GRB 120612A

D. Malesani (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), R. 
Sanchez-Ramirez (IAA-CSIC and DARK/NBI), J. P. U. Fynbo (DARK/NBI), 
report on behalf of the X-shooter GRB GTO collaboration:

We observed the field of GRB 120612A (Pagani et al., GCN 13357
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 ) with the 
ESO VLT equipped with X-shooter. Observations were taken with the 
acquisition camera in the R and z filters, with an exposure time of 45 s 
each. The images were obtained around 23:25 UT (about 21.3 hr after the 
GRB).

Within the revised XRT error circle (Evans et al., GCN 13359
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 ), we do not 
detect any object in either filters, down to a limiting magnitude R = 
22.5 (3 sigma). We confirm the presence of a bright star just outside 
the XRT circle (Swenson et al., GCN 13362
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 ), which brightness is 
consistent with the value reported in the USNO catalog. This object is 
pointlike (with a seeing of 1.3") and is significantly outside the XRT 
error circle, so it is very likely unrelated to the GRB.

We acknowledge excellent support from the observing staff in Paranal, in 
particular Alain Smette and Claudio Melo.

C.A. Swenson (PSU) and C. Pagani (U Leicester) report on
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB
120612A 148 s after the BAT trigger (Pagani et al., GCN Circ.
13357
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 ).  No new optical afterglow consistent with the XRT posistion
(Evans et al., GCN Circ. 13359
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 ) is detected in the initial UVOT
exposures.

We note that there is a DSS source, which complicates the UVOT
analysis, located at RA, DEC = 126.72113, -17.57439.  This source
lies 3.05 arcsec from the XRT position and may or may not be related
to GRB 120612A, though we see no sign of variability in the source
in the first 1500 s of UVOT observations.  The source is also listed
in the USNOB catalog with a color of (B-R) = 0.728, corrected for
Galactic reddening.

Follow-up observations are encouraged to determine a redshift for
the DSS source to determine whether this is potentially the host galaxy.

D.N. Burrows (PSU), O.M. Littlejohns (U. Leicester), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), V. Mangano (INAF-IASFPA), A.
Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), J.A. Kennea (PSU),
M.C. Stroh (PSU) and C. Pagani report on behalf of the Swift-XRT team:

We have analysed 13 ks of XRT data for GRB 120612A (Pagani  et al. GCN
Circ. 13357
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 ), from 144 s to 30.4 ks after the  BAT trigger. The data
comprise 91 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 13359).

The light curve can be modelled with an initial power-law decay with an
index of alpha=3.27 (+0.26, -0.22), followed by a break at T+485 s to
an alpha of 0.90 (+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 2.20 (+0.23, -0.22). The
best-fitting absorption column is  1.9 (+/-0.6) x 10^21 cm^-2, in
excess of the Galactic value of 5.5 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 (5.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.9 (+/-0.6) x 10^21 cm^-2
Galactic foreground: 5.5 x 10^20 cm^-2
Excess significance: 3.9 sigma
Photon index:	     2.20 (+0.23, -0.22)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00524128.

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

D. M. Palmer (LANL), 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), C. Pagani (U Leicester),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120612A (trigger #524128)
(Pagani, et al., GCN Circ. 13357
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 ).  The BAT ground-calculated position is
RA, Dec = 126.723, -17.598 deg which is 
   RA(J2000)  =  08h 26m 53.5s 
   Dec(J2000) = -17d 35' 52.9" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.
 
The mask-weighted light curve shows a broad peak starting at ~T+15 sec,
peaking at roughtly T+35 sec, and ending around T+150 sec with a long
low-level tail out to about T+380 sec.  T90 (15-350 keV) is 90 +- 14 sec
(estimated error including systematics).
 
The time-averaged spectrum from T+16.9 to T+125.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.36 +- 0.16.  The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+30.20 sec in the 15-150 keV band
is 0.5 +- 0.2 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/524128/BA/

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

Using 1361 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 120612A, 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 = 126.72179, -17.57496 which is equivalent
to:

RA (J2000): 08h 26m 53.23s
Dec (J2000): -17d 34' 29.9"

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.

J.C. Tello (IAA-CSIC), A.J. Castro-Tirado (IAA-CSIC),  J.
Gorosabel (IAA-CSIC),  W. Allen (Vintage Lane Obs.), Ph. Yock and Kuan-Yu
Lin (Auckland Univ.), P. Kubanek (IP AS CR & IAA-CSIC), report on behalf of
a larger collaboration:

"We observed the field of GRB 120612A (Pagani et al., GCNC 13357), detected
by Swift/BAT, with the 0.6m Yock-Allen robotic telescope (BOOTES-3) located
in Blenheim, New Zealand. Unfiltered images were obtained starting
05:58:29UT (3h53m after the burst, limited by sunset). The first 40 images,
each of 60 seconds, were combined (with the last exposure ending at
06:39:14 UT). This resulted in a limiting magnitude of 18.0 when calibrated
with the R1Mag value of USNO-B1.0 catalogue stars."

This message may be cited.

C. Pagani (U Leicester), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (NASA/UMBC),
S. T. Holland (STScI), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and M. H. Siegel (PSU) report on behalf of the
Swift Team:

At 02:05:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120612A (trigger=524128).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 126.726, -17.578 which is 
   RA(J2000)  =  08h 26m 54s
   Dec(J2000) = -17d 34' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows s single broad peak
with a duration of about 30 sec.  The peak count rate
was ~1250 counts/sec (15-350 keV), at ~7 sec after the trigger. 

The XRT began observing the field at 02:07:38.1 UT, 138.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 126.72350,
-17.57649 which is equivalent to:
   RA(J2000)  = 08h 26m 53.64s
   Dec(J2000) = -17d 34' 35.4"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 10 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 5.49
x 10^20 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 5.98e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 147 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 typical 3-sigma upper limit has been about 19.6 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
0.07. 

Burst Advocate for this burst is C. Pagani (cp232 AT star.le.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.)