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 flare_icrc.tex Proc ICRC 2007
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%arXiv:0710.1537v1 <http://lanl.arxiv.org/abs/0710.1537v1>

%%
% International Cosmic Ray Conference 2007 Merida Yucatan Mexico
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% By: Victor De la Luz
% vdelaluz@inaoep.mx
% Mexico City

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\documentclass[dvips]{article}
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%\documentclass[pdftex]{article}
%The ICRC Style
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\usepackage{icrctc07}

%The paper title
\title{Simultaneous H.E.S.S. and Chandra observations of Sgr A$^{\star}$ 
during an X-ray flare}
%Short title to print in the headers to the final publication (Not 
showed in this print).
\shorttitle{Observations of Sgr A$^{\star}$ during an X-ray flare}

%All paper authors
\authors{Jim Hinton$^{1}$, Matthieu Vivier$^{2}$,
Rolf B\"uhler$^{3}$,
Gerd P\"uhlhofer$^{4}$, Stefan Wagner$^{4}$ \\
for the H.E.S.S. Collaboration}
%Short title to print in the headers to the final publication (Not shown 
in this print).
\shortauthors{H.E.S.S. Collaboration}
%All the affiliations.
\afiliations{
$^1$School of Physics \& Astronomy, University of Leeds, Leeds LS2 9JT, UK\\
$^2$DAPNIA/DSM/CEA, CE Saclay, F-91191 Gif-sur-Yvette, Cedex, France\\
$^3$Max-Planck-Institut f\"ur Kernphysik, P.O. Box 103980, D 69029 
Heidelberg, Germany\\
$^4$Landessternwarte, Universit\"at Heidelberg, K\"onigstuhl, D 69117 
Heidelberg, Germany
}

\email{j.a.hinton@leeds.ac.uk}

%The abstract.
\abstract{The rapidly varying non-thermal X-ray emission observed from 
Sgr A$^{\star}$ points to
particle acceleration taking place close to the supermassive black hole. 
The TeV
$\gamma$-ray source HESS\,J1745$-$290 is coincident with Sgr A$^{\star}$ 
and may be closely related
to the X-ray emission. Simultaneous X-ray and TeV observations are 
required to
elucidate the relationship between these two objects. Here we report on 
joint
H.E.S.S./Chandra observations in July 2005, during which an X-ray flare 
was detected.
Despite a factor $>10$ increase in the X-ray flux of Sgr~A$^{\star}$, no 
evidence
is found for an increase in the TeV $\gamma$-ray flux. We find that an 
increase
of the $\gamma$-ray flux of a factor 2 or greater can be excluded at a
confidence level of 99\%. This finding disfavours scenarios in which the 
bulk
of the $\gamma$-ray emission observed is produced close to Sgr A$^{\star}$.
}