Changeset 6778

Timestamp:

03/07/05 19:05:11 (20 years ago)

Author:

hbartko

Message:

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File:

• trunk/MagicSoft/GC-Proposal/GC.tex (modified) (3 diffs)

trunk/MagicSoft/GC-Proposal/GC.tex

@@ -242 +242 @@
 \subsection{Emission from Sgr A$^*$}
 
-
-\cite{Aharonian2005,Atoyan2004}
+Production of high-energy gamma rays within 10 Schwarzschild radii of a black hole (of any mass) could be copious because of effective acceleration of particles by the rotation-induced electric fields close to the event horizon or by strong shocks in the inner parts of the accretion disk. However, these energetic gamma rays generally cannot escape the source because of severe absorption due to interactions with the dense, low-frequency radiation through photon-photon pair production. But fortunately the supermassive black hole in our Galaxy is an exception because of its unusually low bolometric luminosity. The propagation effects related to the possible cascading in the photon filed may extend the high-energy limit to 10 TeV or even beyond \cite{Aharonian2005}.
+
+
 
 \subsubsection{Leptonic Models}
 
+Advection dominated accretion flow models, \cite{Atoyan2004}.
+
+A viable site of acceleration of highly energetic electrons could be the compact region within a few gravitational radii of the black hole. In this case the electrons produce not only curvature radiation, which peaks around 1 GeV, but also inverse Compton gamma rays (produced in the Klein-Nishina regime) with the peak emission around 100 TeV. As these high energy gammas cannot escape the source the observed gamma rays would be due to an electromagnetic cascade.
 
 \subsubsection{Hadronic Models}
 
-
-Highest energy protons: \cite{Hayashida1999}.
+One scenario is related to protons accelerated to about $10^{18}$ eV \cite{Aharonian2005}. These protons produce gamma rays via photo-meson processes. This scenario also predicts detectable fluxes of  $10^{18}$ eV neutrons and perhaps gamma rays and neutrinos. A hint of an excess of highest energy neutrons from the galactic center has been reported in \cite{Hayashida1999}.
+
+TeV gamma rays can also be produced by significantly  lower energy protons, accelerated by the electric filed close to the gravitational radius or by strung shocks in the accretion disk. In this case the gamma-ray production is dominated by interactions of $10^{13}$ eV protons with the accretion plasma. This scenario predicts a neutrino flux which should be observable with northern neutrino telescopes like NEMO. It also predicts strong TeV--X-ray--IR correlations.
 
 
@@ -340 +345 @@
 \section{Feasibility} 
 
-Plot: sensitivity limits from MAGIC compared to predicted gamma flux.
 
 The observed differential gamma flux by the HESS collaboration is given by \cite{GC_hess}:
@@ -381 +385 @@
 Cangaroo and HESS spectrum. The observed Cangaroo and HESS spectra differ
 substantially in the spectral index. While the Cangaroo spectrum only extends
-to about 2 TeV, the recently published HESS spectrum goes up to about 9 TeV. 
+to about 2 TeV, the recently published HESS spectrum goes up to about 9 TeV. Figure \ref{fig:MAGIC_flux_limits} shows the HESS and Cangaroo observed fluxes together with the mimimum detectable flux with MAGIC in 20 hours observation time.
 
 MAGIC will be able to solve the obvious discrepancy between the observed fluxes. Due to the observation under high zenith angle of about 60 deg MAGIC will be able to extend the source spectrum to higher energies.
 
 
-
-?? How long do we have to observe to get a good spectrum above 7 TeV??
+\begin{figure}[h!]
+\begin{center}
+\includegraphics[totalheight=8cm]{MAGIC_flux_limits.eps}
+\end{center}
+\caption[Flux limits.]{Observed gamma spectra of the HESS and Cangaroo experiments compared to the minimum detectable flux with the MAGIC telescope in 20 hours observation time.} \label{fig:MAGIC_flux_limits}
+\end{figure}
+
+
+
+%?? How long do we have to observe to get a good spectrum above 7 TeV??