  The recent {\em Chandra} observation of the radio source at the center of our
Galaxy, Sgr A$^*$, puts new constraints on its theoretical models. The spectrum
is very soft, and the source is rapidly variable. We consider different models
to explain the observations. We find that the features of the x-ray spectrum
can be marginally explained with an advection-dominated accretion flow (ADAF)
model while it does not well fit the radio spectrum. An ADAF with strong winds
(ADIOS) model is not favored if we assume that the wind does not radiate.
Alternatively, we propose a coupled jet plus accretion disk model to explain
the observations for Sgr A$^*$. The accretion flow is described as an ADAF fed
by Bondi-Hoyle accretion of hot plasma in the Galactic Center region. A small
fraction of the accretion flow is ejected near the black hole, forming a jet
after passing through a shock. As a result, the electron temperature increases
to $\sim 2 \times 10^{11}{\rm K}$, which is about 10 times higher than the
highest temperature attained in the ADAF. The model is self-consistent since
the main jet parameters are determined by the underlying accretion disk at the
inner edge. The emergent spectrum of Sgr A$^*$ is the sum of the emission from
jet and underlying ADAF. The very strong Comptonization of synchrotron emission
from the jet dominates the bremsstrahlung from the ADAF, therefore, a very
short variability timescale is expected and the predicted X-ray slope and the
radio spectrum is in very good agreement with the observations.
