Changeset 6220 for trunk/MagicSoft/GRB-Proposal

Timestamp:

02/03/05 09:18:27 (20 years ago)

Author:

gaug

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• trunk/MagicSoft/GRB-Proposal/Introduction.tex (modified) (2 diffs)

trunk/MagicSoft/GRB-Proposal/Introduction.tex

@@ -23 +23 @@
 as well as photon-pion production~\cite{WAXMAN,BAHCALL,BOETTCHER} and inverse-Compton scattering
 in the burst environment~\cite{MESZAROS93,CHIANG,PILLA,ZHANG2,BELOBORODOV}.
-Long-term HE $\gamma$ emission from accelerated protons in the forward-shock has been predicted in~\cite{LI}. This model predicts GeV inverse Compton emission even one day after the burst.
-Even considering pure electron-synchrotron radiation, measurable GeV emission for a significant fraction of GRBs is predicted~\cite{ZHANG2}.\\
+Long-term HE $\gamma$-emission from accelerated protons in the forward-shock has been predicted in~\cite{LI}. 
+This model predicts GeV inverse Compton emission even one day after the burst.
+Even considering pure electron-synchrotron radiation, measurable GeV-emission for a significant 
+fraction of GRBs is predicted~\cite{ZHANG2}.\\
 
-GeV emission in GRBs is particularly sensitive to the Lorentz factor and the photon density of the emitting material -
-and thus to the distance of the radiating shock from the source - due to the \linebreak
-$\gamma~\gamma \rightarrow$ \textit{e$^+$~e$^-$} absorption in the emission region. Direct comparison of the prompt GRB flux at $\sim$ 10\,GeV and $\sim$ 100\,keV may allow to determine the magnetic field strength~\cite{ASAF2}.
+GeV-emission in GRBs is particularly sensitive to the Lorentz factor and the photon density of the 
+emitting material --
+and thus to the distance of the radiating shock from the source -- due to the 
+$\gamma \gamma \rightarrow \textrm{e}^+\textrm{e}^-$ absorption in the emission region. 
+Direct comparison of the prompt GRB flux at $\sim$\,10\,GeV and $\sim$\,100\,keV may 
+allow to determine the magnetic field strength~\cite{ASAF2}.
 
 \par
@@ -34 +39 @@
 Several attempts have been made in the past to observe GRBs in the GeV range,
 each indicating some excess over background but without stringent evidence.
-The only significant detection was performed by \eg which detected seven GRBs emitting high energy (HE)
+The only significant detection was performed by \eg which was able to observe seven GRBs 
+emitting high energy (HE)
 photons in the 100\,MeV to 18\,GeV range~\cite{EGRET, DINGUS1}. The data shows no evidence of a HE cut-off in the GRB spectrum~\cite{DINGUS2}. Recent results indicate that the spectrum of some GRBs contains a very hard, luminous, long-duration component~\cite{GONZALES}.
 There have been results suggesting gamma rays beyond the GeV range from the TIBET air shower array
 in coincidence with BATSE bursts~\cite{AMENOMORI}, rapid follow-up observations by the
-Whipple Air Cherenkov Telescope~\cite{CONNAUGHTON1}, and coincident and monitoring studies by HEGRA-AIROBICC~\cite{PADILLA}, Whipple~\cite{CONNAUGHTON2} and the Milagro prototype Milagrito~\cite{MILAGRO}. The GRAND array has reported some excess of observed muons during seven BATSE bursts~\cite{GRAND}. In this context, especially the publication from the TASC detector on \eg is important~\cite{GONZALES}, finding a HE spectral component presumably due to ultra-relativistic acceleration of hadrons and producing a spectral index of $-1$ with no cut-off up to the detector energy limit (200\,MeV).\\
+Whipple Air Cherenkov Telescope~\cite{CONNAUGHTON1}, and coincident and monitoring studies by 
+HEGRA-AIROBICC~\cite{PADILLA}, Whipple~\cite{CONNAUGHTON2} and the Milagro prototype Milagrito~\cite{MILAGRO}. 
+The GRAND array has reported some excess of observed muons during seven BATSE bursts~\cite{GRAND}. 
+In this context, especially the publication from the TASC detector on \eg is important~\cite{GONZALES}, 
+finding a HE spectral component presumably due to the ultra-relativistic acceleration of hadrons and 
+producing a spectral index of $-1$ with no cut-off up to the detector energy limit at 200\,MeV.\\
 
-Concerning estimates of \ma GRB observability, a very detailed study of GRB spectra obtained from the
-third and fourth \ba catalogue has been made in~\cite{ICRC,NICOLA}. The spectra were extrapolated to GeV energies with a simple continuation of the observed high-energy power law behaviour and the calculated fluxes compared with \ma sensitivities. Setting conservative cuts on observation times and significances,
-and assuming an energy threshold of 15~GeV, a GRB detection rate of $0.5-2$ per year
-was obtained for an assumed observation delay between 15 and 60 sec. and a \ba trigger rate ($\sim$\,360/year).
+Concerning estimates of the \ma GRB observability, a study of GRB spectra obtained from the
+third and fourth \ba catalogue has been made in~\cite{ICRC,NICOLA}. The spectra were extrapolated to GeV 
+energies with a simple continuation of the observed high-energy power law behaviour and the calculated 
+fluxes compared with \ma sensitivities. Setting conservative cuts on observation times and significances,
+and assuming an energy threshold of 15~GeV, a 5\,$\sigma$-signal rate of $0.5-2$ per year
+was obtained for an assumed observation delay between 15 and 60\,sec. and a \ba trigger rate 
+($\sim$\,360/year). As the \sw alert rate is about a factor~2 lower including even fainter bursts than 
+those observed by \ma, this number will still have to be lowered.
 
-Taking into account the local rate of GRBs estimated in~\cite{GUETTA}, late afterglow emission from few tens of GRBs per year
-should be observable above our energy threshold. The model of~\cite{ASAF2} predict delayed GeV emission that should be significantly detectable by MAGIC in 100\,seconds.
+Taking into account the local rate of GRBs estimated in~\cite{GUETTA}, late afterglow emission from a 
+few tens of GRBs per year should be observable over the whole sky above our energy threshold.
+The model of~\cite{ASAF2} predict delayed GeV-emission that should be significantly detectable by \ma 
+in 100\,sec.
 
 \subsection{Observation of XRFs}
 
-While the major energy from the prompt GRBs is emitted in $\gamma$-rays ($E_p \sim$ 200~keV), XRFs are characterized
-by peak energies below 50~keV and a dominant X-ray fluence. Because of similar properties a connection between XRFs and GRBs is
-suggested. The most popular theories say that XRFs are produced from GRBs observed ''off-axis''.
-Alternatively, an increase of the baryon load within the fireball itself or low efficiency shocks can produce XRFs.
+While the major energy from the prompt GRBs is emitted in $\gamma$-rays with a peak energy of 200\,keV, 
+X-ray flashes (XRFs) are characterized
+by peak energies below 50~keV and a dominant X-ray fluence. Because of similar properties, a connection 
+between XRFs and GRBs is suggested. 
+The most popular theories suggest that XRFs are produced from GRBs observed ''off-axis''.
+Alternatively, an increase of the baryon load within the fireball itself or low efficiency shocks could 
+produce XRFs.
 If there is a connection between the XRFs and GRBs, they should originate at rather low redshifts (z $<$ 0.6).\\
 
-Gamma-ray satellites react in the same way to XRFs and GRBs. In case of a detection the coordinates are distributed
+Gamma-ray satellites react in the same way to XRFs and GRBs. 
+In case of a detection the coordinates are distributed
 to other observatories (see section 2.1). Only from later analysis the difference can be established.
 
 \par
 
-In this case we include also the observation of XRFs by MAGIC in our proposal.
+We include therefore the observation of XRFs by \ma in this proposal.
 
 \subsection{Observation of SGRs}
 
-Soft Gamma Repeaters (SGRs) are extremely rare strong magnetic neutron stars that periodically emit $\gamma$-rays. Only four identified SGRs were discovered in the last 20 years: SGR0526-66, SGR1806-20, SGR1900+14, SGR1627-41. GRBs and SGRs can be explained with an unique processing gamma jet model observed at different beam-angle and at different ages.\\
+Soft Gamma Repeaters (SGRs) are believed to be extremely rare strong magnetic neutron stars that 
+periodically emit $\gamma$-rays. Only four identified SGRs were discovered in the last 20 years: 
+SGR0526-66, SGR1806-20, SGR1900+14, SGR1627-41. 
+GRBs and SGRs can be explained within one same gamma jet model where the jet is observed at different 
+beam-angles and at different ages.\\
 
-The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on 30. January 2005. The fluence was $\sim$ 1$\times$10$^{-5}$erg/cm$^2$(15-350keV). This event was five orders of magnitude smaller than the giant flare from this source on the 27. December 2004. If a giant flare from SGR occurs as SGR1806-20, MAGIC would be able to detect the $\gamma$-ray emission from the source with 100 seconds observationes time.
+The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on 30. January 2005. 
+The fluence was about $10^{-5}$\,erg/cm$^2$ in the range between 15 and 350\,keV. 
+This event was five orders of magnitude smaller than the giant flare from this source on the 
+December 27$^{th}$, 2004. 
+If a giant flare from SGR occurs as SGR1806-20, MAGIC would be able to detect the $\gamma$-ray 
+emission from the source with 100\,sec. observationes time.