Index: /trunk/MagicSoft/GRB-Proposal/Introduction.tex =================================================================== --- /trunk/MagicSoft/GRB-Proposal/Introduction.tex (revision 6219) +++ /trunk/MagicSoft/GRB-Proposal/Introduction.tex (revision 6220) @@ -23,10 +23,15 @@ 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 @@ -34,38 +39,63 @@ 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.