GRB 050922B

J. Norris (GSFC), L. Barbier (GSFC), S. Barthelmy (GSFC), P. Boyd (GSFC),
D. Burrows (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC),
S.T. Holland (GSFC/USRA), J. Kennea (PSU), H. Krimm (GSFC/USRA),
F. Marshall (GSFC), O. Godet (U. Leicester), D. Palmer (LANL),
T. Sakamoto (GSFC)
on behalf of the Swift team:

At 15:02:00 UT, Swift-BAT triggered and located GRB050922B (trigger=156434).
This was an image trigger with a 168-sec duration.  The spacecraft slewed
immediately after the end of the image trigger.  The BAT on-board
calculated location is RA,Dec 5.800d,-5.599d {00h 23m 12s,-05d 35' 55"} (J2000),
with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys).
The TDRSS lightcurve does not show any significant emission, but these
lightcurves are problematic for long image triggers.  We will have to wait
for the full Malindi data set (~8 hrs) to make a mask-tagged lightcurve.
We note that this source is at a high galactic latitude of -67 degrees.
We also note that the recent long-duration image trigger GRB 050904
was at high redshift.

XRT began observing the field at 15:07:42, 342 seconds after the BAT trigger.
Onboard centroiding found a bright fading uncatalogued X-ray source
in the field of view at the following coordinates:
RA(J2000):   0:23:13.3,
Dec(J2000): -5:36:12.9.
We estimate the uncertainty of this position to be 8 arcseconds (radius, 90% 
containment).  This position is 26 arcseconds from the BAT position above. 

UVOT began observing at 343 sec after the trigger.  The small UVOT TDRSS image
does not overlap the BAT error circle.   However, the full-field UVOT source
list contains only catalogued sources, in particular no source is found inside
the XRT error circle.  At the present time it is not possible to determine
a limiting magnitude for this field.  The V-band extinction in this direction
is A_V = 0.12 mag.

E.Sonoda,S.Maeno,Y.Tokunaga,M.Yamauchi
(University of Miyazaki)


"We have observed the field covering the error circle of
GRB 050922(GCN4008
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 ;Swift-BAT Trigger time is 15:02:00 UT)
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 15:28:46 UT on Sep.22.
After co-adding a set of 6 images (15:28:46 - 15:37:46 UT)
of 30 sec exposures, we have compared with the USNO A2.0 catalog.
Preliminary analysis shows there is no new source brighter than
16.1 mag."

B. E. Schaefer (Louisiana State), R. Quimby (U Texas), S.A. Yost (U Mich), 
W. Rujopakarn (U Mich) report on behalf of the ROTSE collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded to 
GRB 050922B (Swift trigger 156434), producing images beginning 5.6 s after 
the GCN notice time. An automated response took the first image at 
15:05:06.6 UT, 186.3 s after the burst, under excellent conditions. We 
took 10 5-sec, and 140 20-sec exposures. These unfiltered images are 
calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma error circles for both the BAT and the XRT, for both single images 
and coadding into sets of 10. The field is not crowded but the gibbous 
moon was 57 degree away. Individual images have limiting magnitudes 
ranging from 15.4-16.5; we set the following specific limits.

start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
15:05:06.6 15:07:30.6 144 17.3 186.3 Y

D. Hullinger (UMD), L. Barbier (GSFC), S. Barthelmy (GSFC), 
J. Cummings (GSFC/NRC), E. Fenimore (LANL), F. Marshall (GSFC), 
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), 
G. Sato (ISAS), A. Smale (NASA HQ), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Using the data set from T-120 to T+450 sec from the recent telemetry
downlink, we report further analysis of Swift-BAT GRB 050922B
(trigger #156434)  (Norris, et al., GCN 4008
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 ).  The refined BAT ground 
position is (RA,Dec) = 5.789, -5.602 {00:23:09,-05:36:08} [deg; J2000]
+-2.3 arcmin, (radius, sys+stat, 90% containment).  The partial coding 
was 12%.  

The light curve shows a broad peak from T+15 to T+65 and a second peak 
from T+80 to T+110.  There is no extended emission T>120 sec.  
T90 (15-350 keV) is (80 +- 10) sec (estimated error including systematics).  

The power law index of the time-averaged spectrum is 1.89 +- 0.23.  
The fluence in the 15-150 keV band is (1.8 +- 0.3) x 10^-6 erg/cm2.  
The 1-sec peak photon flux measured from T0+98 sec in the 15-150 keV 
band is (1.1 +- 0.4) ph/cm2/sec.  All the quoted errors are at the 90% 
confidence level.

K. Torii (Osaka U.) reports:

 The error region of Swift GRB 050922B (Norris et al. GCN 4008
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 ) was
observed by the 14 inch Automated Response Telescope. BVRcIc imaging
started at 2005 September 22, 15:07:42 UT (342 s after the trigger)
and 60 s integration was repeated.

 Due to low transparency and intermittent clouds, useful images were
obtained after 15:16:47 UT. Preliminary analysis gives the following
3-sigma upper limits for an optical counterpart of the Swift XRT
afterglow (GCN 4008
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 ).

------------------------------------------
StartUT	Filter	Limit	Exposure
------------------------------------------
15:17:55 Rc	15.5	60s	
17:02:44 Ic	17.1	40x60s	
------------------------------------------

S. Guziy, M. Jelinek, J. Gorosabel, A.J. Castro-Tirado, 
A. de Ugarte Postigo (IAA-CSIC Granada, Spain),
Ernesto Rodriguez Flores (IGA, La Habana, Cuba) and 
K. Vijanen (IAC-CSIC La Laguna, Spain) 

report:

"We have acquired r' image of the GRB 050922B  XRT error box
(Norris et al. GCN 4008
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 ) with INT 2.5m telescope at
Observatorio del Roque de los Muchachos on La Palma starting
on September 23.1943 UT (i.e. 0.5678d after the GRB) with 600s
exposure. No sources brighter than r'=22.5 (3-sigma) are
detected within the 8" radius of the XRT error circle"

This message can be cited.

M. De Pasquale (MSSL), J. Norris (GSFC),
T. Kennedy (GSFC), K. Mason (PPARC), N. Gehrels
(GSFC) on behalf of the Swift/UVOT team

The Swift/UVOT began observing the field of
GRB050922B at 15:07:42 UT, 342 seconds after the
BAT trigger (Hullinger et al., GCN 4019
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 ).
There is no detection of an optical counterpart
in the first 100 sec exposure finding chart
down to a 3 sigma upper limit of V=18.7.

  There is also no optical/UV counterpart
detected in the summed images from all filters,
down to the following 3 sigma magnitude upper
limits:

  Filter  T_range(sec)  Exp(sec)  3sig UL

    V      342-5997      1158     20.1
    B      489-1720       258     20.2
    U      474-11434      720     20.5
    UVW1   580-7616       873     20.3
    UVM2   446-6904      1068     20.6
    UVW2   503-1826       258     20.1

Where T_range is the time post-trigger over which
the summed images were accumulated and Exp is the
total exposure time. The magnitudes upper limits
are not corrected for extinction.

  These magnitudes are based on preliminary zero-
points, measured in orbit, and will require
refinements with further calibrations.

O. Godet, K.L. Page, J. Kennea (PSU), J.P. Osborne (U. Leicester),
D. N. Burrows (PSU), N. Gehrels (NASA/GSFC), K. Hurley (Berkeley),
M. Chester (PSU)  report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data of the burst GRB 050922B from the
first 3 orbits (~4 ks). The refined coordinates are:

RA(J2000) =  00h 23min 13.2s
Dec(J2000) = -05d 36' 16.4"

with an uncertainty of 7 arcseconds radius (90% containment).  This
position is consistent with that reported by Norris et al. (GCN 4008
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 ).

Initial data show two flares peaking at ~370 s and ~846 s after the
trigger (T0), followed by a steep temporal decline decay (power law
decline index ~ 2.75+/-0.14). Later data from the second and third
orbits show a shallow decline with an temporal index ~ 0.95 +/- 0.41.

The X-ray spectrum after T0+5021 s is well fit by a power-law with
Gamma = 1.9+0.3/-0.2 (90% confidence) and a Galactic absorbing column
of 3.4e20 cm^-2.

If the light-curve is still unbroken at T0+24 h, the predicted
unabsorbed 0.3-10 keV flux is ~1.6e-13 erg cm^-2 s^-1.

[GCN OPS NOTE(23sep05): Per author's request, J. Kennea as was added
to the author list.]

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

We report a correction to Hullinger et al. (GCN circ. 4019
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 ).  There
are two additional peaks in the interval T+260 to T+275 sec besides 
the broader, somewhat more intense peaks reported earlier.  We had 
mistakenly stated that there was no emission after T+120.  We have 
no mask-weighted data from T+300 to T+330 sec, but the raw rates show 
no peaks in this interval.  There is no significant emission after 
T+330 sec; in particular, there does not seem to be any emission in 
the BAT energy range at the times of the Xray flares reported by Godet 
et al. (GCN circ. 4031
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 ).

The two later peaks are softer, shorter, and sharper.  The total
fluence from T+0 to T+300 sec is (2.6 +- 0.4) x 10^-6 ergs/cm^2 in the 
15-150 keV band.  The power-law photon index for the total burst is 
2.1 +- 0.2.  T90 is 250 +- 20 sec.  Errors are 90% confidence 
including systematics.

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

We have observed the error box of the Swift GRB050922B (Norris et al. GCN 
4008
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 ) with 0.4m telescope of  Ussuriysk Astrophysical Observatory (UAPhO) in 
R-band starting on Sep. 22 15:22 (UT). No new source was found in the GRB 
error box.  Upper limit of a stacked image (10x60 s) calibrated against  of 
USNO-A2.0 (R) is following:

Mid time,    Exposure, Filter, Limiting mag.
(UT)           (s)

Sep.22 15:37   10x60    R       16.0

The message may be cited.