GRB 080319B

Alexander Kappes for the IceCube collaboration (http://www.icecube.wisc.edu 
) reports:

IceCube is a 1 km^3 neutrino telescope located at the geographic South  
Pole sensitive to neutrinos above ~100 GeV. We used the data from  
IceCube in its 9-string configuration to search for high-energy muon  
neutrinos from the position of GRB 080319B (Racusin et al., GCN 7427
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 )  
using an unbinned likelihood method. The search was performed in a  
narrow time window of 66 s (T_0 - 3.8s to T_0 + 62.2s) corresponding  
to the observed prompt gamma-ray emission, and in a wider window of  
about 5 minutes (T_0 - 173s to T_0 + 130 s).

We do not find any indications for a deviation from the background- 
only hypothesis in either of the two time windows. Therefore, we use  
the null result from the prompt window to place an upper limit (90%  
C.L.) on the prompt muon neutrino flux from GRB 080319B of 9.0e-3 erg  
cm^-2 in the energy range between 145 TeV and 2.1 PeV.

A corresponding paper has been submitted to ApJ. The preprint version  
can be found at arXiv:0902.0131.

A.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester), A.S. Fruchter (STScI) 
and J. Graham (STScI) report:

We have obtained a second epoch of HST observations of GRB 080319B on 11 
May 2008. 2 orbits (3200s) of observations were taken in the F606W and 
F814W filters. The afterglow has clearly faded from our first epoch of 
observations and a faint host galaxy is now visible at the afterglow 
location. We measure magnitudes for the combined (afterglow+host) source 
of;

F606W(AB)=26.3 +/ -0.1
F814W(AB)=25.9 +/ -0.1

Relative astrometry between the two epochs of HST observations suggests 
that the afterglow is marginally (0.1 +/- 0.05 arcseconds) offset from the 
centroid of the host galaxy in the F606W image. This implies that the 
afterglow may not be the dominant source of light at the current epoch, 
and is likely significantly fainter than the magnitudes quoted above.

D. A. Kann, S. Schulze (TLS Tautenburg) & A. C. Updike (Clemson 
University) report:

In light of recent reports on the further evolution of GRB 080319B, we did 
a preliminary analysis of the multiwavelength data set.

Jet Break:
Racusin et al. (GCN 7567
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 ) reported the existence of a potential jet break 
at 1.04 +/- 0.43 Ms in the X-ray band, with a hint of a steeper decay seen 
in the optical as well. Using the most up-to-date data from  the Swift XRT 
light curve repository (Evans et al. 2007), we confirm the  findings of 
the Swift team and derive (using data starting at 0.5 days after the GRB):

chi^2/d.o.f. = 39/58
alpha_1 = 1.01 +/- 0.05
alpha_2 = 2.40 +/- 0.39
t_b = 9.43 +/- 1.73 days (0.815 +/- 0.149 Ms)
n = 5 fixed, no "host galaxy"

These values are in agreement with those of the Swift team, with 
significantly reduced errors. We note that there seems to be a steep decay 
in the X-ray light curve from 0.35 to 0.5 days, and a similar evolution 
has been reported in the optical (Krugly et al., GCN 7519
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 ) at about the 
same time. This is reminiscent of the X-ray light curve of GRB 070110 
(Troja et al. 2007).

In the optical, we add data from Perley et al. (GCN 7535
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 ) and Tanvir et 
al. (GCN 7621
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 ) to the data set from Bloom et al. 2008 (arXiv:0803.3215). 
Tanvir et al. report a significant reddening, which we confirm. 

At the moment, it is unclear how much the host galaxy and a potential 
supernova contribute in the g band, but a roughly achromatic steepening is 
seen in this band (Tanvir et al.) in comparison to the X-ray light curve.

Energetics:
Using the prompt emission data derived from Konus-Wind (Golenetskii et 
al., GCN 7482
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 ), we find in the bolometric band (1 - 10000 keV, host 
frame):

E_iso = 1.32 +/- 0.03 x 10^54 erg (log E_iso = 54.12)

In the sample of Kann et al. 2007 (arXiv:0712.2186), only two GRBs (000131 
and 990123) exceed this value.

Using the jet break time derived above, as well as the redshift z=0.937 
(Vreeswijk et al., GCN 7444
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 ), and assuming standard parameters 
(constant-density medium, circumburst density n = 10 cm^-3, efficiency eta 
= 0.2), we find:

theta_jet = 10.24 +/- 0.71 degrees
E_jet = 2.11 +/- 0.30 x 10^52 erg (log E_jet = 52.3)

This value is comparable to or higher than for GRB 050904 (Tagliaferri et 
al. 2005, Frail et al. 2006), GRB 050820A (Cenko et al. 2006) and GRB 
070125 (Updike et al. 2008, Chandra et al. 2008), implying that this is 
the fourth hyper-energetic GRB (cf. Chandra et al. 2008). We note that 
broadband modeling may refine the circumburst density; if it is 
significantly higher than 10 cm^-3, the colimation-corrected energy 
will also be significantly higher.

Supernova:
In the i' band, the afterglow does not show a late steep decay, indicating 
the possibility of a supernova that is by now contributing to the optical 
transient (Tanvir et al.). Using the composite light curve (Bloom et al.) 
shifted to the i' band (using the early Rc - i' color), and assuming an 
achromatic break (t_b, alpha_2 fixed from the X-ray fit) and no host 
galaxy, we find, using data after 0.7 days (after the steep decay + 
plateau phase, Krugly et al.):

chi^2/d.o.f. = 44/10 (scatter)
alpha_1 = 1.33 +/- 0.02
k = 2.40 +/- 0.15
s = 1 fixed (stretch factor)

k is the peak luminosity in units of the SN 1998bw peak luminosity. This 
is a high value (Ferrero et al. 2006) and represents an upper limit on the 
SN flux. Assuming m_host(i') = 25, we find k = 1.24 +/- 0.14, a more 
reasonable result, indicating the contribution of a host galaxy to 
the late afterglow.

This message may be cited.

N. R. Tanvir (U. Leicester), D. A. Perley (UC Berkeley),
A. J. Levan (U. Warwick), J. S. Bloom (UC Berkeley),
A. S. Fruchter (STScI) and E. Rol (U. Leicester) report:

We obtained a further epoch of observations of GRB 080319B with
Gemini-North/GMOS on April 14 UT. These observations yielded the
following magnitudes: g=25.80+/-0.09, r=24.93+/-0.07, i=24.22+/-0.05.

Although the r-band magnitude is consistent with a continued power-law
decline in flux, the source is now clearly much redder than it was at
early times, suggesting it is likely contaminated by light from a host
galaxy and/or associated supernova.  The g-band observation, which
would be less contaminated by any SN light, indicates a steeper
decline which may be consistent with a break in the underlying
afterglow light curve (GCN 7567
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 ).

The absence of any extended emission in the previous HST observations
(GCN 7569
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 ) argues against a significant host contribution, although a very
compact host is not ruled out.

Further analysis is ongoing.

We thank Gemini staff astronomers, particularly Sandy Leggett, for
their support in obtaining these observations.

N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick),
A. S. Fruchter, J. Graham (STScI), K. Wiersema, E. Rol (U. Leicester)
report on behalf of a larger collaboration:

We obtained observations of GRB 080319B (GCN 7427
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 ) with HST/WFPC2 in
F606W and F814W filters on 2008 April 7th (2 orbits in each filter).

These data show the fading afterglow at magnitude F(814W_AB)=24.2
and F(606W_AB)=24.5.  This fading is consistent within
the errors with a continued power-law decline in optical
brightness.

PSF subtraction reveals no obvious sign of an underlying host galaxy,
although there is what appears to be a separate galaxy 1.5 arcsec to
the south, which might be producing one of the foreground absorption
systems (GCN 7451
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 ).

A colour image showing the field around the GRB is available at:

 http://www.star.le.ac.uk/~nrt3/080319b.html

Further analysis is ongoing.

J.L. Racusin (PSU), S.R. Oates (UCL-MSSL), P. Schady (UCL-MSSL), S. T.
Holland (CRESST/USRA/GSFC), D.N. Burrows (PSU), report on behalf of the
Swift XRT and UVOT teams:

We have analyzed the first 19 days of Swift XRT data from GRB 080319B
(Racusin et al. GCN 7427
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 ), with a total exposure time of 200 ks.  The
light curve can be fit by a triple broken power-law with initial decay
slope of 1.54+/-0.01, breaking at 2790+/-664 s to a slope of 1.85+/-0.05,
breaking again at 41.4+/-9.0 ks to a slope of 1.17+/-0.06, and finally
breaking at 1.04+/-0.43 Ms to a slope of 2.9+/-2.3.

If this last break is interpreted as a jet break, the jet opening
half-angle is 8 degrees x (n/10 cm^-3)^(1/8).  We obtained Eiso=1.3x10^54
ergs (25 kev - 7 MeV) from Golenetskii et al. (GCN 7482
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 ), assuming
cosmological parameters of H_0=70 km/s/Mpc, Omega_M=0.3, Omega_Lambda =
0.7.  The corresponding beaming corrected energy is 1.3 x 10^52 ergs.

The uncertanties in the post-jet break slope and time are large.
Therefore, the evidence for a break is preliminary and further
observations will be required to confirm it.

Late-time UVOT white filter observations are also suggestive of a break at
approximately the same time as the X-ray break.  However, further
observations are needed to confirm the break because the afterglow flux is
near the UVOT detection limit.

We strongly encourage additional late-time optical follow-up to further
test for achromaticity and constrain the possible jet break.

This circular is an official product of the Swift Team.

S. Karpov, G. Beskin (SAO RAS, Russia), S. Bondar (RIPI, Russia), C. Bartolini,
G. Greco, A. Guarnieri, A. Piccioni (Astronomy Department of Bologna
University, Italy), D. Nanni, F. Terra (Second University of Roma "Tor
Vergata", Italy), E. Molinari, G. Chincarini, F.M. Zerbi, S. Covino, V. Testa
(Osservatorio Astronomico di Brera, Italy), G. Tosti (Universita di Perugia,
Italy), F. Vitali, L.A. Antonelli (Osservatorio Astronomico di Roma, Italy),
P. Conconi, G.  Cutispoto (Osservatorio Astronomico di Catania, Italy),
G. Malaspina (Osservatorio Astronomico di Brera, Italy), L. Nicastro (Istituto
di Astrofisica Spaziale e Fisica Cosmica, Palermo, Italy), E. Palazzi (Istituto
di Astrofisica Spaziale e Fisica Cosmica, Bologna, Italy), E. Meurs (Dunsink
Observatory, Ireland), P.  Goldoni (APC, SAp/CEA, Paris)

report on behalf of TORTOREM team:

We performed additional analysis of Tortora data on early optical
transient of GRB 080319B (GCN 7427
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 , Racusin et al.)  reported by us in
GCN 7502
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  and found the systematic error of 6.1 s in the time zero
point. To compensate it, all data points have to be shifted 6.1 s to
earlier times. The modified light curve, also including minor
photometric adjustments, is available at

http://vo.astronet.ru/~karpov/grb080319b_lc_10_shifted.gif

We apologize for any inconvenience this may have caused.

D. A. Perley, J. S. Bloom (UC Berkeley) and H.-W. Chen (U Chicago) report:

We have continued to monitor the optical afterglow of GRB 080319B from 
Gemini-South.  Additional images were taken on UT March 21, 25, and 28. 
  Despite the presence of the Moon and low elevation of the target, the 
afterglow remains detected in all filters.  We report on photometry, 
calibrated to SDSS DR6, as follows (including an improved analysis of 
images obtained on UT March 20, previously reported in GCN 7486
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 ).

t(hr)  filt mag   err
24.808  g   20.83 0.05
25.099  r   20.53 0.02
25.363  i   20.37 0.03
25.686  z   20.32 0.04

48.653  r   21.56 0.03

144.553 g   23.59 0.15
144.886 r   23.49 0.09
145.220 i   23.13 0.06
145.553 z   23.48 0.11

216.703 r   23.56 0.06
217.036 i   23.28 0.06

The object appears visibly extended at late times, with a possible 
projection extending to the south; this may be the host galaxy of this 
gamma-ray burst.  The imaging was acquired under variable seeing 
conditions and we caution that the presence of an underlying host may 
complicate the photometry.

While roughly consistent with simple power-law decay of alpha=1.2-1.3 
(e.g. GCN 7438
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 , Li et al.), in detail the observations deviate slightly 
from a simple power-law, including a flattening in the last two sets of 
observations that may be due host galaxy light (and possibly a small 
amount of supernova contribution.)

In addition, we note the presence of a very red source at an offset of 
2.65" (slightly west of south) from the afterglow.  Preliminary 
photometry of this object gives the following:

g = 24.3  +/- 0.2  (marginal detection)
r = 23.76 +/- 0.06
i = 22.55 +/- 0.03
z = 21.71 +/- 0.03

This offset corresponds to 21 kpc at a redshift of 0.937 (Vreeswijk et 
al., GCN 7451
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 ).  It is dominated by a bright PSF-like center but also is 
visibly extended to the south.  It may be an intervening absorber.

Further follow-up is planned and encouraged.

A. Henden (AAVSO) reports:

While the field of GRB080319B has been observed by SDSS, we have also
obtained a four-night BVRcIc field calibration using the 35cm robotic
telescope at Sonoita Research Observatory.  The calibration file
has a limiting magnitude around V=16, with good standards brighter
than V=11 or so.  The file is available at
ftp://ftp.aavso.org/public/calib/grb/grb080319b.dat

This calibration is based on numerous Landolt standards, and has
an external zeropoint error of about 0.02mag. We are continuing
calibration of this field, moving to the west to pick up the
9th magnitude star SAO 64192, and will extend the calibration
file when that photometry is available.  Our system is available
for any other bright BVRI calibrations (4<V<19) for this field or any
other field; contact the author for such requests.

The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.

Yu. Krugly,  I. Slyusarev (Institute of Astronomy of Kharkiv National 
University), A. Pozanenko (IKI) report on behalf of larger collaboration:

We observed the afterglow of GRB080319B (Racusin et al. GCN 7427
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 ) with 0.7m 
telescope of Institute of Astronomy, Kharkiv National Univ. starting on (UT) 
March 19, 18:20 and continuing to March 20, 02:44. The series consist of 
continuous observations in R and a few frames were taken in V around (UT) 
19:58.

The afterglow  (Racusin et al. GCN 7427
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 , Holland et al. GCN 7428
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 , Li et al. 
GCN 7430
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 ) is detected in the obtained single images.

Preliminary photometry of combined images reveals a possible rapid decline 
of the light curve between (UT, mid time) 18:25 (R~19.1) and 19:04 (R~19.9) 
and then light curve flattering toward the end of observation March 20 (UT) 
02:00 (R~20.1). The light curve between (UT) 19:00 and 02:39 is close to a 
constant and  not compatible with power law decay index of alpha=1.2.

The magnitude of the comparison star is based on SDSS calibration (Cool et 
al, GCN 7465
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 ).
The message may be cited.

Bin-Bin Zhang (University of Nevada Las Vegas), Enwei Liang (Guangxi 
University, China) and Bing Zhang (University of Nevada Las Vegas) report:

We have processed the Swift XRT data of GRB 080319B, paying special 
attention to the possible spectral evolution in the WT mode data 
(Racusin et al. GCN 7459
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 ; cf. Butler GCN 7499
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 ). We perform a 
time-dependent spectral analysis using the method described in (Zhang, 
Liang & Zhang 2007, ApJ, 666, 1002). Since the early data are strongly 
affected by photon pile-up, we use a box annulus region for the WT mode 
data (outer radius 40*20, inner radius 8*20; see also Racusin et al. GCN 
7459
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 ) and time-dependent circle annulus regions for the PC mode data to 
extract spectra and lightcurves. We fit the time-dependent spectra using 
a simple power-law model with the absorption from the MilkyWay Galaxy 
(NH_G=1.12e20 cm^{-2} ) and from the host galaxy (NH_host=7.3e20 
cm^{-2}, obtained from fitting to the integrated 1st orbit WT mode 
spectrum). We confirm Butler (GCN 7499
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 ) that the apparent spectral 
evolution after 200 seconds is due to instrumental "pile up" effect. 
However, in the very early time t ~ (68-100) seconds, an apparent weak 
but significant hard-to-soft spectral evolution sustains even if we take 
into account the pile-up corrections. The photon index evolves from 1.67 
�� 0.02 to 1.77 �� 0.02 during this period. Our results can be found at 
http://grb.physics.unlv.edu/~xrt/xrtweb/080319B/080319B.html.

To make sure that this early-time spectral evolution is not due to the 
pile-up effect, we extract the time-dependent spectra with box annuli 
having different sizes. By excluding the central regions, we enlarge the 
outer radius up to 80 pixel * 20 pixel to make sure that there are 
enough photons for the spectral analysis. Our tests show that even if 
the inner box size is as large as 30 pixel * 20 pixel (spectra in annuli 
with such a large inner radius is not possible to be affected by the 
pile-up effect), the early time (before 200 seconds) XRT WT data still 
show significant spectral evolution. We therefore cautiously conclude 
that this early spectral evolution is likely intrinsic.

Strong hard-to-soft spectral evolution has been seen in the early steep 
decay phase of many GRB X-ray afterglows (e.g. Zhang et al. 2007, 666, 
1002), which points towards a non-forward-shock origin of the emission. 
We notice that the lightcurve before 200 seconds show several weak 
flaring/flicking features, which is more easily seen in linear scale 
(see http://grb.physics.unlv.edu/~xrt/xrtweb/080319B/earlylc.png). In 
view that some steep decay segments with overlapping flares typically 
show hard-to-soft spectral evolution (Group C in Zhang et al. 2007), we 
suspect that the weak spectral evolution in this burst is also related 
to the weak flaring/flicking features. It is however puzzling why this 
segment naturally transforms to a smooth decay after 200 seconds which 
show no further spectral evolution.

Throughout our fit we have fixed the NH_host values. Another possibitly 
is that the apparent spectral evolution is caused by a varying NH_host 
value (Racusin et al. GCN 7459
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 ). We test such a scenario by fixing the 
photon index to \Gamma=1.76 (average value after 200s) and fit the 
time-dependent spectra before 200s using the same model 
(wabs*zbwas*zwabs) but allowing NH_host to be a free parameter.  We 
obtain acceptable fits, and found that the NH_host in the early time 
evolves dramatically to one half of its initiall valve (from ~ 1.1e21 
cm^{-2} to ~ 6.6e20 cm^{-2}). The time evolution of the NH_host value 
can be found at http://grb.physics.unlv.edu/~xrt/xrtweb/080319B/nh.png. 
This is another plausible physical scenario, although a model for the 
rapid depletion of NH_host is called for.

The reduced chi2 in our fitting to the wabs*zwabs*powerlaw model is 
typically ~1. Although a possible thermal component has been suggested 
(cf. Racusin et al. GCN 7459
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 ), in our fitting no thermal component is 
required by the data.

This message can be cited.

H. Teplitz (IPAC), M. Werner (JPL), S. B. Cenko, S. R. Kulkarni and A. Rau
(Caltech) report on behalf of a larger collaboration:

We have imaged the field of GRB080319B (Racusin et al., GCN 7427
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 ) with the
blue filter (15.8 um) of the IRS peak-up camera on board the Spitzer Space
Telescope.  Observations consisted of 60 pointings, each with two dithered
30 s cycles, beginning at March 21.81 UT (~ 2.55 d after the burst).  At
the location of the optical afterglow, we measure a flux density of 35.7
+/- 3.9 uJy.

We wish to thank the entire Spitzer team for the prompt execution of these
observations.

A.J. van der Horst (NASA/ORAU) reports on behalf of a large collaboration:

"We re-observed the position of the GRB 080319B afterglow at 4.9 GHz with
the Westerbork Synthesis Radio Telescope at March 21.84 to 22.03 UT and at
March 22.84 to 23.03 UT, i.e. 2.7 and 3.7 days after the burst (GCN 7427
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 ).

We do not detect a radio source at the position of the optical counterpart
(GCN 7428
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 ) at 2.7 days. The three-sigma rms noise in the map around that
position is 108 microJy per beam. We note that this upper limit is not
consistent with the almost simultaneous VLA detection at 4.86 GHz reported
in GCN 7506
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 .
We tentatively detect a radio source at 4 sigma significance at 3.7 days,
with a flux density of 163 +/- 39 microJy.

We would like to thank the WSRT staff for scheduling and obtaining these
observations."

Alicia Soderberg (Princeton),  Poonam Chandra (U. Virginia), and Dale
Frail (NRAO) report on behalf of a larger collaboration:

"We observed the field of GRB 080319B (GCN 7427
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 ) with the Very 
Large Array beginning at Mar 21.56 UT.  At 4.86 GHz we detect a radio 
source coincident with the optical afterglow position (GCN 7428
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 ) at
coordinates (J2000):

RA =  14 31 41.01   +/-  0.05
Dec = 36 18 09.7    +/-   0.4

with flux density 189 +- 39 microJy.  Further observations are scheduled.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."

We observed GRB 080319B using 40cm Newtonian telescope, SBIG ST-7XMEi
CCD camera and R-band Kron-Cousins filter. We found afterglow to be
R=20.0+-0.3 mag at 2008.03.20 0.125 UT. Given time is mid-exposure
(total exposure: 6.7h). Weather conditions were poor because of clouds
and Moon. We used 13 nearby USNO-B1.0 stars to get R magnitude. An
aperture photometry package Munipack
(http://adsabs.harvard.edu/abs/1998stel.conf...30H) was used for data
reduction.

Rudolf Novak
Nicholas Copernicus Observatory & Planetarium in Brno, Czech Republic
(http://ccd.astronomy.cz)

Filip Hroch
Masaryk University, Brno
(http://monteboo.blogspot.com)

S. Karpov, G. Beskin (SAO RAS, Russia), S. Bondar (RIPI, Russia), C. Bartolini,
G. Greco, A. Guarnieri, A. Piccioni (Astronomy Department of Bologna
University, Italy), D. Nanni, F. Terra (Second University of Roma "Tor
Vergata", Italy), E. Molinari, G. Chincarini, F.M. Zerbi, S. Covino, V. Testa
(Osservatorio Astronomico di Brera, Italy), G. Tosti (Universita di Perugia,
Italy), F. Vitali, L.A. Antonelli (Osservatorio Astronomico di Roma, Italy),
P. Conconi, G.  Cutispoto (Osservatorio Astronomico di Catania, Italy),
G. Malaspina (Osservatorio Astronomico di Brera, Italy), L. Nicastro (Istituto
di Astrofisica Spaziale e Fisica Cosmica, Palermo, Italy), E. Palazzi (Istituto
di Astrofisica Spaziale e Fisica Cosmica, Bologna, Italy), E. Meurs (Dunsink
Observatory, Ireland), P.  Goldoni (Observatori Astronomic - Universitat de
Valencia Edificio de Institutos de Investigacion, Spain)

report on behalf of TORTOREM team:

Following GCN 7452
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  we publish a preliminary light curve of GRB 080319b with
reduced temporal resolution (10 frames time binning, 1.3 seconds effective
exposure, no gaps between frames). The photometry is performed in instrumental
system and calibrated towards the V magnitudes of nearby Tycho2 stars. The
light curve is available online at

http://vo.astronet.ru/~karpov/grb080319b_lc_10.gif

The light curve shows fast (~5 seconds) uprise towards the peak V=5.5 at T+23,
complex multi-peak structure till T+50 and featureless decay then. In total,
the transient has been visible for ~65 seconds; 6 seconds in the T+30 - T+36
interval are currently excluded from the analysis due to repointing of REM
telescope at that time.

The light curve is consistent with the one published by Pi of the Sky (Cwiok et
al, GCN 7445
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 ).

The video sequence of the data is available at

http://vo.astronet.ru/~karpov/grb080319b.avi

and with reduced temporal resolution at

http://vo.astronet.ru/~karpov/grb080319b_lowres.avi

The results of analysis of full-resolution (0.13s exposure) data will be
published later.

G. Greco (Bologna University), F. Terra (Second University of
Roma "Tor Vergata"), C. Bartolini, A. Guarnieri, A. Piccioni
(Bologna University), F. Munz, G. Pizzichini (INAF/IASF Bologna),
D. Nanni (INAF/OAR and Second University of Rome "Tor Vergata"),
A. Shearer (Centre for Astronomy, Galway), R. Gualandi 
(Bologna Observatory) report:

We observed the field of GRB 080319B (GCN 7427
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 , Racusin et al.)  
with the 152 cm telescope located in Loiano under unfavorable
conditions due to the illumination of the full moon. 

By adding four consecutive 10 min exposures in the Rc filter at 
mean time 2008 March 20.947 UT we do not detect any object at
the position of the optical bright afterglow reported by 
Racusin et al. (GCN 7428
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 ).

Our 3-sigma limiting magnitude is R~20.3 (based on Nomad1 catalogue).

The image has been posted in our public directory 
from where it can be retrieved 
by sftp using 
hostname: ermione.bo.astro.it
username: publicGRB
password: GRB_bo.
directory: GRB080319B

Nat Butler (UC Berkeley) reports:

I have applied our time-dependent pileup correction code (Butler &
Kocevski 2007; ApJ, 663, 407) to the XRT spectrum of GRB080319B (see, Racusin
et al., GCN 7459
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 ).  Although I find similar temporal properties in the     
afterglow decay to those quoted by the XRT team, I find significantly
different spectral properties.  Notably, there is no significant evidence
for a time-variation in N_H and no significant need for a thermal component.
The WT model (0.4-10 keV) and PC mode (0.3-10 keV) spectra fitted jointly
and well (chi^2/nu=799.70/788) with an absorbed powerlaw yields:

Gamma = 1.84+/-0.01
N_H = 1.7+/-0.1 x 10^21 cm^(-2) @ z=0.937 (Vreeswijk et al., GCN 7451
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 ), in 
  addition to the expected Galaxy contribution along the line of sight.  Here 
  we assume the solar chemical abundances from Anders & Ebihara (1982).
  This value of N_H implies ~2 mag extinction in the observer frame V band
  assuming the mean Galactic dust+gas properties.

Allowing the photon indices to vary separately: Gamma1=1.84^{+0.1}_{-0.2} and 
Gamma2=1.85+/-0.05, closely consistent.  The fractional possible increase in 
rest-frame N_H between the WT mode data (t=660s to 4.95 ksec) and the PC mode 
data (t=4.95 to 174 ksec) is modest and weakly significant: 
0.74^{+0.43}_{-0.37}%.  I suspect the indicated variations are purely due to 
calibration uncertainties in the WT mode data.  The hard WT mode spectral fit 
in GCN 7459
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  can be reproduced by relaxing our pileup correction.

Additional evidence disfavors an interpretation of an evolving X-ray
spectrum:

Time resolved fits to the WT mode data show no significant evidence for
spectral evolution in the WT mode data considered alone. See,
http://astro.berkeley.edu/~nat/080319B_spec.jpg

The light curve is a simple (broken) powerlaw for the WT mode data, with
no flaring.  Afterglows with such light curves typically exhibit weak
or no spectral evolution (e.g., Butler & Kocevski 2007, ApJ, 668, 400).
There is no significant variations in the X-ray hardness ratio for this event.
See, http://astro.berkeley.edu/~nat/080319B_hardness.jpg

A fit to BAT data (see also, Cummings et al., GCN 7462
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 ) in a time     
region (58s to 303s; chi^2/nu=36.46/55) overlapping the XRT observation has
a roughly consistent powerlaw (Gamma=2.1+/-0.1), and also allows for a
smooth extrapolation in flux between BAT and XRT assuming a simple powerlaw
model connecting the flux in both instruments.

This message can be cited.

S. T. Holland (CRESST/USRA/GSFC) & J. L. Racusin (PSU) report on
behalf of the Swift/UVOT team:

      The Swift/UVOT observed the field of GRB 080319B starting 51 s
after the BAT trigger (Racusin et al., GCN Circ. 7427
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 ).  We detect the
optical afterglow all filters.  Preliminary magnitudes are reported
below.

Filter    T_start (s) T_stop  Exposure      Mag  Err  Comment
    v          175        575      393    <11.5        Saturated
    b          654        664       10     13.39 0.01
    u          630        649       19     12.44 0.01
   uvw1        605        625       19     12.49 0.02
   uvm2        581        600       19     13.39 0.05
   uvw2        685        705       19     13.36 0.04
  white         67        169       98    <13.9        Saturated

The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E_{B-V} = 0 .01 mag (Schlegel et al.,
1998, ApJS, 500, 525).  The photometry is on the UVOT flight system
described in Poole et al. (2008, MNRAS, 383,627).

D. C.-J. Bock (CARMA), P. C. Chandra (NRAO/UVA), S. R. Kulkarni (Caltech),
D. A. Frail (NRAO), and S. B. Cenko (Caltech) report on behalf of a
larger collaboration:

We have observed the position of GRB080319B (Racusin et al.; GCN 7247
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 )
with the Combined Array for Research in Millimeter-wave Astronomy (CARMA)
at 95 GHz on 2008 March 20 (mean time 11:30 UT). We report a non-detection
at the optical afterlow position with a 3-sigma limit of 0.75 mJy.

D. A. Perley, J. S. Bloom (UC Berkeley) and H.-W. Chen (U Chicago) report:

On the night of 2008-03-20 (UT) we observed the optical afterglow of GRB 
080319B (GCN 7427
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 , Racusin et al.) with Gemini-South + GMOS in g, r, i, 
and z filters (4x180s in each filter).  The source is well-detected in 
all bands.  Magnitudes, calibrated to SDSS DR6, are:

UTstart  UTend    t(hr)  filt mag   err
06:52:17 07:10:19 24.808  g   20.95 0.09
07:11:19 07:26:11 25.099  r   20.55 0.03
07:27:10 07:42:04 25.363  i   20.40 0.05
07:43:04 07:57:55 25.686  z   20.32 0.03

We thank the observing staff for performing these observations.

Garrett Keating, Geoffrey Bower, Rick Forster, and J. S. Bloom (UC  
Berkeley) report for the Allen Telescope Array team:

"The Allen Telescope Array observed GRB 080319B (Racusin et al.; GCN  
7247
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 ) at a frequency of 1.43 GHz.  Observations were obtained on 20  
March 2008 between 5 and 7 UT. From this initial dataset, we report a  
non-detection at the location of afterglow with a 3 sigma upper limit  
of 18 mJy.  Observations are continuing."

This message may be cited.

Veli-Pekka Hentunen (Varkaus, Finland), Arto Oksanen (Muurame, Finland),
and Petri Kehusmaa (Hyvinkaa, Finland) report to the AAVSO High Energy
Network the following optical detections and upper limits of GRB 080319B
(Racusin et al., GCN Circular #7427
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 ):

Veli-Pekka Hentunen and Markku Nissinen (Taurus Hill Obs., Varkaus,
Finland) report the detection of the optical afterglow of GRB 080319B
(Racusin et al., GCN Circular #7427
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 ).  The afterglow was observed
unfiltered for a total of 1500 seconds using an SBIG ST8-XME CCD mounted
on a Meade LX200 0.3-m telescope.  Observations commenced approximately
15.3 hours post-burst; the mid-point of the observations was 2008 March
19.8999 UT. The afterglow was clearly detected at an unfiltered
magnitude of 19.08 +/- 0.02, calibrated relative to USNO-A2.0
1200-07324239.

A detailed report of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/Veli-PekkaHentunen_080319B_2454545.53358_.txt

A FITS image of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/Veli-PekkaHentunen_080319B_2454545.53358_.fits


Petri Kehusmaa (Slope Rock Observatory, Hyvinkaa, Finland) reports a
non-detection of the optical afterglow of GRB 080319B.  The afterglow
was observed through a V filter for a total of 1800 seconds using an
SBIG ST-7XME CCD mounted on a 0.2-m telescope.  Observations commenced
approximately 17 hours post-burst; the mid-point of the observations was
2008 March 19.9675 UT.  The afterglow was not detected in the V-band
with an upper limit of R=17.6 (calibrated relative to USNO-A2.0).

A detailed report of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/PetriKehusmaa_GRB080319B_2454545.93778_.txt

A FITS image of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/PetriKehusmaa_GRB080319B_2454545.93778_.fits

Arto Oksanen and Olli-Pekka Reimaala (Hankasalmi Obs., Hankasalmi,
Finland) also report the detection of the optical afterglow of GRB
080319B.  The afterglow was observed unfiltered for a total of 2040
seconds (17 x 120s) using an SBIG STL-1001E CCD mounted on an RC Optical
Systems 0.4-m telescope. Observations commenced approximately 19.3 hours
post-burst; the mid-point of the observations was 2008 March 20.0639 UT.
The afterglow was clearly detected at an unfiltered (CR) magnitude 19.0
+/- 0.1, calibrated relative to USNO-A2.0. Note that this magnitude uses
a different comparison star from that of Hentunen and Nissinen (see
above), and may be offset by a few tenths of a magnitude.

A detailed report of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/ArtoOksanen_GRB080319B_2454545.72325_.txt

A FITS image of this observation is available at the following URL:
ftp://ftp.aavso.org/grb/ArtoOksanen_GRB080319B_2454545.72325_.fits

The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.

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 080319B (Swift-BAT trigger #306757: Racusin et al., GCN 
7427
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 , Cummings et al., GCN 7462
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 ) triggered
Konus-Wind at T0=22370.339 s UT (06:12:50.339).

The burst light curve shows a single complex pulse
with a duration of ~60 s, followed by a long decaying tail
seen up to T-T0 ~200 s in the G1(18-70 keV) and G2(70-300 keV) bands
and even beyond in the G1 band.

Preliminary analysis of the Konus-Wind data
yields the burst fluence of 5.72(-0.13, +0.14)x10^-4 erg/cm2,
and a 64-ms peak flux measured from T0+19.2 s
of (2.17 +/- 0.21)x10^-5 erg/cm2/s
(both in the 20 keV - 7 MeV energy range).

The time-integrated spectrum of the main pulse
(from T0 to T0+59.648 s) can be fitted
(in the 25 keV - 7 MeV range)
by GRBM (Band) model for which:
the low-energy photon index is alpha = -0.822(-0.012, +0.014),
the high energy photon index beta = -3.87(-1.09, +0.44),
the peak energy Ep = 651 (-14, +13) keV (chi2 = 96.2/81 dof).

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

Assuming z = 0.937 (Vreeswijk et al., GCN 7444
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 , 7451
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 ) and a standard
cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda =
0.7, the isotropic energy release is E_iso ~1.32x10^54 erg,
the maximum luminosity is (L_iso)_max ~9.67x10^52 erg/s, and
Ep_rest ~1261 keV.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB080319_T22370/

A.J. van der Horst (NASA/ORAU) reports on behalf of a large collaboration:

"We observed the position of the GRB 080319B afterglow at 4.9 GHz with the
Westerbork Synthesis Radio Telescope at March 19 20.24 UT to March 20
8.22 UT, i.e. 14.0 - 26.0 hours after the burst (GCN 7427
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 ).
We do not detect a radio source at the position of the optical counterpart
(GCN 7428
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 ). The three-sigma rms noise in the map around that position is
84 microJy per beam. The formal flux measurement for a point source at the
position of the optical counterpart is 59 +/- 26 microJy.

We would like to thank the WSRT staff for rapidly scheduling and obtaining
these observations."

Martin Jelinek, Alberto J. Castro-Tirado (IAA-CSIC Granada),
Virginie Chantry (Universit� de Liege) and
Jorge Pl� (IAC La Laguna), on behalf of a larger collaboration,

report:

"We were imaging the naked eye GRB 080319B detected by Swift
(GCN 7427
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 ) using.both the 1.2m Mercator Telescope at Obs. del
Roque de los Muchachos in La Palma, and the 0.8m IAC80 at
Obs. del Teide in Tenerife.

Between two epochs of imaging, one started at 22:56 (~16.75hr
after the GRB), the other at 3:27UT (20h after) we measure an
aproximate decay index of ~1.3. Our R-band magnitude measured
on an image starting at 22:56UT (16.75 hr after the burst) was
about R=19.8. The value reported in the previous GCN 7469
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  has
been incorrect."

This message can be cited.

Y. Urata, K.Y. Huang, C.Y. Shih, T.W. Chen, M. Im, I. Lee,
on behalf of EAFON report:

"We have monitored the GRB 080319B optical afterglow using Lulin 1-m
telescope with B, V, R, I and z' bands from 16:18 to 21:19 (UT).
Comparing with former observations made by the LOAO (Urata et al. GCN
7435
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 ), the R and I band light curves show an apparent temporal break
again at ~0.2 days after the burst. The decay index of the post-break
is ~-0.8."

This message may be cited.

H. Swan (U Mich), F. Yuan (U Mich), W. Rujopakarn (Steward)

ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB  
080319B (Swift trigger 306757; Racusin et al., GCN 7427
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 ) and began  
imaging at 06:13:11.06 UT  (5.3 sec after the GCN notice time) under  
suboptimal conditions, because of condensation present on the CCD.  
Observations continued until about 5 hours after the trigger.  This  
condensation made the analysis very difficult, but we detect the OT  
first reported in GCN 7428
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 .  Further analysis is ongoing.  These  
unfiltered images are calibrated to the USNO B1.0 R2 catalog.

start UT          end UT          mag        mlim(of image)
06:13:11.06   06:13:16.06    5.35        9.8
06:14:30.66   06:14:50.66    8.49        13.0

Martin Jelinek, Alberto J. Castro-Tirado (IAA-CSIC Granada),
Virginie Chantry (Universit� de Liege) and
Jorge Pl� (IAC La Laguna), on behalf of a larger collaboration,

report:

"We are imaging the naked eye GRB 080319B detected by Swift
(GCN 7427
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 ) using.both the 1.2m Mercator Telescope at Obs. del
Roque de los Muchachos in La Palma, and the 0.8m IAC80 at
Obs. del Teide in Tenerife. Our R-band magnitude measured on
an image starting at 22:56UT (16.75 hr after the burst) is
about R=21.0. Further images are planned throughout the whole
night."

This message can be cited.

-- 
Martin Jelinek, +420602105255, +34617840945, sirrah.cz/mates
       Instituto de Astrofisica de Andalucia, Granada

# vim:set ai et sts=8 tw=60:

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
GRB080319B 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/GRB080319B

We supply FITS images in each of the 5 SDSS bands of a 8'x8'
region centered on the GRB position (ra=217.920 (14:31:40.7),
dec=36.3041 (36:18:14.8); GCN 7427
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 ), 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 GRB080319B_sdss.calstar.dat, we report photometry
and astrometry of 193 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 GRB080319B_sdss.objects_flux.dat and
GRB080319B_sdss.objects_magnitudes.dat, we report photometry
of 705 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 GRB080319B_sdss.objects_flux.dat are in nanomaggies while
the magnitudes listed in GRB080319B_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=0.059 mag, A_g=0.043 mag,
A_r = 0.031 mag, A_i=0.024 mag, and A_z=0.017 mag.

The file GRB080319B_sdss.spectro.dat contains a list of the
3 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, PASP 118, 733).  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. (2007, ApJS, 172, 634),
when using the data or referring to the technical documentation.

P. Wozniak, W.T. Vestrand, J. Wren, and H. Davis
(Los Alamos National Laboratory)

The RAPTOR sky monitoring system began observing the location
of GRB 080319B more than an hour before the Swift BAT trigger
306757 (Racusin et al., GCN 7427
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 ). The first exposure with detectable
optical emission started ~2 seconds after the trigger at 06:12:50.9 UT.
A peak brightness of 5.6 mag was recorded in time interval from
06:13:21.2 to 06:13:31.2 UT, before the end of the gamma-ray emission.
Using the redshift z=0.937 from Vreeswijk et al. (GCN 7444
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 ) the
estimated luminosity of GRB 080319B exceeds that of GRB 990123.

Our response arrays RAPTOR-P and T began imaging at 06:14:24.3 UT
following the XRT localization trigger that interrupted the ongoing
follow-up measurements of GRB 080319A. The OT is detected by both
response instruments including all channels (V,R,I,clear) of the
simultaneous multicolor imager RAPTOR-T.

J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), E. Fenimore (LANL),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-120 to T+182 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 080319B (trigger #306757)
(Racusin, et al., GCN Circ. 7427
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 ).  The BAT ground-calculated position is
RA, Dec = 217.919, 36.300 deg which is 
   RA(J2000)  =  14h 31m 40.7s 
   Dec(J2000) = +36d 17' 58.4" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows a large long bump of a peak
starting at ~T-10 sec, ramping up until ~T+10 sec, then mostly a flat top
with some small structure superposed, then starting to decay at ~T+50 sec.
It returns nearly to background by ~T+64 sec at which point there is
a loss of data due to an on-board data product buffer overflow.
The data resumes at T+120 sec.  There is still detectable emission
in the BAT 15-350 keV band out to T+180 sec (the limit of the data
downlinked so far).  From other count rate data products, we can say
that there is no other peaks during the 60-sec missing event data window
and that the low-level emission is about 10-15% of the peak emission.
Given the missing data, T90 (15-350 keV) has to be >50 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-3.8 to T+62.2 and T+120 to T+151 sec
is fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.04 +- 0.02.  The fluence
in the 15-150 keV band is 8.1 +- 0.1 x 10^-05 erg/cm2.
The 1-sec peak photon flux measured from T+16.87 sec in the 15-150 keV band
is 24.8 +- 0.5 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/306757/BA/

Due to a large backlog in downlinking the full data on this burst,
we currently do not have the usual data set out to long times yet.
Should the remaining data show that there is ongoing activity 
for this burst past the data cutoff at T+182sec, then we will
issue an updated 'refined analysis' circular.

M. Schubel, D. Reichart, M. Nysewander, A. LaCluyze, K. Ivarsen, J. A. 
Crain, A. Foster, T. Brennan, J. Haislip, J. Styblova, and A. Trotter report:

Skynet observed the localization of GRB 080319B (Racusin et al., GCN 7427
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 ) 
with three of the 16" PROMPT telescopes at CTIO beginning 32 seconds after 
the trigger (15 seconds after notification) in UVRI.

We detect the afterglow (Racusin et al., GCN 7428
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 ) in all filters.  At 92 
seconds after the burst we measure V ~ 8.6 mag (calibrated to 3 NOMAD 
stars), and at 147 seconds we measure I ~ 8.9 mag (calibrated to 6 USNO B1 
stars).

J. Racusin (PSU), D. N. Burrows (PSU), P. A. Evans (U Leicester), C.
Pagani (PSU), report on behalf of the Swift-XRT Team:

We have analysed the first four orbits of Swift-XRT data obtained for GRB
080319B (Racusin et al. GCN Circ. 7427
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 ), totaling 1.1 ks of Windowed
Timing (WT) data beginning 64 s after the BAT trigger, and 4 ks of Photon
Counting (PC) data beginning 5 ks after the BAT trigger.

The UVOT-enhanced XRT position has been given by Evans et al. in GCN Circ
7449
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 .

The bright X-ray light-curve can be fit by a broken power-law, with an
initial decay index of 1.46 +/- 0.01 followed, after a break at 6100 +/-
440 seconds, by a steeper decay index of 2.48 +/- 0.10.

Both the WT and PC spectra are strongly affected by photon pile-up, which
can alter the spectral fits.  To eliminate these effects, we exclude the
central 8 pixel radius region of the WT data, and the central 3 pixel
radius region of the PC data when creating the spectra.  Preliminary fits
to the WT spectrum (64-4943 seconds), modeled with an absorbed power-law,
result in a photon index of 1.65 +/- 0.02 and an absorbing column at
z=0.937 (Vreeswijk et al., GCN Circ. 7444
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 ) of NH = (5.28 +/- 1.03)e20
cm^-2, in addition to Galactic absorption of 1.12e20 cm^-2 in the
direction of the burst, with a reduced Chi^2=1.05.  The PC spectrum (5-19
ks) can be modeled as an absorbed power-law, with photon index of 1.92 +/-
0.07 and an absorbing column at z=0.937 of NH = (23.5 +/- 5.6)e20 cm^-2,
in addition to the Galactic absorption, with a reduced Chi^2=1.06.  If we
freeze the NH in the PC model to the WT fitted value, we fit a photon
index of 1.73 +/ 0.04, with a reduced Chi^2=1.4, which excludes this model
as a viable fit.  As another attempt to model the spectra without NH
evolution, we freeze the WT NH to the value from the PC spectral fits and
add an additional low energy thermal component.  The resulting fits yield
a photon index of 1.73 +/- 0.02, kT=0.06 +/- 0.01 keV, and a reduced
Chi^2=1.07.  Therefore, the extra thermal component is a possible
explanation for the apparent spectral evolution.

Assuming the source continues to decay with the same decay index of 2.5,
we predict an XRT count rate of 8.8e-4 counts/s at T+24 hours, which
corresponds to an 0.3-10.0 keV observed (unabsorbed) flux of 6.1e-14
(6.2e-14) ergs cm^-2 s^-1.

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

A. Cucchiara & D. B. Fox (PSU) report on behalf of a larger
collaboration:

"Starting on 2008 March 18.49 UT we used the Marcario LRS spectrograph
on the Hobby-Eberly Telescope (R ~ 230 ) to obtain one 1200s spectra
of the optical afterglow (Holland et al., GCN 7428
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 ) of GRB 080319B
(Racusin et al., GCN 7427
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 ).  The spectrum covers the wavelength range
4100 to 10,500 Angstrom.  We observe multiple metal absorption
features including the MgII doublet (2796, 2803 A) and MgI (2852 A) at
z ~ 0.937. We also detect lines at z ~ 0.760 (MnII 2576, MnII 2594 and
CaI 4227), z ~ 0.715 (MgII doublet) and z ~ 0.530 (NaI 5890,5896).
Our observations are consistent with the redshift and features
reported by Vreeswijk et al. (GCN 7444
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 , 7451
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 )."

[GCN OPS NOTE(19mar08): Per author's request, the date in the Subject-line
was changed from "080519B" to "080319B".  And the date in the first line
was changd from "18.49" to 19.49".]

S. Karpov, G. Beskin, S. Bondar, C. Bartolini, G. Greco, A. Guarnieri,
D. Nanni, A. Piccioni, F. Terra, E. Molinari, G. Chincarini, F.M. Zerbi,
S. Covino, V. Testa, G. Tosti, F. Vitali, L.A. Antonelli, P. Conconi, G.
Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P.  Goldoni

report on behalf of the TORTOREM team:

TORTORA wide-field optical camera (12 cm diameter, 20x25 deg FOV, TV-CCD,
unfiltered) mounted on REM robotic 60-cm telescope located at La Silla
(Chile) observed the field of GRB 080319B (GCN 7427
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 , Racusin et al.)
before, during and after the gamma-emission with 0.13 s time resolution.

We observe optical emission at the position given by Swift XRT:

1. We did not detect any transient  brighter than 8.5m (unfiltered,
near B) at T-100 - T+16 s 

2. We detect rapidly rising OT (~5 second rise front) and observe it
between T+16 and T+30, the peak brightness has been around 5 m

3. Between T+30 and T+36 the observations have been paused due to
repointing of REM telescope

4. Since T+36 we continuously observe the transient until it faded below
the detection limit (~8.5m) at T+90 s

The detailed analysis is in progress.

This message may be cited.

P.M. Vreeswijk, Bo Milvang-Jensen (DARK), A. Smette (ESO),
D. Malesani, J.P.U. Fynbo (DARK), P. Jakobsson (U. Hertfordshire),
A.O. Jaunsen (U. Oslo) and C. Ledoux (ESO) report on behalf of a
larger collaboration:

Besides the absorption systems at z=0.937 and z=0.530 reported in GCN
7444
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 , we also note the presence of two other systems at z=0.715 and
z=0.760 along the sightline toward GRB 080319B. The rest-frame
equivalent width of MgII 2796 for both the z=0.937 and z=0.715 systems
is large: greater than 1A.  Finally, we detect several transitions
from FeII fine-structure levels from the z=0.937 system. Assuming that
the GRB afterglow is responsible for the FeII excitation (see
Prochaska et al. 2006, ApJ, 648, 95; Vreeswijk et al. 2007, A&A, 468,
83), this confirms the z=0.937 system to be the host of GRB 080319B.

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

Using 1859 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080319B, 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 = 217.92113, +36.30269 which is equivalent
to:

RA (J2000): 14h 31m 41.07s
Dec (J2000): +36d 18' 09.7"

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).

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

S. Covino, P. D'Avanzo, D. Fugazza, L.A. Antonelli, L.  Calzoletti,  
S. Campana, G.  Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F.  
D'Alessio, F.  Fiore, P. Goldoni, D. Guetta,  C. Guidorzi, G.L.  
Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro,  
E. Palazzi, E. Pian, S. Piranomonte, L.  Stella, G.  Stratta, G.  
Tagliaferri, G. Tosti, V.Testa, S.D. Vergani,  F. Vitali report on  
behalf of the REM team:


We started a refined analysis of the REM observations of GRB 080319B  
(GCN 7427
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 , Racusin et al.). As already reported by Cwiok et al. (GCN  
7439
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  and 7445
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 ) the optical counterpart of this GRB was exceptionally  
bright at early time. We measured, about 1 min after the burst, R~6.4  
assuming R=11.20 for the USNO star at coordinates RA,DEC =  
14:31:23.61, 36:21:56.5. The source was already almost 2 mag fainter  
half a minute later. In the H band the source was H~5 around the same  
epoch.

Further analyses are in progress.

M.Cwiok, W.Dominik, G.Kasprowicz, A.Majcher, A.Majczyna,
K.Malek, L.Mankiewicz, M.Molak, K.Nawrocki, L.W.Piotrowski,
D.Rybka, M.Sokolowski, J.Uzycki, G.Wrochna, A.F.Zarnecki
on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl

Following GCN 7439
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  we give the preliminary light curve of GRB 080319b
(IR-cut filter only):

  start  - end       frame    magnitudo
6:12:33 - 6:12:43    <=96    limit >11.48
6:12:47 - 6:12:57     97     9.83
6:13:01 - 6:13:11     98     5.76
6:13:16 - 6:13:26     99     6.00
6:14:03 - 6:14:13    100     8.26
6:14:17 - 6:14:27    101     8.77
6:14:32 - 6:14:42    102     9.10
6:14:46 - 6:14:56    103    10.27
6:15:27 - 6:14:37    104    10.50
6:15:41 - 6:14:51    105    11.10
6:15:56 - 6:16:06    106    11.21
6:16:40 - 6:16:50    107    11.79
6:16:54 - 6:17:04    108    11.95

More information will be published at http://grb.fuw.edu.pl

P.M. Vreeswijk (DARK), A. Smette (ESO), D. Malesani, J.P.U. Fynbo, Bo
Milvang-Jensen (DARK), P. Jakobsson (U. Hertfordshire), A.O. Jaunsen
(U. Oslo) and C. Ledoux (ESO) report on behalf of a larger
collaboration:

We observed the optical afterglow of GRB 080319B (Racusin et al., GCN
7427
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 ) with the Ultraviolet and Visual Echelle Spectrograph (UVES)
mounted at ESO's VLT Kueyen. Observations were performed in
rapid-response mode starting on 2008 March 19 at 07:18 UT.

The highest redshift system that we identify based on the MgII doublet
and various other features has z=0.937, the presumed redshift of GRB
080319B. Another system is identified at z=0.530.

We acknowledge excellent support from the observing staff at Paranal,
in particular Swetlana Hubrig and Elena Mason.

M.Cwiok, W.Dominik, G.Kasprowicz, A.Majcher, A.Majczyna,
K.Malek, L.Mankiewicz, M.Molak, K.Nawrocki, L.W.Piotrowski,
D.Rybka, M.Sokolowski, J.Uzycki, G.Wrochna, A.F.Zarnecki
on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl

"Pi of the Sky" apparatus located at Las Campanas Observatory
imaged the region of GRB 080319b (Swift triger 306757 at 06:12:49 UT)
before, during and after the GRB with 10s exposures (IR-cut filter only).
We observe optical emission at the position given by Swift XRT.
   start -   end     comment
6:12:33 - 6:12:43   not visible (>12 mag)
6:12:47 - 6:12:57   visible (~10 mag)
6:13:01 - 6:13:11   max. brightness (~6 mag)

Full light curve fill be published later.

W. Li, R. Chornock, D. A. Perley, and A. V. Filippenko, University of
California at Berkeley, on behalf of the KAIT GRB team:

We have analyzed the KAIT data on GRB 080319B (GCN 7472
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 , 7428
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 ) as reported
in GCN 7430
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 . Preliminary reduction of the unfiltered data, calibrated to
SDSS observations of the field, shows a smooth light curve from t = 20 to
120 minutes after the BAT trigger, with an apparent change in power-law
decay index at t ~ 35 minutes. The power-law decay index is measured to be
-1.89 +/- 0.04 between t = 20.1 to 26.3 minutes after the BAT trigger, and
-1.23 +/- 0.02 between t=60.9 to 117.2 minutes after the BAT trigger.
The shallower decay is also observed at t ~ 80 minutes as noted in GCN 7435
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 .
We note this change in power-law decay index is reminiscent of what has
been observed in GRB 990123 (e.g. Akerlof et al. 1999, Nature 398, 400) and
GRB 021211 (e.g. Li et al. 2003, ApJ 586, L9), and suggests a transition from
reverse shock to forward shock emission.

Selected KAIT unfiltered photometry, all unfiltered data calibrated to
the R band via the SDSS calibration:

t(start; seconds after BAT trigger)  exp    mag   merr

       1207                         20.0   14.110 0.008 
       1394                         20.0   14.417 0.011
       1576                         20.0   14.645 0.011
       1991                         20.0   15.063 0.011
       2912                         20.0   15.710 0.014
       3770                         20.0   16.053 0.015
       4380                         20.0   16.247 0.014
       5005                         20.0   16.415 0.019
       6820                         20.0   16.843 0.017

R. J. Foley, D. Perley, and J. S. Bloom (UCB) on behalf of the GRAASP
collaboration report:

We obtained 2x1800 sec exposures of the optical afterglow (GCN 7428
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 , 7430
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 )
of GRB 080319B (GCN 7427
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 ) using GMOS on the Gemini-South telescope with
the R831 grating.  The observations started at 20080319.35 (~2 hours after
the initial Swift trigger).  Initial reductions show a featureless
continuum with no strong absorption systems, emission lines, or breaks.
Given our wavelength range of 595 - 815 nm, we can place the following
constraints on the redshift (in order of descending confidence):

(1) The lack of a Lyman limit implies z < 5.5.
(2) The lack of damped Lya or obvious Lya forest implies z < 3.9.
(3) The lack of obvious Mg II absorption implies z < 1.1.

Further analysis is in progress.

J. S. Bloom, D. Starr, and D. A. Perley (UC Berkeley) report:

We began observations of GRB080319b with PAIRITEL at 2008-03-19   
06:14:51 UT and will continue for several hours until sunrise. The  
source is exceedingly bright in the first few minutes, visible on  
individual 7.8 sec exposures in JHKs bands. Preliminary photometry,  
which may be affected to non-linearities at these bright flux levels,  
is given below.

# t (MJD)       terr (day)      filt     mag     merr
#####################################

54544.262141    0.000454        k       8.613900         
0.033214        0       0
54544.261788    0.000454        j       9.110600         
0.041347        0       0

A comparison with 2MASS may be found at:
    http://lyra.berkeley.edu/~jbloom/grb080319b.png

This message may be cited.

R.J. Smith (Liverpool JMU), A. Gomboc (U. Ljubljana), N. Tanvir (Leicester) A. 
Melandri, C.G. Mundell, I.A. Steele, S. Kobayashi, D. Bersier (Liverpool JMU) 
report:

The 2-m Liverpool Telescope (La Palma) observed the position of
GRB 080319B (SWIFT trigger 306757) starting 30 min after the GRB trigger
time. We detect an optical afterglow candidate in r' filter at
14:31:41 +36:18:09 J2000 consistent with the uncatalogued source
visible in the UVOT data.

Filter    t_mid (min from GRB)    Tot_Exp (s)       R
--------------------------------------------------------------
   r'           30.64                 120           14.9
   r'           32.83                 120           15.1
   r'           35.02                 120           15.2
  -------------------------------------------------------------

Observations were performed in SDSS r' filter and
magnitudes calibrated vs R2 USNO-B1 magnitudes for a few selected stars.

No further observations were possible due to approaching twilight.

P. A. Milne (Steward Observatory) and G. G. Williams (MMTO), on behalf
of the Super-LOTIS Collaboration, report:

The robotic 0.6-m Super-LOTIS telescope began observing the error box
of GRB 080319B (Swift Trigger 306757, Racusin et al. GCN 7427
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 ) at
06:27:00.3 UT, 851 seconds after the trigger.  We identify a bright
source consistent within the UVOT candidate.

Using the USNO-B1.0 star (1263-0223138) at RA=14:31:39.66,
Dec=+36:18:54.5 with R2MAG=14.98 as a reference, we estimate the
following R-band magnitude for the transient:

t_start (UT)	exp t (s)	t_start-t_0 (s)	R Mag
----------------------------------------------------------------
06:27:00.3	60 		851 		R = 13.52 +/- 0.01

Additional observations and analysis are ongoing.

S. Covino, P. D'Avanzo, D. Fugazza, L.A. Antonelli, L.  Calzoletti,   
S. Campana, G.  Chincarini, M.L. Conciatore, S. Cutini, V. D'Elia, F.
D'Alessio, F.  Fiore, P. Goldoni, D. Guetta,  C. Guidorzi, G.L.   
Israel, E. Maiorano, N. Masetti, A. Melandri, E. Meurs, L. Nicastro,
E. Palazzi, E. Pian, S. Piranomonte, L.  Stella, G.  Stratta, G.  
Tagliaferri, G. Tosti, V.Testa, S.D. Vergani,  F. Vitali report on  
behalf of the REM
team:

The robotic 60-cm REM telescope located at La Silla (Chile) observed  
automatically the field of the GRB 080319B  on March 19 06:13:32 UT  
(about 43 seconds after the burst).

We clearly detect the afterglow reported in GCN 7427
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 , 7428
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 , 7430
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(Racusin et
al.; Holland et al.; Li et al.).

The object was still at H~12.5 at about 22 min from the burst time.

Further analyses and observations are in progress.

W. Li, J. S. Bloom, R. Chornock, R. Foley, D. A. Perley, and A. V. Filippenko,
University of California at Berkeley, on behalf of the KAIT GRB team, report:

KAIT responded to GRB 080319B (Swift trigger 306757) and was taking 
images. There is a bright afterglow at position

RA = 14:31:40.97
DEC = +36:18:07.9
(equinox J2000)

The measured magnitude is R = 15.4 at 06:49:07 UT.

This message can be cited.

S. T. Holland (CRESST/USRA/GSFC) and J. L. Racusin (PSU) reports on  
behalf of the Swift/UVOT team:

     The UVOT position of GRB 080319B (Racusin et al. 2008 GCN Circ.  
7427
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 ) is

RA(J2000.0) =  14:31:40.98
Dec(J2000.0) = +36:18:08.8

with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).

Please update my e-mail address in your Address Book to <Stephen.T.Holland@nasa.gov 
 >.

NOMAD: You had mail.
/
\
/

J. L. Racusin (PSU), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), C. Pagani (PSU),
D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU) report on behalf of
the Swift Team:

At 06:12:49 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080319B (trigger=306757).  Swift slewed immediately to
the burst. The BAT on-board calculated location is 
RA, Dec 217.926, +36.303 which is
   RA(J2000) = 14h 31m 42s
   Dec(J2000) = +36d 18' 10"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed one bright but
complex peak with a duration of about 50 sec, with an extended tail.  
The peak count rate was ~70,000 counts/sec (15-350 keV), at ~20 sec 
after the trigger. 

The XRT began observing the field at 06:13:49.7 UT, 60.5 seconds after
the BAT trigger. XRT found a very bright fading, uncatalogued X-ray 
source located at RA, Dec 217.9196, +36.3041 which is equivalent to:
   RA(J2000)  = 14h 31m 40.7s
   Dec(J2000) = +36d 18' 14.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 18 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to assess possible
redshift constraints using X-ray spectroscopy and the nH-z relation
from Grupe et al. (2007). 

UVOT took a finding chart exposure of 400 seconds with the V filter
starting  175 seconds after the BAT trigger. There is a candidate
afterglow in the  rapidly available 2.7'x2.7' sub-image. This
position is consistent with  the XRT error circle, but the source is
so bright that a precise UVOT position  is not possible due to
saturation effects. The estimated magnitude is 11.5 with a  1-sigma
error of about 0.5 mag. No correction has been made for the expected 
extinction of about 0.04 magnitudes. 

Burst Advocate for this burst is J. L. Racusin (racusin 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.)