staff for scheduling these observations. The AMI-GRB 
database is a log of all GRB follow up observations with the AMI, and is 
available at http://4pisky.org/ami-grb/.