GRB 130708A

J. R. Cummings reports on behalf of the Swift-BAT team

At 11:43:03.7 Swift-BAT triggered on GRB 130708A (trigger 560515). No
significant source was found onboard, and rate-trigger processing was
terminated prematurely by a pre-planned slew. A significant source was found
in ground analysis at RA, Dec 17.474, 0.003, which is:

RA (J2000)   01h 09m 53.7s
Dec (J2000)  00d 00' 11.9"

with an estimated 90% error radius of 2.4 arcmin.  This position is 5.0 degrees
from the location found by Fermi-GBM for trigger 394976587, which has an
estimated error of 2.2 degrees.  The partial coding was 11%.

We note that this position is 1.6 arcmin from a Seyfert I galaxy at Z = 0.16,
[VV2003c] J010946.5-000023.

The BAT lightcurve shows a double-peaked long GRB.  The T90 of the GRB was about
9 +/- 1 seconds, with a spectral power-law index of 1.38 +/- 0.28 and a fluence
of (7.8 +/- 1.8) x 10^-6 ergs/cm^2 in the 15-150 keV BAT energy range.  Error
estimates are 90% confidence.

A Swift TOO request has been approved to locate the afterglow with XRT.  Since
this burst was not located onboard, the usual automated analysis products are
not available.

G. Fitzpatrick (UCD) reports on behalf of the Fermi GBM Team:

At 11:43:04.27 UT on 08 July 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 130708A (trigger 394976587/130708488)
which was also detected by the Swift/BAT (Cummings et al., GCN Circ. 14997
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 ).
The GBM on-ground location is consistent with the Swift position.

The GBM light curve consists of a single peak
with a duration (T90) of about 14 s (50-300 keV).
The time-averaged spectrum from T0 s to T0 + 8 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.9 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 158 +/- 16 keV

The event fluence (10-1000 keV) in this time interval is
(2.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+5.8 s in the 10-1000 keV band is 1.0 +/- 0.07 ph/s/cm^2.

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

A. Maselli (INAF-IASF Palermo) and A. Breeveld (MSSL-UCL) report on behalf of the Swift XRT and UVOT teams:

The Swift/XRT started observing the field of the BAT ground-detected GRB 130708A (Cummings, GCN Circ. 14997
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 ) on 2013-07-09 at 14:49:07 UT, 97564 s after the BAT trigger. In 3881 s of XRT data in Photon Counting mode we detected no significant X-ray source within the BAT error circle. The 3-sigma upper limit at the reported BAT position is 4.0E-03 cts/s.

The Swift/UVOT began settled observations of the field of GRB 130708A 97557 s after the BAT trigger. No optical afterglow consistent with the BAT position is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white            97741       107968         1001         >21.6
v                97926       103874         1037         >20.1
u                97557       107909         1804         >21.4

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).

This circular is an official product of the Swift XRT and UVOT teams.