GRB 080703

H. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester),
H. A. Krimm (CRESST/GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Schady (MSSL-UCL),
R. L. C. Starling (U Leicester), M. C. Stroh (PSU),
T. N. Ukwatta (GSFC/GWU), D. E. Vanden Berk (PSU) and
P. A. Ward (MSSL-UCL) report on behalf of the Swift Team:

At 19:00:13 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080703 (trigger=315819).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 101.867, -63.222 which is 
   RA(J2000)  =  06h 47m 28s
   Dec(J2000) = -63d 13' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 5 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Using promptly downlinked data we find a bright, uncatalogued
X-ray source. The position, astrometrically enhanced by aligning promptly
available UVOT field source  positions to the USNO-B1 catalogue, is RA,Dec =
101.80538,  -63.22039 (degrees) which is equivalent to:

RA  (J2000.0) =  06 47 13.29
DEC (J2000.0) =  -63 13 13.4

with an uncertainty of 3.04 arcsec (radius, 90% containment). 
This position is 100.1 arcsec from the BAT position, inside the BAT
error circle and 6.3 arcseconds from the UVOT position. 

UVOT took a finding chart exposure of nominal 100 seconds with the White
(160-650 nm) filter starting 100 seconds after the BAT trigger. There is a
candidate afterglow in the list of sources generated on-board at
  RA(J2000)  =  06:47:12.65 = 101.8027
  DEC(J2000) = -63:13:08.8  = -63.2191
with a 1-sigma error radius of about 0.8 arc sec. This position is 104.9 arc
sec. from the center of the BAT error circle. The estimated magnitude is 17.6
with a 1-sigma error of about 0.5 mag. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.07. 

Burst Advocate for this burst is H. Ziaeepour (hz 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.)

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD),
D. Palmer (LANL), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU), H. Ziaeepour (UCL-MSSL)
(i.e. the Swift-BAT team):
 
Using the data set from T-120 to T+183 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 080703 (trigger #315819)
(Ziaeepour, et al., GCN Circ. 7936
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 ).  The BAT ground-calculated position is
RA, Dec = 101.822, -63.211 deg, which is 
   RA(J2000)  =  06h 47m 17.2s 
   Dec(J2000) = -63d 12' 40.7" 
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.
 
The mask-weighted light curve shows a single peak starting at ~T-5 sec,
peaking at ~T+0 sec, and ending at ~T+4 sec.
T90 (15-350 keV) is 3.4 +- 0.8 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.7 to T+2.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.53 +- 0.22.  The fluence in the 15-150 keV band is 2.0 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.04 sec in the 15-150 keV band
is 1.0 +- 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/315819/BA/

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

Using 3392 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080703, 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 = 101.80180, -63.21893 which is equivalent
to:

RA (J2000): 06h 47m 12.43s
Dec (J2000): -63d 13' 08.2"

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
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.

This circular was automatically generated, and is an official product of the
Swift-XRT team.

D. Malesani, P. M. Vreeswijk, J. P. U. Fynbo, J. Hjorth (DARK/NBI), P. 
Jakobsson (Univ. Hertfordshire), report on behalf of a larger collaboration:

We observed the field of GRB 080703 (Ziaeepour et al., GCN 7936
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 ) with 
the ESO VLT equipped with FORS1. Due to visibility constraints, 
observations could only be carried out during twilight at high airmass.

The optical afterglow first reported by Rykoff & Schaefer (GCN 7935
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 ; see 
also Ziaeepour et al., GCN 7936
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 ) is detected in our image (15 s 
exposure). On 2008 Jul 3.948 UT (3.76 hr after the GRB), the afterglow 
had R ~ 21.6 assuming R = 15.92 for the USNO star at (06:47:12.61, 
-63:12:31.7).

A finding chart is posted at

http://www.astro.ku.dk/~malesani/GRB/080703/080703_finder.png

No further observations are planned. We acknowledge excellent support 
from the ESO staff in executing this challenging observation, 
particularly Thomas Szeifert and Dominique Naef.

P. Ward (MSSL-UCL) and H. Ziaeepour (UCL-MSSL) report on behalf of the 
Swift/UVOT team:

The Swift Ultra-Violet/Optical Telescope (UVOT) started observing
GRB 080703 (Rykoff et al. GCN 7935
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 , Ziaeepour et. al, GCN 7936
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 ) ~100 
seconds after the trigger.

A quickly fading candidate afterglow is found in the UVOT White and V 
filters. The preliminary Swift/UVOT position of the optical afterglow 
candidate is:

  RA(J2000)  = 06:47:12.639 = 101.8027
  DEC(J2000) = -63:13:08.96 = -63.2192

with a 1-sigma error radius of about 0.5 arcsec.
The following table gives the measured magnitudes:

Filter T_start T_stop Exp     Mag

White  101    200    99.8     17.40 +/- 0.03
White  857    956    99.8     20.27 +/- 0.35
White  5905   6102   196.6    21.29 +/- 0.49
White  5905   19222  869.5  > 21.77 (1.9-sigma)
V      207    606    399.8    18.02 +/- 0.10
V      963    1362   399.8    19.06 +/- 0.27
V      6315   6512   196.6  > 19.65 (0.2-sigma)
V      6315   12021  1081.7 > 20.83 (0.9-sigma)
B      687    1788   78.9   > 19.48 (1.8-sigma)
B      663    1764   99.0   > 19.33 (1.5-sigma)
UVW1   638    1885   99.9   > 19.55 (0.1-sigma)
UVM2   613    1878   118.7  > 19.67 (1.7-sigma)
UVW2   718    1829   79.1   > 19.55 (0.9-sigma)


The values quoted above are in the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627). No correction has been
made for the expected extinction corresponding to E(B-V) of
0.071 mag in the direction of the burst (Schlegel et al. 1998).

We analysed 12.1 ks of data in Photon Counting (PC) mode obtained for GRB
080703 (Ziaeepour et al., GCN Circ 7936
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 ) between 106 s and 3.1e4s after the
trigger (T0). The UVOT-enhanced XRT position was given by Osborne et al. in
GCN Circ. 7939
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 .

The X-ray light-curve shows an initial rise from T0+106s to ~T0+200s and
then
decays with a slope of ~1.2. From ~T0+700s to ~T0+2000s, the XRT light-curve
shows some flaring activities. The light-curve after ~T0+1e4s decays with a
slope of 1.57 +/-0.21.

The hardness ratio does not show any significant spectral variation from
T0+106s to T0+3.1e4s. The PC spectrum from T0+106s to T0+3.1e4s is well
fitted
by an absorbed power-law with a photon index of 1.7 +/-0.1 and an absorption
column of (8.9 +3.9/-3.3)e20 cm**-2, in excess with respect to the Galactic
one (5.2e20 cm**-2; Kalberla et al. 2005). The observed 0.3-10 keV flux over
this time interval is (8.2 +0.8/-1.2)e-12 erg/cm**2/s.

If the light-curve continues to decay with alpha = 1.6, the count rate at 24
hours after the trigger is estimated to be 7e-3 counts/s, which
corresponds to
an observed flux of 6.7e-13 erg/cm**2/s.

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

C. Clemens, S. Loew, J. Greiner, A. Yoldas, T. Kruehler (all MPE Garching), A. 
Kupcu Yoldas (ESO) and G. Szokoly (Eoetvoes Univ., Budapest) report on behalf 
of the GROND team:

We observed the field of GRB 080703 (Swift trigger 315819; Ziaeepour et al., 
GCN #7936
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, 
PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory 
(Chile).

Observations started at 23:04 UT on July 3rd, 2008, 4.1 hrs after the GRB 
trigger with 4.7 min of effective exposures in g'r'i'z' and 8.0 min in JHK, 
and were performed at an average seeing of 1.8" during astronomical twilight.

We do not detect any object within the 0.5'' Swift-UVOT error circle reported 
by Ward & Ziaeepour (GCN #7941
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 ) to the following upper limits:

g' > 22.1 mag,
r' > 22.6 mag,
i' > 21.8 mag,
z' > 21.3 mag,
J > 19.3 mag,
H > 18.1 mag and
K > 17.0 mag.

These upper limits are calibrated against USNO-B1 as well as 2MASS field 
stars.