GRB 121201A

V. N. Yershov (UCL-MSSL), D. N. Burrows (PSU),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
S. R. Oates (UCL-MSSL), C. Pagani (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
T. N. Ukwatta (MSU) report on behalf of the Swift Team:

At 12:25:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121201A (trigger=540178).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 13.488, -42.952 which is 
   RA(J2000) = 00h 53m 57s
   Dec(J2000) = -42d 57' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve is incomplete at this time
due to a telemetry drop out, lacking most of the time period covered
by this image trigger.  Activity is visible starting at T-10s,
but this is coincident with a pre-planned slew. 

The XRT began observing the field at 12:27:37.1 UT, 115.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 13.4676,
-42.9432 which is equivalent to:
   RA(J2000)  = 00h 53m 52.22s
   Dec(J2000) = -42d 56' 35.6"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 62 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 (1.99 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 1.9
(+1.03/-0.96) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 119 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:53:52.17 =  13.46736
  DEC(J2000) = -42:56:34.4  = -42.94290
with a 90%-confidence error radius of about 0.66 arc sec. This position is 3.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
19.71 with a 1-sigma error of about  0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.01. 

Burst Advocate for this burst is V. N. Yershov (vny AT mssl.ucl.ac.uk). 
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. Guziy (Mykolaiv Nat. Univ.), R. Sanchez-Ramirez (IAA-CSIC), L.
Monteagudo Narvion (IAC), O. Lara, M. Jelinek (IAA-CSIC), P. Kubanek (IP
AS CR), Y. Fan, X. Zhao, J. Bai, C. Wang, Y. Xin (Yunnan National
Astronomical Observatory), Chenzhou Cui (Beijing National Astronomical
Observatory), R. Cunniffe, A.J. Castro-Tirado, J.C. Tello and J. Gorosabel
(IAA-CSIC), on behalf of a larger collaboration, report:

We have observed the GRB 121201A optical afterglow (GCN 14025
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 , Yershov et
al.) with the 0.6m BOOTES-4/MET robotic telescope at the Lijiang
Astronomical Observatory (China). The afterglow is clear detected in XRT
and UVOT position.

[GCN OPS NOTE(31dec12): As pointed out by E.Helder and confirmed by the author,
the Subject-line was changed from "121123A" to "121201A".]

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

Using 2580 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 121201A, 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 = 13.46759, -42.94306 which is equivalent
to:

RA (J2000): 00h 53m 52.22s
Dec (J2000): -42d 56' 35.0"

with an uncertainty of 1.6 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. Sakamoto (AGU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
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),
G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU), V. N. Yershov (UCL-MSSL)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121201A (trigger #540178)
(Yershov, et al., GCN Circ. 14025
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 ).  The BAT ground-calculated position is
RA, Dec = 13.473, -42.929 deg, which is 
   RA(J2000)  =  00h 53m 53.6s 
   Dec(J2000) = -42d 55' 45.9" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows 3 main peaks starting at ~T-23,
peaking at ~T-18, -8, & +4 sec, and ending at ~T+55 sec.  T90 (15-350 keV) is
85 +- 21 sec (estimated error including systematics).
 
The time-averaged spectrum from T-24.00 to T+71.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.90 +- 0.21.  The fluence in the 15-150 keV band is 7.8 +- 1.0 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-9.00 sec in the 15-150 keV band
is 0.8 +- 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/540178/BA/

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

We have analysed 8.7 ks of XRT data for GRB 121201A (Yershov et al. et
al. GCN Circ. 14025
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 ), from 101 s to 33.6 ks after the  BAT trigger. The
data comprise 24 s in Windowed Timing (WT) mode (the first 7 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
Beardmore et al. (GCN. Circ 14027).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.24 (+0.06, -0.05).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.62 (+0.15, -0.09). The
best-fitting absorption column is  2.15 (+3.39, -0.16) x 10^20 cm^-2,
consistent with the Galactic value of 2.0 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 4.3 x 10^-11 (4.4 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.15 (+3.39, -0.16) x 10^20 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.62 (+0.15, -0.09)

If the light curve continues to decay with a power-law decay index of
1.24, the count rate at T+24 hours will be 1.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-14 (6.0 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00540178.

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

[GCN OPS NOTE(19dec12): Per author's request, in the first sentence
the Yershov/14025 reference was filled in.]

N. P. M. Kuin (MSSL-UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 121201A
120 s after the BAT trigger (Yershov et al., GCN Circ. 14025
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 ).
A source consistent with the XRT position is detected in the
initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  00:53:52.16 =  13.46732 (deg.)
    Dec (J2000) = -42:56:34.5  = -42.94292 (deg.)
with an estimated uncertainty of 0.62 arc sec. (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              120          270          147         20.3 +/- 0.2
white              558          578           20         19.9 +/- 0.4
white             5689         5888          200         21.3 +/- 0.4
v                  608         1080           59        >19.6
b                  534         1178           58         19.4 +/- 0.2
u                  278          528          125        >24.8
u                 6714         6914          200         20.6 +/- 0.5
w1                 830         6710          432        >21.3
m2                 632         6504          413        >21.1
w2                1036         6094          413        >20.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).

[GCN OPS NOTE(17feb13):  The "A" was added to the GRB name in the Subject-line
and in the body of the Circular.]

T. Kruehler (DARK/NBI), S. Klose (TLS Tautenburg) and J. Greiner (MPE Garching) 
report on behalf of the GROND team:

We observed the field of the Swift GRB 121201A (Yershov et al., GCN 14025
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 ) 
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) 
mounted at the 2.2m MPI/ESO telescope at La Silla Observatory (Chile).

Observations started on December 02, 2012, 00:28 UT which is roughly
12.0 hr after the trigger. We clearly detect the afterglow of 
GRB 121201A (Yershov et al., GCN 14025
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 ) in the optical filters, 
but not in the NIR bands. Based on stacked images at
a mid-time of 01:05 UT with an effective integration time of 25 min
in g'r'i'z' and 20 min in JHKs, we estimate preliminary AB magnitudes and 
upper limits of:

g' = 24.2 +- 0.2 
r' = 23.0 +- 0.1
i' = 22.7 +- 0.1
z' = 22.5 +- 0.1
J > 21.5
H > 21.0
Ks > 19.9

These magnitudes and upper limits are calibrated against SDSS standards 
in the optical, and 2MASS field stars in the NIR bands. After correcting 
for the Galactic extinction corresponding to a reddening of E(B-V)=0.01
(Schlegel et al. 1998),  a fit to this SED returns a photometric redshift of 3.6 +0.2 -0.3.

R. Sanchez-Ramirez (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), 
T. Kruehler (DARK/NBI), B. Milvang-Jensen (DARK/NBI), J.P.U. Fynbo (DARK/NBI), 
N. Tanvir (U. Leicester), D. Malesani (DARK/NBI), S. Schulze (PUC & MCSS), 
L. Kaper (U. Amsterdam), H. Flores (Obs. Paris) report on behalf of the X-shooter 
GTO GRB collaboration,

We observed the afterglow of GRB121201A (Yeshov et al., GCN 14025
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 , Kruehler 
et al. GCN 14031
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 ) using the X-shooter spectrograph on the VLT (Paranal Observatory, 
Chile). Observations consisted of 4x1200s exposures in the UVB and VIS arms and 
8x600s exposures in the NIR, and started on 2 December 1:17 UT (12.87 hr after the 
burst).

In a preliminary reduction we detect Ly-alpha in emission as well as several 
absorption features (SiIV, CIV, AlII, AlIII) at a common redshift of z=3.385, which we 
identify as the redshift of the GRB.

We acknowledge the excellent support of the VLT staff, in particular G. Carraro.