GRB 100103A

D.Gotz (CEA-Saclay), S.Mereghetti, A. Paizis, (IASF- Milano), E.  
Bozzo, L. Gibaud, M. Beck (ISDC, Versoix), and  J. Borkowski (CAMK,  
Torun) on behalf of the IBAS Localization Team  report:

a long gamma ray burst has been detected by IBAS in the IBIS/ISGRI  
data at 17:42:32 U.T. on January 3rd. It lasts about 40 s and its  
refined coordinates (J2000) are:
R.A.:     112.366 [degrees]
DEC.:    -34.482 [degrees]

with an uncertainty of 1.6 arcmin (90% c.l.).

A preliminary analysis gives a peak flux in the 20-200 keV range of  
about 3.5 ph/cmsq/s (1 s integration time) and a fluence over the same  
energy range of about  3e-6 erg/cmsq.

A plot of the light curve will be posted at

http://ibas.iasf-milano.inaf.it/IBAS_Results.html

This message can be cited.

J. A. Kennea (PSU) and W. H. Baumgartner (GSFC/UMBC) report on behalf of 
the Swift Team:

Swift began a target of opportunity observation of the INTEGRAL detected 
GRB 100103A (GCN #10307
Loading...
 
 ), at 18:36UT on January 3rd, 2010, approximately 
54 mins after the INTEGRAL detection. In approximately 2.5 ks of Photon 
Counting mode data, we find an uncatalogued source in the XRT field of 
view with a preliminary position of RA, Dec (J2000) = 112.37327, 
-34.487811, which is equivalent to:

RA(J2000)  =  07h 29m 29.5s
Dec(J2000) = -34d 29' 16.1"

with an estimated uncertainty of 6 arcmins radius (90% confidence). This 
position lies 0.5 arcmins from the INTEGRAL reported position. We 
currently cannot confirm if this source is fading.

J. A. Kennea (PSU) and W. H. Baumgartner (GSFC/UMBC) report on behalf of
the Swift Team:

The position error in GCN #10308
Loading...
 
  should be "6 arcseconds radius (90% 
confidence)". We apologize for the error.

M. M. Chester (PSU), M. H. Siegel (PSU), S. Immler (NASA/CRESST/GSFC),  
and W. H. Baumgartner (GSFC/UMBC) report on behalf of the Swift/UVOT  
team:

The Swift/UVOT began observing the INTEGRAL-detected GRB 100103A  
(D.Gotz, et al., GCN Circ. 10307
Loading...
 
 ) at 18:36UT on January 3rd, 2010,  
approximately 54 mins after the INTEGRAL detection.  No optical  
afterglow consistent with the Swift/XRT candidate (J. Kennea, et al.,  
GCN Circ. 10308
Loading...
 
 ) is detected in the UVOT exposures.  Preliminary 3- 
sigma upper limits using the UVOT photometric system (Poole et al.  
2008, MNRAS, 383, 627) are:

Filter    T_start(s)   T_stop(s)   Exp(s)      Mag
----------------------------------------------------------------
v         3244         4409        1165       >20.44
u         4418         5554        1136       >20.70


The values quoted above are not corrected for the Galactic extinction  
due to the reddening of E(B-V) = 0.29 in the direction of the XRT  
candidate (Schlegel et al. 1998).

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long GRB 100103A (Gotz et al., GCN 10307
Loading...
 
 )
triggered Konus-Wind at T0=63766.807s UT (17:42:46.807).

The burst light curve shows a single-pulse structure
with a duration of ~50 s. There is a hint of the soft
extended emission which lasts to ~250 s after T0.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB100103_T63766/

As observed by Konus-Wind the burst
had a fluence of 1.2(+/-0.2)x10-5 erg/cm2,
and a 256-ms peak flux measured from T0+7.168s
of 0.9(+/-0.1)x10-6 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the burst (from T0 to T0+41.216 s)
is well fitted in the 20 keV - 2 MeV range by GRB (Band) model for which:
the low-energy photon index alpha = -0.91 (-0.38,+0.63),
the high energy photon index beta = -2.2(<-1.9),
the peak energy Ep = 157(-51, +83)keV (chi2 = 45/57 dof).

The spectrum of the most intense part of the burst (from T0 to T0+8.448 s)
is well fitted in the 20 keV - 2 MeV range by GRB (Band) model for which:
the low-energy photon index alpha = -0.82 (-0.25,+0.28),
the high energy photon index beta = -2.7(<-2.2),
the peak energy Ep = 204(-38, +56)keV (chi2 = 54.8/57 dof).

All the quoted values are preliminary.
All the quoted errors are at the 90% confidence level.

K.L. Page, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the 
Swift-XRT team:

Using 3971 s of XRT Photon Counting mode data and 2 UVOT images for the 
INTEGRAL burst GRB 100103A, 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 = 112.37270, -34.49020 which is equivalent 
to:

RA (J2000):  07 29 29.46
Dec (J2000): -34 29 24.9

with an uncertainty of 1.7 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, MNRAS, 397, 1177).

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

K.L. Page (U. Leicester) and W.H. Baumgartner (GSFC/UMBC) report on behalf 
of the Swift-XRT team: 

We have analysed 8 ks of XRT data for the INTEGRAL GRB 100103A (Gotz et 
al. GCN Circ. 10307
Loading...
 
 ) obtained during two observations, from 3.3-10.3 ks 
and 196-224 ks after the trigger. The source found by Kennea & Baumgartner 
(GCN Circ. 10308
Loading...
 
 ; improved position given by Page et al. in GCN Circ. 
10312
Loading...
 
 ) is now clearly fading, with a decay slope of alpha = 0.87 (+0.14, 
-0.10). We therefore confirm that this is, indeed, the X-ray afterglow.

A spectrum formed from the PC mode data can be fitted with an absorbed 
power-law with a photon spectral index of 2.86 (+0.32, -0.30). The 
best-fitting absorption column is 6.5 (+1.3, -0.7) x 10^21 cm^-2, in 
excess of the Galactic value of 2.4 x 10^21 cm^-2 (Kalberla et al. 2005). 
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor 
deduced from this spectrum is 3.9 x 10^-11 (1.7 x 10^-10) erg cm^-2 
count^-1. 

The results of the XRT-team automatic analysis are available at 
http://www.swift.ac.uk/xrt_products/00020125.

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

R. Filgas, F. Olivares, J. Greiner, T. Kruehler (all MPE Garching)
and S. Klose (Tautenburg Observatory) report on behalf of the GROND team:

We observed the field of GRB 100103A (INTEGRAL trigger #5970; Gotz et al.,
GCN #10307
Loading...
 
 ) 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 on January 4, 2010 at
00:48 UT, 7.1 hours after the GRB trigger. They were performed at
variable seeing of 2-3" and at an average airmass of 1.4.

No source is found within the 1.7" XRT error circle (Page et al., GCN #10312
Loading...
 
 ).
Comparison to the Digital Sky Survey and 2MASS also reveals no new sources
within a 10 arcsec surrounding. Co-added images of 24.6 min of integration time
in g'r'i'z' and 20 min in JHK, centered at 01:29 UT yield the following 
specific upper limits (AB system):

g' > 24.9
r' > 24.2
i' > 23.6
z' > 23.8
J > 21.2 
H > 20.6 
K > 19.2 

calibrated against USNO and 2MASS field stars. No correction for the Galactic
foreground extinction was made, which correspond to a reddening of 
E(B-V)=0.29 mag in the direction of the burst (Schlegel et al. 1998).