GRB 090429B

T. N. Ukwatta (GSFC/GWU), S. D. Barthelmy (GSFC),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
C. B. Markwardt (CRESST/GSFC/UMD), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. A. Rowlinson (U Leicester),
M. H. Siegel (PSU), M. Stamatikos (NASA/ORAU) and L. Vetere (PSU)
report on behalf of the Swift Team:

At 05:30:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090429B (trigger=350854).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 210.704, +32.163 which is 
   RA(J2000) = 14h 02m 49s
   Dec(J2000) = +32d 09' 48"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed three peaks
with a duration of about 5 sec.  The peak count rate
was ~4000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 05:31:50.0 UT, 106.6 seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with an enhanced position: RA, Dec 210.6670,
32.1707 which is equivalent to:
   RA(J2000)  = 14h 02m 40.09s
   Dec(J2000) = +32d 10' 14.6"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 116 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
1.2e+20 cm^-2 (Kalberla et al. 2005). 

UVOT took a finding chart exposure of 150 seconds with the White 
filter  starting 99 seconds after the BAT trigger. No credible 
afterglow candidate has  been found in the initial data products. The
 2.7'x2.7' sub-image covers 25% of  the BAT error circle but does not 
overlap the XRT error circle. The typical 3-sigma upper limit has 
been about 19.6 mag. The 8'x8' region for the list of sources 
generated on-board covers 100% of the BAT error circle and 100% of
the XRT error circle. The list of  sources is typically complete to
about 18 mag. No correction has been  made for the expected
extinction corresponding to E(B-V) of  0.01. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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.)

Adria C. Updike (Clemson University), G. Grant Williams (MMTO
Observatory), Peter A. Milne (Steward Observatory), and Dieter H. Hartmann
(Clemson University) report:

The 0.6m Super-LOTIS telescope at Kitt Peak National Observatory began
observing the field of GRB 090429B 40 seconds after the trigger (Ukwatta
et al., GCN 9281
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 ) under good conditions.  Observations consisted sets of
10, 20, and 60 second exposures.  No new sources are found in the XRT
error circle.
The results of the stacked exposures are given below; time is given in
seconds after the trigger (midtime of stack).  Magnitudes were determined
relative to the USNO B1.0 catalog.


Band    Exposures      Time       Mag
-------------------------------------------
R        5 x 10sec     80        > 17
R       10 x 60sec    580        > 19


Observations are continuing.  This message may be cited.

F. Olivares (MPE Garching), A. Kupcu Yoldas (ESO), J. Greiner, T. 
Kruehler, A. Yoldas (both MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 090429B (Swift trigger 350854; Ukwatta et 
al., GCN #9281
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 
2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla 
Observatory (Chile).

Observations started at 05:43 UT, ~13 minutes after the GRB trigger and 
continued until the source reached the 20 deg horizon limit. They are 
performed at an average seeing of 1.2 and at an average airmass of 2.5.

We do not detect any source within the Swift-XRT error circle reported 
by Ukwatta et al. (GCN #9281
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 ) down to the following limits (based on 4 
minutes of exposure time, all in AB system):

g' > 23.4 mag
r' > 23.3 mag
i' > 22.4 mag
z' > 21.8 mag
J > 21.5 mag
H > 20.2 mag
K > 19.6 mag

Quoted upper limits have been derived using USNO and 2MASS field stars
as reference.

Paolo D'Avanzo (Univ. Milano-Bicocca & INAF/Brera), Andrew J. Levan 
(Univ. Warwick), Daniele Malesani (DARK/NBI), Christina C. Thoene 
(INAF/Brera), Johan P. U. Fynbo, Jens Hjorth (DARK/NBI), Nial Tanvir 
(Univ. Leicester), report on behalf of a larger collaboration:

We observed the field of GRB 090429B (Ukwatta et al. GCN 9281
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 ) with the 
ESO-VLT in imaging mode with the FORS2 camera. Observations started 
about 1 hr after the burst. In our stacked images, no afterglow is 
detected down to the following 3sigma limits:

R > 25.3
z > 23.5

Photometry has been calibrated against USNOB1 catalogue and the SDSS.

We acknowledge support from the Paranal staff, in particular E. Mason 
and P. Lynam.

A. Cucchiara (PSU), A. Levan (U. Warwick), N. Tanvir (U. Leicester),
D. B. Fox (PSU) and E. Berger (Harvard U.) report:

"On April 29.35 UT we imaged the field of Swift GRB 090429 (Ukwatta et
al., GCN 9281
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 ) with NIRI on the Gemini-North telescope.  We obtained
images in J,H and K for a total exposure time of 9, 4.5 and 9 minutes
respectively.
In the coadded images we identify a possible IR counterpart inside the
XRT error circle at the coordinates:

RA (J2000): 14:02:40.05
Dec (J2000): +32:10:14.32

with an uncertainty of 0.5".

The estimated magnitude are:

J = 21.79 +- 0.1
H = 20.08 +- 0.05
K = 19.15 +- 0.03

These values are calibrated using the 2MASS star at RA=14:02:42.20,
Dec= +32:10:50.36.

Although variability remains to be confirmed, the red J-H colour,
coupled with the relatively blue (H-K) is suggestive of a break.
Although this may be caused by dust the lack of apparent excess N_H in
the X-ray spectrum (GCN 9281
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 ) suggests this may not be the case.
Hence GRB 090429B should be considered a high-z candidate."
 
We thank the Gemini-N staff for the support in performing this
observations, in particular Scott Fisher and Kathy Roth."

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

Using 862 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 090429B, 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 = 210.66707, +32.17072 which is equivalent
to:

RA (J2000): 14h 02m 40.10s
Dec (J2000): +32d 10' 14.6"

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) and Evans
et al. (2009, arXiv:0812.3662).

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

M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090429B (trigger #350854)
(Ukwatta, et al., GCN Circ. 9281
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 ).  The BAT ground-calculated position is
RA, Dec = 210.672, 32.167 deg, which is 
   RA(J2000)  =  14h 02m 41.2s 
   Dec(J2000) = +32d 10' 02.0" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 84%.
 
The mask-weighted light curve shows a main peak starting at ~T-4 sec,
peaking at ~T-0.1 sec, and ending around T+3 sec.  There are two very
weak peaks: ~T+30 to ~T+70 sec, and ~T+100 to ~T+110 sec.
T90 (15-350 keV) is 5.5 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-4.5 to T+2.4 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.47 +- 0.77, 
and Epeak of 42.1 +- 5.6 keV (chi squared 29.6 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.1 +- 0.3 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T-0.28 sec in the 15-150 keV band is
1.6 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.96 +- 0.13 (chi squared 45.3 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/350854/BA/

K.Kono, E.Sonoda, N.Ohmori, H.hayasi,
K.Noda, A.Daikyuji, Y.Nisioka, M.Yamauchi
(University of Miyazaki)

We have observed the field covering the error circle of
GRB09042 (Swift trigger 350854, GCN 9281
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 , T. N. Ukwatta et al.)
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 11:29:13 UT, about 6.0 hr
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 9281
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 , T. N. Ukwatta et al. GCN 9288
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 , A.P. Beardmore et al.
 GCN 9290
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 , M. Stamatikos et al.)

the upper limits are as follows:
--------------------------------------------------------------
Start(UT)   End(UT)    Num. of frames    Limit (mag.)
--------------------------------------------------------------
11:29:13    11:29:33          1            16.4
11:29:13    12:04:10         28            17.9
---------------------------------------------------------------

A. Rowlinson (U. Leicester) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift-XRT team:

We have analysed 8.9 ks of XRT data for GRB 090429B (Ukwatta et al. GCN
Circ. 9281
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 ), from 104 s to 29.9 ks after the BAT trigger. The data are
entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Beardmore et al. (GCN. Circ 9288).

The light curve initially shows a slow rise, which can be fitted with a
power-law of index 0.89 (+0.36, -0.46). At around T+642 s the light
curve breaks to a power-law decay, with index 1.20 (+0.11, -0.10).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.00 (+0.15, -0.24). The
best-fitting absorption column is 10.0 (+4.2, -5.3) x 10^20, in excess
of the Galactic value of 1.2 x 10^20 cm^-2 (Kalberla et al. 2005). The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.8 x 10^-11 (4.9 x 10^-11) erg cm^-2
count^-1.

If the light curve continues to decay with a power-law decay index of
1.20, the count rate at T+24 hours will be 0.0014 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.3 x
10^-14 (6.9 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00350854.

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

A. Levan (U. Warwick), A. Cucchiara (PSU), N. Tanvir (U. Leicester),
D. Fox (PSU) & E. Berger (Harvard U.) report:

We re-observed the field of GRB 090429B with NIRI on Gemini-N,
beginning about 30-Apr 08:00 (UT).  The infra-red source reported by
Cucchiara et al. (GCN 9286
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 ) is detected, but has faded significantly
to K=20.0 +/- 0.2 mag.  We thus confirm that this source is the
afterglow of the burst.

M. M. Chester (PSU) and T. N. Ukwatta (GSFC/GWU) report on the behalf
of the Swift/UVOT team:

      The Swift/UVOT observed the field of GRB 090429B starting 78 s
after the BAT trigger (Ukwatta et al. 2009, GCN Circ. 9281
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 ). Settled
exposures started at T+99 s.  We do not find any new source at the
position of the XRT afterglow (Beardmore et al. 2009, GCN Circ. 9288
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 ).
Preliminary 3-sigma upper limits for detecting a source in the white
finding chart and the co-added images, using a 5 arcsecond radius
circular aperture, are:

Filter      T_start   T_stop    Exp(s)     Mag
----------------------------------------------
white (fc)       99      249    150    >21.0
white           591    10856   1241    >22.2
v               640    12550   1213    >20.6
b               567     6769    381    >20.8
u               311     6621    669    >20.8
uvw1            690     6416    419    >20.5
uvm2            665     6211    439    >21.4
uvw2            616    11762   1339    >20.3
----------------------------------------------

      The quoted upper limits have not been corrected for the expected
Galactic extinction corresponding to a reddening of E_{B-V} = 0.015
in the direction of the XRT position (Schlegel, et al. 1998, ApJS,
500, 525).  All photometry is on the UVOT photometry system described
in Poole et al. (2008, MNRAS, 383, 627).

Dale A. Frail (NRAO), Ashley Zauderer (Harvard), Edo Berger (Harvard)
and Poonam Chandra (RMC) report on behalf of a larger collaboration:

We used the EVLA to image a field toward the Swift burst GRB 090429B
(GCNs 9281
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 , 9288
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 , 9290
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 , 9298
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 ), for which a photometric redshift of
z=9.4 has been recently claimed (Cucchiara et al. astro-ph/1105.4915).

The EVLA observed at two frequencies (1 GHz bandwidth each) centered
at 4.93 GHz and 6.68 GHz on 2011 April 4.38 UT and 2011 May 6.13 UT.
No radio source is detected at the NIR afterglow position. Combining
the data from both epochs we derive a 3-sigma limit of 16.6 microJy.
This limit corresponds to a spectral luminosity of 2e31 erg/s/Hz.

We also reduced archival data taken at a frequency of 8.46 GHz on 2009
April 30.28 UT. The 3-sigma limit for this observation is 132 microJy.