GRB 120714B

S. Klose (TLS), J. Greiner (MPE), J. Fynbo (DARK), A. Nicuesa Guelbenzu, 
S. Schmidl (both TLS), A. Rau (MPE), T. Kruehler (DARK), report on behalf 
of a larger collaboration:

GROND has been following the afterglow of GRB 120714B (Saxton et al., GCN 
13471
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 ) at z=0.398 (Fynbo et al., GCN 13477
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 ) since July 15 (Nicuesa 
Guelbenzu et al., GCN 13478
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 ). The light of the optical transient has been 
fading in all GROND optical bands during the first 1.5 days, was then 
flattening in r',i',z', and finally rising at about 3 days after the 
trigger (while it is flattening in g'). The data suggested that this 
behavior can be interpreted as an upcoming supernova component with a an 
early rise similar to the SN associated with GRB 011121 at z=0.36 (Bloom 
et al. 2002, ApJ 672, 45; Garnavich et al. 2003, ApJ 582, 924; Greiner et 
al. 2003, ApJ 599, 1223; Price et al. 2002, ApJ 572, 51).

Spectroscopy of the optical transient with VLT/FORS2 was performed on 
August 1/2, 18.3 days after the burst. Observations were done with the 
300V grism, covering the wavelength range from 445 to 865 nm, and lasted 
7200 sec. The spectrum reveals very broad features in the continuum with a 
prominent peak around 6500 A and broad lines of Si II and Ca II, in 
agreement with a broad-lined SN dominating the light of the optical 
transient. At present a decision between type Ib and Ic cannot be 
performed due to an uncomfortable presence of atmospheric features in the 
spectrum.

We thank the staff at ESO Paranal and ESO Garching for their excellent 
support and for performing the spectroscopy. GROND observations are 
continuing.

N. P. M. Kuin (MSSL-UCL), F. Marshall (NASA/GSFC), and C. J. Saxton (UCL-MSSL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120714B
129 s after the BAT trigger (Saxton et al., GCN Circ. 13471
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 ).
The UVOT source candidate reported by Marshall and Saxton
(GCN Circ. No.  13473) is found to decay.

The preliminary UVOT position is RA, Dec (J2000) = (355.40864,-46.18387),
or in sexagesimal coordinates:

RA = 23h41m38.1s
Dec = -46d11'02"

with 90% confidence error radius of 0.58".

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              129          165           35         18.40 +/- 0.20
white            10034        10184          147        >20.8
b                10195        11102          885        >21.5

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).

O. M. Littlejohns, K. Page (U. Leicester) & C. J. Saxton (UCL-MSSL)
reports on behalf of the Swift-XRT team:

We have analysed 2.4 ks of XRT data for GRB 120714B (Saxton  et al. GCN
Circ. 13471
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 ), from 110 s to 75.0 ks after the  BAT trigger. The data
comprise 9 s in Windowed Timing (WT) mode (taken while Swift was
slewing), with the remainder in Photon Counting (PC) mode.

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.87 (+0.13, -0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.0 (+0.9, -0.6). The
best-fitting absorption column is  1 (+11, -0) x 10^20 cm^-2,
consistent with the Galactic value of 1.2 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 3.4 x 10^-11 (3.6 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1 (+11, -0) x 10^20 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.0 (+0.9, -0.6)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00526642.

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

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), C. J. Saxton (UCL-MSSL),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120714B (trigger #526642)
(Saxton, et al., GCN Circ. 13471
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 ).  The BAT ground-calculated position is
RA, Dec = 355.412, -46.196 deg, which is 
   RA(J2000)  =  23h 41m 38.9s 
   Dec(J2000) = -46d 11' 47.3" 
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
 
The mask-weighted light curve shows a broad peak starting at ~T-35 sec,
peaking around T+0 sec, and ending at ~T+55 sec with a tail out to ~T+150 sec.
T90 (15-350 keV) is 159 +- 34 sec (estimated error including systematics).
 
The time-averaged spectrum from T-23.0 to T+154.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.52 +- 0.17.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-21.71 sec in the 15-150 keV band
is 0.4 +- 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/526642/BA/

A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg), and J. Greiner (MPE 
Garching) report on behalf of the GROND team:

We observed the field of GRB 120714B (Swift trigger 526642; Saxton et al., 
GCN 13471
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 ) simultaneously in g'r'i'z'JHKs 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 at 3:01 UT on 2012-07-15, about 6 hrs after the GRB 
trigger, at a airmass of 2.2, and a mean seeing of 2.4". Based on an exposure 
of 460 seconds in the optical and 480 seconds in the NIR, at a mean time 
of 03:27 UT we detect the UVOT afterglow candidate (Marshall et al., GCN 13473
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 ) 
with preliminary AB magnitudes

  g' = 22.3 +/- 0.2
  r' = 22.1 +/- 0.2
  i' = 21.5 +/- 0.2
  z' = 20.5 +/- 0.2
  J  > 20.7
  H  > 20.1
  Ks > 19.2.

This suggests a fading relative to the white light magnitude of 18.6 mag as
reported by Marshall et al. (GCN 13473
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 ), suggesting this to be the 
afterglow of GRB 120714B. Observations are ongoing.

The magnitudes are derived based on GROND zeropoints (g'r'i'z') and 2MASS 
stars (JHK). We note that the Galactic reddening along the line of sight 
is E_(B-V)= 0.01 mag (Schlegel et al. 1998).

J.P.U. Fynbo (DARK/NBI), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), 
V. D'Elia (ASDC, INAF), D. Xu (WIS), and D. Malesani (DARK/NBI) report 
on behalf of the X-shooter GRB GTO collaboration:

We observed the field of GRB 120714B (Saxton et. al GCN 13471
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 , Marshall & 
Saxton GCN 13473
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 ) with X-shooter at VLT (Paranal, Chile). Observations started 
on 15 July at 5:06 UT (7.8 hr after the burst) and consisted of a total observing 
time of 4800 s in each of the UVB, VIS and NIR arms, covering the range 
between 3000 and 18000 A.

The spectrum shows a faint continuum where we detect MgII absorption as well 
as emission lines of [OII], H-beta, [OIII] and H-alpha at a common redshift of 
z=0.3984.

We acknowledge excellent support from the ESO staff, in particular Dimitri 
Gadotti.

F. E. Marshall (NASA/GSFC) and C. J. Saxton (UCL-MSSL)
report on behalf of the Swift team:

The positions reported for GRB 120714B in GCN Circular 13471
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are incorrect because of an unusally large attitude error
on the spacecraft. Using the initial UVOT exposure, we find
the corrected XRT position is:
  RA  (J2000) =  23h 41m 38.35s
  DEC (J2000) = -46d 11' 07"

There is a candidate afterglow in the initial UVOT exposure
of 36 seconds starting 129 seconds after the trigger.
The source has a mag of 18.6 in the white filter and is
located at the following position:
  RA  (J2000) =  23h 41m 38.05s
  DEC (J2000) = -46d 11' 03"

C. J. Saxton (UCL-MSSL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),
D. N. Burrows (PSU), N. P. M. Kuin (UCL-MSSL),
C. B. Markwardt (NASA/GSFC), S. R. Oates (UCL-MSSL),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 21:18:46.57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120714B (trigger=526642).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 355.433, -46.186 deg, which is 
   RA(J2000)  =  23h 41m 44s
   Dec(J2000) = -46d 11' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers (64 sec),
the realtime TDRSS lightcurve does not show anything significant. 

The XRT began observing the field at 21:20:46.6 UT, 120.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 355.3993, -46.1764 which is equivalent to:
   RA(J2000)  = +23h 41m 35.83s
   Dec(J2000) = -46d 10' 35.0"
with an uncertainty of 5.2 arcseconds (radius, 90% containment). This
location is 90 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 1.59e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT results will not be available until further data are processed. 

Burst Advocate for this burst is C. J. Saxton (cjs2 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.)