GRB 050626

D. Gotz, S. Mereghetti (IASF, Milano), N. Mowlavi, S. Shaw, M. Beck, A. 
Neronov (ISDC, Versoix), J. Borkowski (CAMK, Torun) on behalf of the IBAS 
Localization Team report

A 60 s long GRB has been detected in IBIS/ISGRI data by IBAS (Alert 
Number 2587) at 03:45:16 UT. Its coordinates (J2000) are

RA: 186.7445 
DEC: -63.1342

with an uncertainty of 2 arcmin (90% c.l.).

The preliminary peak flux is 0.4 ph (3E-8 erg) cmsq/s, while the fluence 
is 8.7E-7 erg/cmsq. Both values refer to the 20-200 keV band.

A preliminary spectral analysis shows that this event is X-ray rich.

A light curve will be posted at 

http://ibas.mi.iasf.cnr.it/IBAS_Results.html

This message can be cited.

[GCN OPS NOTE(26jun05): Per author's request, 050625 was changed to 050626.]

D. Gotz (IASF, Milano) on behalf of the IBAS Localization Team reports:

The subject of GCN 3552
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  should refer to GRB 050626 and not to 050625.
We aplogize for the misprint.

This messages can be cited.

V. Mangano, T. Mineo, V. La Parola, G. Cusumano (INAF-IASF/Palermo),
S. Hunsberger (PSU), D. Morris (PSU), A. Beardmore, K. Page (U. Leicester),
P. Boyd (GSFC-UMBC), L. Angelini (GSFC-JHU)
and D. N. Burrows (PSU) report on behalf of the Swift XRT team:

Swift observed GRB 050626 (D. Gotz at al, GCN3552
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 ) with XRT in Photon 
Counting (PC) mode for three times starting between 2005-06-29 03:38:54 and 
2005-07-01 12:10:42 and collected a total of 38.6 ks. (Observations were 
delayed by several days because the Integral source was initially located 
near the Swift orbital pole, and was within the Swift Earth avoidance 
angle.)  The three observations were performed in manual state to avoid the 
automatic switching in Windowed Timing (WT) mode caused  by the presence of 
two bright optical stars within 3 arcmin of the INTEGRAL position.

Only one uncataloged X-ray source was detected within the INTEGRAL error 
circle, at

RA(J2000) = 12h 27m 01.2s  Dec(J2000) = -63:08:13.9,

i.e. 20 arcsec from the INTEGRAL position.  The count rate of this source 
has been found to be steady within errors at the average level of (1.6 +/- 
0.4)E-3 counts/s, making it unlikely to be the X-ray afterglow of the GRB.

No afterglow candidate was detected within the INTEGRAL error circle.
We estimate 3 sigma upper limits of 7.9E-14, 6.6E-14, and 1.6E-13
erg cm-2 s-1 for the flux of the GRB afterglow in the first, second and third
observations, respectively and a 3 sigma upper limit of 3.8E-14 erg cm-2 s-1
in the sum of the three observations.

J.  Gorosabel,  A.J. Castro-Tirado,  (IAA-CSIC), P. Tristam,
T.  Britton, Ph. Yock  (Univ. of Auckland),  S. Guziy,  A. de
Ugarte Postigo, M. Jelinek (IAA-CSIC), O. Bogdanov  (Nikolaev
State Univ.),  report:

"We have  observed the error box  of the INTEGRAL GRB  050626 (Gotz
et al. GCN Circ. 3552
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 ).  The observations were carried out ~4 hours  
after
the gamma-ray event with the 0.6 m telescope at Mt.  John Astronomical
Observatory  (MOA) using the  MOA wide  red filter  (Texp=5x300s).  We
note  the presence of  Alpha Crucis  (R=1.3) close  to the  error box,
which produces a  strong background gradient in our  images. Thus, the
deepness  of the  combined  image ranges  approximately  from R~14  to
R~20.5 depending on the position within the error box. Comparison with
the DSS did not reveal any  variable source in the INTEGRAL error box,
including  the position of  the unlikely  X-ray afterglow  (Mangano  
et al.,
GCN Circ.   3564
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 ). At  this X-ray  source position  the limiting  
magnitude
of our combined image is approximately R~20."

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