GRB 060805

H. Z. Ziaeepour (UCL-MSSL), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMD), N. Gehrels (NASA/GSFC),
C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD),
K. L. Page (U Leicester), M. J. Page (UCL-MSSL), D. M. Palmer (LANL)
and T. Sakamoto (NASA/ORAU) report on behalf of the Swift Team:

At 04:47:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060805 (trigger=222683).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is RA,Dec 220.919, +12.592
{14h 43m 41s, +12d 35' 32"} (J2000) 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. 

The XRT began taking data at 04:49:22 UT, 93 seconds after the BAT
trigger. Although the XRT on-board centroid algorithm did not find a
source in the image, ground analysis reveals a faint source at RA,
Dec 14h 43m 43.59s, +12 35 11.8 (J2000) with an uncertainty of 5.9
arcsec. 

UVOT took a finding chart exposure of 100 seconds with the white filter
starting 97 seconds after the BAT trigger. No afterglow candidate
has been found in the initial data products. Image catalog data are
not available at this time. The 8'x8' region for the list of sources
generated on-board covers 100% of the BAT error circle. The list of
sources is typically complete to about 18.0 mag. No correction has
been made for the expected extinction of about 0.1 magnitudes.

Richard J. Cool (Arizona), Daniel J. Eisenstein (Arizona),
David W. Hogg (NYU), Michael R. Blanton (NYU), David J. Schlegel
(LBNL), J. Brinkmann (APO), Donald Q. Lamb (Chicago), Donald
P. Schneider (PSU), and Daniel E. Vanden Berk (PSU) report:

The Sloan Digital Sky Survey (SDSS) imaged the field of burst
GRB060805 prior to the burst.  As these data should be useful
as a pre-burst comparison and for calibrating photometry,
we are supplying the images and photometry measurements for
this GRB field to the community.

Data from the SDSS, including 5 FITS images, 3 JPGS, and
3 files of photometry and astrometry, are being placed at
http://mizar.as.arizona.edu/~grb/public/GRB060805

We supply FITS images in each of the 5 SDSS bands of a 8'x8'
region centered on the GRB position (ra=220.932 (14:43:43.6),
dec=12.5866 (12:35:11.8); Swift-BAT TRIGGER 222683), as well
as 3 gri color-composite JPGs (with different stretches). The
units in the FITS images are nanomaggies per pixel.  A pixel
is 0.396 arcsec on a side. A nanomaggie is a flux-density unit
equal to 10^-9 of a magnitude 0 source or, to the extent that
SDSS is an AB system, 3.631e-6 Jy.  The FITS images have WCS
astrometric information.

In the file GRB060805_sdss.calstar.dat, we report photometry
and astrometry of 379 bright stars (r<20.5) within 15' of the
burst location.  The magnitudes presented in this file are asinh
magnitudes as are standard in the SDSS (Lupton 1999, AJ, 118,
1406). Beware that some of these stars are not well-detected
in the u-band; use the errors and object flags to monitor
data quality.

In the files GRB060805_sdss.objects_flux.dat and
GRB060805_sdss.objects_magnitudes.dat, we report photometry
of 1683 objects detected within 6' of the GRB position.
We have removed saturated objects and objects with model
magnitudes fainter than 23.0 in the r-band.  The fluxes listed
in GRB060805_sdss.objects_flux.dat are in nanomaggies while
the magnitudes listed in GRB060805_sdss.objects_magnitudes.dat
are asinh magnitudes.

All quantities reported are standard SDSS photometry, meaning
that they are very close to AB zeropoints and magnitudes are
quoted in asinh magnitudes.  Photometric zeropoints are known
to about 2% rms.  None of the photometry is corrected for
dust extinction.  The Schlegel, Finkbeiner, and Davis (1998)
predictions for this region are A_U=0.124 mag, A_g=0.092 mag,
A_r = 0.066 mag, A_i=0.050 mag, and A_z=0.036 mag.

The file GRB060805_sdss.spectro.dat contains a list of the
8 objects with SDSS spectroscopy within 6 arcminutes of the
GRB position.  In addition to the redshift and 1-sigma error
for each object, this file also lists the object spectroscopic
classification.

SDSS astrometry is generally better than 0.1 arcsecond per
coordinate.  Users requiring high precision astrometry should
take note that the SDSS astrometric system can differ from
other systems such as those used in other notices; we have
not checked the offsets in this region.

More detailed information pertaining to our SDSS GRB releases
can be found in our initial data release paper (Cool et
al. 2006, astro-ph/0601218).  See the SDSS DR4 documentation
for more details: http://www.sdss.org/dr5.

These data have been reduced using a slightly different
pipeline than that used for SDSS public data releases.
We cannot guarantee that the values here will exactly match
those in the data release in which these data are included.
In particular, we expect the photometric calibrations to differ
by of order 0.01 mag.

This note may be cited, but please also cite the SDSS data
release paper, Adelman-McCarthy et al. (2006, ApJS, in press,
astro-ph/0507711), when using the data or referring to the
technical documentation.

W. Li, University of California, Berkeley, on behalf of the 
KAIT GRB team, reports: 

The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT)
at Lick Observatory observed GRB 060805 detected with Swift
(Trigger 222683; Ziaeepour et al. GCN 5398
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 ). A combination of
filters is used: V, I, and clear. The first 15 s unfiltered
image started at 04:49:48 UT, 119 s after the BAT trigger.
Our automatic image processing pipeline did not identify any
new source relative to the DSS II red image. We set the following
limiting magnitudes (calibrated to USNO B1.0 catalog):

start UT    Exposure    Filter    Limiting mag

04:49:48    15 s        clear     17.7
04:50:48    15 s        I         16.7
04:51:13    20 s        clear     18.0
04:51:45    45 s        V         16.8

S. B. Cenko (Caltech) reports on behalf of a larger collaboration:

We have imaged the field of GRB 050805 (Ziaeepour et al.; GCN 5398
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 ) with
the automated Palomar 60-inch telescope.  We obtained 2 x 60 s images in
Kron R and Sloan i' and z' beginning approximately 3 minutes after
the burst, before closing due to high humidity.  We find no sources inside
the XRT error circle to a limiting magnitude of R > 19.0 (calculated with
respect to the USNO-B catalog).

S. B. Pandey, M. J. Page, H.Z. Ziaeepour and S. R. Oates (UCL-MSSL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began observing the field of GRB 060805 at 04:49:25 UT,
79 s after the BAT trigger (Ziaeepour et al. GCN 5398
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 ).  No optical
afterglow candidate has been found in the coadded images within the
XRT error circle (Ziaeepour et al. GCN 5398
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 ).

The 3-sigma limiting magnitudes for the coadded images for the
7 filters are listed below:

Filter       T_range(s)  Exposure(s)     3sig_Upper limit

WHITE        96-6633       511           20.1
V            79-11779      1583          20.3
B            680-6428      412           20.6
U            656-6223      432           20.2
W1           632-6019      432           19.7
M2           4182-12507    1105          20.6
W2           708-10866     1165          20.7


T_range is calculated from the time of the burst. These
upper limits have not been corrected for the estimated
Galactic reddening of E(B-V) = 0.024 mag (Schlegel et
al. 1998).

L. Barbier (GSFC),  S. Barthelmy (GSFC), J. Cummings (GSFC/ORAU),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho),
M. Koss (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (GSFC/JSPS/USRA), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
on behalf of the Swift-BAT team:

Using the data set from T-240 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 060805
(trigger #222683)  (Ziaeepour, et al., GCN Circ. 5398
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 ).  The BAT
ground-calculated position is (RA,Dec) = 220.925, 12.576 deg
{14h 43m 41.9s, 12d 34' 35.0"} (J2000) +- 2.7 arcmin,
(radius, sys+stat, 90% containment).  The partial coding was 96%.

The currently available event data record has several gaps, most significantly
from T+14.3 to T+19.5 sec. Based on the available data, the mask weighted light
curve shows a single peak with a roughly square profile and a duration
of ~6 sec.  Emission was only seen below 100 keV, which is consistent with the
very soft spectrum found. T90 (15-350 keV) is 5.4 +- 0.5 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.6 to T+4.7 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.23 +- 0.42. The fluence in the 15-150 keV band is 7.4 +- 2.0 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T+0.71 sec in the 15-150 keV
band is 0.3 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90%
confidence level.

K.L. Page, O. Godet (U Leicester) & H.Z. Ziaeepour (UCL-MSSL) report on
behalf of the Swift-XRT team:

We have analysed the first 4 orbits of the XRT data obtained for GRB
060805 (trigger 222683), comprising 8.4 ks of Photon Counting mode data
between 101 s - 18.3 ks after the BAT trigger. Using these data, we obtain
a refined position of:

RA(J2000)  =  14 43 43.59
Dec(J2000) = +12 35 13.2

with an uncertainty of 3.9 arcsec (90% containment). This is 47.9 and 1.4
arcsec from the initial BAT and XRT positions respectively (GCN Circ 5398
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 ;
Ziaeepour et al).

The X-ray afterglow is faint, with a count rate of ~0.1 count s^-1 at 100
seconds after the trigger. After the first orbit, during which the count
rate was close to constant, the afterglow decays with a slope of alpha =
1.06 +/- 0.35.

The spectrum (using the combined data from all 4 orbits) can be well
fitted by a simple power-law, of Gamma = 2.39 +0.64/-0.51, with a total
absorbing column of about 1e21 cm^-2 (compared to the Galactic column
density of 1.57e20 cm^-2). During the first orbit (between 101 and 935
seconds after the trigger), the 0.3-10 keV unabsorbed flux was 4.72e-12
erg cm^-2 s^-1.

If the afterglow continues to fade with alpha ~ 1.06, the count rate at 24 
hours is predicted to be 1.6e-3 count s^-1, corresponding to an observed 
(unabsorbed) flux of 5.92e-14 (8.92e-14) erg cm^-2 s^-1.

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

M. Muehlegger, S. Duscha, A. Stefanescu, G. Kanbach, N. Primak, F. Schrey,
H. Steinle (MPE Garching) of the OPTIMA-Burst team report from
the 1.3m Skinakas Observatory (University of Crete, Heraklion, Greece): 

We observed the position of the XRT errorcircle of GRB 060805 (trigger
#222683, Ziaeepour, et al., GCN Circ. 5398
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 ) on 2006 Aug 05, 18:43 UT 
(mid-exposure; about 14 hours post burst): in a 30 min R-filter exposure we 
do not detect a counterpart candidate brighter than R=21.5

E. Rol (U of Leicester) reports on behalf of the RoboNet telescope
network:

We observed the field of GRB060805 (Ziaeepour et al, GCN Circular
5398
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 ) with the 2m Liverpool Telescope during the night of
2006-08-05/06, in Sloan r' and i' filters.  At the position of the
refined XRT position (Page et al, GCN Circular 5404
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 ), we do not detect
any source.  The observations and limiting magnitude are detailed
below. Calibration has been performed using the available SDSS data
(Cool et al, GCN Circular 5399
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 ).


  start time      T-delta    exposure time  filter  limiting magnitude
     UT      (mid-obs; days)   (seconds)              (5 sigma)

  21:59:40        0.725         5 x 300       r'         22.9
  22:27:28        0.748         7 x 300       i'         22.6