GRB 121229A

E. Sonbas (NASA/GSFC/Adiyaman Univ.), V. D'Elia (ASDC),
J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), T. Sakamoto (AGU)
and M. H. Siegel (PSU) report on behalf of the Swift Team:

At 05:00:21 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121229A (trigger=544347).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 190.100, -50.594 which is 
  RA(J2000) = 12h 40m 24s
  Dec(J2000) = -50d 35' 37"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Since this is an image trigger, the BAT light 
curve does not show any particular structure.  The peak count rate 
was ~1000 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 05:02:47.8 UT, 145.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 190.09755, -50.59366 which
is equivalent to:
  RA(J2000)  = 12h 40m 23.41s
  Dec(J2000) = -50d 35' 37.2"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 5.7 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 1.35
x 10^21 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 1.21e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 155 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 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 expected extinction corresponding to E(B-V) of
0.16. 

Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.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. LaCluyze, N. Frank, D. Reichart, J. Haislip, K. Ivarsen, J. Moore, H. T. 
Cromartie, R. Egger, A. Foster, N. Frank, M. Nysewander, A. Oza, E. 
Speckhard, A.Trotter, and J. A. Crain report:

Skynet began observing the field of GRB121229a beginning ~2 minutes after 
the burst using three of the PROMPT telescopes located at CTIO in Chile in 
B,R, and I.  No optical afterglow is detected in the early observations.

Calibrating to several nearby USNO B1.0 stars, and co-adding the early 
observations, the following 3-sigma limiting magnitudes are obtained, at a 
mean observing time of ~30 minutes post burst:

Filt	Time	3-Sig Limit
B	29.7m	>20.6
R	29.7m	>20.7
I	33.1m	>20.5


Further observations are ongoing.

K. Varela (MPE Garching), V. Sudilovsky (MPE Garching), S. Klose (TLS
Tautenburg), and J. Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 121229A (Swift trigger 544347; Sonbas et al.,
GCN 14115
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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 MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started on December 29, 2012, at 05:09 UT, 540 s after the
GRB trigger. They were performed at an average seeing of 1.0" and at an
average airmass of 1.8.

We find a point source at the border of the XRT error
circle at a position

RA (J2000.0) = 12:40:24.29
DEC (J2000.0) = -50:35:39.48

with an uncertainty of 0.5" in each coordinate.

Based on a total exposure time of 1500 s in g'r'i'z' and 1200 s in JHK,
at a midtime of 3840s after the burst, we estimate preliminary
AB magnitudes of

g' = 22.2 +/- 0.2,
r' = 21.5 +/- 0.1,
i' = 21.3 +/- 0.1,
z' = 21.1 +/- 0.1,
J  = 20.9 +/- 0.1,
H  = 20.2 +/- 0.1, and
K  > 19.7.

This source's spectral energy distribution is best fit with a power-law of
slope beta = 0.8 +/- 0.2.
We suggest that this source is the afterglow of GRB 121229A.

Given magnitudes are calibrated against GROND zeropoints in g'r'i'z' and
2MASS
field stars in JHK, and are not corrected for the Galactic foreground
extinction
corresponding to a reddening of E(B-V)= 0.16 mag in the direction of the
burst (Schlegel et al. 1998).

S. Nakahira (JAXA), Y. Ogawa, Y. Nishimura, T. Hanayama (Miyazaki U.),
Y. Ueda, K. Hiroi, M. Shidatsu, R. Sato, T. Kawamuro (Kyoto U.),
N. Kawai, M. Morii, R. Usui, K. Ishikawa (Tokyo Tech),
K. Yamaoka (ISAS), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, K. Morihana, T. Yamamoto,
J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN),
A. Yoshida, T. Sakamoto, Y. Nakano (AGU), H. Tsunemi, M. Sasaki (Osaka U.),
H. Negoro, M. Nakajima, M. Asada (Nihon U.), Y. Tsuboi, M. Higa (Chuo U.),
M. Yamauchi, K. Yoshidome (Miyazaki U.)$B!!(B
report on behalf of the MAXI team

At 2012-12-29T05:01:08 UT, the MAXI/GSC detected an uncatalogued X-ray
transient source. Assuming that the source flux was constant over the
transit, we obtain the source position at
(R.A., Dec.) = (189.70deg, -50.84deg) = (12:38:48.98, -50:50:36.0)(J2000)
with a 90% C.L. statistical error of 0.4 deg and an additional systematic
uncertainty of 0.1 deg (90% containment radius).

The position and time are consistent with those of GRB 121229A (Sonbas
et al, GCN #14115
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 ). The transit by MAXI occurred from 2012/12/29
05:00:47 (=T0+26 s, where T0 is the Swift/BAT trigger time) to T0+70s.
The averaged X-ray flux was 103 +/- 23 mCrab (2-20 keV).
The spectrum is fitted by a power-law model with a photon index of
1.85 (-0.58/+0.68). There was no significant excess flux at the previous
transit at 2012/12/28 18:12 UT and at the next transit at 2012/12/29
06:43 UT with an upper limit of 20 mCrab for each.

J. P. U. Fynbo (DARK/NBI), N. R.  Tanvir (U. Leicester), V. D'Elia
(ASDC, INAF), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI),
D. Malesani (DARK), O. E. Hartoog (Uva, NL), D. Xu (DARK), H. Flores
(Obs. Paris), A. J. Levan (U. Warwick), B. Milvang-Jensen (DARK/NBI)

We observed the field of GRB 121229A (Sonbas et al., GCN 14115
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 ; Varela
et al., GCN 14117
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 ) with the ESO VLT equipped with the X-shooter
spectrograph. Observations started at 07:00 UT on 2012-12-29 (2 hr
after the BAT trigger), for a total exposure time of ~30 min in each
of the UVB, VIS, and NIR arms, covering the wavelength range
3000-21000A.

The spectrum exhibits two relatively broad troughs (centered at ~ 3800
and 4500 A) which we interpreted as Lyman-beta and -alpha features,
respectively, at z=2.707. We measured the HI column density,
logN(HI)~21.7, from the Lyman-alpha feature. At this redshift there
are tentative indications of other metal absorption features, although
they are weak and we have yet to establish their significance. The
lack of strong resonance metal lines, together with the low X-ray
absorption (Sonbas et al., GCN 14115
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 ), suggests a low metallicity. We
also report a tentative evidence for an intervening MgII absorber at
z=1.658

We acknowledge the excellent support of the ESO observing staff, in
particular Maja Vu?kovi?.


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

Using 2407 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 121229A, 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 = 190.10130, -50.59414 which is equivalent
to:

RA (J2000): 12h 40m 24.31s
Dec (J2000): -50d 35' 38.9"

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.

S. R. Oates (MSSL-UCL) and E. Sonbas (NASA/GSFC/Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121229A
155 s after the BAT trigger (Sonbas et al., GCN Circ. 14115
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 ).
No optical afterglow consistent with the optical position
(Varela et al. GCN Circ. 14117
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 )
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           155          305          147         >20.9
u_FC               314          563          246         >19.9
white              155         6156          363         >21.2
v                  644         6466          116         >18.9
b                  570         5952          216         >20.5
u                  314         5747          442         >20.1
w1                3947         4136          186         >20.0
m2                 670          690           19         >17.6
w2                 620         6362          216         >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.16 in the direction of the burst
(Schlegel et al. 1998).

H. A. Krimm (GSFC/USRA),S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC),J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC),C. B. Markwardt (GSFC),D. M. Palmer (LANL),
T. Sakamoto (AGU), E. Sonbas (NASA/GSFC/Adiyaman Univ.),
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 121229A (trigger #544347)
(Sonbas, et al., GCN Circ. 14115
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 ).  The BAT ground-calculated position is
RA, Dec = 190.095, -50.588 deg which is
    RA(J2000)  =  12h 40m 22.7s
    Dec(J2000) = -50d 35' 16.9"
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.  The mask-weighted light curve shows a broad
structure beginning at least at T-60 seconds and lasting until T+60 sec.
Since there is no data from before the start of the burst, T90 cannot be
accurately calculated at this time.  It is approximately 100 seconds.

The time-averaged spectrum from T+0.00 to T+64.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.43 +- 0.46.  The fluence in the 15-150 keV band is 4.6 +- 1.3 x 10^-7erg/cm2.
The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band
is 0.1 +- 0.0 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/544347/BA/

G. Stratta (ASDC), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), 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) and E.
Sonbas report on behalf of the Swift-XRT team:

We have analysed 13 ks of XRT data for GRB 121229A (Sonbas  et al. GCN
Circ. 14115
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 ),  from 135 s to 68.4 ks after the	BAT trigger. The data
comprise 438 s in Windowed Timing (WT) mode (the first 9 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 Goad et al.
(GCN. Circ 14121).

The late-time light curve (from T0+3.9 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.23 (+0.20, -0.22).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.14 (+/-0.05). The
best-fitting absorption column is  1.62 (+0.24, -0.23) x 10^22 cm^-2,
at a redshift of 2.707, in addition to the Galactic value of 1.4 x
10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon
index of 2.14 (+0.33, -0.13) and a best-fitting absorption column
consistent with the Galactic value. The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum  is 3.4 x
10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.4 x 10^21 cm^-2
Intrinsic column:    0 (+8.4, -0) x 10^21 cm^-2 at z=2.707
Photon index:	     2.14 (+0.33, -0.13)

If the light curve continues to decay with a power-law decay index of
2.00, the count rate at T+24 hours will be 7.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.6 x
10^-13 (3.7 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/00544347.

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