GRB 070704

C. Kira, M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
M. Tashiro, Y. Urata, A. Endo, K. Onda, M. Suzuki, N. Kodaka, K. Morigami (Saitama U.),
T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo),
S. Hong (Nihon U.),
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA),
E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara (Univ. of Miyazaki),
T. Tamagawa, Y. Terada (RIKEN), 
and Suzaku WAM team report:

The Suzaku WAM preliminary result of GRB 070704 (Kira et al. GCN Circ. 6616
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 ) 
contained a wrong value in a 1-s peak flux in the 100-1000 keV band.
The correct value is 1.2 +/- 0.1 photons/cm^2/s. 

We apologize for this mistake.

A. Meshcheryakov, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), 
I. Khamitov, Z. Tunca (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.),
I. Bikmaev, and N. Sakhibullin (KSU/AST) report:

We observed the field of GRB 070704 (Sakamoto et al., GCN 6594
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 ) with
Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe,TUBITAK National
Observatory, Turkey). The observations consisted of a series 30-second
exposures in g',r',i' filters, until ~1h after the burst time we
continue only r'-filter exposures. The first exposure in g' started at
20:15:13.9UT, i.e.556 s after the BAT trigger. The observations were
finished ~1.5 hour after the burst time.

In 30-second images as well as in combined images we do not detect any
new object at the revised XRT position (Godet & Sakamoto, GCN 6598
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 ) down
to following limiting magnitudes:

Filter  T_start(sec after trigger) Exp(s)  Lim    
----------------------------------------------------------------------------
  g'     556                       30      20.1    first
                                  240      21.2    combined
  r'     641                       30      20.1    first
                                 1720      22.3    combined
  i'     721                       30      20.3    first
                                  180      21.3    combined

This message may be cited.

[GCN OPS NOTE(12jul07): Per author's request, IK was added to the author list,
and the extra period after 'filter' in the 4th line was removed.]

C. Kira, M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa (Hiroshima U.),
K. Yamaoka, Y. E. Nakagawa, S. Sugita (Aoyama Gakuin U.),
K. Morigami, N. Kodaka, K. Onda, M. Tashiro, M. Suzuki,Y. Urata, A. Endo (Saitama U.),
T. Enoto, R. Miyawaki, K. Nakawaza, K. Makishima (Univ. of Tokyo),
S. Hong (Nihon U.),
M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA),
E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara(Univ. of Miyazaki),
T. Tamagawa, Y. Terada (RIKEN), 
and Suzaku WAM team report:

The long burst, GRB 070704 (Swift/BAT trigger #283791; T. Sakamoto et al., GCN Circ. 6594
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 ;
A. Melandri et al., GCN Circ. 6602
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 ; S. Karpov et al., GCN Circ.6603
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 ) was triggered 
at T0=2007-07-04 20:05:02 UT by Suzaku Wide-band All-sky Monitor (WAM)
which covers the energy range of 50 keV - 5 MeV.
The observed light curve shows the multiple peaked structures 
with a duration (T90 in the 50-5000 keV band) of nearly 35 seconds.
According to the GCN Report 69.2, the light curve observed by Swift BAT shows an upsurge
around T0+350, while in the light curve by Suzaku WAM, there is no such a structure.

The fluence in the 100-1000 keV band was (8.4+/-1.7)*10^-6 erg/cm^2,
and the 1-s peak flux in the same band was 0.19+/-0.06 photons/cm^2/s.
Preliminary result shows that the time-averaged spectrum from T0-5 to T0+40 is
well fitted by single power law with a photon index of 2.0+/-0.4 in 100-1000 keV range.

All the quoted errors are at the 90% confidence level, 
while systematic errors are not included.

The WAM light curve of this event is available at the following URL.
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html

S. Karpov, G. Beskin (Special Astrophysical Observatory of Russian Academy of
   Sciences, Russia), S. Bondar, E. Ivanov, E. Katkova (Research Institute for 
Precision Instrumentation, Russia), A. Pozanenko (Space Research Institute, Russia)

report on behalf of the FAVOR team:

The field of GRB 070704 (Sakamoto et al, GCN 6594
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 ) has been observed by the
FAVOR (FAst Variability Optical Registrator) wide-field fast camera (15 cm
diameter, 16x21 deg FOV) located in Russia, North Caucasus, near 6-m telescope
since UT 20:05:17 (40 seconds before BAT trigger, 25 seconds after actual burst
onset), during the event and for 20 minutes after it with 7.5 frames per second
acquisition rate (0.128 s frame exposure). The event occured on the edge of CCD
detector and has been affected by the image distortion. The authomatic data
reduction and transient detection pipeline, based on the inspection of each
pixel statistical properties in time, has not detected any transient event at
the XRT position of the source with the limiting magnitude of 10.8 (3-sigma) in
the unfiltered light close to V on a single frame.

We performed additional study of the data on T-40s - T+142s time interval
(i.e. prior to Swift/UVOT observations). Combining the sets of 100 consecutive
images we obtained an upper limit of 13.0 m (3-sigma) on the optical emission
over this time span with temporal resolution of 12.8 s.

The message may be cited.

A. Melandri (Liverpool JMU), E. Rol, N. Tanvir (U. Leicester)
report on behalf of the RoboNet GRB collaborationon:


We observed the field of GRB 070704 (trigger=283791, Sakamoto
et al., GCN 6594
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 ) with the 2-m Liverpool Telescope about 4.2
hours after the trigger time.

At the revised XRT position (Godet & Sakamoto, GCN 6598
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 ) we do
not detect any new object in stacked images down to:


Filter    t_mid (hr from GRB)    Tot_Exp (s)       Lim
--------------------------------------------------------------
   r'           4.26                 1800           23.0
   i'           5.10                 1800           23.3
--------------------------------------------------------------


Magnitudes were calibrated vs R2 and I USNO-B1 magnitude for
few selected stars.

O. Godet (U. Leicester) & T. Sakamoto (GSFC/ISAS) report on behalf the
Swift/XRT team

We have analysed the first 8.5ks of Swift XRT PC and WT data of GRB
070704 (Sakamoto et al., GCN Circ. 6594
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 ) taken from T0+153s to T0+3e4s. 
Using 129 s of overlapping XRT Photon Counting mode and UVOT V-band
data, 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 = 354.69915, +66.25328 which is equivalent to:

RA (J2000):  23 38 47.80
Dec (J2000): +66 15 11.8

with an uncertainty of 2.7 arcsec (90% confidence). This is 3.7 arcsec
from the initially reported XRT position and 39.4 arcsec from the BAT
position (GCN Circ. 6594
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 ).

The XRT light curve exhibits an initial decay on which is superposed a
large flare peaking around T0+300s. We note that between T0+250s and T0
+410s an emission was also detected in the BAT (Markwardt et al., GCN
Circ. 6596
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 ). The light-curve from T0+600s to T0+3e4s is fit well by a
power-law with a decay index of 0.87 +0.11/-0.12. 

The spectrum of the WT data from T0+153s to T0+527s is fit well by an
absorbed power-law with a photon index of 1.85 +/-0.06 and column
density of N_H = (1.08+/-0.06)e22 cm^-2 in excess of the Galactic value
(8.6E21 cm^-2; Dickey & Lockman, 1990). The absorbed (unabsorbed)
0.3-10.0keV flux for that spectrum is (1.57+/-0.05)E-9 (2.85E-9) ergs
cm^-2 s^-1. The spectrum of the PC data from T0+530s to T0+3e4s is fit
well by an absorbed power-law with a photon index of 1.97+/-0.27 with
N_H fixed at 1.08e22 cm^-2. The absorbed (unabsorbed) 0.3-10.0keV flux
for that spectrum is (3.3 +0.6/-0.8)E-12 (6.54E-12) ergs cm^-2 s^-1.

Assuming the source continues to decay at the same rate, we predict an
XRT count rate of 0.0044 counts/s at T0+24 hours, which corresponds to
an observed (unabsorbed) flux of 6.2E-13 (2.9E-12) ergs cm^-2 s^-1.

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

P. Schady (MSSL-UCL) and T. Sakamoto (NASA/ORAU) report on the behalf of the 
Swift UVOT team:

The Swift/UVOT observed the field of GRB 070704 starting 142 s after the 
BAT trigger (Sakamoto et al. 2007, GCN Circ. 6594
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 ).  We do not find any 
source, in any of the UVOT observations, inside the XRT error circle 
(Sakamoto et al. 2007, GCN Circ. 6594
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 ).

The 3-sigma upper limits for detecting a source inside the refined XRT 
error circle in the initial data products are:

Filter    T_mid(s) Exp(s) Mag (3-sigma upper limit)
-------------------------------------------------------
V         654      597    19.16
B         749      10     17.56
U         729      20     17.64
UVW1      5603     439    18.91
UVM2      4431     239    19.36
UVW2      5697     220    19.27
White     574      209    19.65
-----------------------------------------------------------------

where T_mid is the weighted mid time of the coadded exposure. The values 
quoted above are not corrected for the expected Galactic extinction 
corresponding to a reddening of E_{B-V} = 1.81 mag in the direction of the 
burst (Schlegel et al. 1998).

C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+523 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 070704 (trigger #283791)
(Sakamoto, et al., GCN Circ. 6594
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 ).  The BAT ground-calculated position is
RA, Dec = 354.707, 66.257 deg  which is 
   RA(J2000)  = 23h 38m 49.6s 
   Dec(J2000) = 66d 15' 25" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 42%.
 
The mask-weighted light curve shows the burst started at ~T-65 sec when
Swift was executing a preplanned slew.  There are multiple peaks with
decreasing amplitude with time.  The burst almost returns to background
during T+110 to T+230 sec, but then has emission from T+250 to T+410 sec.
T90 (15-350 keV) is 380 +- 10 sec (estimated error including systematics).
 
The time-averaged spectrum from T-57.3 to T+400.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.79 +- 0.08.  The fluence in the 15-150 keV band is 5.9 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-53.10 sec in the 15-150 keV band
is 2.1 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

T. Sakamoto (NASA/ORAU) on behalf of the Swift Team:

The XRT paragraph in the GCN 6594
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  contains a error.  We stated 
that the XRT position was "outside" the BAT error circle -- it is, 
in fact, inside.  The corrected XRT paragraph is:

The XRT began observing the field at 20:08:30 UT, 153 seconds after the
BAT trigger. The on-board XRT position was not correct, because the 
algorithm centroided on a hot pixel.  From the ground data analysis,  
a moderately bright and uncatalogued X-ray source was found 
at RA, Dec 354.69922, + 66.25226 which is
   RA(J2000)  =  23h 38m 47.8s
   Dec(J2000) =  66d 15' 08.1"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). 
This location is 40.8 arcseconds from the BAT on-board position 
and within the BAT error circle.  The initial flux in the 2.5s 
image was 3.7e-10 erg/cm2/s (0.2-10 keV). 

We apologize for the mistake.  We would like to thank Alex Kann 
for pointing the error.

T. Sakamoto (NASA/ORAU), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), M. M. Chester (PSU),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester),
S. T. Holland (CRESST/GSFC/USRA), S. Immler (GSFC/UMCP),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
D. M. Palmer (LANL), G. Sato (GSFC/ISAS), B. Sbarufatti (INAF-IASFPA)
and R. L. C. Starling (U Leicester) report on behalf of the Swift
Team:

At 20:05:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070704 (trigger=283791).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 354.723, +66.248 which is 
   RA(J2000)  =  23h 38m 54s
   Dec(J2000) = +66d 14' 52"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve does not show anything
significant, as is typical for image-trigger events.  There is a possibility
that the burst started at ~T-70 sec, but since Swift was executing
a preplanned slew from ~T-35 to T_0 sec, it is difficult to interpret
the TDRSS lightcurve. 

The XRT began observing the field at 20:08:30 UT, 153 seconds after the
BAT trigger. The on-board XRT position was not correct, because the algorithm 
centroided on a hot pixel. 
From the ground data analysis,  a moderately bright and uncatalogued X-ray 
source was found at RA, Dec 354.69922, + 66.25226 which is
   RA(J2000)  =  23h 38m 47.8s
   Dec(J2000) =  66d 15' 08.1"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). 
This location is 40.8 arcseconds from the BAT on-board position,
outside the BAT error circle. The initial flux in the 2.5s image
was 3.7e-10 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 158 seconds after the BAT trigger, and a
finding chart exposure of 400 seconds with the V filter starting 265
seconds after the BAT trigger. No afterglow candidate has been found
in the initial data products. The 8'x8' region for the list of
sources generated on-board covers 100% of the BAT and XRT error
circles. The 2.7'x2.7' sub-image does not cover the XRT error circle. 
The list of sources is typically complete to about 18.0 mag. No
correction has been made for the large, but uncertain extinction
expected. 

Burst Advocate for this burst is T. Sakamoto (takanori AT milkyway.gsfc.nasa.gov). 
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.)