GRB 090117

Aquib Moin (Curtin Institute of Radio Astronomy / Australia Telescope
National Facility), Steven Tingay (Curtin Institute of Radio Astronomy),
Chris Phillips (Australia Telescope National Facility), Gregory Taylor
(University of New Mexico), Mark Wieringa (Australia Telescope National
Facility) and Ralph Martin (Perth Observatory) report:

We observed the SuperAGILE-GRID position of the GRB090117 (GCN 8817
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 ) at
4.800 and 4.928 GHz with the Australia Telescope Compact Array (ATCA)
between 01:00:00 UT and 22:00:00 UT on February 21/22, 2009.

We did not detect a radio source at the position of the GRB090117 (GCN
8817
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 ). The data at 4.800 and 4.928 GHz were merged and the radio flux
density at the GRB position found out to be -0.0109 +/- 0.189 mJy/beam
(1-sigma).

The Australia Telescope Compact Array (/ Parkes telescope / Mopra
telescope / Long Baseline Array) is part of the Australia Telescope
which is funded by the Commonwealth of Australia for operation as a
National Facility managed by CSIRO.

See the 4.800 & 4.928 GHz combined image at:

http://cira.ivec.org/dokuwiki/doku.php/grb/grb090117/grb090117_field_image

K.L. Page & A.P. Beardmore (U. Leicester) report on behalf of the 
Swift-XRT team:

Following the collection of further XRT data, we see that the source found 
by Beardmore & Evans (GCN Circ. 8818
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 ) is fading, so confirm it as the 
X-ray afterglow of GRB 090117 (Donnarumma et al., GCN Circ. 8817
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 ; 
Connaughton, GCN Circ. 8821
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 ).

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

Valerie Connaughton (UAH) reports on behalf of the Fermi GBM Team:

"At 15:22:01.05 UT on 17 Jan 2009, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 090117 (trigger 253898523 / 090117640)
which was also detected by SuperAGILE (Donnarumma et al. 2009,
GCN 8817
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 ).

The GBM on-ground location is consistent with the reported
position from SuperAGILE. The angle from the Fermi LAT boresight is
51 degrees.

The GBM light curve shows a soft event with a single peak lasting
about 2 seconds superimposed on a lower-level continuum.
The burst duration (T90) is about 21 s (8-1000 keV).
The time-averaged spectrum from T0-5 s to T0+4 s is
best fit by a Band function with Epeak = 25 +/- 2 keV,
alpha = -0.4 +/- 0.5, and beta = -2.5 +/- 0.1

The event fluence (8-1000 keV) in this time interval is
(1.8 +/- 1.3)E-6 erg/cm^2, with a 1 sec peak flux starting
at T0 of 9.6 +/- 4.2 ph/cm^2/s and a 0.256 sec peak flux starting
at T0+0.256 sec of 18.6 +/- 8.0 ph/cm^2/s.

In view of the soft spectrum and the position of the burster close to
the Galactic plane, other spectral forms were investigated that are
more typical of galactic transient sources.   Of these, the best fit was
obtained using a thermal Bremmstrahlung model with kT = 49. 
The Band GRB function was preferred statistically with delta chi2
= -5 for 1 extra parameter. It is likely, therefore, that this is a soft
GRB rather than a new galactic transient.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

A. Rossi (Tautenburg Obs.), F. Olivares (MPE Garching), A. Kupcu Yoldas (ESO), J. Greiner, and A. Yoldas (both MPE Garching) report on behalf
of the GROND team:

We observed the field of GRB 090117 (SuperAGILE trigger, Donnarumma et al. GCN #8817
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPI/ESO telescope at La Silla (Chile).
Observations started at 01:40 UT, about 9 hrs after the GRB.

We do not detect any new sources within the 5-sigma Swift/XRT error circle  (Breadmore & Evans, GCN #8818
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 ). Note that there is a R~16 magnitude star within the XRT position contaminating the search for the GRB afterglow. Co-added images of the first 8 minutes yield the following specific limits (in AB magnitudes):

g' > 23.7
r' > 24.1
i' > 23.2
z' > 22.2
J > 21.9
H > 20.9
K > 20.3

The magnitudes are calibrated against the GROND zeropoints and 2MASS field stars.

P. Schady (MSSL-UCL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began observing the field of SuperAGILE GRB 090117  
(Donnarumma et al., GCN 8817
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 ) at 2009-01-017 19:10:14 UT, 13.7 ks  
after the burst. We do not detect any source at the Swift XRT position  
(Beardmore et al., GCN 8818
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 ), although we note that there is a bright  
star with v-band magnitude v = 17.7 that lies within the XRT error  
circle.

The UVOT 3-sigma upper limits are reported below:

Filter   T_start   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
white      14.4       455      > 17.18
v              15.1       595      > 16.18
b              13.8       627      > 17.08
u              13.7       63        > 17.27
-------------------------------------------------------------

The quoted upper limits have not been corrected for the expected  
Galactic extinction along the line of sight of E_(B-V) = 1.63 mag. All  
photometry is on the UVOT photometric system described in Poole et al.  
(2008, MNRAS, 383, 627).

A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the
Swift-XRT team :

The Swift-XRT began observing the field of the SuperAGILE GRB 090117 at 
2009-01-17 19:10:13 UT, 13.7 ks after the burst. In a 1.9 ks Photon 
Counting mode X-ray image covering the 0.3-10 keV band, we detect an 
uncatalogued source within the SuperAGILE error circle at the 
astrometrically corrected X-ray position (using the XRT-UVOT alignment and 
matching UVOT field sources to the USNO-B1 catalogue) of RA, Dec = 
164.0444, -58.2336 which is equivalent to:

RA (J2000):  10 56 10.66
Dec (J2000): -58 14 00.8

with an uncertainty of 2.4 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. The
position  enhancement is described by Goad et al. (2007, A&A, 476, 1401 
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is 
an extension of this method.

At this stage we cannot tell if the source is fading to confirm that it
is the X-ray counterpart of the SuperAGILE  burst.

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

I. Donnarumma, E. Del Monte, Y. Evangelista, M. Feroci, F. Lazzarotto,
L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda
(INAF/IASF Rome), A. Giuliani, S. Vercellone, A. Chen,
S. Mereghetti, A. Pellizzoni, F. Perotti, P.
Caraveo (INAF/IASF Milan), A. Bulgarelli, F. Gianotti,
M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi,
M. Galli, (INAF/IASF Bologna), M. Tavani, G. Pucella, F. D'Ammando, V.
Vittorini, A. Argan, A. Trois, G. Piano, S. Sabatini (INAF/IASF Rome), 
G. Barbiellini, F. Longo, E. Moretti (INFN Trieste), P. Picozza, 
A. Morselli (INFN Roma-2), M. Prest, E. Vallazza (Universita` 
dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), and  P. Giommi, C. 
Pittori, B. Preger, P. Santolamazza, F. Verrecchia (ASDC) and L. Salotti 
(ASI), on behalf of the AGILE Team, report:

"SuperAGILE detected a gamma ray burst on 17 January 2009, at 15:21:54 UT.
The event had a duration of about 10.0 s in the 20-60 keV energy range,
with a precursor followed by the main peak. Assuming a crab-like energy 
spectrum, the peak flux on 1-s timescale was about 
2.7E-07 erg/cm2/s. 
The burst position was reconstructed  as (RA, Dec)
(164.003 deg, -58.249 deg), which is:

RA(J2000)  = 10h 56m 00.75s
Dec(J2000) = -58d 14' 57.84"

with an uncertainty of 3' radius. The given uncertainty accounts
for both the statistical and systematic errors.

An analysis of the AGILE Gamma Ray Imager (GRID) data is in progress."

This message may be cited.