GRB 081222

D. Grupe (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
D. M. Palmer (LANL), J. L. Racusin (PSU), M. Stamatikos (NASA/ORAU)
and M. C. Stroh (PSU) report on behalf of the Swift Team:

At 04:53:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081222 (trigger=337914).  Swift slewed immediately to the 
burst.  The BAT on-board calculated location is 
RA, Dec 22.751, -34.128 which is 
   RA(J2000) = 01h 31m 00s
   Dec(J2000) = -34d 07' 41"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multipeaked
structure with a duration of about 20 sec.  The peak count rate
was ~10000 counts/sec (15-350 keV), at 3 sec after the trigger. 

The XRT began observing the field at 04:54:51.7 UT, 51.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source located at RA, Dec 22.74067, -34.09556 which
is equivalent to:
   RA(J2000)  = 01h 30m 57.76s
   Dec(J2000) = -34d 05' 44.0"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 120 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 consistent with the Galactic value of
2.24e+20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 3.91e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 60 seconds after the BAT trigger. There is a
candidate afterglow in  the rapidly available 2.7'x2.7' sub-image
consistent with the XRT candidate.  A precise location and magnitude
estimate are not available at this time. 

This burst is consistent with the Fermi GBM burst   Trigger 251614441. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 
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.)

S. Covino, P. D'Avanzo, L.A. Antonelli, D. Malesani, D. Fugazza, L.  
Calzoletti,  S. Campana, G. Chincarini, M.L. Conciatore, S. Cutini,   
V. D'Elia,  F. D'Alessio, F. Fiore, P. Goldoni, D. Guetta, C.  
Guidorzi, G.L. Israel, E. Maiorano, N. Masetti, A. Melandri, E.J.A.  
Meurs, L. Nicastro, E. Palazzi, E. Pian, S. Piranomonte, L. Stella,   
G. Stratta, G. Tagliaferri, G. Tosti, V. Testa, S.D. Vergani, F.  
Vitali report on behalf of the REM team:

The robotic 60-cm REM telescope located at La Silla (Chile) observed  
automatically the field of the GRB 081222 (Grupe et al. GCN8691
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 )  
starting about 28s after the burst.  We detect a bright object in  
our  first H-band image inside the XRT error box at the following  
coordinates (J2000):

R.A. = 01:30:57.59
Dec = -34:05:41.7

with an uncertainty of about 1.0". The object is approximately H~11.1  
at about 1min after the burst and faded rapidly during the next  
observations.

Further observations are in progress

A. Updike (Clemson University), P. Afonso, C. Clemens, and J. Greiner (all
MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 081222 (Swift trigger 337914, Grupe et al.,
GCN #8691
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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 ESO/MPI telescope at La Silla
Observatory (Chile).

Observations started at 05:26 UT on Dec 22, 2008, 32 min after the GRB
trigger. They were performed at an average seeing of 1.0" and at high
airmass.

We detect the source within the Swift-XRT error circle reported by
Grupe et al. (GCN #8691
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 ) and Covino et al. (GCN #8692
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 ) at

RA (J2000.0) = 01h 30m 57.56s
DEC (J2000.0) = -34d 05' 41.5''

with an uncertainty of 0.5".

We obtained 8 min of total exposures in g'r'i'z'JHK.  Preliminary
magnitudes (calibrated against field stars in the USNO B1.0 and 2MASS
catalogs), exposure length (in seconds, NIR bands co-added), and midtimes
are as follows.

BAND     MAGNITUDE        EXP   MIDTIME (UT)
--------------------------------------------
g'      19.08 +/- 0.01    115    05:27:13
i'      18.04 +/- 0.01    115    05:27:13
z'      18.24 +/- 0.01    115    05:27:13
J       16.12 +/- 0.03    480    05:29:18
H       15.45 +/- 0.02    480    05:29:18
K       14.92 +/- 0.03    480    05:29:18


Tracking problems made data reduction difficult, especially in the r'
band, in which we detect the object but could not properly calibrate the
field.  The object is seen in g' band, implying a redshift smaller than
3.5.  No correction has been made for galactic extinction.

A.A. Breeveld (MSSL/UCL) and D. Grupe (PSU) report on behalf of the  
Swift UVOT team:

The Swift/UVOT started settled observations of the burst GRB081222  
(Grupe et al. GCN Circ. 8691
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 ) with the finding chart exposure in  
white, 60s after the BAT trigger. The afterglow is detected in the  
white and u filters at:
01h 30m 57.59s  -34d 05' 41.49" with a 0.5" 90% confidence limit.
This position is consistent with the XRT (Grupe et al. GCN Circ.  
8691
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 ), REM (Covino et al. GCN Circ. 8692
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 ) and GROND (Updike et al. GCN  
Circ. 8693
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 ) positions. The two white exposures show that the afterglow  
is fading with an estimated temporal slope of alpha = 0.85. The  
initial UVOT magnitudes are as follows:
Filter   Tstart(s)   Tstop(s)   Exp(s)   Magnitude
white   60            210           147.4     14.84+/-0.02
white   873          1023         147.4     17.36+/-0.03
u          272           522           245.8     16.32+/-0.03
The values quoted above are in the UVOT photometric system (Poole et  
al. 2008, MNRAS, 383, 627) and are not corrected for the expected  
Galactic extinction corresponding to a reddening of E(B-V)=0.021 mag  
in the direction of the burst (Schlegel et al. 1998).

E.Sonoda, H.Tanaka, R.Hara, N.Ohmori, K.Kono, H.hayasi, 
A.Daikyuji, K.Noda, Y.Nisioka, M.Yamauchi
(University of Miyazaki)


 We have observed the field covering the error circle of
GRB081222 (Swift trigger 337914, Grupe et al., GCN 8691
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 ) 
with the unfiltered CCD camera on the 30-cm telescope 
at University of Miyazaki.
The observation was started 08:41:19 UT, about 3.78 hr
after the Swift trigger time.
We have compared our data of 30 sec exposures
with the USNO-A2.0 catalog,
the upper limits are as follows:
--------------------------------------------------------------
Start(UT)   End(UT)    Num. of frames    Limit (mag.)
--------------------------------------------------------------
10:36:04    10:36:19          1            ~16
10:36:04    10:49:52         12            ~17
---------------------------------------------------------------

A. Melandri (Liverpool JMU), C. Guidorzi (U. Ferrara), D. Carter 
(Liverpool JMU)
report on behalf of a larger collaboration:

On 2008 December 22 (10:17:46 UT) we began observing the field of GRB 081222
(Grupe et al. GCN Circ. 8691
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 ) with the Faulkes Telescope South.
Observations consisted of two sequences of 6x300s exposures acquired
using the SDSS-i and SDSS-r filters, respectively.

We clearly detect the optical afterglow reported by REM (Covino et al.
GCN Circ. 8692
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 ) and GROND (Updike et al. GCN Circ. 8693
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 ), with the following
magnitudes:

Telescope   Filter  T_mid[hr]   Exposure[s]      Mag
--------------------------------------------------------------
FTS          SDSS-i    5.47        2x300        20.45 +/- 0.25
FTS          SDSS-r    6.01        2x300        21.34 +/- 0.30
--------------------------------------------------------------

The calibration was performed using the R2 and I magnitudes of several
USNOB-1 catalogue field objects. Uncertainties include the different
zero points of the USNOB-1 stars. Compared with the value reported by GROND
(Updike et al. GCN Circ. 8693
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 ), we estimate a power-law index between the
two epochs of about 1.1 .

Dirk Grupe (PSU) reports on behalf of the Swift-XRT team:


The XRT began observing the field of GRB 081222 (trigger=337914; Grupe et al.,
GCN Circ 8691
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 ) on 2008-December-22 at 04:54:51.7 UT, 51.8 seconds after
the BAT trigger.


The 0.3-10 keV X-ray light curve of the first five orbits
displays a smooth light curve that can be fitted with an initial decay slope
alpha1 = 0.90+/-0.02 with a break at 1420+/-100s followed by a steeper decay
slope alpha2=1.20+/-0.02.

The spectrum of the Windowed Timing data of the first orbit
can be well fitted by an absorbed single
power law model with a photon
index Gamma = 2.01 +/- 0.20 and a column density
NH=(4.61+/-0.80)e20 which is in excess of the Galactic column density in the
direction of the burst of NH-gal=2.24e20 (Kalberla et al. 2005).
The photon counting mode data of the first five orbits are consistent 
with this
result.


If the underlying power law decay of 1.2
continues as is, we predict an XRT count rate
of 0.030 counts/s at T+24 hours or 1e-12 ergs/s/cm2 and at T+48 hours 0.015
counts/s or 5e-13 ergs/s/cm2.

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

[GCN OPS NOTE(23dec08):  Per author's request, the "081221" in the first line
was changed to "081222".]

M.Cwiok, W.Dominik, G.Kasprowicz, A.Majcher, A.Majczyna,
K.Malek, L.Mankiewicz, K.Nawrocki, L.W.Piotrowski,
D.Rybka, M.Sokolowski, J.Uzycki, G.Wrochna, M.Zaremba, A.F.Zarnecki
on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl

During the night 20081222 the "Pi of the Sky" apparatus observed the
position of GRB081222 in the sky scan mode.
Three 10s images of this field have been taken at 02:10:44 - 02:11:21
( 2 hours 43 min 16 sec before the GRB).
No new object is seen within the error box and the limit is 12.5 
magnitudo.

After receiving the trigger from Swift, the field was observed 63s after
the GRB. No new object has been found within the Swift-BAT error box.
The limiting magnitude (unfiltered) on single 10s exposures is:

         04:55:03 - 04:55:13 - 12.0 mag
         04:55:16 - 04:55:26 - 12.0 mag
         04:55:28 - 04:55:38 - 12.0 mag

The field was observed until 06:00:17, no new object brighter then 12.0mag
was observed. The limit on 20 coadded images is 12.5 mag.

E. E. Fenimore (LANL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), D. Grupe (PSU), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):

Using the data set from T-119 to T+183 sec from the recent telemetry 
downlink,
we report further analysis of BAT GRB 081222 (trigger #337914)
(Grupe, et al., GCN Circ. 8691
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 ).  The BAT ground-calculated position is
RA, Dec = 22.748, -34.095 deg which is
  RA(J2000)  =  01h 30m 59.5s
  Dec(J2000) = -34d 05' 41.4"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The burst was in the fully-coded field of view.

The mask-weighted light curve shows a main peak with several subpeaks
from about T+0 to T+20 sec and an exponential tail visible to about
T+70 sec.  T90 (15-350 keV) is 24 +- 3 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.6 to T+38.0 sec is best fit by a 
power law
with an exponential cutoff.  This fit gives a photon index 1.08 +- 0.15,
and Epeak of 131 +- 31 keV (chi squared 45.61 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 4.8 +- 0.1 x 10^-06 
erg/cm2
and the 1-sec peak flux measured from T+3.45 sec in the 15-150 keV band is
7.7 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.48 +- 0.03 (chi squared 68.25 for 57 d.o.f.).  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/337914/BA/

Alice Breeveld (MSSL), Wayne Landsman (GSFC), Paul Kuin (MSSL) and  
Dirk Grupe (PSU) report on behalf of the Swift/UVOT team:

Further analysis of Swift/UVOT data of GRB081222 (Grupe et al., GCN  
Circ. 8691
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 ), shows that the burst was detected in the v and b filters  
in addition to the white and u filters described in the initial  
circular (Breeveld et al., GCN Circ. 8696
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 ). The source is not detected  
in any of the UV filters, in single or co-added exposures. The initial  
magnitudes and upper limits are given in the table below:

Filter    Tstart(s) Tstop(s)     Exp(s)   Magnitude
white   60            210           147        14.84+/-0.02
white   873          1023         147       17.36+/-0.03
v           602          622           20          16.20+/-0.02
b           528          548           20          16.86+/-0.02
u           272           522           246       16.32+/-0.03
uvw1    652          1815         142        >20.9  (3-sigma UL)
uvm2    627          1790         127        >21.0  (3-sigma UL)
uvw2    577          1914         124        >21.1  (3-sigma UL)

A 49s UV grism spectrum was obtained beginning 216s after the  
trigger.  The very low S/N quicklook spectrum shows a continuum of  
about 3e-15 erg/s/cm2/A longward of ~3400 A.  No flux is detected  
shortward of 3400 A, even though the grism sensitivity increases  
toward shorter wavelengths.  If this is the wavelength of the Lyman  
edge, then the redshift of GRB081222 is ~2.7.  The detection of  
GRB081222 in the u filter and the non-detection in UVW1 filter are  
consistent with this redshift.

The values quoted above are in the UVOT photometric system (Poole et  
al. 2008, MNRAS, 383, 627) and are not corrected for the expected  
Galactic extinction corresponding to a reddening of E(B-V)=0.021 mag  
in the direction of the burst (Schlegel et al. 1998).

A. Cucchiara, D. B. Fox (Penn State), S. B. Cenko  (Berkeley) and E. Berger
(Harvard) report on behalf of a larger collaboration:

Starting at 01:02 UT on 2008 December 23  we observed the optical
counterpart of GRB 081222 (Grupe et al., GCN 8691
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 , Covino  et al.,
GCN 8692
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  and Updike et al. 8693) using Gemini-South with the GMOS-South
spectrograph (R~1600).
We acquired 2x900s spectra covering the wavelength range 4000A-8000A.

We detect a damped Lyman-alpha system (DLA) at redshift z=2.77.

We also detect several metal absorption features which we interpret as
SiIV(1393,1402), SiII1526 and 1260, SiII*1264, CII1334, CII*1335,
CIV(1548,1550), FeII1608 and NiII(1454) at the same redshift.

In combination with the strong metal absorption features, the detection of
a DLA at z = 2.77 confirms that this is the redshift of GRB 081222 and its
host galaxy.

We thank the Gemini staff, in particular Henry Lee, for conducting
these observations.

E.Bissaldi (MPE) and S. McBreen (UCD/MPE)
report on behalf of the Fermi GBM Team: 


"At 04:54:00.25 UT on 22 December 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 081222 (trigger 251614441 / 081222204),
which was also detected by the Swift-BAT (Grupe et al., GCN Circular 8691
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and Fenimore et al., GCN Circular 8709
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 ).
 
The angle from the Fermi LAT boresight is 50 degrees.

This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of a main pulse with a
duration (T90) of about 30 s (8-1000 keV) and T50
of about 10 s (8-1000 keV). 

The time-averaged spectrum from T0 to T0+11.52 s is 
best fit by a Band function with Epeak = 134 +/- 9,
alpha = -0.55 +/- 0.07 and beta  = -2.10 +/- 0.06.

The event fluence (8-1000 keV) in this time interval is 
(1.35 +/- 0.08)E-05 erg/cm^2. The 1-sec peak photon flux 
measured starting from T0+3.3 s in the 8-1000 keV band
is 14.8 +/- 1.4 ph/s/cm^2.


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

Poonam Chandra (RMC) 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
optically bright GRB 081222 (GCN 8691
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 ) at a frequency of 8.46 GHz
on 2008 Dec 23.17 UT. The GRB radio afterglow is undetected and
the peak radio flux at the REM optical afterglow position (GCN 8692
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 )
is 54 � 53 uJy.

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

Rupak Roy, Brajesh Kumar, S. B. Pandey
and Brijesh Kumar (ARIES, NainiTal, India, on behalf of larger
Indian GRB collaboration) 


GRB 081222, localized by Swift (Grupe
et al. GCN 8691
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 ), was observed with 1.04m telescope at NainiTal
starting ~ 9 hours after the burst in R_c  and I_c
filters.
Photometry of the co-added R_c frames (300 sec x 6)
did not detect the optical afterglow candidate (Covino et al. GCN
8692
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 ) down to a limiting magnitude of ~ 21 mag in comparison to
nearby USNO stars.
This message may be cited.

J. F. Graham (STScI/JHU), N. R. Tanvir (U. Leicester), A. S. Fruchter 
(STScI), K. Wiersema (U. Leicester), A. J. Levan (U. Warwick) report on 
behalf of a larger collaboration:

We observed the afterglow of GRB 081222 with Gemini-North/GMOS Nod & 
Shuffle spectroscopy beginning 22 Dec 2008 06:38 UT, approximately 105 
minutes post-burst. From absorption lines of SiII, CIV, and FeII, we 
confirm the redshift reported in GCN 8713
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  (Cucchiara et al.) of z=2.77. 
We also find tentative evidence for a lower redshift system at z=2.74.

We thank the Gemini staff, in particular Ricardo Schiavon, for 
conducting these observations.

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

The long GRB 081222 (Swift-BAT trigger #337914: Grupe et al., GCN 8691
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 ; 
Fenimore et al., GCN 8709
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 ) triggered Konus-Wind at T0=17642.534 s UT 
(04:54:02.534).

The burst light curve shows a single pulse with a duration of ~12 s.
There is a hint of the weak tail detected by the Swift-BAT (Fenimore et 
al., GCN 8709
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 ) in the K-W G1 band (~20-80 keV).

As observed by Konus-Wind the burst
had a fluence of 1.32(-0.40, +0.48)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+4.688 s
of 2.22(-0.73, +0.87)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+16.640 s) can be fitted (in the 20 keV - 1 MeV
range) by GRB (Band) model for which:
the low-energy photon index is alpha = -0.67(-0.33, +0.39),
the high energy photon index beta = -2.35(-1.25, +0.30),
the peak energy Ep = 165(-29, +47) keV (chi2 = 63.0/51 dof).

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

Assuming z = 2.77 (Cucchiara et al., GCN 8713
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 ; Graham et al., GCN 8718
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 ) 
and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, 
Omega_\Lambda = 0.73, the isotropic energy release E_iso ~2.4x10^53 erg, 
the peak luminosity (L_iso)_max ~ 1.5x10^53 erg/s, and Ep_rest ~600 keV.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB081222_T17642/

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

We observed the field of GRB 081222 (Grupe et al. GCN 8691
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 ) with
the optical three color (g', Rc and Ic) imager attached to the
MITSuME 50cm telescope of Okayama Astrophysical Observatory on
Dec.22 2008 UT. We detected a fading point source at the position
of the X-ray - optical afterglow candidate (Covino et al. GCN 8692
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 ;
Updike et al. GCN8693
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 ; Grupe GCN 8705
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 ) in Rc band. Photometric
results are listed below. We used GSC2.3 catalog for flux
calibration.

# Mid-MJD      Mid-UT   EXP-T    g'       Rc          Ic
-------------------------------------------------------------
54822.401100  09:37:36  540.0  >18.3  18.0+/-0.3  >17.8
54822.438455  10:31:23 2940.0  >19.2  18.9+/-0.3  >18.2
54822.469650  11:16:18 4500.0  >19.2  19.3+/-0.4  18.6+/-0.3
-------------------------------------------------------------