GRB 111212A

S. Campana (INAF-OAB), J. R. Cummings (NASA/UMBC), V. D'Elia (ASDC),
P. A. Evans (U Leicester), B. Gendre (ASDC), C. Guidorzi (U Ferrara),
O. M. Littlejohns (U Leicester), A. Melandri (INAF-OAB),
P. T. O'Brien (U Leicester), C. Pagani (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU),
C. A. Swenson (PSU), E. Troja (NASA/GSFC/ORAU) and B.-B. Zhang (PSU)
report on behalf of the Swift Team:

At 09:23:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 111212A (trigger=509543).  Swift could not slew immediately
to the burst due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 310.404, -68.617 which is 
   RA(J2000) = 20h 41m 37s
   Dec(J2000) = -68d 37' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a weak emission
with a duration of at least 20 sec, but a more detailed description 
will require the ground-linked data.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to an observing constraint, Swift will not slew until T0+47.6
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is C. A. Swenson (cswenson 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.)

J.A. Kennea (PSU), G. Tagliaferri (INAF-OAB), S. Campana (INAF-OAB),
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) and D.N. Burrows
(PSU) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 111212A at 10:17:35.0 UT,
3267.9 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 310.43423,
-68.61205 which is equivalent to:
   RA(J2000)  = 20h 41m 44.22s
   Dec(J2000) = -68d 36' 43.4"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 43 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 in excess of the Galactic value (3.07 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2
(+0.94/-0.88) x 10^21 cm^-2 (90% confidence).

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

Using 2469 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 111212A, 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 = 310.43132, -68.61251 which is equivalent
to:

RA (J2000): 20h 41m 43.52s
Dec (J2000): -68d 36' 45.0"

with an uncertainty of 1.5 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.

T. N. Ukwatta (MSU) S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
S. Campana (INAF-OAB), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), (i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 111212A (trigger #509543)
(Campana, et al., GCN Circ. 12667
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 ).  The BAT ground-calculated position is
RA, Dec = 310.442, -68.585 deg, which is 
   RA(J2000)  =  20h 41m 46.0s 
   Dec(J2000) = -68d 35' 04.5" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 35%.
 
The mask-weighted light curve shows a FRED-like pulse starting at ~T-2 sec,
peaking at ~T+6 sec, and returning to background around T+60 sec.  Since
Swift slewed due to an observing constraint, the burst location left
the BAT FoV at ~T+70 sec, so we can not say if there was further actitivty
in the lightcurve.
 
The time-averaged spectrum from T-5.77 to T+62.74 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.67 +- 0.18.  The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.76 sec in the 15-150 keV band
is 0.8 +- 0.3 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/509543/BA/

C. A. Swenson (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 111212A
3272 s after the BAT trigger (Campana et al., GCN Circ. 12667
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 ).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 12670
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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          3272         3422          147 >20.3
white             3272         5481          541 >21.3
v                 4255         5751          255 >19.2
b                 3637         5276          393 >20.1
u                 3432         5071          393 >20.1
w1                4665         4865          197 >20.1
m2                4460         4660          197 >20.3
w2                4050         5687          393 >21.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).

B.-B. Zhang (PSU) reports on behalf of the Swift-XRT team:

We have analysed 6.5 ks of XRT data for GRB 111212A (Campana  et al.
GCN Circ. 12667
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 ), from 3.3 ks to 17.3 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Osborne et al. (GCN. Circ 12670).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.39 (+0.11, -0.10).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.05 (+0.13, -0.07). The
best-fitting absorption column is  9.5 (+3.0, -1.6) x 10^20 cm^-2, in
excess of the Galactic value of 3.1 x 10^20 cm^-2 (Kalberla et al.
2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.5 x 10^-11 (4.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     9.5 (+3.0, -1.6) x 10^20 cm^-2
Galactic foreground: 3.1 x 10^20 cm^-2
Excess significance: 6.6 sigma
Photon index:	     2.05 (+0.13, -0.07)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00509543.

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

D. A. Kann, A. Rossi (TLS Tautenburg), V. Sudilovsky, P. Schady and J.
Greiner, (MPE Garching) report on behalf of the GROND team:

We observed the field of the Swift GRB 111212A (Swift trigger 509543;
Campana et al., GCN #12667
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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/MPG
telescope at La Silla Observatory (Chile). Observations started on
December 13, 2011, at 00:35 UT, in twilight, and are centered 0.658 days
after the GRB trigger. They were taken at an average seeing of 1".2 and at
an airmass of 2. Integration times were 1734 sec in the optical and 2640
sec in the NIR. These observations were obtained under challenging
conditions, with thick cirrus preventing guiding.

A second epoch was obtained on December 14, 2011, starting at 00:57 UT and
centered at 1.667 days after the GRB. It was taken at an average seeing of
1".2 and at an airmass of 2. Integration times were 2420 sec in the
optical and 2160 sec in the NIR. Conditions were much better, with clear,
moonless skies.

At the position of the X-ray afterglow (Osborne et al., GCN #12670
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 ), we do
not detect any significant sources in any bands. We derive the following
limits (3 sigma, AB magnitude system):

0.658 days after the trigger:

g' > 24.1
r' > 24.2
i' > 23.4
z' > 22.8
J > 20.5
H > 20.0
K > 18.1

1.667 days after the trigger:

g' > 24.8
r' > 24.8
i' > 23.8
z' > 23.4
J > 21.6
H > 21.0
K > 19.3

Magnitudes were calibrated against GROND zero points in g'r'i'z' and 2MASS
field stars in JHK.