GRB 050123

GRB 050123 (=H3666):  A GRB Localized in Real Time by HETE

K. Hurley, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley,
on behalf of the HETE Science Team;

T. Donaghy, E. Fenimore, M. Galassi, C. Graziani, M. Matsuoka,
Y. Nakagawa, T. Sakamoto, R. Sato, Y. Shirasaki, M. Suzuki,
T. Tamagawa, Y. Urata, T. Yamazaki, Y. Yamamoto, and A. Yoshida, 
on behalf of the HETE WXM Team;

R. Vanderspek, N. Butler, G. Crew, J. Doty, G. Prigozhin, J. Villasenor, 
J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga, R. Manchanda, and 
G. Pizzichini, on behalf of the HETE Operations and HETE Optical-SXC Teams;

M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE
FREGATE Team;

report:

HETE detected GRB 050123 at 10:22:54 (37374 s SOD) on 23 January 2005.
GRB 050123 consists of a single peak of ~10 seconds duration and is
clearly seen in both the 7-30 keV and 30-400 keV bands.

The burst was localized in flight to coordinates RA = 10h 31m 33.5s,
Dec = -11d 34m 15s (J2000) with a radius of 14'.  The first flight 
localization was distributed 22 seconds after the burst trigger.

Ground analyses of the burst allow us to refine the error box of GRB 050123
to a box with corners

    RA = 10h 31m 49.2s Dec = -11d 41m 31s (J2000)
    RA = 10h 30m 48.7s Dec = -11d 37m 01s
    RA = 10h 31m 23.2s Dec = -11d 15m 25s
    RA = 10h 32m 23.7s Dec = -11d 20m 02s

Preliminary spectral analysis of the burst give a 30-400 keV fluence of
2e-6 erg/cm2 and an Epeak of 80 keV.

Details of this burst may be found at
  
  http://space.mit.edu/HETE/Bursts/GRB050123

This message may be cited.

Derek B. Fox (Caltech) reports on behalf of the Caltech-NRAO-Carnegie
GRB collaboration:  

"We have observed the WXM localization region of GRB050123 (=H3666;
Hurley et al., GCN 2966
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 ) with the robotic Palomar 60-inch telescope,
in a series of R-band exposures beginning at 10:36:15 UT.  A mosaic of
our first exposure set reaches exposures of 30s to 120s over >95% of
the final 15' x 24' error box, at a mean epoch of 11:02 UT.
Comparison of this mosaic to the Digitized Sky Survey reveals no new
sources to a limit of R>~19 mag.

Further analysis of these and later images is ongoing."

W. Li, A. V. Filippenko, R. Chornock, and S. Jha (University of 
California, Berkeley) report:

"The Katzman Automatic Imaging Telescope (KAIT; see Li et al. 2003, 
PASP, 115, 844) at Lick Observatory robotically observed GRB 050123
(HETE Trigger #3666; Hurley et al., GCN 2966
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 ). Three batches of
unfiltered images were taken, covering a 12.6' x 12.6' field centered
on R.A. = 10h30m31s, DEC = -11d 52'17" (J2000) (from 10:23:38 UT to
10:54:37 UT), R.A. = 10h31m33s, DEC = -11d 34'14" (J2000) (from
10:58:31 UT to 11:58:53 UT), and R.A. = 10h31m26s, DEC = -11d 28'28"
(J2000) (from 12:11:26 UT to 12:32:26 UT), respectively. We detected no
new objects in our observations when compared to the DSS II images.
The following 3-sigma limiting magnitudes are derived (calibrated with 
USNO-A2.0 red magnitudes) from selected images: R~17.5 mag for a
3 x 5 s grid image (6.6' x 6.6') started at 10:23:38 UT (44 s after
the burst), R~19.0 for a 60 s image (6.6' x 6.6') started at 10:30:36
UT (462 s after the burst), and R~20.0 for a 2 x 2 mosaic 120 s image
(12.6' x 12.6') centered at 10:51:57 UT (1743 s after the burst)."

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


"We have observed the field covering the error box of
GRB 050123 (HETE trigger 3666;trigger time 10:22:53 UT) 
with the unfiltered CCD camera on the 30-cm telescope
at University of Miyazaki.
The observation was started 17:05:26 UT on Jan.23.
Observed field of view is 43 arcmin centerd on 
R.A.=10h 31m 58s
Dec=-11d 26' 00"
After co-adding a set of 5 images of 30 sec exposures,
we have compared with the USNO A2.0 catalog. Preliminary analysis
shows there is no new source brighter than 17.4 mag.

M.Cwiok, K.Krupska, K.Kwiecinska, L.Mankiewicz, K.Nawrocki,
B.Pilecki, L.W.Piotrowski, G.Pojmanski, M.Sokolowski, D.Szczygiel,
G.Wrochna, on behalf of "Pi of the Sky / ASAS" collaboration
http://grb.fuw.edu.pl

The GRB 050123 (GCN 2966
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 ) error box was observed by "Pi of the Sky"
apparatus at Las Campanas Observatory at 8:35 UT, i.e. 1h 48min
before the GRB. 3 exposures, 10s each, have been taken by 2 cameras.
No new object has been found within the HETE error box.
The limiting magnitude on 3 coadded frames is 12m (unfiltered).

GRB 050123 : I-band follow-up observation

Z.Y. Lin, K.Y. Huang, W.H. Ip (NCU), Y. Urata, T. Tamagawa (RIKEN),
Y. Qiu (BAO), Y.Q. Lou(THCA) on behalf of the East Asian collaboration
report:

"We have observed the GRB 050123 error range reported by Hurley et
al.(GCN 2966
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 ) using Lulin 1-m telescope at Taiwan. Our observations
with I band started from 15.87 UT to 16.72 UT (~5.49 to 5.79 hours
after the burst). These images cover 70 % error region of GRB 050123
(Hurley et al., GCN 2966
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 ).  Comparing DSS-II image, no candidate was
detected in our I band images. The average of limiting magnitude is
about 19 (S/N=3, compared with USNO-B1 I magnitude)."

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