GRB 121217A

M. H. Siegel (PSU), B. N. Barlow (PSU), D. N. Burrows (PSU),
M. M. Chester (PSU), V. D'Elia (ASDC), D. Grupe (PSU),
N. P. M. Kuin (UCL-MSSL), C. B. Markwardt (NASA/GSFC),
D. M. Palmer (LANL) and M. Stamatikos (OSU/NASA/GSFC) report on behalf
of the Swift Team:

At 07:17:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121217A (trigger=542441).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 153.724, -62.304 which is 
   RA(J2000) = 10h 14m 54s
   Dec(J2000) = -62d 18' 13"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak
with some substructure, with a duration of about 60 sec.  The peak count rate
was ~3200 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:18:51.8 UT, 64.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 153.70643, -62.35064 which
is equivalent to:
   RA(J2000)  = 10h 14m 49.54s
   Dec(J2000) = -62d 21' 02.3"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 170 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 3.72
x 10^21 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 1.93e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 72 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 8'x8'
region for the list of sources generated on-board covers 0.00% of the
XRT error circle. Because of the density of catalogued stars,  further
analysis is required to report an upper limit for any afterglow in the
region. No correction has been made for the large, but uncertain
extinction  expected. 

Burst Advocate for this burst is M. H. Siegel (siegel 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.)

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

Using 2474 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 121217A, 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 = 153.70999, -62.35047 which is equivalent
to:

RA (J2000): 10h 14m 50.40s
Dec (J2000): -62d 21' 01.7"

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.

J. Elliott (MPE Garching), S. Schmidl (TLS Tautenburg), and J.Greiner (MPE
Garching) report on behalf of the GROND team:

We observed the field of GRB 121217A (Swift trigger 542441; Siegel et al.,
GCN 14089
Loading...
 
 ) 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 17, 2012, at 07:21 UT, 210 s after the
GRB trigger. They were performed at an average seeing of 1.6" and at an
average airmass of 1.2.

We found a fading point source at the border of the enhanced XRT error
circle given in Evans et al. (GCN 14090
Loading...
 
 )

RA (J2000.0) = 10:14:50.407
DEC (J2000.0) = -62:21:03.53

with an uncertainty of 0.5" in each coordinate.

Based on a total exposure time of 456 s in g'r'i'z' and 480 s in JHK,
at a midtime of 1882 s after the burst, we estimate preliminary
AB magnitudes of

g' = 20.3 +/- 0.1,
r' = 19.3 +/- 0.1,
i' = 18.9 +/- 0.1,
z' = 18.6 +/- 0.1,
J  = 18.1 +/- 0.1,
H  = 17.7 +/- 0.1,
K  = 17.4 +/- 0.1.

In the r' band the source faded with a decay slope of 0.7 +/- 0.1
between 2000 s and  4200 s after the trigger. The SED can be fit
with a power-law with a slope of beta = 0.8 +/- 0.1.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the Galactic foreground extinction
corresponding to a reddening of E(B-V)= 0.38 mag in the direction of the
burst (Schlegel et al. 1998).

The extinction-corrected SED suggests a photo-z of 3.0 +/- 0.2. We
caution, however, that the high Galactic extinction along the line of
sight might affect this result.

S. R. Oates (MSSL-UCL) and M. H. Siegel (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121217A
73 s after the BAT trigger (Siegel et al., GCN Circ. 14089
Loading...
 
 ).
A source consistent with the GROND optical position (Elliott et al. GCN Circ. 14091
Loading...
 
 )
is detected in the initial UVOT exposures. The preliminary UVOT position is: 

    RA (J2000) = 10:14:50.32 = 153.7097  (deg)
   Dec (J2000) = -62:21:03.3 = -62.35096 (deg)

with an estimated uncertainty of 0.6 arcsec (radius, 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               73          222          147         19.58 +/- 0.13
v                  616         5906          313         19.01 +/- 0.22
b                  541          560          19          18.76 +/- 0.36
u                  285         6522          540         20.09 +/- 0.34
w1                 666         6317          313        >19.96
m2                 641         6112          313        >19.85
w2                 591         7138          510        >20.37

The magnitudes in the table are not corrected for the significant Galactic extinction
due to the reddening of E(B-V) = 0.37 in the direction of the burst
(Schlegel et al. 1998).

P.A. Evans (U. Leicester), O.M. Littlejohns (U. Leicester), A. Melandri
(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), M.C. Stroh
(PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), J.P. Osborne (U.
Leicester) and M.H. Siegel report on behalf of the Swift-XRT team:

We have analysed 7.1 ks of XRT data for GRB 121217A (Siegel  et al. GCN
Circ. 14089
Loading...
 
 ),  from 70 s to 30.3 ks after the  BAT trigger. The data
comprise 655 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN. Circ 14090).

The late-time light curve (from T0+5.5 ks) can be modelled with  a
power-law decay with a decay index of alpha=0.63 (+/-0.08).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 2.15 (+0.11, -0.08). The
best-fitting absorption column is  consistent with the Galactic value
of 3.7 x 10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a
photon index of 1.92 (+0.11, -0.10) and a best-fitting absorption
column of 4.02 (+0.51, -0.30) x 10^21 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.6 x 10^-11 (7.3 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.02 (+0.51, -0.30) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.92 (+0.11, -0.10)

If the light curve continues to decay with a power-law decay index of
0.52, the count rate at T+24 hours will be 0.091 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x
10^-12 (6.7 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00542441.

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

David Yu and David Gruber (both MPE)
report on behalf of the Fermi GBM Team:

"At 07:30:01.58 UT on 17 December 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located a burst (trigger 377422204 / 121217313), whose
location is consistent with the Swift GRB 121217A (Siegel et al. GCN 14089
Loading...
 
 )
which triggered BAT ~13 minutes prior to the GBM.
Upon closer examination, we found that GRB 121217A is also present in the 
GBM data. GBM did not trigger on this earlier emission period owing to the
triggering being disabled while Fermi was passing through a
region of high geomagnetic latitude.

The GBM light curve consists of two epochs of emission,
separated by an epoch of quiescence of about 700 s.
The duration of the first pulse is about 50 s while 
the second pulse is about 30 s long. The overall event T90 is 
about 780 s (50-300 keV).
The time-averaged spectrum of the first emission epoch,
from T0-749.6 s to T0-704.5 s, is well fit by a power law 
function with an exponential high-energy cutoff.  The power law index 
is -1.20 +/- 0.12 and the cutoff energy, parameterized as Epeak, 
is 264 +/- 75 keV. The time-averaged spectrum of the 
second emission epoch, from T0-8.2 s to T0+24.6 s, is well fit 
by the same model, having a power law index of -1.29 +/- 0.14 and an 
Epeak of 184 +/- 56 keV.

The event fluence (10-1000 keV) over the overall event is
(1.11 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.68 s in the 10-1000 keV band
is 3.47 +/- 0.29 ph/s/cm^2.

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

R. Ruffini, L. Izzo, G.B. Pisani, C.L. Bianco, on behalf of a larger collaboration, report:

GRB 121217A, following our theoretical considerations based on the Induced
Gravitational Collapse scenario for GRBs-SNe, allows also for a different
solution with a cosmological redshift of z=0.8 (+- 0.1). We base this
result on a preliminary analysis of the superposition of the late X-ray
afterglow emission, considering GRB 090618 as the prototype of the class.
We have considered the first 75 ks of the X-ray afterglow light curve of
GRB 121217A in this preliminary analysis.
More details on the model will appear soon on the arXiv.

We also predict a presence of a SN emerging after about 18 (+- 3) days
from the GRB trigger, e.g. in the first days of January 2013.
Assuming an interstellar extinction obtained from the Schlegel et al.
(1998) extinction map and a supernova emission similar to the 1998bw one,
we estimate an observed magnitude of +24.5 (+- 0.5) in the J filter. We
further notice that, given the galactic latitude less than 5 deg (-4.89
deg), the calculated extinction value can differ at least of 1 mag.

Follow-up photometric and possibly spectroscopical observations are
strongly requested.

J. R. Cummings (GSFC/UMBC), T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
A. M. Parsons (GSFC), G. Sato (ISAS), M. H. Siegel (PSU),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(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 121217A (trigger #542441)
(Siegel, et al., GCN Circ. 14089
Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 153.708, -62.354 deg, which is 
   RA(J2000)  =  10h 14m 50.0s 
   Dec(J2000) = -62d 21' 15.5" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.
 
The mask-weighted light curve shows two well-separated periods of emission.
The first starts at ~T-110 sec with weak emission, then peaks at ~T+1 sec,
and returns to baseline at ~T+80 sec.  The second period of emission starts
at ~T+500 sec, with weak peaks at ~T+500 and ~T+610 sec and the main peak
at ~T+730 sec and returns to baseline out past T+960 sec (where the data ends).
There are enough differences in the profiles of these two periods of emission
to conclude they are not gravitationally lensed.
T90 (15-350 keV) is 778 +- 16 sec (estimated error including systematics).
 
The time-averaged spectrum from T-17.7 to T+783.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.53 +- 0.08.  The fluence in the 15-150 keV band is 6.2 +- 0.3 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+735.96 sec in the 15-150 keV band
is 1.8 +- 0.1 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/542441/BA/

P. Hancock, T. Murphy, B. Gaensler, M. Bell, D. Burlon (University of
Sydney/CAASTRO), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI)

We observed GRB121217A (GCN 14809
Loading...
 
 ) with the Australia Telescope
Compact Array at 44GHz for 90 minutes centered on 12:55UT Dec 21 2012
(T0+4.234days) in poor weather.

We detect no radio source at the optical location of the GRB (GCN
14091
Loading...
 
 ) and place a 3sigma upper limit of 0.6mJy on the flux of an
afterglow.

These observations were obtained as part of ATCA project C2689. We
thank the observatory staff for their support and scheduling the
observations. The Australia Telescope is funded by the Commonwealth of
Australia for operation as a National Facility managed by CSIRO.