------------------------------------------------------------------------
 ZNDI.tex Phys.Rev.D, 2007, in press
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%arXiv:0707.4423v1
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\begin{document}
\preprint{}
\title{Apoastron Shift Constraints on Dark Matter Distribution at the Galactic
Center}% Force line breaks
%with \\
\author{A.F. Zakharov}
\email{zakharov@itep.ru}
\affiliation{National Astronomical Observatories of Chinese
Academy of Sciences, Beijing 100012, China} \altaffiliation[Also
at~]{Institute of
Theoretical and Experimental Physics, Moscow, 117259, Russia;\\
CAMP, %\\
National University of Sciences and Technology, Rawalpindi, Pakistan;\\
BLTP, Joint Institute for Nuclear Research, Dubna,   Russia
%Lines break
%automatically or can be forced with \\
}
\author{A.A. Nucita}%
 \email{anucita@sciops.esa.int}
%\altaffiliation[Now at~]{XMM-Newton Science Operations Centre,
%ESAC, ESA, PO Box 50727, 28080 Madrid, Spain }
\affiliation{Department of Physics and {\it INFN}, University of
Lecce, CP 193, I-73100 Lecce, Italy;\\
XMM-Newton Science Operations Centre, ESAC, ESA, PO Box
50727, 28080 Madrid, Spain} %\altaffiliation[Now at~]{XMM-Newton
%Science Operations Centre, ESAC, ESA, PO Box 50727, 28080 Madrid,
%Spain }\emph{}
\author{F. De Paolis}%
\email{Francesco.DePaolis@le.infn.it} \affiliation{Department of
Physics and {\it INFN}, University of Lecce, CP 193, I-73100
Lecce, Italy}
\author{G. Ingrosso}
\email{Gabriele.Ingrosso@le.infn.it}
% \homepage{http://www.Second.institution.edu/~Charlie.Author}
\affiliation{Department of Physics and {\it INFN}, University of
Lecce, CP 193, I-73100 Lecce, Italy}

\date{\today}
\begin{abstract}
The existence of dark matter (DM) at scales of few pc down to
$\simeq 10^{-5}$ pc around  the centers of galaxies and in
particular in the Galactic Center region has been considered in
the literature. Under the assumption that such a DM clump,
principally constituted by non-baryonic matter (like WIMPs) does
exist at the center of our galaxy, the study of the $\gamma$-ray
emission from the Galactic Center region allows us to constrain
both the mass and the size of this DM sphere. Further constraints
on the DM distribution parameters may be derived by observations
of bright infrared stars around the Galactic Center. Hall and
Gondolo \cite{hallgondolo} used estimates of the enclosed mass
obtained in various ways and tabulated by Ghez et al.
\cite{Ghez_2003,Ghez_2005}. Moreover, if a DM cusp does exist
around the Galactic Center it could modify the trajectories of
stars moving around it in a sensible way depending on the DM mass
distribution. Here, we discuss the constraints that can be
obtained with the orbit analysis of stars (as S2 and S16) moving
inside the DM concentration with present and next generations of
large telescopes. In particular, consideration of the S2 star
apoastron shift may allow improving limits on the DM mass and
size.
\end{abstract}
\pacs{04.80.Cc, 04.20.-q, 04.25.Nx, 04.50.+h, 95.30.Sf, 96.12.Fe}% PACS, the
Physics and Astronomy
\keywords{black hole physics --- galaxies: Nuclei --- Galaxy:
center
--- stars: dark matter: individual (Sgr A$^*$)}%Use showkeys class option if
keyword
\maketitle
\end{document}