GRB 120106A

S. Immler (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),
H. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU),
O. M. Littlejohns (U Leicester), F. E. Marshall (NASA/GSFC),
C. J. Mountford (U Leicester), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), J. L. Racusin (NASA/GSFC),
C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/PSU),
M. H. Siegel (PSU), R. L. C. Starling (U Leicester),
T. N. Ukwatta (MSU) and B.-B. Zhang (PSU) report on behalf of the
Swift Team:

At 14:16:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120106A (trigger=511235).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 66.129, +64.028, which is 
   RA(J2000)  =  04h 24m 31s
   Dec(J2000) = +64d 01' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve show several overlapping peaks
starting ~T-8 sec with a total duration of about 20 sec.  The peak count rate
was ~2400 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 14:17:39.0 UT, 74.9 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 66.11105, 64.03810 which
is equivalent to:
   RA(J2000)  = 04h 24m 26.65s
   Dec(J2000) = +64d 02' 17.2"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 46 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 in excess of the Galactic value (2.65 x
10^21 cm^-2, Kalberla et al. 2005), with an excess column of 4.8
(+4.97/-3.87) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 1.88e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 84 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. 
Data from the list of sources generated on-board are not available at this
time. No correction has been made for the expected extinction corresponding to
E(B-V) of 1.19. 

Burst Advocate for this burst is S. Immler (stefan.immler 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.)

K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Gres,
O.Chuvalaev,E.Konstantinov,
  Irkutsk State University

  E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, A.Belinski,
N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov,  A.Kuznetsov,
D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov,
A.Sankovich, S. Shurpakov
Moscow State University,  Sternberg Astronomical Institute



  V.Krushinski, I.Zalozhnich, A. Popov
  Ural State University, Kourovka


E. Sinykov, V.Yurkov, Yu.Sergienko, D.Varda,
  Blagoveschensk Educational State University, Blagoveschensk



  A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
  Kislovodsk Solar Station of the Pulkovo Observatory


MASTER II  robotic double telescope (MASTER-Net: http://observ.pereplet.ru) 
located at Tunka (Baykal) was pointed
to the  120106A (Immler et al., GCN Circ 12810
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 ) 19 s after notice time and 
46 sec after GRB time at 14:16:24.24 UT.

On our first (10s exposure) west telescope image (| polasizations) we 
haven`t found optical transient  within SWIFT error-box.
The 5-sigma upper limit has been about 15.8 mag.

On our first (10s exposure) east telescope image (- polasizations) we
haven`t found optical transient  within SWIFT error-box.
The 5-sigma upper limit has been about 15.9 mag.




The message may be cited.

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (OCA-CNRS), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 120106A detected by SWIFT
(trigger 511235) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 169 min. after the GRB trigger,
just at the beginning of the night over Calern.
The elevation of the field increased from
52 degrees above horizon and weather conditions
were excellents.

We co-added a series of exposures. We did not found
any optical counterpart in the error box of the XRT
candidate (Immler et al. GCNC 12810):

Start    End       Rlim
169 min  212 min   19.3

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

This message may be cited.

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

Using 3180 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 120106A, 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 = 66.10754, +64.03837 which is equivalent
to:

RA (J2000): 04h 24m 25.81s
Dec (J2000): +64d 02' 18.1"

with an uncertainty of 1.4 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.

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 the MITSuME collaboration:

We observed the field of GRB 120106A (Immler et al., GCNC 12810)
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 2012-01-06 14:17:12 UT (~48 sec after
the burst). We did not find any new point source within the enhanced
XRT circle (Evans et al., GCNC 12813) in all the three bands.


Three sigma upper limits of the OT are listed below. We used
GSC2.3 catalog for flux calibration.

T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic
------------------------------------------------------
0.00400    14:22:10     540.0   >19.3  >19.4  >18.7
0.04247    15:17:33    6420.0   >20.6  >20.2  >19.6
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

S. D. Barthelmy (GSFC), T. Sakamoto (GSFC/UMBC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
S. Immler (CRESST/GSFC/UMD), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120106A (trigger #511235)
(Immler, et al., GCN Circ. 12810
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 ).  The BAT ground-calculated position is
RA, Dec = 66.129, 64.050 deg, which is 
   RA(J2000)  =  04h 24m 30.9s 
   Dec(J2000) = +64d 03' 00.0" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.
 
The mask-weighted light curve shows the first peak starting at ~T-7 sec,
peaking at ~T+1 sec, and ending at ~T+13 sec. There is a second, weaker peak
starting at ~T+50 sec and ending at ~T+65 (possibly T+85) sec. 
T90 (15-350 keV) is 61.6 +- 4.1 sec (estimated error including systematics).
 
The time-averaged spectrum from T-6.24 to T+60.24 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.53 +- 0.17.  The fluence in the 15-150 keV band is 9.7 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.46 sec in the 15-150 keV band
is 1.5 +- 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/511235/BA/

P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), V. Mangano (INAF-IASFPA),
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
S. Immler report on behalf of the Swift-XRT team:

We have analysed 12 ks of XRT data for GRB 120106A (Immler  et al. GCN
Circ. 12810
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 ), from 64 s to 29.5 ks after the  BAT trigger. The data
comprise 273 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 Evans et
al. (GCN. Circ 12813).

The light curve can be modelled with an initial power-law decay with an
index of alpha=4.3 (+/-0.3), followed by a break at T+152 s to an alpha
of 0.91 (+0.05, -0.04).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.15 (+0.12, -0.15). The
best-fitting absorption column is  7.6 (+6.8, -0.7) x 10^21 cm^-2,
consistent with the Galactic value of 7.0 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 4.8 x 10^-11 (1.0 x
10^-10) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     7.6 (+6.8, -0.7) x 10^21 cm^-2
Galactic foreground: 7.0 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.15 (+0.12, -0.15)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00511235.

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

V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, 
A.Belinski, N.Tyurina, N.Shatskiy, P.Balanutsa, V.V.Chazov,  A.Kuznetsov,
D.Zimnukhov, M. Kornilov, A.Kuznetsov, D.Zimnukhov, M. Kornilov,
A.Sankovich, S. Shurpakov
Moscow State University,  Sternberg Astronomical Institute

K.Ivanov, V.A.Poleshchuk, S.Yazev, N.M.Budnev, O.Gres,
O.Chuvalaev,E.Konstantinov,
  Irkutsk State University

  V.Krushinski, I.Zalozhnich, A. Popov
Ural State University, Kourovka

E. Sinykov, V.Yurkov, Yu.Sergienko, D.Varda,
Blagoveschensk Educational State University, Blagoveschensk

A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik
Kislovodsk Solar Station of the Pulkovo Observatory


MASTER II  robotic double telescope (MASTER-Net: 
http://observ.pereplet.ru) located at Tunka (Baykal) was pointed to the 
120106A (Immler et al., GCN  Circ 12810
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 ) 19 s after notice time and 46 sec 
after GRB trigger time at  14:16:24.24 UT (Ivanov et al., GCN CIRC 12811
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 ).

On our first (10s exposure) set  we haven`t
found optical transient  within preliminary SWIFT XRT error-box (Immler
et al., GCN Circ 12810
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 ).

But we found marginally OT at East telescope (- polarizations) outside
preliminary X-ray  error box (Immler et al., GCN Circ 12810
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 ). The position
of this OT is coincided with enhanced Swift-XRT position (Evans et al.,
GCN CIRC 12813
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 ).

      UT               T-T_GRB  Exp      mag      Tel    Filter

2012-01-06 14:17:10     46      10   17.0+-0.3   East    P-
2012-01-06 14:17:10     46      10     >16.8     West    P|
2012-01-06 14:22:23    359      70     >18.0     East    P-
2012-01-06 14:22:23    359      70     >18.0     West    P|
2012-01-06 14:26:45    720     120     >18.2     East    P-
2012-01-06 14:26:45    720     120     >18.2     West    P|
2012-01-06 14:31:49   1024     180     >18.3     East    P-
2012-01-06 14:31:49   1024     180     >18.4     West    P|


The images will be available at 
http://observ.pereplet.ru/images/GRB120106A/grb.html  .
The message may be cited.

Kenshi Yanagisawa, Daisuke Kuroda, Yasuhiro Shimizu, Kiichi Okita
(OAO/NAOJ), Michitoshi Yoshida (Hiroshima-U), Kouji Ohta(Kyoto-U),
and Nobuyuki Kawai(Tokyo Tech.) report on behalf of the MITSuME
collaboration:

We observed the field of GRB120106A (Immler et al., GCNC 12810) 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 15:19 UT on 5th January, 1.05 hours after
the BAT trigger, to 16:20 UT.  The total exposure of 49 min was
successfully obtained.

In our co-add image, we did not find any new point source within the
enhanced XRT error circle (Evans et al., GCNC 12813) down to limiting
magnitude of  Ks= 15.6(Vega, S/N=3). The photometric calibration was
made against 2MASS field stars.

T0+[min]    MID-UT     T-EXP[min]      Ks
---------------------------------------------------
  +93.6     15:50         49.0       >15.6 (S/N=3)
---------------------------------------------------
T0+ : Elapsed time after the burst [sec]
T-EXP: Total Exposure time [sec]

U.Quadri, L.Strabla and R.Girelli report:We imaged the field of GRB 120106A detected by SWIFT(trigger 511235) with the robotic telescopeof (565)Bassano Bresciano Observatory, Italy.The observations started 223 min. after the GRB trigger,with our schmidt telescope (320/400/1000).Weather conditions were excellents.We co-added a series of 15 exposures. We did not foundany optical counterpart in the error box of the XRTcandidate.Start������ End������������ Vlim223 min�� 252 min���� 19.5Magnitudes were estimated with the UCAC-3 catalog.

S. Immler (CRESST/GSFC/UMD) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120106A
65 s after the BAT trigger (Immler et al., GCN Circ. 12810
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 ).
No optical afterglow consistent with the XRT position
(Evans et al., GCN Circ. 12813
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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 coadded exposures are:

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

white              687         6326          451   >20.3
v                   65         11570         619   >20.0
b                  551         6736          452   >20.8
u                  296         6531          924   >20.8
w1                 678         6326          452   >20.3
m2                 652         6121          454   >20.2
w2                 603         11220         1239   >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.195 in the direction of the burst
(Schlegel et al. 1998).

We carried out a detailed analysis of GRB 120106A and found the optical
afterglow in only Ic-band. This results indicated the possibility of
a Rc-band dropout.
Although we reported the three sigma upper limits in the previous circular
(Kuroda et al., GCNC 12814), we updated our results as follows.

Three sigma upper limits and photometric result of the OT are listed below.
We used GSC2.3 catalog for flux calibration.

T0+[day]   MID-UT   T-EXP[sec]    g'     Rc     Ic  Ic_err
-----------------------------------------------------------
0.00400    14:22:10     540.0    >19.3  >19.4  19.1  0.3
-----------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

A. Volnova (SAI MSU), E. Litvinenko (UBAI), A. Pozanenko (IKI) on behalf of 
larger GRB follow up collaboration report:

We observed the field of the Swift GRB 120106A (Beardmore  et al., GCN 
12810
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 ) with ORI-40 telescope of Kitab ISON observatory on Jan. 6 starting on 
(UT) 18:49:24. We obtained several unfiltered images between (UT) 18:49:24 - 
19:20:20.  On the stacked image we do not detect any source within the 
enhanced XRT error box (Evans et al., GCN  12813
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 ). The photometry is based 
on nearby  reference stars of USNO-B1.0 (R2 magnitudes):

 Tstart UT, T0+,       Filter, Exposure, OT, UL (3 sigma)
                 (mid, d)             (s)

 18:49:24  0.2003    none  30*60       n/d  18.5