GRB 100704A

D. Grupe (PSU), S. D. Barthelmy (GSFC), J. R. Cummings (NASA/UMBC),
J. M. Gelbord (PSU), C. Gronwall (PSU),
S. T. Holland (CRESST/USRA/GSFC), N. P. M. Kuin (UCL-MSSL),
D. M. Palmer (LANL), M. H. Siegel (PSU) and T. N. Ukwatta (GSFC/GWU)
report on behalf of the Swift Team:

At 03:35:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100704A (trigger=426722).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 133.636, -24.216 which is 
   RA(J2000) = 08h 54m 33s
   Dec(J2000) = -24d 12' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a bright FRED
peak structure with a duration of about 30 sec, followed by further
activity beginning at T+140 s.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 03:36:34.9 UT, 86.2 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 133.64103,
-24.20306 which is equivalent to:
   RA(J2000)  = 08h 54m 33.85s
   Dec(J2000) = -24d 12' 11.0"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 48 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 (1.05e+21
cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+1.43/-1.30) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 3.53e-09 erg cm^-2 s^-1 (0.2-10
keV). 


UVOT took a finding chart exposure of 150 seconds with the White filter
starting 96 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
0.17. 




Burst Advocate for this burst is D. Grupe (grupe AT astro.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.)

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

Using 3449 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 100704A, 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 = 133.64132, -24.20269 which is equivalent
to:

RA (J2000): 08h 54m 33.92s
Dec (J2000): -24d 12' 09.7"

with an uncertainty of 1.7 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.

K. Omori, D. Suzuki, S. Kobara, H. Naito and T. Sako (STE Lab., Nagoya Univ.)
on behalf of the MOA Collaboration report:

We searched for an optical afterglow of GRB100704A (GCN 10929
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 , D. Grupe et al.)
starting from 06:59:33 UT on 2010 July 4 (204 minutes after the burst)
with the MOA-II 1.8m telescope at Mt. John observatory in New Zealand.
In a single image of a 180 sec exposure with a wideband Red filter (center
wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object
within the error circle of the Swift XRT source position (GCN 10930
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 , J.P. Osborne et al.).
A 3 sigma upper limit is set in the I magnitude at 22.0 mag.

This photometry was done by using the DoPHOT and calibrated against the
USNO-B1.0 catalog stars, and not corrected for the Galactic extinction.

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), D. Grupe (PSU),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 100704A (trigger #426722)
(Grupe, et al., GCN Circ. 10929
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 ).  The BAT ground-calculated position is
RA, Dec = 133.639, -24.202 deg, which is 
   RA(J2000)  =  08h 54m 33.3s 
   Dec(J2000) = -24d 12' 08.0" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.
 
The mask-weighted light curve shows an initial very weak peak starting at ~T-70 sec
and peaking at ~T-60 sec.  Then comes the main peak starting at ~T-5 sec,
peaking at ~T+1.5 sec, and ending at ~T+50 sec.  That is followed by a small peak
at ~T+100 sec, and then a larger peak from ~T+140 to ~T+210 sec.
T90 (15-350 keV) is 197.5 +- 23.3 sec (estimated error including systematics).
 
The time-averaged spectrum from T-62.3 to T+202.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.73 +- 0.06.  The fluence in the 15-150 keV band is 6.0 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.76 sec in the 15-150 keV band
is 4.3 +- 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/426722/BA/

S. McBreen (UCD/MPE) reports on behalf of the Fermi GBM Team:

"At 03:35:06.10  UT on 04 July 2010, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 100704A (trigger 299907308 / 100704149)
which was also detected by the Swift-BAT (Grupe et al. 2010, GCN 10929
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 ).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight is 63 degrees.

The GBM light curve rises slowly before the trigger and
consists of an initial pulse lasting about ~20 s followed
a softer pulse beginning about T0+150 seconds.
The burst has a duration (T90) of about 214 (+/- 6) s (50-300 keV).

The spectrum from T0-2.3 s to T0+20.2 s is
well fit by a power law function with an exponential
high energy cutoff.  The power law index is -0.80 (+0.06/-0.06)
and the cutoff energy, parameterized as Epeak, is
193.90 (+14.00/-12.10) keV (CSTAT for 781 for 607 d.o.f.).

The event fluence (10-1000 keV) in this time interval is
(5.8 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.3 s in the 10-1000 keV band
is 7.0 +/- 0.2 ph/s/cm^2.

A Band function fits the spectrum equally well (CSTAT 779 for 606 d.o.f.)
with Epeak= 178.30 (+16.30/-17.50)  keV, alpha = -0.76 (+0.08/-0.07)
and beta = -2.53 (+0.29/-0.54) .

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

D. Grupe (PSU) reports on behalf of the Swift-XRT team:

We have analyzed 6162 s of XRT data for GRB 100704A (Grupe  et al.
GCN Circ. 10929
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 ), from 92 s to 18.5 ks  after the  BAT trigger.
The data comprise 317 s in Windowed Timing (WT) mode with the
remainder in Photon Counting (PC) mode. The X-ray light curve displays
a strong flare starting at about 140s and peaking at 190s after the
burst. As mentioned in GCN Circ. 10929
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 , this flare coincides with a
flare seen in the BAT. The rest of the light curve can be  modeled
with a series of power-law decays. After the flare the afterglow
decays with a slope of 0.32 and breaks at about 1 ks after the burst
followed  by a decay slope of 0.76+/-0.06.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.96 (+/-0.04). The
best-fitting absorption column is  3.23 (+/-0.14) x 10^21 cm^-2, in
excess of the Galactic value of 1.0 x 10^21 cm^-2 (Kalberla et al.
2005). With an excess absorption column density of 2.32 x 10^21 cm^-2
the NH-redshift relation by Grupe et al. (2007, AJ 133, 2216)
suggests a redshift z<3.0.
The PC mode spectrum has a photon index of 2.6 (+/-0.3) and a
best-fitting absorption column of 3.1 (+0.9, -0.8) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.5 x 10^-11 (8.3 x 10^-11) erg cm^-2
count^-1.

If the light curve continues to decay with a power-law decay index of
0.76, the count rate at T+24 hours will be 0.045 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-12 (3.7 x 10^-12) erg cm^-2 s^-1 and 0.027 counts s^-1 T+48h.

The  UVOT-enhanced position of the afterglow has already been reported
by Osborne et al. (GCN Circ. 10930
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 ).

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00426722.

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

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 100704A (Swift-BAT trigger=426722;
Grupe et al., GCN 10929
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 ; Cummings et al., GCN 10932
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 )
triggered Konus-Wind at T0=12905.409s UT (03:35:05.409)

The burst light curve consists of a single FRED-like pulse
with a total duration of ~30 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB100704_T12905/

As observed by Konus-Wind the burst
had a fluence of 6.6(+/-0.7)x10-6 erg/cm2,
and a 256-ms peak flux measured from T0+0.768s
of 1.1(+/-0.2)x10-6 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+16.640 s) is best fit
in the 20 keV - 2 MeV range by a power law
with exponential cutoff model, for which
alpha = -0.75(-0.28, +0.33),
and Ep = 176(-24, +35) keV (chi2 = 34/58 dof).

The spectrum at the maximum count rate
(measured from T0+0.256 to T0+8.848 s) is best fit
in the 20 keV - 2 MeV range by a power law
with exponential cutoff model, for which
alpha = -0.65(-0.27, +0.31),
and Ep = 214(-29, +43) keV (chi2 = 44/58 dof).

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

S. Campana (INAF-OAB) and D. Grupe (PSU) report on behalf of the 
Swift-XRT team:

Swift XRT observed the bright GRB 100704A (Grupe et al. 2010, GCN 10929
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 )
starting 86 s after the BAT trigger. After strong X-ray flares the light 
curve started decaying
following a power law (Grupe 2010, GCN 10935
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 ).
We selected the time interval 4,510-28,896 s after the burst onset to 
collect the Photon
Counting (PC) spectrum. During this interval the spectrum is almost 
constant as testified by
a constant power law photon index (chi2=102 with 123 degrees of freedom).

We fit the PC spectrum (comprising 2002 counts) with a (Galactic plus 
intrinsic) absorbed
cutoff power-law model (tbabs*ztbabs*cutoff) within XSPEC (the cutoff 
power-law model
provides much better results in terms of column density evaluation with 
respect to a simple
power-law model when small spectral variations are present).
We assume a Galactic column density of 1.1x1021 cm-2 (Kalberla et al. 
2005, A&A 440 775)
and allowed for a 30% variability given its high value (and sampling all 
the values obtained
within 1 degree from the source).
We fit the spectrum using C-statistics. In the intrinsic column density 
vs. redshift plane there
is a low significance (3 sigma) solution at low redshifts but the 
minimum lies at higher redshifts
with a 2 sigma confidence level solution of z=3.6^+1.1 _-1.2 and N_H 
(z)=(9.7^+9.9 _-5.6 )x10^22 cm^-2 .
Thus, even if we cannot exclude that GRB100704A is at low redshift, a 
high redshift (z~3.5),
highly absorbed (N_H (z)~1x10^23 cm^-2 ) solution is preferred.
This compares well with the non-detection with UVOT (Kuin and Grupe 
2010, GCN 10934
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 )
and MOA robotic telescope (Omori et al. 2010, GCN 10931
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 ).
We also note that if no interviening systems are present along the line 
of sight a 90% lower
limit on the metallicity of 0.03 solar can be set (based on the 
assumption that the absorbing
medium is not Thomson thick).

The contour plot is available at
http://www.brera.inaf.it/utenti/campana/100704.gif