GRB 120703A

B.-B. Zhang (PSU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
M. M. Chester (PSU), N. Gehrels (NASA/GSFC), D. Grupe (PSU),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC) and T. N. Ukwatta (MSU) report on behalf of
the Swift Team:

At 17:25:22 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120703A (trigger=525671).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 339.357, -29.736 which is 
   RA(J2000) = 22h 37m 26s
   Dec(J2000) = -29d 44' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiply-peaked
structure with a duration of about 50 sec.  The peak count rate
was ~14000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 17:26:48.9 UT, 86.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 339.35607, -29.72444 which is
equivalent to:
   RA(J2000)  = 22h 37m 25.46s
   Dec(J2000) = -29d 43' 28.0"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 41 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 (1.21 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 3.5
(+1.97/-1.72) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 91 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  =	22:37:25.71 = 339.35711
  DEC(J2000) = -29:43:23.5  = -29.72320
with a 90%-confidence error radius of about 1.10 arc sec. This position is 5.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.51. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.02. 

Burst Advocate for this burst is B.-B. Zhang (bbzhang AT 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.)

D. Xu (WIS), D. Malesani, J. P. U. Fynbo (DARK/NBI), N. R. Tanvir (U.
Leicester), K. Karhunen (U. Turku) report on behalf of a larger
collaboration,

We observed the field of GRB 120703A (Zhang et al., GCN 13408
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 ) using
the 2.5m Nordic Optical Telescope (NOT) equipped with StanCam.
Observations started at 04:02:42 UT on 2012-07-04 (i.e., 10.62 hr
after the BAT trigger) and 6x300s R-band frames were obtained.

An optical source was marginally detected in the stacked image at coordinates

RA (J2000)  = 22:37:25.61
Dec (J2000) = -29:43:23.7

with an uncertainty of ~0.5 arcsec radius, being consistent, but
slightly offset, with the UVOT position. The source had R~21.7
calibrated against nearby USNO star.

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long GRB 120703A (Swift-BAT trigger #525671:
B.-B. Zhang et al., GCN 13408
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 )
triggered Konus-Wind at T0=62723.578s UT (17:25:23.578)

The burst light curve shows a single peak
with a total duration of ~12.5 s.
The emission is seen up to ~7 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120703_T62723/

As observed by Konus-Wind the burst
had a fluence of (7.7 � 1.0)x10-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.960 s,
of (5.4 � 1.3)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+8.448 s)
is well fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which:
alpha = -0.81 (-0.25, +0.30),
and Ep = 295(-56, +88) keV,
chi2 = 96.8/84 dof.
Fitting this spectrum with the GRB (Band) function yields
the following model parameters:
the low-energy photon index alpha = -0.67 (-0.37, +0.54),
the high energy photon index beta = -2.7 (<-2.3),
the peak energy Ep = 256(-75, +100) keV,
chi2 = 96.4/83 dof.

The spectrum at the maximum count rate
(measured from T0 to T0+0.256 s) is best fitted
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which:
alpha = -0.50 (-0.37, +0.46),
and Ep = 410(-90, +150) keV,
chi2 = 21.5/22 dof.

All the quoted results are preliminary.
All the quoted errors are at the 90% confidence level.

M. Stamatikos (OSU), 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),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC),
T. N. Ukwatta (MSU), B.-B. Zhang (PSU) (i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120703A (trigger #525671)
(Zhang, et al., GCN Circ. 13408
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 ).  The BAT ground-calculated position is
RA, Dec = 339.353, -29.726 deg, which is 
   RA(J2000)  =  22h 37m 24.7s 
   Dec(J2000) = -29d 43' 34.9" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
 
The mask-weighted light curve shows the burst started at ~T-45 sec with a weak
pulse with a width of about 20 sec.  The burst continues with a moderate increase
to a strong central pulse from T-0.2 to T+1.0 sec, and then a decay back
to baseline at ~T+45 sec.  T90 (15-350 keV) is 25.2 +- 4.3 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-7.27 to T+32.60 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.51 +- 0.06.  The fluence in the 15-150 keV band is 3.5 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.06 sec in the 15-150 keV band
is 10.5 +- 0.4 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/525671/BA/

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

Using 7867 s of XRT Photon Counting mode data and 16 UVOT
images for GRB 120703A, 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 = 339.35690, -29.72350 which is equivalent
to:

RA (J2000): 22h 37m 25.66s
Dec (J2000): -29d 43' 24.6"

with an uncertainty of 1.4 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.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U.
Leicester), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), G.
Stratta (ASDC), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU)
and B.-B. Zhang report on behalf of the Swift-XRT team:

We have analysed 12 ks of XRT data for GRB 120703A (-B. Zhang  et al.
GCN Circ. 13408
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 ), from 70 s to 68.9 ks after the  BAT trigger. The data
comprise 374 s in Windowed Timing (WT) mode (the first 9 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 Goad et al.
(GCN. Circ 13415).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.69 (+0.04, -0.06), followed by a break at T+4130 s to
an alpha of 1.04 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.00 (+0.13, -0.12). The
best-fitting absorption column is  1.4 (+/-0.3) x 10^21 cm^-2, in
excess of 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 3.7 x 10^-11 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.4 (+/-0.3) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^20 cm^-2
Excess significance: 7.0 sigma
Photon index:	     2.00 (+0.13, -0.12)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00525671.

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

Andrew C. Collazzi (NASA/ORAU) reports on behalf of the Fermi GBM 
Team:

"At 17:25:17 UT on 03 July 2012, the Fermi Gamma-ray Burst Monitor
(GBM) triggered and located GRB 120703A (trigger 363029120 / 
120703.726). This burst was also detected by Swift/BAT (Zhang, B.-B. 
et al., GCN 13408
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 ).  The GBM on-ground position is consistent with 
the Swift location.  The burst was also detected by Konus-Wind 
(Golenetskii, R. et al., GCN 13412
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 ).

The burst triggered an ARR (Automatic Repointing Request), causing 
Fermi to slew so the LAT would point to the source.

The GBM light curve is similiar to the Swift detection. We observe a
strong central pulse with fainter wings, the total pulse having a 
width of ~20s. We measure the duration (T90) of about 9.216s 
(50-300 keV). The time-averaged spectrum from T0-2.048 to T0+14.336 s 
is best fit by a Comptonized power-law function, with Epeak = 
305.6 +/- 21.1 keV and alpha = -1.06 +/- 0.03.  The fluence 
(10-1000 keV) in this time interval is (9.154 +/- 0.246)E-06 erg/cm^2.

The burst is also fit well with a Band function with Epeak = 
238.5 +/- 26.5, keV alpha = -0.98 +/- 0.05, and beta = -2.08 +/- 0.12.

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

C. A. Swenson (PSU) and B.-B. Zhang (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120703A
90 s after the BAT trigger (Zhang et al., GCN Circ. 13408
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 ).
A source consistent with the XRT position (Goad et al., GCN Circ.
13415
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 ) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  22:37:25.67 = 339.35694 (deg.)
     Dec (J2000) = -29:43:23.8  = -29.72327 (deg.)
with an estimated uncertainty of 0.52 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               90          240          147         18.48 � 0.06
v                 4299         4499          197        >19.5
b                 3684         5249          325        >20.9
u                  304          416          110         18.07 � 0.13
w1                4710         4909          197        >19.5
m2                4504         4704          197        >21.4
w2                4095         4294          197        >21.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).

B. E. Cobb (GWU) reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 120703A
(GCN 13408
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 , Zhang et al.) with a mid-exposure time of 13.7 hours
post-burst (2012-07-04 07:07 UT).  Total summed exposure
times amounted to 15 minutes in I and V and 12 minutes in J and K.

No source is detected at the position of the optical
afterglow (e.g. GCN 13411
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 , Xu et al.; GCN 13418
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 , Swenson
et al.) to approximate limiting magnitudes of I > 20.5, J > 18.5
and K > 17.4.  Magnitudes are calibrated using USNO-B1.0 stars in I,
and 2MASS stars in J and K.