GRB 070330

D. Grupe (PSU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester),
M. M. Chester (PSU), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), B. Sbarufatti (INAF-IASFPA),
M. Stamatikos (NASA/ORAU) and M. C. Stroh (PSU) report on behalf of
the Swift Team:

At 22:51:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070330 (trigger=273180).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 269.519, -63.779 which is 
   RA(J2000)  =  17h 58m 05s
   Dec(J2000) = -63d 46' 44"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 10 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began taking data at 22:52:39 UT, 68 seconds after the BAT
trigger.  The XRT on-board centroid algorithm did not find a source,
however analysis of TDRSS data reveals a bright, fading uncatalogued point 
source at RA, Dec  269.5407, -63.7933 which is:
   RA(J2000)  =  17h 58m 09.8s
   Dec(J2000) = -63d 47' 35.7"
with an estimated uncertainty of 3.8 arcseconds radius (90% confidence). 
This position lies 62 arcsec from the BAT position. 

UVOT took a finding chart exposure of 400 seconds with the V filter
starting 65 seconds after the BAT trigger. Automated source detection
did not find an afterglow candidate, but visual inspection suggests a
marginal detection at RA, DEC = 269.5418, -63.7930 with an estimated
magnitude of 18.6. The 2.7'x2.7' sub-image covers 100% of the XRT
error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is
typically complete to about 18.0 mag. No correction has been made for
the expected extinction of about 0.2 magnitudes.

J.French (UCD), P.Kubanek (U. Valencia) and M.Jelinek (IAA), report on
behalf of the Watcher collaboration:

The Watcher 40cm automated telescope at the Boyden Observatory, South
Africa, began imaging the field of GRB 070330 (Grupe et al, GCN 6232
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 ) at
22:57:40 UTC, 6.15min after the BAT trigger. An initial series of 10s
unfiltered exposures shows no new source down to a limiting magnitude of
approx. 16 mag. Stacking multiple frames to create a combined 848s
exposure with a mean time of 23:06:40 UTC (15.15min post-trigger) fails
to reveal any new source down a 3-sigma limiting magnitude of 18.2 mag.
Further observations are continuing.

GRB 070330: Swift-XRT refined analysis

D. Grupe (PSU) reports on behalf of the Swift/XRT team



We have analyzed the first two orbits of GRB 070330 (Grupe et al., GCN 
6232
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 )
with total observing times of 2.7 ks in photon counting mode in the 
Swift XRT.
The Photon Counting mode image provides a refined XRT position at
Ra, Dec= 269.5407, -63.7934, which is

RA(J2000) = 17h 58m 09.8s
Dec(J2000) = -63d 47' 36.1"

with an error of 3.6" (90% confidence). This position is 0.4"
away from the preliminary XRT position reported in GCN 6232
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 .

The X-ray light curve displays  a flare at the beginning of the
XRT observation with a peak at about 230s after the burst. The decay 
slope after
the flare is 1.10+/-0.12. The prediction 24h after the burst is a 
0.3-10.0 keV
flux of 6e-14 ergs/s/cm2 or about 1.3e-3 XRT counts/s.

The photon counting mode data can be fitted by a single absorbed power law
model with a photon index Gamma=1.72+/-0.11 and an absorption column 
density
consistent with the Galactic value (7.14e20 cm^-2; Dickey & Lockman, 1990).


More analysis of the data will be presented in the
GCN report.

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

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 070330 detected by SWIFT
(trigger 273180) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 2.5 hours after the GRB trigger
(the field was not risen when the burst occured).

The date of trigger : t0 = 2007-03-30T22:51:30.816

We co-added a series of 180s exposures:
We do not detect any OT at the XRT position
(Grupe et al. GCNC 6234) with a limiting magnitude of:

t0+2.5h to t0+3.5h : R > 17.4

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=329.9005 lat=-18.5620
and the galactic extinction in R band is 2.0 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.

B. E. Cobb, part of the larger SMARTS consortium, reports:

Using the ANDICAM instrument on the 1.3m telescope at CTIO, we
obtained optical/IR imaging of the error region of GRB 070330
(Grupe et al. GCN 6232
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 ) with a mid-exposure time of ~7.6 hours
post-burst (2007-03-31 06:25 UT).  Total summed exposure
times amounted to 36 minutes in I and 30 minutes in J.

No source is detected at the position of the X-ray
afterglow (Grupe et al. GCN 6234
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 ) to approximate
limiting magnitudes of I > 20.5 and J > 18.6. Magnitudes
are calibrated using USNO-B1.0 values for I, and 2MASS 
values for J.

E. Fenimore (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), N. Gehrels (GSFC), D. Grupe (PSU),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
 
Using the data set from T-240 to T+963 sec from the full telemetry
downlink, we report further analysis of BAT GRB 070330 (trigger
#273180) (Grupe et al., GCN Circ. 6232
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 ).  The BAT ground-calculated
position is RA, Dec = 269.533, -63.799 deg which is
   RA(J2000)  =  17h 58m  7.9s 
   Dec(J2000) = -63d 47' 54.7" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90%
containment).  The partial coding was 80%.

The mask weighted light curve consists of a single FRED-like peak.
T90 (15-350 keV) is 9.0 +- 1 sec (estimated error including
systematics).
 
The time-averaged spectrum from T-1.1 to T+8.9 is best fit by a power
law with an exponential cutoff.  This fit gives a photon index 
-0.33 +- 1.76, and Epeak of 36.3 +- 6.1 keV (chi squared 56.05 for 56
d.o.f.).  For this model the total fluence in the 15-150 keV band is
1.8 +- 0.3 x 10^-07 erg/cm2 and the 1-sec peak flux measured from
T-0.06 sec in the 15-150 keV band is 0.9 +- 0.1 ph/cm2/sec.  A fit to
a simple power law gives a photon index of 2.06 +- 0.22 (chi squared
66.7 for 57 d.o.f.).  All the quoted errors are at the 90% confidence
level.

N.P.M. Kuin (MSSL-UCL), D. Grupe (PSU), P. Brown (PSU) report
on behalf of the Swift/UVOT team:

The Swift/UVOT began taking data in the field of GRB070330 54s after the BAT 
trigger (Grupe et al., GCN 6232
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 ). The afterglow is only detected in the first 
UVOT V exposure, with a magnitude of V=18.69+/-0.24, after which the afterglow 
had decayed below the UVOT detection threshold, suggesting a decay rate of 
alpha_V > 0.8. The refined UVOT afterglow position is
RA (J2000)  = 17:58:09.98 (269.5426)
Dec (J2000) = -63:47:34.80 (-63.7930)
We note that the refined position is 0.5" away from the preliminary UVOT 
position reported in GCN 6232
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 . The photometry results are given below for the 5 
UVOT filters in which observations were made. Due to the presence of a bright 
star no observations could be obtained in the UVW2 and white filters.

Filter  Mid_T(s)   Exp(s)  Mag
V       266        393     18.69+/-0.24
V       33978      1632    > 21.45 (3-sigma upper limit)
M2      25521      2814    > 18.35 (3-sigma upper limit)    `
W1      20282      1998    > 18.36 (3-sigma upper limit)
U       25521      2814    > 21.60 (3-sigma upper limit)
B       30318      3305    > 18.15 (3-sigma upper limit)

Mid_T is the weighted mid time of the exposure since the BAT trigger. These 
magnitudes are not corrected for the expected reddening of E(B-V)=0.063.

For the time being it is not possible to provide a redshift given the low 
signal-to-noise ratio of the data. Further analysis is ongoing. A high (~4) 
redshift is possible and we encourage further ground follow-up.

[GCN OPS NOte(25aug07): Per UVOT Team request, the Mid_T value
for the first V exposure ws changed from 462 to 266. Acknowledgements
to F. Marshall.]

P. Schady (MSSL-UCL), D. Grupe (PSU) report on behalf of the Swift/UVOT team

An error has been noted in the UVOT position for the optical afterglow of 
GRB 070330 (GCN 6238
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 ). There is a typo in the RA expressed as degrees. The 
correct refined UVOT afterglow position is
RA (J2000)  = 17:58:09.98 (269.5416)
Dec (J2000) = -63:47:34.80,6 (-63.7930)
to a certainty of 0.5".