Changeset 6550
- Timestamp:
- 02/16/05 19:32:46 (20 years ago)
- Location:
- trunk/MagicSoft/GRB-Proposal
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trunk/MagicSoft/GRB-Proposal/GRB_proposal_2005.tex
r6251 r6550 58 58 \author{N. Galante\\ \texttt{<nicola.galante@pi.infn.it>}\\ 59 59 M. Garczarczyk\\ \texttt{<garcz@mppmu.mpg.de>}\\ 60 M. Gaug\\ \texttt{<markus@ifae.es>} \\ 61 S. Mizobuchi\\ \texttt{<satoko@mppmu.mpg.de>} 60 M. Gaug\\ \texttt{<markus@ifae.es>}\\ 61 S. Mizobuchi\\ \texttt{<satoko@mppmu.mpg.de>}\\ 62 D. Bastieri\\ \texttt{<denis.bastieri@pd.infn.it>} 62 63 } 63 64 -
trunk/MagicSoft/GRB-Proposal/Introduction.tex
r6275 r6550 3 3 \subsection{Observation of GRBs} 4 4 5 The \ma telescope's support structure and mirrors have been designedexceptionally light in order to6 react quickly to GRB alerts from satellites. \cite{design} and~\cite{PETRY} set7 the objective to turn the telescope to the burst position within 10-30\,sec. 5 The support structure and mirrors of the \ma telescope were designed to be exceptionally light in order to 6 react quickly to GRB alerts from satellites. The aim was to turn the telescope toward the burst position 7 within 30\,s~\cite{design,PETRY}, 8 8 in order to have a fair chance to detect a burst when the prompt $\gamma$--emission is still ongoing. 9 During the commissioning phase, it could be proven that our goal was reached.10 The telescope is able to turn 180\,deg. in azimuth within 20\,sec. and 90\,deg. in zenith within 10\,sec.\\9 During the commissioning phase, it could be proven that the goal was achieved. 10 The telescope is able to turn $180^\circ$ in azimuth within 20\,s and $90^\circ$ in zenith within 10\,s.\\ 11 11 12 12 Very high energy (VHE) GRB observations have the potential to constrain the current GRB models 13 on both prompt and extended phasesof GRB emission~\cite{HARTMANN,MANNHEIM}.14 Models based on both internal andexternal shocks predict VHE gamma-ray fluences comparable to,13 on both the prompt and the extended phase of GRB emission~\cite{HARTMANN,MANNHEIM}. 14 Models based on either internal or external shocks predict VHE gamma-ray fluences comparable to, 15 15 or in certain situations stronger than, the keV-MeV radiation, 16 16 with durations ranging from shorter than the keV-MeV burst to extended TeV … … 19 19 \par 20 20 21 In many publications, the possibility has been explored that more energetic $\gamma$-rayscome along with the22 (low-energy) GRB. Proton-synchrotron emission~\cite{TOTANI} have been suggested23 as well as photon-pion production~\cite{WAXMAN,BOETTCHER} andinverse-Compton scattering21 Many publications foresee that high-energy $\gamma$-rays can come along with the 22 (low-energy) GRB. Possible causes range from proton-synchrotron emission~\cite{TOTANI} to 23 photon-pion production~\cite{WAXMAN,BOETTCHER} to inverse-Compton scattering 24 24 in the burst environment~\cite{MESZAROS93,CHIANG,PILLA,ZHANG2,BELOBORODOV}. 25 Long-term high energy (HE) $\gamma$-emissionfrom accelerated protons in the26 forward-shock has beenpredicted in~\cite{LI}.25 A long-term high energy (HE) $\gamma$-emission can come from accelerated protons in the 26 forward-shock, as predicted in~\cite{LI}. 27 27 This model predicts GeV inverse Compton emission even one day after the burst. 28 28 Even considering pure electron-synchrotron radiation, measurable GeV-emission for a significant … … 38 38 \par 39 39 40 Several attempts have beenmade in the past to observe GRBs in the GeV range,40 Several attempts were made in the past to observe GRBs in the GeV range, 41 41 each indicating some excess over background but without stringent evidence. 42 The only significant detection was performed by \eg which was able to observe seven GRBs 43 emitting HE 44 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}. 42 The only significant detection was performed by \eg, that was able to observe seven GRBs 43 emitting HE photons with energies between 100\,MeV and 18\,GeV~\cite{EGRET, DINGUS1}. 44 The data shows no evidence of a HE cut-off in the GRB spectrum~\cite{DINGUS2}. 45 Recent results indicate that the spectrum of some GRBs contains a very hard, luminous, long-duration component~\cite{GONZALES}. 45 46 There have been results suggesting gamma rays beyond the GeV range from the TIBET air shower array 46 47 in coincidence with BATSE bursts~\cite{AMENOMORI}, rapid follow-up observations by the … … 52 53 producing a spectral index of $-1$ with no cut-off up to the detector energy limit at 200\,MeV.\\ 53 54 54 Concerning estimates of the \ma GRB observability, a study of GRB spectra obtained fromthe55 third and fourth \ba catalogue has been made in~\cite{ICRC,NICOLA}. The spectra were extrapolated to GeV56 energies with a simple continuation of the observed high-energy power law behaviour and the calculated57 fluxescompared with \ma sensitivities. Setting conservative cuts on observation times and significances,55 To estimate the observability of GRB by \ma, sources of the 56 third and fourth \ba catalogue were studied~\cite{ICRC,NICOLA}. Their spectra were extended to GeV 57 energies with a simple power-law and using the observed high-energy spectral index: the extrapolated fluxes 58 were at last compared with \ma sensitivities. Setting conservative cuts on observation times and significances, 58 59 and assuming an energy threshold of 15~GeV, a 5\,$\sigma$-signal rate of $0.5-2$ per year 59 was obtained for an assumed observation delay between 15 and 60\,s ec.and a \ba trigger rate60 ($\sim$\,360/year). As the \sw alert rate is about factor~2 lower, including even fainter bursts than60 was obtained for an assumed observation delay between 15 and 60\,s and a \ba trigger rate 61 ($\sim$\,360/year). As the \sw alert rate is about a factor~2 lower, including even fainter bursts than 61 62 those observed by \ma, this number still have to be lowered. 62 63 63 64 Taking into account the local rate of GRBs estimated in~\cite{GUETTA}, late afterglow emission from a 64 65 few tens of GRBs per year should be observable over the whole sky above our energy threshold. 65 The model of~\cite{ASAF2} predict delayed GeV-emission that should be significantly detectable by \ma66 in 100\,s ec.66 The model of~\cite{ASAF2} predicts delayed GeV-emission that should be significantly detectable by \ma 67 in 100\,s. 67 68 68 69 \subsection{Observation of XRFs} … … 75 76 Alternatively, an increase of the baryon load within the fireball itself~\cite{HUANG} or low efficiency 76 77 shocks~\cite{BARRAUD} could produce XRFs. 77 If there is a connection between XRFs and GRBs, they should originate at rather low redshifts ( z $<$ 0.6)78 If there is a connection between XRFs and GRBs, they should originate at rather low redshifts ($z < 0.6$) 78 79 because otherwise, the XRF energies would not fit into the observed correlation 79 80 between GRB peak energy and isotropic energy release~\cite{LEVAN}. \\ … … 92 93 periodically emit $\gamma$-rays. Only four identified SGRs were discovered in the last 20 years: 93 94 SGR0526-66, SGR1806-20, SGR1900+14, SGR1627-41. 94 GRBs and SGRs can be explained within one same gamma jet model where the jet is observed at different95 beam-angles and at different ages~\cite{FARGION}.\\95 GRBs and SGRs can be explained within the same gamma jet model where the jet is observed at different 96 beam-angles and different times~\cite{FARGION}.\\ 96 97 97 The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on 30. January2005.98 The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on January $30^{\mathrm{th}}$, 2005. 98 99 The fluence was about $10^{-5}$\,erg/cm$^2$ in the range between 15 and 350\,keV. 99 100 This event was five orders of magnitude smaller than the giant flare from this source on the 100 December 27$^{th}$, 2004~\cite{GCN3002}. MAGIC have a enough sensitivity for observing the event which have a fluence more than 2.5 $\times$ 10 $^{-2}$ erg/cm$^{2} \cdot$\,sec at 100\,keV, when power law index of -2.0 and 100 sec. observation time are assumpted. Therefore if a giant flare from SGR occurs as SGR1806-20, MAGIC would be able to detect the $\gamma$-ray emission from these source. 101 102 103 104 101 December 27$^{\mathrm{th}}$, 2004~\cite{GCN3002}. 102 MAGIC has enough sensitivity for observing events with fluences bigger than $2.5 \times 10^{-2}\mathrm{erg}\cdot\mathrm{cm}^{-2}\mathrm{s}^{-1}$ at 100\,keV, when a spectral index of $-2.0$ and 100\,s of observation time are assumed. 103 Therefore if an SGR as the giant flare of SGR1806-20 occurs, MAGIC would be able to detect its $\gamma$-ray emission. 105 104 106 105 %%% Local Variables: -
trunk/MagicSoft/GRB-Proposal/Monitor.tex
r6548 r6550 136 136 \subsection{Experience from SWIFT GRBs until now} 137 137 138 According to the \sw home page~\cite{SWIFT}, the satellite has detected 12 GRBs since mid-December last year. 139 The bursts were detected by chance during the commissioning phase. The satellite did not send 140 the coordinates to the \g on time. The current sample contains two bursts 141 which could have been observed by \ma:\\ 138 According to the \sw home page~\cite{SWIFT}, the satellite has detected 16 GRBs since mid-December last year. 139 The bursts were detected by chance during the commissioning phase. Since 15th of February the satellite sends 140 burst allerts to the \g in real time. The current sample contains three bursts 141 which could have been observed by \ma. The coordinates of the last burst from 15th February were send via an 142 alert within few seconds. The weather conditions did not allow any observation in this nights.\\ 142 143 143 144 \begin{tabular}{lllcc} 144 145 19th & December & 2004 & 1:42 am & Zd $\sim 65^\circ$ \\ 145 26th & December & 2004 & 20:34 am & Zd $\sim 52^\circ$ \\ \\ 146 26th & December & 2004 & 8:34 pm & Zd $\sim 52^\circ$ \\ 147 15th & Februar & 2005 & 2:33 am & Zd $\sim 17^\circ$ \\ \\ 146 148 \end{tabular} 147 149 … … 212 214 %%% TeX-master: "GRB_proposal_2005" 213 215 %%% End: 214 \section{The Burst Alarm System at La Palma}215 216 {\bf Current status:}217 218 \par219 220 The Burst Alarm System {\it gspot} (Gamma221 Sources Pointing Trigger) is working in La Palma since last summer.222 It performs a full-time survey of the {\it GRB Coordinates Network} (\g) alerts~\cite{GCN}.223 Different satellite experiments224 send GRB coordinates to the \g which distributes225 the alerts to registered users.226 The Burst Alarm System is composed of a core program which227 manages the monitoring of the \g and the communication with the Central Control (CC).228 It also handles three communication channels to notice the shifters229 about an alert. It is a C based daemon running 24230 hours a day on the {\it www} machine, our external server, in a231 {\it stand alone} mode. It does not need to be operated and is232 fully automatic. It manages network disconnections233 within the external net and/or the internal one.234 235 236 \subsection{The Connection to the GCN}237 238 The connection to the \g is performed by {\it gspot} through a239 TCP/IP connection to a computer at the Goddard Space Flight Center (GSFC).240 This computer distributes the alerts from the satellite241 experiments through an internet socket connection. {\it gspot}242 acts as a server while the client, running at the GSFC,243 manages the communication of the data concerning the GRBs244 and concerning the status of the connection. \\245 246 The format of the data distributed through the \g differ between the individual satellites247 and the kind of package. Currently, three satellites participate in the GRB survey:248 HETE-2~\cite{HETE}, INTEGRAL~\cite{INTEGRAL} and SWIFT~\cite{SWIFT}.249 The alerts include the UTC, the GRB coordinates (not always), error on coordinates250 (not always) and intensity (photon counts) of the burst.251 The first notices from HETE-2 and INTEGRAL usually do not include the coordinates.252 In few cases only coordinates are distributed in refined notices.253 The \sw alerts are predicted to arrive with coordinates between 30-80 sec after the onset of the burst.254 The error on the coordinates from the BAT detector will be 4 arcmin which is smaller than the size of one255 inner pixel of the \ma camera.\\256 257 In case of alert, {\it gspot} stores the informations and enters258 an {\bf Alarm State}. The duration of the alarm depends on the following parameters:259 260 \begin{itemize}261 \item {\bf Darkness of the sky}: The Sun has to be below262 the astronomical horizon or have a zenith angle larger than 108$^\circ$.263 \item {\bf Position of GRB}: The GRB equatorial264 coordinates are transformed into local horizontal coordinates.265 The resulting GRB zenith angle has to be smaller than 70$^\circ$. If the Moon is266 shining, the maximal zenith angle is reduced to 65$^\circ$.267 \item {\bf Position of Moon}: The angular268 distance from the GRB to the moon has to be at least 30$^\circ$.269 \end{itemize}270 271 If one or more of these conditions fail, {\it gspot} enters into a272 {\color[rgb]{0.9,0.75,0.}\bf Yellow Alarm State}: The GRB is not observable at the moment.273 Currently, the program does not calculate if and when the GRB will become observable for \ma.274 If all the mentioned conditions are satisfied,275 {\it gspot} enters into a \textcolor{red}{\bf Red Alarm State}, meaning that the GRB is observable.\\276 277 In both cases (\textcolor{red}{\bf RED} or {\color[rgb]{0.9,0.75,0.}\bf YELLOW} Alarm State), {\it gspot} establishes the communication with the CC and sends the GRB equatorial coordinates (RA/DEC J2000).278 For the communication with CC the format defined in~\cite{CONTROL} is used. At the same time,279 the shifters and the GRB-MAGIC group is contacted.280 281 \subsection{The Interface to the Central Control}282 283 An interface of {\it gspot} sends all the relevant information to the CC.284 When {\it gspot} is not in alarm state, standard packages are continuously exchanged between CC and {\it gspot}.285 These packages contain the main global status of the two subsystems.286 In case of alert, {\it gspot} starts to send special alert packages to the CC,287 containing information about the GRB and the ``color'' of the alert.288 The exchange of the alert packages continues until:289 290 \begin{itemize}291 \item {\it gspot} receives from the CC the confirmation292 that the alert notice has been received; The CC must send back the alert in order293 to perform a cross-check of the relevant data.294 \item the alarm state expires after {\bf 5 hours}295 \end{itemize}296 297 The CC informs the shift crew about the alert and undertakes298 further steps only in case of a \textcolor{red}{\bf red alerts}.299 In this case, a pop-up window300 appears with all the alert information received by the burst monitor.301 The operator has to confirm the notice by closing the pop-up window.302 He can decide whether to stop the current scheduled observation and to point the GRB.303 A new button will be displayed in the CC allowing to point the telescope to304 the GRB coordinates.305 306 \subsection{GRB Archive and Emails to the GRB-mailing List}307 308 In case of alert -- even if it did not contain the necessary coordinates -- the309 information is translated into ``human language'' and stored in ASCII files.310 At the same time, an e-mail is sent to the MAGIC GRB-mailing list311 {\it grb@mppmu.mpg.de}.312 313 \subsection{The GRB Web Page}314 315 The status of the GRB Alert System and relevant informations about the latest316 alerts are displayed on a separate web page. The page is hosted at the web server in La Palma a317 and can be accessed under:\\318 319 \qquad \qquad http://www.magic.iac.es/site/grbm/\\320 321 The web page updates itself automatically every 10 seconds. In this way322 the status of the Burst Alarm System can be checked by the shifters and from outside.323 324 \subsection{The Acoustic Alert}325 326 A further CC-independent acoustic alarm called {\it phava}327 (PHonetic Alarm for Valued Alerts) will be installed328 in La Palma soon. It will provide a loud acoustic signal329 even if the CC is switched off, so that persons in the counting house330 can be noticed about the alert situation. The signal will be on as long as331 {\it gspot} remains in alarm state for a minimum of 1 minute.332 The device features also a display with the status of the system and the alert.333 334 \subsection{Summary of Alerts Received Until Now}335 336 Since July 15$^{\mathrm{th}}$, 2004, {\it gspot} has been working stably at La Palma.337 It received about 100 alerts from HETE-2 and INTEGRAL, out of which338 21 contained GRB's coordinates. Time delays to the onset of the burst339 were of the order of several minutes to tens of minutes. The Burst Monitor can be considered stable340 since November, 2004. Since then, we have received the following two significant alerts:\\341 342 \begin{tabular}{lllcccl}343 19th & December & 2004 & 1:44 am & INTEGRAL satellite & Zd $\sim 60^\circ$ & Time delay 71 sec.\\344 28th & January & 2005 & 5:36 am & HETE-2 satellite & Zd $\sim 65^\circ$ & Time delay 73 min. \\ \\345 \end{tabular}346 347 In both cases the weather conditions at La Palma were bad.348 349 \subsection{Experience from SWIFT GRBs until now}350 351 According to the \sw home page~\cite{SWIFT}, the satellite has detected 12 GRBs since mid-December last year.352 The bursts were detected by chance during the commissioning phase. The satellite did not send353 the coordinates to the \g on time. The current sample contains two bursts354 which could have been observed by \ma:\\355 356 \begin{tabular}{lllcc}357 19th & December & 2004 & 1:42 am & Zd $\sim 65^\circ$ \\358 26th & December & 2004 & 20:34 am & Zd $\sim 52^\circ$ \\ \\359 \end{tabular}360 361 \subsection{Comparison between the Satellite Orbits}362 363 Figure~\ref{fig:orbit} shows the orbits of the \sw, \he and \ig satellites.364 The \sw and \he satellites are situated in a circular orbit with365 20.6$^\circ$ and 2$^\circ$ inclination, respectively.366 One revolution of the \sw and \he satellites last about 100\,min.367 The \ig satellite has a368 highly eccentric orbit with a revolution period of three sidereal days around the Earth.369 370 \par371 372 It is difficult to draw strong conclusions from the individual satellites' orbits.373 The orientation of the satellites' FOV is influenced by the scheduled targets.374 However, \sw is the satellite with the largest inclination and overlaps mostly with the FOV of \ma.375 This increases the chance to receive {\bf Red Alarms} from this satellite.376 377 \begin{figure}[htp]378 \centering379 \includegraphics[width=0.7\linewidth]{GCNsatellites.eps}380 \caption{Orbits of the \sw (top), \he (center) and \ig (bottom) satellites: The pointed lines381 show the orbit while the drawn lines show the horizon of the Sun. Here, a typical night at382 La Palma is shown. The \sw satellite passes over the Roque seven times each night.}383 \label{fig:orbit}384 \end{figure}385 386 \subsection{Routines to Be Defined}387 388 The Burst Alarm System is currently able to provide the minimum389 features needed to point and to observe a GRB. However, in order to improve the efficiency390 to point and observe GRBs, several procedures have to be defined:391 392 \begin{itemize}393 \item {\bf Yellow Alarm strategy}:394 The strategy to follow a {\bf Yellow Alarm} is not defined yet.395 In such a case, the CC does not undertake any steps,396 except confirming the alarm notice to the Burst Monitor. We have not397 calculated yet if and when the GRB will become observable.398 It would make sense to check if we could point to the burst during the period of 5 hours.399 The Alarm System should change to a {\bf Red Alarm State}, then.400 401 \item {\bf Sequence of alerts}:402 How to deal with new alerts that are distributed during the time403 that {\it gspot} is in alarm state? Currently, {\it gspot}404 locks its alert status until it exits the alarm state (see session 2.2).405 This feature was implemented to avoid any loss of GRB information.406 Such a situation can occur for example if more than one burst alert is sent before407 the shift crew launches the CC.408 To solve this problem, we will change the {\it gspot} routine409 by implementing a list of all available GRB alerts.410 411 412 \par413 414 If more than one alert is present in the list, the program415 will weight the possible GRBs according to the following criteria:416 (1) the total time of observability within the canonical 5 hours,417 (2) the intensity of the burst and418 (3) the time until the GRB becomes observable.419 The information of the best GRB will be sent to the CC.420 421 \end{itemize}422 423 %%% Local Variables:424 %%% mode: latex425 %%% TeX-master: "GRB_proposal_2005"426 %%% End: -
trunk/MagicSoft/GRB-Proposal/Requirements.tex
r6478 r6550 3 3 In the previous sessions we described the status and tasks we still plan to do 4 4 in order to complete the GRB Alarm System. 5 Parallel to our system also thedifferent subsystems of the MAGIC telescope have5 At the same time, also the other different subsystems of the MAGIC telescope have 6 6 to implement and test strategies for the GRB survey. 7 7 … … 12 12 to make a one week shift where the experts meet and test the GRB 13 13 strategies. In order to avoid good observation time we suggest to make the shift 14 during a moon period. This shift should take place, in arrangement with the14 during a Moon period. This shift should take place, in arrangement with the 15 15 different subsystem managers, before April this year. The time limitation is 16 based on the moment when SWIFT will finish its comissioning phase. The sattelite17 started mid of February to sendalerts in real time to the ground stations.16 based on the moment when SWIFT will start to work fully automatically and send 17 alerts in real time to the ground stations. 18 18 \par 19 19 … … 26 26 27 27 One of the most important issues is to implement and test the fast slewing capability 28 of the telescope. Especiallythe communication between CC and Cosy has still to be implemented for28 of the telescope. In particular, the communication between CC and Cosy has still to be implemented for 29 29 the case of fast movements. 30 30 31 31 \item {\bf Use of look-up tables:}\ 32 32 33 The use of look-up tables to correct the mirror focus during the movementto the GRB33 The use of look-up tables to correct the mirror focus during the slewing to the GRB 34 34 coordinates is desirable. In the alert situation it is a waste of time if we would have to 35 close the camera lids and carry out the full laser adjustment ( \~5~min) before starting the observation.35 close the camera lids and carry out the full laser adjustment ($\sim 5$~min) before starting the observation. 36 36 The reproducibility of the focus with the use of look-up tables has to be proven. 37 37 In case of using lookup-tables during the slewing, it is necessary to change the protocol between the AMC and CC. … … 39 39 \item {\bf Behaviour of the camera during moon:}\ 40 40 41 It has to be checked what happens when during the pointing to a GRB position the telescope move over the 42 moon. It is excluded by the GRB Alert System that a burst closer than 30$\deg$ to the moon will be pointed. 43 However, it can happen that during the movement of the telescope the moon will pass the FOV. 41 It has still to be checked what happens when the telescope points directly at the Moon while 42 slewing toward a new position. The GRB Alert System prevents a burst closer than $30^\circ$ 43 from the Moon to be pointed. 44 However, it can happen that during the movement of the telescope the Moon will enter the FoV. 44 45 In this case the HV of the PMTs will be reduced automatically and will not increase fast enough for the 45 46 GRB observation. 46 47 47 \end{itemize} 48 48 -
trunk/MagicSoft/GRB-Proposal/Strategies.tex
r6256 r6550 28 28 29 29 In these duty-cycle studies also full-moon nights were considered (requiring 30 a minimum angular distance between the GRB and the moon of 30$^\circ$) yielding in31 total 10\%.30 a minimum angular distance between the GRB and the Moon of 30$^\circ$) yielding a 31 total of 10\%. 32 32 33 33 \par 34 34 35 35 The duty-cycle in~\cite{NICOLA} will be increased by taking into account that \ma should also observe the 36 afterglow emission of a n burst that occurred up to 5 hours before the start of the shift.36 afterglow emission of a burst that occurred up to 5 hours before the start of the shift. 37 37 The afterglow observation is equivalent to an increase of the duty-cycle of about 6 days per month. 38 38 However, taking off the full-moon time, we remain with the anticipated 10\%.\\ … … 51 51 52 52 We determine the maximum zenith angle for GRB observations by requiring that the overwhelming 53 majority of possible GRBs will have an in principleobservable spectrum. Figure~\ref{fig:grh}53 majority of possible GRBs will have in principle an observable spectrum. Figure~\ref{fig:grh} 54 54 shows the gamma-ray horizon (GRH) as computed in~\cite{KNEISKE,SALOMON}. The GRH is defined as the 55 gamma-ray energy at which a part of $1/e$ of a hypothetical mono-energetic flux gets absorbed after55 gamma-ray energy at which a fraction of $1/\mathrm{e}$ of a hypothetical mono-energetic flux gets absorbed after 56 56 travelling a distance, expressed in redshift $z$, from the source. One can see that at typical 57 GRB distances of $z=1$, all gamma-rays above 100\,GeV get absorbed before they can reach the earth.57 GRB distances of $z=1$, all gamma-rays above 100\,GeV get absorbed before they can reach the Earth. 58 58 59 59 \par … … 75 75 76 76 \begin{equation} 77 E_{thr}(\theta) = E_{thr}(0) \cdot \cos(\theta)^{-2.7}77 E_{thr}(\theta) = E_{thr}(0) \cdot (\cos\theta)^{-2.7} 78 78 \label{eq:ethrvszenith} 79 79 \end{equation} … … 88 88 \subsection{GRB Observations in Case of Moon Shine} 89 89 90 {\it gspot} allows only GRBs with an angular distance of $> 30^\circ$ from the moon.91 T he telescope'sslewing in case of a GRB alert will be done90 {\it gspot} allows only GRBs with an angular distance of $> 30^\circ$ from the Moon. 91 Telescope slewing in case of a GRB alert will be done 92 92 without closing the camera lids, so that the camera could be 93 flashed by the moon during such a movement. In principle94 a fast moon-flash shouldn't damage the PMTs, but the behaviour93 flashed by the Moon during such movement. In principle, 94 a fast Moon flash should not damage the PMTs, but the behaviour 95 95 of the camera and the Camera Control {\it La Guagua} must 96 96 be tested. On the other hand, if such tests conclude that it is not safe 97 to get even a short flash from the moon, the possibility 98 to implement a new feature into the Steering System must be considered 99 which follow a path around the moon while slewing. 97 to get even a short flash from the Moon, the Steering System, while slewing, 98 will have to follow a path around the Moon. 100 99 101 100 \par 102 101 103 There was a shift observing the Crab-Nebula with half-moon at La Palma in December 2004. 104 That experience showed that the nominal HV could be maintained and gave no 105 currents higher than 2\,$\mu$A. This means that moon-periods can be used for GRB-observations 106 without fundamental modifications except for full-moon periods. We want to stress that 107 these periods increase the chances to catch GRBs by 80\%. 102 In December 2004, the shift in La Palma observed the Crab-Nebula even during half-moon. 103 During the observation, the nominal HV could be maintained while the currents were kept below 104 2\,$\mu$A. This means that only full-moon periods are not suitable for GRB-observations. 105 We want to stress the fact that observations at moon-time increase the chances to catch GRBs by 80\%. 108 106 It is therefore mandatory that the shifters keep the camera in fully operational conditions with 109 107 high-voltages switched on from the beginning of a half-moon night until the end. 110 108 This includes periods where no other half-moon observations are scheduled. 111 If no other data can be taken during th e those periods, the telescope should be pointed109 If no other data can be taken during those periods, the telescope should be pointed 112 110 to a Northern direction, close to the zenith. This increases the probability to overlap 113 111 with the FOV of \sw. … … 115 113 \par 116 114 117 Because of higher background with moon-light, we suggest to decrease the maximum zenith angle from118 $\theta_{max} = 70^\circ$ to $\theta_{max} = 65^\circ$ , there.115 In these conditions, because of higher background with moon-light, we suggest to decrease the maximum zenith angle from 116 $\theta_{max} = 70^\circ$ to $\theta_{max} = 65^\circ$. 119 117 120 118 \subsection{Active Mirror Control Behaviour} … … 142 140 \begin{itemize} 143 141 \item In case of a repeated outbursts for a longer time period of direct observation. 144 \item In the other casefor having off-data at exactly the same sky location.142 \item Or else, for having off-data at exactly the same sky location. 145 143 \end{itemize} 146 144 -
trunk/MagicSoft/GRB-Proposal/Timing.tex
r6272 r6550 8 8 9 9 Different models predict prompt and delayed HE $\gamma$-ray emission. 10 Most of them predict HE photons parallel tothe keV-MeV burst,11 but also delayed emission is possible.10 Most of them predict HE photons to be simultaneous with the keV-MeV burst, 11 but also a delayed emission is possible. 12 12 Our main goal should be to observe the GRB location as quickly as possible. 13 13 However, in order to confirm or rule out different predictions, … … 53 53 54 54 Based on the model in~\cite{DERISHEV}, three different components of VHE emission exists in an GRB. 55 The corresponding components are illustrated in figure~\ref{fig:timeline}. 56 (a) There is the prompt 100\,GeV peak before and during the first keV-MeV peak, 57 (b) the VHE emission due to Inverse Compton scattering lasting for the whole duration of the GRB pulse and 58 (c) the reprocessed Inverse Compton emission which may last up to hours after the GRB onset. 55 The corresponding components are illustrated in figure~\ref{fig:timeline}. 56 \renewcommand{\theenumi}{\alph{enumi}} 57 \begin{enumerate} 58 \item There is the prompt 100\,GeV peak before and during the first keV-MeV peak, 59 \item the VHE emission due to Inverse Compton scattering lasting for the whole duration of the GRB pulse and 60 \item the reprocessed Inverse Compton emission which may last up to hours after the GRB onset. 61 \end{enumerate} 62 \renewcommand{\theenumi}{\arabic{enumi}} 59 63 (b) and (c) are the components which may be detectable by \ma and other ground based $\gamma$-ray detectors. 60 64 … … 66 70 \begin{equation} 67 71 B_{min} \sim \frac{5\times10^{-2}}{\Gamma^{3}}\, 68 \frac{\epsilon_{2ph}}{1 TeV}\,69 \frac{t_{ GRB}}{10s}\, G72 \frac{\epsilon_{2ph}}{1\,\mathrm{TeV}}\, 73 \frac{t_{\mathrm{GRB}}}{10\,\mathrm{s}}\,\mathrm{G} 70 74 \label{eq:minimal} 71 75 \end{equation} … … 73 77 If the magnetic field is much stronger than $B_{min}$, 74 78 the delay of reprocessed photons may become observable. 75 For this perpendicular case it can be calculated via the following asymptotic expression: 79 Taking into account only the components of $B$ orthogonal to the electron path, 80 the delay can be calculated via the following asymptotic expression: 76 81 77 82 \begin{equation} … … 81 86 82 87 For typical values of the absorption threshold $\epsilon_{2ph}=1\,TeV$, 83 the duration time of GRB main pulse $t_{ GRB}=10^{2}\,s$ and Lorentz factor of the GRB shell88 the duration time of GRB main pulse $t_{\mathrm{GRB}}=10^{2}\,\mathrm{s}$ and Lorentz factor of the GRB shell 84 89 $\Gamma=10^{2}$, the duration of delayed VHE emission will be 0.8 hours for the component of magnetic 85 field perpendicular to electron's trajectory $B_{\perp}=0.1\, Gauss$,86 3.6 hours for $B_{\perp}=1.0\, Gauss$ and 17.3 hours for $B_{\perp}=10\,Gauss$.\\90 field perpendicular to electron's trajectory $B_{\perp}=0.1\,\mathrm{G}$, 91 3.6 hours for $B_{\perp}=1.0\,\mathrm{G}$ and 17.3 hours for $B_{\perp}=10\,\mathrm{G}$.\\ 87 92 88 93 The observation of the delayed VHE emission and the time correlation will give informations … … 95 100 constraints on model parameters of GRB sources.\\ 96 101 97 In the case of an\textcolor{red}{\bf Red Alarm}, we propose to take data for {\bf 5 hours}.102 In case of a \textcolor{red}{\bf Red Alarm}, we propose to take data for {\bf 5 hours}. 98 103 \par 99 In the case of an \textcolor{yellow}{\bf Yellow Alarm},100 we propose to observe the source from the time when it will become observable until the {\bf 5 hours} pass.104 In case of a \textcolor{yellow}{\bf Yellow Alarm}, we propose to observe the source 105 from the time when it will become observable until {\bf 5 hours} after the GRB beginning. 101 106 102 107 %%% Local Variables:
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