GRB 080307

K. Kinugasa, S.Honda, O.Hashimoto, H.Taguchi (Gunma Astronomical
Observatory)  report:

 The field of GRB 080307 (Holland et al. GCN 7362
Loading...
 
 ) was observed
with the 150 cm telescope of the Gunma Astronomical Observatory.
Starting at 13:06 UT (1.67 hours after the burst), Rc, Ic, and
V frames were acquired for 3 x 5-min, 6 x 5-min, and 2 x 5-min
exposures, respectively.

 We do not identified the optical counterpart reported by
Tanvir et al. (GCN 7369
Loading...
 
 ) to 3-sigma limiting magnitudes of
Rc=21.5 and Ic=21.0 relative to USNO-B1.0 magnitudes.

T. Minezaki (IoA, Tokyo), P.A. Price (IfA, Hawaii), Y. Yoshii (IoA,
Tokyo), L. Cowie (IfA, Hawaii) and Y. Kakazu (IfA, Hawaii) report:

We observed the localisation of GRB 080307 with the MAGNUM telescope +
MIP dual-beam imager. We do not find any afterglow in the RIYJHK images
within the XRT error circle (GCN #7366
Loading...
 
 ), and at the Gemini-N i-band
candidate position (GCN #7369
Loading...
 
 ). We estimated the upper limits in JHK
based on flux calibration with a nearby 2MASS star as follows:

  Filter   t - t_GRB (hour)    Limit (mag)
  J        +18.9               20.8
  H        +19.8               20.1
  K        +19.5               19.2

This message may be cited.

G. Kornienko, A. Erofeeva (UAFO), A. Pozanenko (IKI) on behalf of larger GRB 
follow up collaboration report:

We observed the error box of  GRB080307 (Holland  et al. GCN 7362
Loading...
 
 ) on March 
05 with SR-22 telescope of UAFO observatory. A set of 20 unfiltered images 
of 60 s exposure was obtained starting (UT) 11:36:55, i.e. 13.5 minutes 
after burst onset. No new object is detected within enhanced XRT error 
circle (Goad et al. GCN 7366
Loading...
 
 ). Based on USNO-A2.0 (R) we estimated upper 
limit as following

T0+           Exposure     UL
(mid)
23.5 m        10x60 s      18.8

The message may be cited.

H. Tanaka, R. Hara, K.Kono, N.Ohmori, H.hayasi, M.Yamauchi, E.Sonoda
(University of Miyazaki)


We have observed the field covering the error circle of
GRB080307 (GCN 7366
Loading...
 
 , M.R. Goad et al.) with
the unfiltered CCD camera on the 30-cm telescope at
University of Miyazaki.
The observation was started 11:25:17 UT,
but it was cloudy then,so we got first image at 13:44:43 UT, ~141 min
after the Swift trigger time.

We have compared our data of 30 sec exposures
with the USNO-A2.0 catalog,there is no new source
at the reported position (GCN 7369
Loading...
 
 , N. R. Tanvir)


the upper limits are as follows:
--------------------------------------------------------------
Start(UT) End(UT)	Num. of frames 	Limit (mag.)
--------------------------------------------------------------
14:01:59 14:02:29 	1 		~16.36
14:01:59 17:26:12 	20 		~16.99
---------------------------------------------------------------

M. Im, I. Lee, Y. Urata, W.K. Zheng, K.Y. Huang,
on behalf of EAFON team.

   We re-analyzed the I-band images taken with the 1.8m telescope
  of the Bohyunsan Optical Astronomy Observatory, Korea.
  The I-band observation started at 76.1 min after the burst (Holland
  et al. #7362), and continued for 2100 secs.
  Our reanalysis of the stacked image show the detection of a possible
  optial transient within the error circle of the XRT position (Goad et al.
  #7366), and the reported Gemini-N i-band position (Tanvir et al.7369).
  The brightness of the OT, calibrated against USNO-B1 star at
  (09:06:31.6,+35:08,06.4), is I ~ 21.9 +- 0.3 mag with the error arising
  mostly from the uncertainty associated with the subtraction of
  the fringe pattern.
  Further deeper imaging is encouraged.

  We thank J. Seo and Yeon-Bom Jeon for their assistance with
  the BOAO observation.
  This message may be cited.

K.L. Page, J.P. Osborne (U. Leicester) & S.T. Holland (CRESST/GSFC/USRA) 
report on behalf of the Swift-XRT team:

We have analysed the first four orbits of data obtained for GRB 080307
(Holland et al., GCN Circ. 7362
Loading...
 
 ), which includes 509 seconds in Windowed 
Timing (WT) mode and 7.9 ks in Photon Counting (PC mode).

The UVOT-enhanced XRT position has been given by Goad et al. in GCN Circ 
7366
Loading...
 
 .

In the first orbit of the XRT data, the emission rises slowly, peaking 
around 200-300 seconds after the BAT trigger, after which the decay can be 
modelled with a single power-law with alpha = 1.83 +/- 0.08. The shape of 
the early light-curve is reminiscent of GRB 060218 (Campana, S. et al, 
2006, Nature, 442, 1008).

As the X-ray emission rises, it also softens; the hardness ratio then 
becomes close to constant as the light-curve decay sets in. The PC data at 
the end of the first orbit can be fitted with an absorbed power-law, with 
Gamma = 1.74 +0.23/-0.21 and NH = (1.5 +0.8/-0.6)e21 cm^-2, which is in 
excess of the Galactic value of 2.37e20 cm^-2.  From the relation in Grupe 
et al. (2007, AJ, 133, 2216), this indicates a redshift of less than 4.0. 

The mean observed (unabsorbed) flux for the PC data at the end of the 
first orbit (615-1030 seconds) is 7.86e-11 (9.83e-11)  erg cm^-2 s^-1. The 
corresponding counts to (observed) flux conversion is 1 count s^-1 = 
4.9e-11 erg cm-2 s^-1.

If the light-curve continues to decay following a power-law of 1.83, the 
count rate at 24 hours is predicted to be 3.6e-4 count s^-1 (an observed 
flux of 1.8e-14 erg cm^-2 s^-1).

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

S. T. Holland (CRESST/GSFC/USRA) reports on the behalf of the Swift
UVOT team:

        The Swift/UVOT observed the field of GRB 080307 starting 105 s
after the BAT trigger (Holland et al. 2008, GCN Circ. 7362
Loading...
 
 ).  We do not
find any source, in any of the UVOT observations, at the location of
the Gemini-North source (Tanvir, 2008 GCN Circ. 7369
Loading...
 
 ).

        The 3-sigma upper limits for detecting a source at this
location in the co-added images are:


Filter    T_start   T_stop    Exp(s)    Mag (3-sigma upper limit)
-----------------------------------------------------------------
   v         212      5754       676     >20.7
   b         691      6574       412     >21.4
   u         666      6369       432     >21.1
  uvw1       642      6164       432     >20.9
  uvm2       618      5959       413     >20.6
  uvw2       721      6816       245     >20.7
white       105      6779       599     >22.3
-----------------------------------------------------------------

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight corresponding to a
reddening of E_{B-V} = 0.03 mag.  All photometry is on the UVOT flight
system described in Poole et al. (2008, MNRAS, 383, 627).

J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis
of Los Alamos National Laboratory report:

Our Raptor telescopes responded to Swift trigger 305011
(Holland et al., GCN 7362
Loading...
 
 ) at 11:24:30.8 UTC, 60.0 seconds
after the trigger and 7.3 seconds after receipt of the GCN
packet.  We detect no new optical source at the Swift XRT
position.  Five sigma limiting magnitudes are given for
three of our unfiltered response images in the table below.
Calibration was performed using the USNO B1.0 R-band
magnitudes.

T-start (UTC)           T-exp (s)    mag limit
-------------------------------------------------
2008-03-07 11:24:30.81    5            16.9
2008-03-07 11:25:53.96    10           17.3
2008-03-07 11:30:12.01    30           18.0

G. Sato (GSFC/ISAS), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 080307 (trigger #305011)
(Holland, et al., GCN Circ. 7362
Loading...
 
 , and Palmer, et al., GCN Circ. 7365
Loading...
 
 ).
The BAT ground-calculated position is RA, Dec = 136.629, 35.151 deg
which is
    RA(J2000)  = 9h 6m 31.0s
    Dec(J2000) = 35d 9' 4"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.

The mask-weighted light curve shows an initial FRED-like peak
starting at T+0 sec, and ending around T+140 sec.  A strong spectral
evolution can be seen in the BAT four energy band light curves.
T90 (15-350 keV) is 125.9 +- 24.6 sec (estimated error including
systematics).

The time-averaged spectrum from T+1.7 to T+146.1 sec is best fit by a
simple power-law model.  The power law index of the time-averaged
spectrum is 1.78 +- 0.21.  The fluence in the 15-150 keV band is
8.7 +- 1.2 x 10^-07 erg/cm2.  The 1-sec peak photon flux measured from
T+1.90 sec in the 15-150 keV band is 0.4 +- 0.1 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/305011/BA/

This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria
(Ukwatta et al. arXiv:0802.3815):
1) The power law photon index (= 1.78) is less than 2,
2) The 1-s peak photon flux (= 0.4) is less than 1.0 ph/cm2/s,
3) The light curve variance (= 9.4e-06) is less than 0.0001,
4) The T90/Peak_photon_flux (= 350) is greater than 100.
Based on a limited sample of bursts, these criteria yield
an 85% chance it has a redshift greater than 3.5.

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
GRB080307 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/GRB080307

We supply FITS images in each of the 5 SDSS bands of a 8'x8'
region centered on the GRB position (ra=136.633 (09:06:31.9),
dec=35.1680 (35:10:04.8); Swift-BAT TRIGGER 305011), 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 GRB080307_sdss.calstar.dat, we report photometry
and astrometry of 301 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 GRB080307_sdss.objects_flux.dat and
GRB080307_sdss.objects_magnitudes.dat, we report photometry
of 1032 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 GRB080307_sdss.objects_flux.dat are in nanomaggies while
the magnitudes listed in GRB080307_sdss.objects_magnitudes.dat
are asinh magnitudes.

**Be aware that at least a portion of the photometry provided in
this release has been flagged as non-photometric. As photometry
for objects with this flag set may have non-optimal calibration,
we do not recommend these objects be used for photometric
calibration.  Non-photometric imaging may still be valuable
as a pre-burst comparison and for astrometric calibration.

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=0.137 mag, A_g=0.101 mag,
A_r = 0.073 mag, A_i=0.055 mag, and A_z=0.039 mag.

The file GRB080307_sdss.spectro.dat contains a list of the
2 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.

L.P. Xin, X.M. Meng, M. Zhai, J.S. Deng,
Y.L. Qiu, J.Y. Wei, J.Y. Hu, J. Wang, W.K. Zheng
Y. Urata, M. Im, I. Lee, K.Y. Huang, Y.
on behalf of EAFON report:

We have imaged the field of GRB080307 (Holland et al., GCN 7362
Loading...
 
 ) 
using the TNT 0.8 telescope at Xinglong observatory under good
condition. A set of White and R band images were obtained.
Preliminary result shows we margianally detected the afterglow
candidate (Tanvir, GCN 7369
Loading...
 
 ) in our combined images. By performing
PSF photometry, we have the following magnitude calibrated to the
USNO B1.0 R2 mag:

T_mid(min)  Mag    Band  Exp   Merr
-------------------------------------
15.71       20.9   W    10*20s  0.3
24.50       21.3   R    10*60s  0.3
70.28       22.1   R    8*300s  0.3

The source faded during our observation epoch, we confirm this
is the afterglow of GRB 080307.

This message may be cited. For more information about Xinglong
GRBs Follow-up observations, please visit the website:
http://www.xinglong-naoc.org/grb/

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

We performed optical imaging observations (g', Rc, and Ic) of
the field of GRB 080307 (Holland et al. GCN 7362
Loading...
 
 ) with the
50cm MITSuME telescope at Okayama Astrophysical Observatory
from UT 11:25:50 to UT 12:47:00 on March 7 2008.

Flux calibration was made using USNO B1.0 catalog. We could
not identify any new source at the XRT position (Holland et al.
GCN 7362
Loading...
 
 ) or the UVOT positions (Schady et al. GCN 7367
Loading...
 
 ).
Three sigma upper limits are listed below.

mid-UT                exp.time     g'     Rc      Ic
-------------------------------------------------------
2008-03-07 11:31:20    10 min.   >19.6   >19.3   >18.7
2008-03-07 12:12:00    57 min.   >20.5   >20.3   >19.5
-------------------------------------------------------

N. R. Tanvir (U. Leicester) reports on behalf of a larger collaboration.

We observed the field of GRB 080307 with Gemini-N/GMOS, beginning
at 12:50 (UT), approximately 85 minutes post-burst.  We detect a
point source in the i-band image within the XRT error circle (GCN 7366
Loading...
 
 )
with (J2000) coordinates:

 09 06 30.78  +35 08 20.0

Provisional photometry relative to field SDSS stars gives a magnitude
of i=22.4 at this time.

We thank the Gemini staff, particularly Ricardo Schiavon, for
support in obtaining these observations.

M. Im, I. Lee, W.K. Zheng, K.Y. Huang, Y. Urata
on behalf of EAFON team.

  Earlier, we reported the detection of the after glow of GRB080307
  (GCN Circular, #7364). Our reported afterglow at the UVOT position
  turned out to be a known star, and we retract our earlier report.
  We do not detect the GRB afterglow at the enhanced XRT position
  (GCN Circular #7366
Loading...
 
 ), and we place the limit of R > 21.2 at 3 sigma.
  Further analysis is ongoing.

  This message may be cited.

P. Schady (MSSL/UCL) and S. T. Holland (CRESST/USRA/GSFC) report on 
behalf of the Swift UVOT team:

There was a typo in the position for the optical afterglow candidate 
for GRB 080307 reported by Holland et al., (GCN 7362
Loading...
 
 ), and this should, 
in fact, be

    RA(J2000.0) =  09:06:25.5
    Dec(J2000.0) = +35:08:29

with an estimated uncertainty of 1 arcsec. However, we note that the 
new UVOT position is 0.2" from a known source, and is therefore 
unlikely to be the optical afterglow of GRB 080307.

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

Using 161 s of overlapping XRT Photon Counting mode and UVOT
data for GRB 080307, 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 = 136.62799, +35.13896 which is equivalent
to:

RA (J2000): 09h 06m 30.72s
Dec (J2000): +35d 08' 20.3"

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).

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

D. Palmer (LANL), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/USRA/GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD),
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 only a small amount of data set from the first telemetry downlink
(from T-119 to T+183 sec), we report preliminary analysis of BAT GRB 080307
(trigger #305011) (Holland, et al., GCN Circ. 7362
Loading...
 
 ).
The BAT ground-calculated position is RA, Dec = 136.626, 35.156 deg, which is 
   RA(J2000)  = 09h 6m 30.2s 
   Dec(J2000) = 35d 9' 20" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.
 
The mask-weighted light curve shows an initial FRED-like peak
starting at T+0 sec, and ending around T+80 sec.  There is evidence
for emission out to T+135 sec (and the end of the downlinked data ends
at T+183 sec).  T90 (15-350 keV) is 64 +- 22 sec (estimated error
including systematics).
 
Using this partial data set, the time-averaged spectrum from T-7.4 to T+56.6 sec
is best fit by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.41 +- 0.19.  The fluence in the 15-150 keV band is
7.3 +- 0.9 x 10^-7 erg/cm2.  The 1-sec peak photon flux measured from T+16.06 sec
in the 15-150 keV band is 0.2 +- 0.0 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/305011/BA/
 
This burst satisfies Sakamoto/Ukwatta Swift-BAT possible high-z criteria
(Ukwatta et al. arXiv:0802.3815):
1) The power law photon index (= 1.41) is less than 2,
2) The 1-s peak photon flux (= 0.19) is less than 1.0 ph/cm2/s,
3) The light curve variance (= 2.11e-05 is less than 0.0001,
4) The T90/Peak_photon_flux (= 336) is greater than 100.
Based on a limited sample of bursts, these criteria yield
an 85% chance it has a redshift greater than 3.5. 
We must stress however, that we have downlinked data out to only T+180 sec
and there is evidence of continued emissin out to T+135 sec.  So if there
is further activity in this burst past T+180 sec, then the spectral and
temporal values used in this hi-z indicator test may change
and no longer fit the hi-z criteria.  We are publishing this preliminary
refined circular on that chance the hi-z indicator is correct
and follow-up observsers can choose to make observations sooner.

We will issue the regular 'refined' circular when the full data set
becomes available.

M. Im, I. Lee, W.K. Zheng, K.Y. Huang, Y. Urata
on behalf of EAFON report:

"We have been imaging the GRB 080307 optical afterglow (Holland et
al. #7362) using the 1.8 m telescope of the Bohyunsan Optical
Astronomy Observatory, Korea. The optical afterglow brightness at 
67 min after the burst is R~20.3 mag. 
Further deeper imaging are encouraged."

We thank J. Seo, and Y. Jeon for their assistance with the BOAO observation.
This message may be cited.

M. Doi, S. Sako, J. Hayano, Y. Ihara, N. Takanashi, 
H. Kuncarayakti (The Univresity of Tokyo), D. Kuroda (NAOJ), 
K. S. Kawabata, and M. Uemura (Hiroshima Univ.)
report on behalf of the DMC team:

  We took optical CCD images of the field of GRB 080307 (GCNC 7362)
with Dichroic Mirror Camera (DMC; http://www.ioa.s.u-tokyo.ac.jp/dmc/)
attached to the 1.5-m KANATA telescope.  
DMC enables us to simultenaously obtain 15 band images in the 
optical range (typical delta lambda = 35 nm). 
We started observations at 11:31:18 (UT) 7 March 2008, 
467 s after the burst.  The exposure time was 60 s.  

No candidate of its optical afterglow brighther than 
r=17.13 mag (USNO B1.0 1251-0170228; RA=09:06:33.62, Dec=+35:08:44.1)
was found in our all images.

YYYYDDMM(UT)    limit mag.   center of wavelengths   
20080307.4804    17.13 r     641nm (chanel 07 of DMC)

S. T. Holland (CRESST/USRA/GSFC), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC),
G. Cusumano (INAF-IASFPA), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester),
C. Guidorzi (INAF-OAB), S. D. Hunsberger (PSU), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
A. Moretti (INAF-OAB), P. T. O'Brien (U Leicester),
J. P. Osborne (U Leicester), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
D. Perez (U Leicester), P. Romano (INAF-IASFPA), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester) and
E. Troja (U Leicester/INAF-IASFPA) report on behalf of the Swift
Team:

At 11:23:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080307 (trigger=305011).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 136.633, +35.168 which is 
   RA(J2000) = 09h 06m 32s
   Dec(J2000) = +35d 10' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a FRED
structure with a duration of at least 30 sec.  The peak count rate
was ~600 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 11:25:10.1 UT, 99.3 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading
uncatalogued X-ray source with an enhanced position: RA, Dec 136.62833,
35.13866 which is equivalent to:
   RA(J2000)  = 09h 06m 30.80s
   Dec(J2000) = +35d 08' 19.2"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 106 arcseconds from the BAT onboard position, within the
BAT error circle. No prompt spectrum is yet available to assess possible
redshift constraints using X-ray spectroscopy and the nH-z relation
from Grupe et al. (2007). 

The initial flux in the 2.5 s image was 7.63e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 105 seconds after the BAT trigger. A possible fading source
that is not present in the DSS has been found in the initial data products at

    RA(J2000.0) =  09:06:25.5
   Dec(J2000.0) = +35:08:39

with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).  This
source is approximately 1 arcminute from the XRT position, which is too far
away to be consistent with the X-ray source.  The estimated white magnitude
 is 19.6 +/- 0.1.  No correction has been made for the expected
extinction corresponding to E(B-V) of 0.03 mag. 

Burst Advocate for this burst is S. T. Holland (sholland AT milkyway.gsfc.nasa.gov). 
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.)