GRB 080605

B. Sbarufatti (INAF-IASFPA), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), V. La Parola (INAF-IASFPA),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (NASA/UMBC),
T. N. Ukwatta (GSFC/GWU) and D. E. Vanden Berk (PSU) report on behalf
of the Swift Team:

At 23:47:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080605 (trigger=313299).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 262.127, +4.002 which is 
   RA(J2000)  = 17h 28m 31s
   Dec(J2000) = +04d 00' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple overlapping
peaks lasting at least to T+8 sec (at which the TDRSS lightcurve is
truncated).  The peak count rate was ~17000 counts/sec (15-350 keV),
at ~1 sec after the trigger. 

The XRT began observing the field at 23:49:28.2 UT, 90.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 262.1249, +4.0153 which is equivalent to:
   RA(J2000)  = 17h 28m 29.9s
   Dec(J2000) = +04d 00' 55.0"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 48 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The UVOT detects a new source within the XRT error circle.  We are unable to 
obtain a position or magnitude at this time.  The source is very close to a 
known source in the DSS.  Further information will be provided when it is available. 

Burst Advocate for this burst is B. Sbarufatti (sbarufatti AT ifc.inaf.it). 
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.)

This is a multi-part message in MIME format.

--bound1212711210
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D. A. Kann, U. Laux, S. Klose, S. Ertel (TLS Tautenburg) and J. Greiner (Garching) report:

We observed the location of Swift GRB 080605 with the TLS Tautenburg 1.34m Schmidt telescope in RRM Mode (Klose et al., GCN 3609
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 ).

At the in-flight XRT position, in a 120 sec Ic band frame, we detect a new source not present in the DSS at:

RA (J2000) = 17:28:29.96
Dec. (J2000) = +04:00:57.5

The source is blended with a star to the southeast but clearly discernible.

We propose this to be the afterglow of GRB 080605. Spectroscopy is encouraged.

This message may be cited.

--bound1212711210--

S. T. Holland (CRESST/USRA/GSFC) and B. Sbarufatti (INAF-IASFPA)
report on behalf of the Swift Team:

Swift/UVOT began observing the field of GRB 080605 (Sbarufatti et
al. 2008, GCN Circ. 7828
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 ) with a 99 s white exposure starting 104 s
after the BAT trigger.  The preliminary Swift/UVOT position of the
optical afterglow candidate is

  RA(J2000.0) =  17:28:30.07
Dec(J2000.0) = +04:00:56.0

with an estimated position uncertainty of 1.0 arcsec.  There is a
known source (USNO-B1.0 940-028965) 3 arcsec from this position.

A. Gomboc (U. Ljubljana), A. Melandri, R.J. Smith, C.G. Mundell, I.A. 
Steele, D. Bersier, S. Kobayashi, D. Carter, M. Burgdorf, M.F. Bode 
(Liverpool JMU), C. Guidorzi (INAF-OAB) report:

The Liverpool Telescope (La Palma) automatically reacted to the Swift 
trigger 313299 and started observing the field 3 min after the trigger.

We find an un-catalogues source at
RA 17:28:29.9,
dec +04:00:55.0
consistent with the XRT position.

The magnitude of the source is R=18.3 at 11.3 min after the trigger.

Pall Jakobsson (U. Hertfordshire), Paul M. Vreeswijk,
Dong Xu and Christina C. Thoene (DARK, NBI) report on behalf 
of a larger collaboration:

Using FORS2 on the Very Large Telescope, we have obtained
a 10 min spectrum (grism 300V) of the optical afterglow of
GRB 080605 (Sbarufatti et al., GCN 7828
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 ). The acquisition 
image shows it to have R = 20.4 on June 6.063 (1.7 hours
post burst).

A firm upper limit of z < 2.1 can be placed on the redshift
of GRB 080605 from the lack of Ly-alpha forest lines in the
spectrum of the afterglow.

The spectrum is rich in absorption features, including Si II,
C IV, Al II, Al III, Zn II, Fe II, Mg II and Mg I, corresponding 
to a redshift of z = 1.6398 +/- 0.0006.

We thank the Paranal staff for excellent support, especially
Linda Schmidtobreick.

V. Rumyantsev (CrAO),  A. Pozanenko (IKI) report on behalf of larger GRB 
follow-up collaboration:

We observed the optical afterglow (Kann,  et al., GCN 7829
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 ; Holland et al., 
GCN 7830
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 ; Gomboc et al., GCN 7831
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 ) of  Swift GRB 080605 (Sbarufatti  et al., 
GCN 7828
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 ) in R and I bands on June 05  Zeiss-1000 (Simeiz) telescope of CrAO 
observatory under not optimal weather conditions.  Based on  USNO-B1.0 star 
RA (J2000) = 17 28 29.92, Dec.
(J2000) = +04 00 36.5, R2=15.90 we estimated brightness of  the optical 
afterglow in first frames:

UT,       Exposure,   R_mag,
(start time)

2008-06-05T23:55:58    120 s     17.9
2008-06-06T00:00:34    120 s     18.4

During observations the afterglow is clearly faded.
Coordinates of the afterglow with uncertainties of 0.3":

RA(2000):  17 28 30.01
Dec(2000): +04 00 56.4

A finding chart can be found at 
http://grb.rssi.ru/GRB080605/grb080605_080605_z1000.gif
The message may be cited.

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

We observed the field of GRB 080605 (Swift trigger 313299; Sbarufatti et al., 
GCN #7828
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, 
PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory 
(Chile).

Observations started at 01:10:59 UT on June 6th, 2008, 83 mins after the GRB 
trigger, and are continuing.

We found a single and relatively bright point source within the 1.0'' 
Swift-UVOT error circle reported by Holland et al. (GCN #7830
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 ) at

RA (J2000.0) = 17h 28m 30.05s
DEC (J2000.0) = +04d 00' 56.2"

with a typical uncertainty of 0.8", which is consistent with the sources 
reported by Kann et al. (GCN #7829
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 ) and Gomboc et al. (GCN #7831
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 ).

Based on 460 s and 1500 s of effective exposures taken 1.65 hrs and 2.78 hrs 
after the trigger, we estimate preliminary magnitudes of

r' = 20.3 and i' = 19.4, as well as
r' = 20.7 and i' = 19.9

with typical errors of +/- 0.1. (Given magnitudes are calibrated against 
USNO-B1 field stars and might be affected by the bright, nearby star.)

This indicates a clear fading of the source, which we therefore suggest to be 
the optical afterglow of GRB 080605.

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

Using 426 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080605, 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 = 262.12533, +4.01608 which is equivalent
to:

RA (J2000): 17h 28m 30.08s
Dec (J2000): +04d 00' 57.9"

with an uncertainty of 1.8 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.

MASTER-Net Team:

D.Kuvshinov, V. Lipunov, V.Kornilov,  E.Gorbovskoy,
A.Belinski, N.Shatskiy, N.Tyurina,
Sternberg Astronomical Institute, Moscow Union 'Optic'

A. Tlatov, I.Golubov
Kislovodsk Solar Station of the Pulkovo observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University


MASTER Very Wide Field Camera located at Kislovodsk Solar Station
(http://observ.pereplet.ru, D=50 mm, 1015 square degrees, 35'' per pix) 
has moved to the Swift-BAT trigger 313299 (23:47:57 UT) and it has taken a 
series of 5s exposures  starting 46s after the GRB time and 12 s after 
notice arrivel time at   23:48:43 UT under good weather  condition, but 
large zenit distance.

These unfiltered images are calibrated relative to USNO A2.0 (R).
There is no OT was found inside Swift error box
(B. Sbarufatti, S. D. Barthelmy et al., GCN Circ 7828
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 ).

T-Tgrb    Mean Time     Limit   Coadd?           Note

46s        48.5s      >9.0      no             moving

51s        53.5s      >10.0     no

51s        56.0s      >10.2     2

51s        76.0s      >11.0    10

51s       101.0s      >11.5    20

The message can be cited.
mailto: lipunov@sai.msu.ru

PS. AT = After Trigger

M. Jelinek, A.J.Castro-Tirado, J. Gorosabel (IAA CSIC Granada),
Petr Kubanek (GACE Valencia), S. Vitek (FEL CVUT Praha),
A. de Ugarte Postigo (ESO Santiago), on behalf of a larger
Collaboration:

report:

"We observed the optical afterglow of GRB 080605 (Kann et al.
GCN 7829
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 , Sbarufatti et al. GCN 7828
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 , Gomboc et al. GCN 7831
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 )
with the 30cm BOOTES-1B and with the 60cm BOOTES-2/TELMA
robotic telescopes in southern Spain.

The sequence of observations started 43s after the GRB trigger.
We clearly detect a 15th mag transient outshining the nearby star
in R-band (BOOTES-2/TELMA) and without filter (BOOTES-1B). "

B. Sbarufatti, V. Mangano, V. La Parola (INAF-IASF Pa) report on
behalf of the Swift-XRT team

The XRT began observations of GRB 080605 (trigger=313299,
Sbarufatti et al., GCN circ. 7828
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 ) started on 2008 May 05 at 23:49:36 UT,
97 s after the BAT trigger. The data consist of 642 s in Windowed Timing
mode and 4.3 ks s in Photon Counting mode.

The light curve is described by a powerlaw with initial slope
0.65 (+/-0.05) until T+ 280s (+90, - 45), at which point the decay
steepens to an index 1.32 (+/-0.03).

The spectrum of the WT mode data can be fitted by a powerlaw with
photon index 1.78 (+/- 0.04) and an intrinsic absorbing column of
6.6 (+/-0.9)E21 cm^-2 at z=1.6398 (Jakobsson et al., GCN circ. 7832
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 ),
in excess over the Galactic value of 6.67E20 cm^-2.
The observed (unabsorbed) flux is 7.5 (8.1)E-10 erg cm^-2 s^-1.
The first orbit PC mode spectrum  (379 s of exposure) can be
fit by a powerlaw with photon index 1.6 (+/- 0.2) and an
intrinsic absorbing column of 4.8 (+/-4)E21 cm^-2. The observed
(unabsorbed) flux is 3.0 (3.3)E-10 erg cm^-2 s^-1.

The countrate to flux conversion factor is 4.87e-11 erg cm^-2 s^-1.
The predicted countrate 24 h after the trigger is 1.6E-2 counts/s,
equivalent to an observed flux of 7.8E-13 erg cm^-2 cts^-1.

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

J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), B. Sbarufatti (INAF-IASFPA), J. Tueller (GSFC),
T. 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 080605 (trigger #313299)
(Sbarufatti, et al., GCN Circ. 7828
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 ).  The BAT ground-calculated position is
RA, Dec = 262.130, 4.010 deg, which is 
   RA(J2000)  =  17h 28m 31.1s 
   Dec(J2000) = +04d 00' 35.6" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 41%.
 
The mask-weighted light curve shows a cluster of overlapping peaks
starting at ~T-3 sec, the largest peak at ~T+8 sec, and all ending at ~T+70 sec.
At the 1-2 sigma level, there is appears to be persistant emmission
in the T+300 to T+700 sec range.  T90 (15-350 keV) is 20 +- 1 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-5.5 to T+30.0 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.11 +- 0.14, 
and Epeak of 223 +- 133 keV (chi squared 28.10 for 56 d.o.f.).   For this
model the total fluence in the 15-150 keV band is 1.33 +- 0.02 x 10^-5 erg/cm2
and the 1-sec peak flux measured from T+7.57 sec in the 15-150 keV band is
19.9 +- 0.6 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.36 +- 0.03 (chi squared 37 for 57 d.o.f.).  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/313299/BA/

J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), B. Sbarufatti (INAF-IASFPA), J. Tueller (GSFC),
T. 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 080605 (trigger #313299)
(Sbarufatti, et al., GCN Circ. 7828
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 ).  The BAT ground-calculated position is
RA, Dec = 262.130, 4.010 deg, which is 
   RA(J2000)  =  17h 28m 31.1s 
   Dec(J2000) = +04d 00' 35.6" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 41%.
 
The mask-weighted light curve shows a cluster of overlapping peaks
starting at ~T-3 sec, the largest peak at ~T+8 sec, and all ending at ~T+70 sec.
At the 1-2 sigma level, there is appears to be persistant emmission
in the T+300 to T+700 sec range.  T90 (15-350 keV) is 20 +- 1 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-5.5 to T+30.0 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.11 +- 0.14, 
and Epeak of 223 +- 133 keV (chi squared 28.10 for 56 d.o.f.).   For this
model the total fluence in the 15-150 keV band is 1.33 +- 0.02 x 10^-5 erg/cm2
and the 1-sec peak flux measured from T+7.57 sec in the 15-150 keV band is
19.9 +- 0.6 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.36 +- 0.03 (chi squared 37 for 57 d.o.f.).  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/313299/BA/

N. P. M. Kuin (MSSL/UCL),  B. Sbarufatti (INAF-IASFPA), F. Marshall (GSFC),
and P.Schady (MSSL/UCL), report on behalf of the Swift UVOT team

The Swift UltraViolet/Optical Telescope (UVOT) began observations
of GRB 080605, on June 5, 2008, at  23:49:19 UT,  82 seconds after
the initial Swift BAT trigger (Mangano et al., GCN Circ. 7794
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 ), and
started the finding chart exposure in the white filter at 102
seconds after the trigger.

The refined uvot position of GRB080605 is RA=262.12522, Dec=+4.01555
deg.(= 17:28:30.05 +04:00:55.97), with an accuracy of 0.5", consistent
with the positions reported in GCN Circ. 7830
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  (Holland et al.) and
7835 (Goad et al.).

The GRB is found close (about 4" distant) to a star, which may cause
an error in the measured flux, especially at later times. For this
analysis we use a small 2" aperture which which reduces the
contamination, and apply a standard aperture correction. We note that
the DSS image indicates the presence of a weak, possibly extended
source near the position of the afterglow.

The magnitudes with 1-sigma errors for GRB080605 are given below
for the initial observation sequence.

Filter Tstart(s) Tstop(s) Exp(s) Magnitude

wh      102      201     98.2    18.11 +/- 0.06
v       208      607    393.5    18.53 +/- 0.11
wh      858      957     98.2    20.02 +/- 0.17
uvm2    615      788     38.9   >18.38 (3 sigma UL)
uvw1    639      813     38.9   >18.95 (3 sigma UL)
uvw2    720      739     19.5   >18.16 (3 sigma UL)
b     27679    28264    571.7    21.10 +/- 0.27
u     18432    41856    550.7    21.17 +/- 0.43

The values quoted above are on the UVOT Photometric System
(Poole et al, 2008, MNRAS 383,627). They are not corrected for the
expected galactic reddening of E(B-V) = 0.137 in the direction of
the burst (Schlegel et al. 1998).

D. A. Kann, U. Laux and S. Ertel (TLS Tautenburg) report:

We continue observations of the afterglow of GRB 080605 (independently 
discovered by Sbarufatti et al., GCN 7828
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 , Kann et al., GCN 7829
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 , and 
Gomboc et al., GCN 7831
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 ). We acquired one 300 sec image each in V, R, and 
I around 0.95 days after the GRB, and further imaging 0.1 days later until 
dawn. Astonishingly, the afterglow is still clearly visible in R and I 
bands.

As mentioned in the above-cited GCNs, the afterglow is close to a star and 
affected by its PSF in images with low-quality seeing or large pixel 
scale, such as the TLS camera. To obtain a qualitative description of the 
afterglow evolution, we perform aperature photometry in a 3 pixel 
aperature, and derive the aperature correction for each image by comparing 
the counts for a reference star in the 3 pixel aperature with that in a 7 
pixel (which is typically seeing-matched) aperature. As a reference star, 
we use the star to the south of the afterglow, USNOB1.0 ID 0940-0289655 at 
(catalog position): RA = 17:28:29.920, Dec. = +04:00:36.51, which has R2 = 
15.90 mag, I = 14.54 mag. We derive the following magnitudes for selected 
images in the I band (the error is estimated to be 0.1 magnitudes in all 
cases):

dt		I

0.00478791	16.74
0.00674681	17.18
0.00869923	17.36
0.01064872	17.61
0.01849396	18.19
0.02433042	18.19
0.05922051	18.48
0.96109933	18.51
1.05275325	18.71

The early afterglow decay (0.00479 to 0.01849 days) is well-described by a 
power-law with decay slope alpha=0.97. After this, the afterglow decay 
seems to flatten. Between 0.06 days and 0.95 days, the afterglow magnitude 
remains unchanged, indicating a plateau phase. As the afterglow has 
resumed its decay 0.1 days later, this probably implies that the 
afterglow underwent a strong rebrightening which we caught after the 
peak. This is reminiscent of GRB 071003, which lies at a very similar 
redshift (Perley et al. 2008, ApJ, submitted, arXiv:0805.2394) of ~ 1.6 
(Jakobsson et al., GCN 7832
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 ).

Furthermore, we determined the R band magnitude at two epochs:

dt		R

0.01655957	19.87
0.95457023	20.75

Corrected for the moderate Galactic foreground extinction of E(B-V) = 
0.136, we find R - I ~ 2 mag. This is a very red color for an afterglow, 
indicating strong internal reddening due to dust. We caution that the 
USNOB1.0 comparison star may have incorrect photometry, on the other hand, 
a simple image comparison shows that the R band magnitude is much fainter 
than the I band magnitude.

The strong rebrightening combined with the large correction for dust 
extinction that is needed imply that this is an intrinsically extremely 
luminous afterglow. Further follow-up, especially in the NIR bands, is 
highly encouraged.

This message may be cited.

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

We observed the field of GRB 080605 for a second time at 02:43 UT on June 7th, 
2008 about 1.12 days after the GRB trigger with 25 mins of effective 
exposures in g'r'i'z'.

We still detect the bright afterglow within the refined 0.5'' Swift-UVOT error 
circle (Kuin et al., GCN #7844
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 ) to the following preliminary magnitudes of

r' = 22.3,
i' = 21.7 and
z' = 21.4

with typical errors of +/- 0.1. Given magnitudes are calibrated against 
USNO-B1 field stars and might be affected by the bright, nearby star.

This indicates a clear fading of the optical afterglow compared to our first 
epoch observations (C. Clemens et al., GCN #7834
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 ).

Please note, that no correction for the galactic foreground reddening of 
E(B-V) = 0.136 mag (Schlegel et al., 1998) has been applied.

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:

The bright GRB 080605 (Swift-BAT trigger #313299: Sbarufatti et al., GCN
7828
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 , Cummings et al., GCN 7839
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 ) triggered Konus-Wind at T0=85682.336 s 
UT (23:48:02.336).

The burst light curve shows a multipeaked structure with a total 
duration of ~20s.

As observed by Konus-Wind the burst
had a fluence of 3.02(-0.12, +0.13)x10^-5 erg/cm2,
and a 16-ms peak flux measured from T0+7.984 s
of (1.60 +/- 0.33)x10^-5 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+18.944 s) can be fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.03 +/- 0.07,
and Ep = 252(-17, +20) keV (chi2 = 57.2/61 dof).
Fitting by GRBM (Band) model yields:
the low-energy photon index is alpha = -1.02 +/- 0.08,
the high energy photon index beta < -2.75,
the peak energy Ep =  246(-18, +23) keV (chi2 = 56.7/60 dof).

The spectrum of the most intense peak (from T0+7.168 s to T0+8.960 s)
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model
with alpha =  -0.94 +/- 0.10
and Ep = 333(-34, +42) keV (chi2 = 60.6/54 dof).
Fitting by GRBM (Band) model yields:
the low-energy photon index is alpha = -0.87(-0.12, +0.13),
the high energy photon index beta = -2.58(-0.84, +0.31),
the peak energy Ep =  297(-40, +46) keV (chi2 = 56.6/53 dof).

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

Assuming z = 1.640 (Jakobsson et al., GCN 7832
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 ) and a standard
cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, Omega_\Lambda =
0.73, the isotropic energy release is E_iso ~2.1x10^53 erg,
the maximum luminosity is (L_iso)_max ~3.0x10^53 erg/s, and
Ep_rest ~660 keV.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080605_T85682/

V. Rumyantsev (CrAO),  A. Pozanenko (IKI) report on behalf of larger GRB 
follow-up collaboration:

We observed the optical afterglow of  Swift GRB 080605 (Sbarufatti  et al., 
GCN 7828
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 ) in second epoch on June 06  with Zeiss-1000 (Simeiz) telescope of 
CrAO observatory with favorable weather conditions and seeing about 2".  Our 
first epoch astrometry of the source  (Rumyantsev et al., GCN 7833
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 ) is in 
agreement with  refined UVOT position of GRB080605 (Kuin et al.,  GCN 7844
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 ).
The observation of the first epoch started  8 minute after burst onset 
(Rumyantsev et al., GCN 7833
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 ) was performed under descending weather 
conditions with seeing about 3". Improved photometry of the first epoch 
observation as well as observation on June 6 is based on USNO-B1.0 star RA 
(J2000) = 17 28 29.92, Dec.(J2000) = +04 00 36.5, assuming R=15.90, I=14.54:


T0+          Exposure,   Filter,  mag,
(d,mid time)

  0.006251 120    R  18.04 +/- 0.08
  0.007698 120    R  18.43 +/- 0.06
  0.009457 120    R  18.62 +/- 0.06
  0.010985 120    R  18.63 +/- 0.23
  0.015163 120    R  18.93 +/- 0.23
  0.018068 120    R >19.04
  0.019504 120    R  18.86 +/- 0.20
  0.026031 120    I  18.12 +/- 0.28
  0.033219 120    V >17.50
  0.034654 120    V >18.20
  0.904028 34x120 R  21.13 +/- 0.06

The photometry is still preliminary and not corrected for Galaxy extinction 
and  might be affected by the bright, nearby star.

It is evident that the source is faded between June 5 and June 6. Power law 
index of early afterglow decay ~0.8 is compatible with index obtained in 
I-band (Kann et al., GCN 7845
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 ). However our absolute photometry in R-band 
have a significant offset in comparison with early observations by Kann et 
al. (GCN 7845
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 ) and compatible with photometry of Gomboc et al. (GCN 7831
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 ). 
Our early observation suggests R-I ~ 1.2, however we caution the color of 
the afterglow is also depending on photometry which is affected by bright, 
nearby star.

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M. Yoshida, K. Yanagisawa, D. Kuroda, Y. Shimizu, S. Nagayama,
H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf
of the MITSuME collaboration:

We performed optical imaging observation (Rc, and Ic) of the field
of GRB 080605 (Sbarufatti et al., GCN 7828
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 ) with 50cm MITSuME
telescope at Okayama Astrophysical Observatory June 6 2008 UT.
We detected a point source at the UVOT position of the optical
afterglow (Kuin et al., GCN 7844
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 ). Differential photometry was
made using a USNO B1.0 star, USNO-ID 0940-0289655 (Kann et al.,
GCN 7845
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 ). The Ic-band magnitude of the source was almost constant
from T-T0 = 0.516 to 0.756. The source is about 1.5 magnitude
fainter in Rc-band than in Ic-band. These results are consistent
with other reports (Kann et al., GCN 7845
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 , Rumyantsev et al.,
GCN 7857
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 ).


MITSuME observation start: 2008-06-06 11:35:11 UT

mid-UT        T-T0(days)   exp-T         Ic
(2008-06-06)
---------------------------------------------------
12:11:27      0.516314     60 min    19.03 +/- 0.38
12:48:05      0.541753     60 min    19.00 +/- 0.29
14:00:54      0.592315     60 min    18.85 +/- 0.18
15:15:44      0.644288     60 min    19.03 +/- 0.22
16:30:50      0.696429     60 min    18.82 +/- 0.21
17:56:24      0.755856     80 min    18.87 +/- 0.30
---------------------------------------------------

mid-UT
(2008-06-06)  T-T0(days)   ext-T          Rc
---------------------------------------------------
15:52:20      0.669745     120 min   20.58 +/- 0.32
---------------------------------------------------

D. A. Kann, U. Laux & S. Ertel (TLS Tautenburg) report:

We obtained further images of the Swift GRB 080605 (Sbarufatti et al., GCN 
7828
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 ). A 300 second Ic frame obtained under excellent observing conditions 
shows the field remains unchanged in comparison to the second epoch as 
well as the final images of the first epoch (Kann et al., GCN 7845
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 ). 
Recently, Yoshida et al. (GCN 7863
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 ) also claimed detection of a plateau 
phase. Clemens et al. (GCN 7851
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 ), on the other hand, report a clear fading 
of the afterglow, as well as only a moderately red color in comparison to 
Kann et al. (GCN 7845
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 ), which can possibly be explained by the moderate 
Galactic reddening alone.

Comparison with a multicolor finding chart taken by GROND (C. Clemens, 
priv. comm.) reveals the culprit: source confusion. Near the position of 
the afterglow, there are in total three sources, all seemingly stellar in 
GROND images, along a line. The star to the southeast (Source #1) was 
immediately reported (Sbarufatti et al., GCN 7828
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 , Kann et al., GCN 7829
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 ) 
and is clearly visible in the DSS. To the northwest, there is another 
source (Source #2), also clearly visible in the DSS. An inspection of the 
DSS IR frame reveals that #2 is hardly visible at all, but a new source 
(Source #3), inbetween #1 and #2, now becomes clearly visible. This source 
is extremely red, possibly a red dwarf, and it is THIS source which begins 
to dominate the photometry reported in Kann et al. (GCN 7845
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 ) (and 
presumably Yoshida et al., GCN 7863
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 ), which is mostly I band. The small 
offset from source #1 lead us to believe that this is the afterglow (and 
explained the puzzling observation that it seemed to slightly shift 
position).

Therefore, we retract the identification of a plateau phase of the 
afterglow of GRB 080605, as well as the claim of extreme redness and the 
resulting high lumonisity around 1 day in the observer frame. On the other 
hand, the afterglow IS clearly detected on the early I band frames of the 
TLS RRM observation, as well as in the R band and a stacked V band frame. 
The early photometry, which leads to a decay slope of alpha ~ 1, is still 
valid. Image subtraction will have to be performed to see how many 
detections we have actually gotten.

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