GRB 061222, GRB 061222A

Poonam Chandra (NRAO/UVA) and Dale A. Frail (NRAO) report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:

"We used the Very Large Array to observe the field of view toward GRB
061222A (GCN 5954
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 ) at a frequency of 8.46 GHz on 2006 December 23 at
0.15 UT.  The peak radio brightness at the XRT position
(GCN 5966
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 ) is 285 uJy � 68 uJy.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."

Yu. Efimov, V. Rumyantsev (CrAO), A. Pozanenko (IKI), D. Sharapov (MAO) on
behalf of larger GRB follow up collaboration report:

We observed error box of GRB061222a (Grupe et al., GCN 5954
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 )  with Shajn
2.6m telescope of CrAO. A set of  60 s exposures was taken on Dec. 22 in R
between (UT) 18:28 - 19:29.   We do not detect afterglow registered in Ks
(Cenko et al., GCN 5975
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 , GCN 5978
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 ).  No object is also detected in refined
XRT error box (Grupe, GCN 5966
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 ). Based on the USNO A2.0 star (23 53 02.73
+46 32 18.50   17.60 R) we estimate 3 sigma limiting magnitude of a combined
image (48*60 s) as R=23.8.

Finding chart can be found in
http://grb.rssi.ru/GRB061222a/GRB061222a_R_ZTSh.GIF

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:

The most intense part of the long GRB 061222A (Swift-BAT trigger
#252588; Grupe et al., GCN 5954
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 ; Tueller et al., GCN 5964
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 )
triggered Konus-Wind at T0=12614.682 s UT (03:30:14.682).
The emission is clearly seen in the Konus-Wind data
starting at T-T0~-80 s.

As observed by Konus-Wind the burst had a duration of ~100 s,
fluence 2.66(-0.23, +0.43)x10^-5 erg/cm2,
the 64-ms peak flux measured from T0+5.312 s
5.65(-1.19, +1.42)x10^-6  erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The spectrum integrated over the most intense part of the burst
(from T0 to T0+15.104 s) is well fitted (in the 20 keV - 2 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -0.94(-0.13, +0.14),
the high energy photon index beta = -2.41(-1.21, +0.28),
the peak energy Ep = 283(-42, +59) keV (chi2 = 64/60 dof).
The fitting by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
in the same energy range yields
alpha = 1.02(-0.11, +0.10)
and Ep = 324(-41, +54) keV (chi2 = 67/61 dof).

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB061222_T12614/

[GCN OPS NOTE(28dec06): Per author's request, the author list
was added.]

T. Ishimura, Y. Yatsu, T. Shimokawabe, N. Vasquez, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:
 
We observed the error box of GRB061222A (Grupe et al., GCN 5954
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 )
with the 3-color 50cm MITSuME Telescope at Akeno, Japan starting 
at 8:48:53 UT, 5.3 hours after the trigger.   
In the co-added images of Ic, Rc, and g' bands, we did not detect
any new source in the XRT error circle.  The 3-sigma limiting
magnitudes based on USNO-B1.0 (I-band) and NOMAD (R-band,g'-band)
stars are following.

Filter   start time   end time    Exp(s)    Mag (3-sigma upper limit)
-----------------------------------------------------------------
Ic        8:48:53    09:32:23     60s * 36         19.6 
Rc        8:48:53    09:32:23     60s *	36	   20.4 
g'        8:48:53    09:32:23     60s * 36	   20.6
-----------------------------------------------------------------

S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:

We have further refined the processing of our first epoch of Gemini
Ks-band imaging of GRB061222A (see GCN 5975
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 ).  Using 12 2MASS stars in the
field, we report a refined position for the afterglow candidate of:

	RA: 23:53:03.419
	Dec: +46:31:58.60

with an uncertainty of +/- 0.2" in each coordinate (J2000.0).  Using our
full set of Ks-band images, we calculate a magnitude of Ks = 20.7 +/- 0.3
at a mean epoch of 5:35 Dec. 22 UT (~ 2.1 hr after the burst).

We obtained a second epoch of Ks-band imaging from Gemini on the following
evening (mean epoch 4:53 Dec. 23 UT, ~ 25.4 hr after the burst).  The
object reported above faded by ~ 1.2 mag, confirming this source as the
afterglow of GRB061222A.  The corresponding decay rate is quite shallow,
with a decay index alpha ~ 0.4 (assuming no contribution from the host
galaxy).

M.Zhai, L.P. Xin, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng and W.K. Zheng
on behalf of EAFON report:

We have imaged the field of GRB 061222A with the 2.16m telescope at
Xinglong Observatory. A 30 minutes R band image is obtained 9.97 hours
after the burst.The afterglow candidate (S.B. Cenko et al., GCN5975
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 )
was not detected and no new source was seen with 3-simga limit magnitude
R~22.4 derived from USNO B1.0

This message may be cited.

S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:

We have imaged the field of GRB061222A (Grupe et al, GCN 5954
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 ) with the
Near-Infrared Imager mounted on the Gemini-North telescope.  Observations
were taken in the Ks filter at a mean epoch of ~ 5:50 Dec. 22 UT.  Inside
the revised XRT error circle (Grupe et al, GCN 5966
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 ), we find one faint
source at location (J2000.0):

	RA: 23:53:03.40
        Dec: +46:31:58.5

(+/- 1.0").  Based on several 2MASS stars in the field, we measure a
magnitude of Ks ~ 20.5, with large uncertainty dominated by both the
faintness of the object and photometric uncertainty.  At this point we
cannot determine if the object is variable or not.

Further observations are planned.

S.R Oates(UCL-MSSL), D. Grupe(PSU), S.B.Pandey(UCL-MSSL)
report on the behalf of the Swift UVOT team:

The Swift/UVOT began observing the field of GRB 061222A
92 seconds after the BAT trigger (Grupe et al., GCN Circ.5954
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 ).
No optical afterglow candidate is detected in the XRT error circle
within the first V and White exposures or in later coadded images.

The 3 sigma upper limits for each UVOT filter are given
below:

Filter        Tstart    Tend     Exposure    3sigUL
-------------------------------------------------
V finding       215     615       393        19.6
White finding   111     209       97         20.0

V               745      24842    5310       20.4
B               693      24112    2713       20.8
U               669      1591     78         19.4
w1              645      1711     83         19.2
m2              621      1701     97         19.3
w2              721      1653     58         19.3
White           110      1629     322        20.6
-------------------------------------------------

The values quoted above are not corrected for the expected Galactic
extinction of E_{B-V} = 0.099 mag (Schlegel et al. 1998).

M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.), 
report on behalf of the KANATA GRB team:

  We perfomed optical imaging of the field of GRB061222A (GCN 5954
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 , 5964
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 , 
5966
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 ) at 9:43-10:05 UT 22 Dec. using the TRISPEC attached to the KANATA 
1.5-m telescope at Higashi-Hiroshima Observatory, Japan.  
We obtained 7 R-band images with a 123-s exposure time.  The images were
calibrated with neighbor stars in the USNO A2.0 catalog (r mag.). 

No new object was found within the XRT error circle.  
The limit magnitude is estimated to be 21.6 (3-sigma).  

UT            Time after the burst (s)    Limit mag in R   Exp. Time
Dec. 22.41537        23355                    21.6          123 * 7

D. Grupe (PSU) reports on behalf of the Swift/XRT team



We have analyzed the first orbit of GRB 061222A (Grupe et al., GCN 5954
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 )
with total observing times of 117s in Windowed Timing mode and
1476s in Photon Counting mode in the Swift XRT. The Photon Counting mode 
image
provides a refined XRT position at RA, Dec= 358.263708, +46.53297, which is

RA(J2000) = 23h 53m 03.29s
Dec(J2000) = +46d 31' 58.7"

with an error of 3.5" (90% confidence). This position is 2.4"
away from the preliminary XRT position reported in GCN 5954
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 .

The X-ray light curve displays the end of a flare as seen in the BAT (at 
the beginning of the
XRT observation this flare had an initial count rate of about 100 
counts/s) and decays
with a slope of 0.26+/-0.03.

Spectral fits to the Windowed Timing mode data show an
absorption column density  significantly in excess of the Galactic value 
(1.01e21 cm**-2)
with an excess absorption column density of (3.7+/-0.3)e21 cm**-2 and a 
energy spectral
slope beta-x=1.34+/-0.08. Following the relation given in Grupe et al. 
2006 (AJ submitted,
astro-ph/0612104) the high excess absorption column density suggests 
that this
burst is at a redshift z<3.0.

Even though the observations were shortly interrupted by a new burst, 
GRB 06122B
(Racusin et al., GCN 5957
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 ), we continue observing GRB 061222A with Swift
throughout the next hours. More analysis of the data will be presented 
in the
GCN report.

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

GRB 061222A, Swift-BAT refined analysis
 
J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), T. Ukwatta (UMD)
on behalf of the Swift-BAT team:
 
Using the data set from T-240 to T+302 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 061222A (trigger #252588)
(Grupe, et al., GCN Circ. 5954
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 ).  The BAT ground-calculated position
is RA, Dec = 358.258, 46.527 deg which is 
   RA(J2000)  = 23h 53m  1.9s 
   Dec(J2000) = 46d 31' 37.3" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 70%.
 
The mask-weighted lightcurve shows the emision starting at T-100 sec
with a small peak at T_zero, and then a 10-sec FRED peak starting at T+25 sec.
It is followed by two 10-sec peaks at T+50 and T+65 sec; then a large peak
at T+88 sec with a FWHM of ~12 sec and the emission returns to background
at T+115 sec.  T90 (15-350 keV) is 72 +- 3 sec (estimated error including
systematics).  At this time, there is a gap in the downlinked data
from T-180 sec to T-110.  A further Circular will be issued if there is
burst activity in this interval.
 
The time-averaged spectrum from T-2.5 to T+117.7 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.39 +- 0.04.  The fluence in the 15-150 keV band is 8.3 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+86.54 sec in the 15-150 keV band
is 9.2 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence level.

E.S. Rykoff (U Mich), F. Yuan (U Mich), B. E. Schaefer (Louisiana 
State), report on behalf of the ROTSE collaboration:

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 
061222A (Swift trigger 252588, GCN 5954
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 , Gruppe, et al), producing 
images beginning 7.3 s after the GCN notice time. An automated response 
took the first image at 03:29:39.3 UT, 47.1 s after the burst, under 
excellent conditions. We took 10 5-sec, 10 20-sec and 10+ 60-sec 
exposures. These unfiltered images are calibrated relative to USNO A2.0 
(R). We note that several of our images, with limiting magnitudes ~17.0, 
overlap the main peak in the BAT emission.  Imaging is ongoing.

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma BAT error circle or the XRT error circle, for both single images 
and coadding into sets of 10; however, we are limited as the field is 
somewhat crowded. Individual images have limiting magnitudes ranging 
from 16.5-18.0; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
03:29:39.4   03:29:44.4         5     16.5           47.2       N
03:30:14.4   03:30:19.4         5     17.0           82.2       N
03:30:21.4   03:30:26.4         5     17.0           89.2       N
03:29:39.4   03:30:47.4        68     18.1           47.2       Y
03:30:55.4   03:35:50.8       295     18.5          123.2       Y

D. Grupe (PSU), L. M. Barbier (NASA/GSFC), P. J. Brown (PSU),
M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
K. M. McLean (LANL/UTD), D. M. Palmer (LANL), J. L. Racusin (PSU) and
M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team:

At 03:28:52 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061222 (trigger=252588).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 358.243, +46.526 which is 
   RA(J2000) = 23h 52m 58s
   Dec(J2000) = +46d 31' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed three peaks of 
increasing  size from about 0 to 10, 25 to 35 and 70 to 110 seconds 
after the trigger. The peak count rate was ~13000 counts/sec (15-350 keV), 
at ~86 sec after the trigger. 

The XRT began observing the field at 03:30:33 UT, 101 seconds after
the BAT trigger. XRT found a bright, fading, uncatalogued X-ray
source located at 
  RA(J2000) = 23h 53m 03.45s, 
  Dec(J2000) = +46d 32' 00.4", 
with an estimated uncertainty of 3.7 arcseconds (90%
confidence radius). This location is 59 arcseconds from the BAT
on-board position, within the BAT error circle. The initial flux in
the 0.1s image was 1.5e-08 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 110 seconds after the BAT trigger, and a
finding chart exposure of 400 seconds with the V filter starting 215
seconds after the BAT trigger. No 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 3-sigma upper limit in the White image is
19.7 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 0.10.