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  • trunk/MagicSoft/GRB-Proposal/GRB_proposal_2005.tex

    r6251 r6550  
    5858\author{N. Galante\\ \texttt{<nicola.galante@pi.infn.it>}\\
    5959  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>}
    6263}
    6364
  • trunk/MagicSoft/GRB-Proposal/Introduction.tex

    r6275 r6550  
    33\subsection{Observation of GRBs}
    44
    5 The \ma telescope's support structure and mirrors have been designed exceptionally light in order to
    6 react quickly to GRB alerts from satellites. \cite{design} and~\cite{PETRY} set
    7 the objective to turn the telescope to the burst position within 10-30\,sec.
     5The support structure and mirrors of the \ma telescope were designed to be exceptionally light in order to
     6react quickly to GRB alerts from satellites. The aim was to turn the telescope toward the burst position
     7within 30\,s~\cite{design,PETRY},
    88in 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.\\
     9During the commissioning phase, it could be proven that the goal was achieved.
     10The telescope is able to turn $180^\circ$ in azimuth within 20\,s and $90^\circ$ in zenith within 10\,s.\\
    1111
    1212Very high energy (VHE) GRB observations have the potential to constrain the current GRB models
    13 on both prompt and extended phases of GRB emission~\cite{HARTMANN,MANNHEIM}.
    14 Models based on both internal and external shocks predict VHE gamma-ray fluences comparable to,
     13on both the prompt and the extended phase of GRB emission~\cite{HARTMANN,MANNHEIM}.
     14Models based on either internal or external shocks predict VHE gamma-ray fluences comparable to,
    1515or in certain situations stronger than, the keV-MeV radiation,
    1616with durations ranging from shorter than the keV-MeV burst to extended TeV
     
    1919\par
    2020
    21 In many publications, the possibility has been explored that more energetic $\gamma$-rays come along with the
    22 (low-energy) GRB. Proton-synchrotron emission~\cite{TOTANI} have been suggested
    23 as well as photon-pion production~\cite{WAXMAN,BOETTCHER} and inverse-Compton scattering
     21Many 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
     23photon-pion production~\cite{WAXMAN,BOETTCHER} to inverse-Compton scattering
    2424in the burst environment~\cite{MESZAROS93,CHIANG,PILLA,ZHANG2,BELOBORODOV}.
    25 Long-term high energy (HE) $\gamma$-emission from accelerated protons in the
    26 forward-shock has been predicted in~\cite{LI}.
     25A long-term high energy (HE) $\gamma$-emission can come from accelerated protons in the
     26forward-shock, as predicted in~\cite{LI}.
    2727This model predicts GeV inverse Compton emission even one day after the burst.
    2828Even considering pure electron-synchrotron radiation, measurable GeV-emission for a significant
     
    3838\par
    3939
    40 Several attempts have been made in the past to observe GRBs in the GeV range,
     40Several attempts were made in the past to observe GRBs in the GeV range,
    4141each 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}.
     42The only significant detection was performed by \eg, that was able to observe seven GRBs
     43emitting HE photons with energies between 100\,MeV and 18\,GeV~\cite{EGRET, DINGUS1}.
     44The data shows no evidence of a HE cut-off in the GRB spectrum~\cite{DINGUS2}.
     45Recent results indicate that the spectrum of some GRBs contains a very hard, luminous, long-duration component~\cite{GONZALES}.
    4546There have been results suggesting gamma rays beyond the GeV range from the TIBET air shower array
    4647in coincidence with BATSE bursts~\cite{AMENOMORI}, rapid follow-up observations by the
     
    5253producing a spectral index of $-1$ with no cut-off up to the detector energy limit at 200\,MeV.\\
    5354
    54 Concerning estimates of the \ma GRB observability, a study of GRB spectra obtained from the
    55 third and fourth \ba catalogue has been made in~\cite{ICRC,NICOLA}. The spectra were extrapolated to GeV
    56 energies with a simple continuation of the observed high-energy power law behaviour and the calculated
    57 fluxes compared with \ma sensitivities. Setting conservative cuts on observation times and significances,
     55To estimate the observability of GRB by \ma, sources of the
     56third and fourth \ba catalogue were studied~\cite{ICRC,NICOLA}. Their spectra were extended to GeV
     57energies with a simple power-law and using the observed high-energy spectral index: the extrapolated fluxes
     58were at last compared with \ma sensitivities. Setting conservative cuts on observation times and significances,
    5859and 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\,sec. and a \ba trigger rate
    60 ($\sim$\,360/year). As the \sw alert rate is about factor~2 lower, including even fainter bursts than
     60was 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
    6162those observed by \ma, this number still have to be lowered.
    6263
    6364Taking into account the local rate of GRBs estimated in~\cite{GUETTA}, late afterglow emission from a
    6465few 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 \ma
    66 in 100\,sec.
     66The model of~\cite{ASAF2} predicts delayed GeV-emission that should be significantly detectable by \ma
     67in 100\,s.
    6768
    6869\subsection{Observation of XRFs}
     
    7576Alternatively, an increase of the baryon load within the fireball itself~\cite{HUANG} or low efficiency
    7677shocks~\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)
     78If there is a connection between XRFs and GRBs, they should originate at rather low redshifts ($z < 0.6$)
    7879because otherwise, the XRF energies would not fit into the observed correlation
    7980between GRB peak energy and isotropic energy release~\cite{LEVAN}. \\
     
    9293periodically emit $\gamma$-rays. Only four identified SGRs were discovered in the last 20 years:
    9394SGR0526-66, 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 different
    95 beam-angles and at different ages~\cite{FARGION}.\\
     95GRBs and SGRs can be explained within the same gamma jet model where the jet is observed at different
     96beam-angles and different times~\cite{FARGION}.\\
    9697
    97 The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on 30. January 2005.
     98The BAT instrument on the SWIFT satellite triggered on an outburst from SGR1806-20 on January $30^{\mathrm{th}}$, 2005.
    9899The fluence was about $10^{-5}$\,erg/cm$^2$ in the range between 15 and 350\,keV.
    99100This 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 
     101December 27$^{\mathrm{th}}$, 2004~\cite{GCN3002}.
     102MAGIC 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.
     103Therefore if an SGR as the giant flare of SGR1806-20 occurs, MAGIC would be able to detect its $\gamma$-ray emission.
    105104
    106105%%% Local Variables:
  • trunk/MagicSoft/GRB-Proposal/Monitor.tex

    r6548 r6550  
    136136\subsection{Experience from SWIFT GRBs until now}
    137137
    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:\\
     138According to the \sw home page~\cite{SWIFT}, the satellite has detected 16 GRBs since mid-December last year.
     139The bursts were detected by chance during the commissioning phase. Since 15th of February the satellite sends
     140burst allerts to the \g in real time. The current sample contains three bursts
     141which could have been observed by \ma. The coordinates of the last burst from 15th February were send via an
     142alert within few seconds. The weather conditions did not allow any observation in this nights.\\
    142143
    143144\begin{tabular}{lllcc}
    14414519th & December & 2004 & 1:42 am & Zd $\sim 65^\circ$ \\
    145 26th & December & 2004 & 20:34 am & Zd $\sim 52^\circ$ \\ \\
     14626th & December & 2004 & 8:34 pm & Zd $\sim 52^\circ$ \\
     14715th & Februar & 2005 & 2:33 am & Zd $\sim 17^\circ$ \\ \\
    146148\end{tabular}
    147149
     
    212214%%% TeX-master: "GRB_proposal_2005"
    213215%%% End:
    214 \section{The Burst Alarm System at La Palma}
    215 
    216 {\bf Current status:}
    217 
    218 \par
    219 
    220 The Burst Alarm System {\it gspot} (Gamma
    221 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 experiments
    224 send GRB coordinates to the \g which distributes
    225 the alerts to registered users.
    226 The Burst Alarm System is composed of a core program which
    227 manages the monitoring of the \g and the communication with the Central Control (CC).
    228 It also handles three communication channels to notice the shifters
    229 about an alert. It is a C based daemon running 24
    230 hours a day on the {\it www} machine, our external server, in a
    231 {\it stand alone} mode. It does not need to be operated and is
    232 fully automatic. It manages network disconnections
    233 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 a
    239 TCP/IP connection to a computer at the Goddard Space Flight Center (GSFC).
    240 This computer distributes the alerts from the satellite
    241 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 GRBs
    244 and concerning the status of the connection. \\
    245 
    246 The format of the data distributed through the \g differ between the individual satellites
    247 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 coordinates
    250 (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 one
    255 inner pixel of the \ma camera.\\
    256 
    257 In case of alert, {\it gspot} stores the informations and enters
    258 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 below
    262 the astronomical horizon or have a zenith angle larger than 108$^\circ$.
    263 \item {\bf Position of GRB}: The GRB equatorial
    264 coordinates are transformed into local horizontal coordinates.
    265 The resulting GRB zenith angle has to be smaller than 70$^\circ$. If the Moon is
    266 shining, the maximal zenith angle is reduced to 65$^\circ$.
    267 \item {\bf Position of Moon}: The angular
    268 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 a
    272 {\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 confirmation
    292 that the alert notice has been received; The CC must send back the alert in order
    293 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 undertakes
    298 further steps only in case of a \textcolor{red}{\bf red alerts}.
    299 In this case, a pop-up window
    300 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 to
    304 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 -- the
    309 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 list
    311 {\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 latest
    316 alerts are displayed on a separate web page. The page is hosted at the web server in La Palma a
    317 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 way
    322 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 installed
    328 in La Palma soon. It will provide a loud acoustic signal
    329 even if the CC is switched off, so that persons in the counting house
    330 can be noticed about the alert situation. The signal will be on as long as
    331 {\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 which
    338 21 contained GRB's coordinates. Time delays to the onset of the burst
    339 were of the order of several minutes to tens of minutes. The Burst Monitor can be considered stable
    340 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 send
    353 the coordinates to the \g on time. The current sample contains two bursts
    354 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 with
    365 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 a
    368 highly eccentric orbit with a revolution period of three sidereal days around the Earth.
    369 
    370 \par
    371 
    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 \centering
    379 \includegraphics[width=0.7\linewidth]{GCNsatellites.eps}
    380 \caption{Orbits of the \sw (top), \he (center) and \ig (bottom) satellites: The pointed lines
    381 show the orbit while the drawn lines show the horizon of the Sun. Here, a typical night at
    382 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 minimum
    389 features needed to point and to observe a GRB. However, in order to improve the efficiency
    390 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 not
    397 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 time
    403 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 before
    407 the shift crew launches the CC.
    408 To solve this problem, we will change the {\it gspot} routine
    409 by implementing a list of all available GRB alerts.
    410 
    411 
    412 \par
    413 
    414 If more than one alert is present in the list, the program
    415 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 and
    418 (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: latex
    425 %%% TeX-master: "GRB_proposal_2005"
    426 %%% End:
  • trunk/MagicSoft/GRB-Proposal/Requirements.tex

    r6478 r6550  
    33In the previous sessions we described the status and tasks we still plan to do
    44in order to complete the GRB Alarm System.
    5 Parallel to our system also the different subsystems of the MAGIC telescope have
     5At the same time, also the other different subsystems of the MAGIC telescope have
    66to implement and test strategies for the GRB survey.
    77
     
    1212to make a one week shift where the experts meet and test the GRB
    1313strategies. 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 the
     14during a Moon period. This shift should take place, in arrangement with the
    1515different subsystem managers, before April this year. The time limitation is
    16 based on the moment when SWIFT will finish its comissioning phase. The sattelite
    17 started mid of February to send alerts in real time to the ground stations.
     16based on the moment when SWIFT will start to work fully automatically and send
     17alerts in real time to the ground stations.
    1818\par
    1919
     
    2626
    2727One of the most important issues is to implement and test the fast slewing capability
    28 of the telescope. Especially the communication between CC and Cosy has still to be implemented for
     28of the telescope. In particular, the communication between CC and Cosy has still to be implemented for
    2929the case of fast movements.
    3030
    3131\item {\bf Use of look-up tables:}\
    3232
    33 The use of look-up tables to correct the mirror focus during the movement to the GRB
     33The use of look-up tables to correct the mirror focus during the slewing to the GRB
    3434coordinates 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.
     35close the camera lids and carry out the full laser adjustment ($\sim 5$~min) before starting the observation.
    3636The reproducibility of the focus with the use of look-up tables has to be proven.
    3737In case of using lookup-tables during the slewing, it is necessary to change the protocol between the AMC and CC.
     
    3939\item {\bf Behaviour of the camera during moon:}\
    4040
    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.
     41It has still to be checked what happens when the telescope points directly at the Moon while
     42slewing toward a new position. The GRB Alert System prevents a burst closer than $30^\circ$
     43from the Moon to be pointed.
     44However, it can happen that during the movement of the telescope the Moon will enter the FoV.
    4445In this case the HV of the PMTs will be reduced automatically and will not increase fast enough for the
    4546GRB observation.
    46 
    4747\end{itemize}
    4848
  • trunk/MagicSoft/GRB-Proposal/Strategies.tex

    r6256 r6550  
    2828
    2929In 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 in
    31 total 10\%.
     30a minimum angular distance between the GRB and the Moon of 30$^\circ$) yielding a
     31total of 10\%.
    3232
    3333\par
    3434
    3535The duty-cycle in~\cite{NICOLA} will be increased by taking into account that \ma should also observe the
    36 afterglow emission of an burst that occurred up to 5 hours before the start of the shift.
     36afterglow emission of a burst that occurred up to 5 hours before the start of the shift.
    3737The afterglow observation is equivalent to an increase of the duty-cycle of about 6 days per month.
    3838However, taking off the full-moon time, we remain with the anticipated 10\%.\\
     
    5151
    5252We determine the maximum zenith angle for GRB observations by requiring that the overwhelming
    53 majority of possible GRBs will have an in principle observable spectrum. Figure~\ref{fig:grh}
     53majority of possible GRBs will have in principle an observable spectrum. Figure~\ref{fig:grh}
    5454shows 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 after
     55gamma-ray energy at which a fraction of $1/\mathrm{e}$ of a hypothetical mono-energetic flux gets absorbed after
    5656travelling 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.
     57GRB distances of $z=1$, all gamma-rays above 100\,GeV get absorbed before they can reach the Earth.
    5858
    5959\par
     
    7575
    7676\begin{equation}
    77 E_{thr}(\theta) = E_{thr}(0) \cdot \cos(\theta)^{-2.7}
     77E_{thr}(\theta) = E_{thr}(0) \cdot (\cos\theta)^{-2.7}
    7878\label{eq:ethrvszenith}
    7979\end{equation}
     
    8888\subsection{GRB Observations in Case of Moon Shine}
    8989
    90 {\it gspot} allows only GRBs with an angular distance of $> 30^\circ$ from the moon.
    91 The telescope's slewing in case of a GRB alert will be done
     90{\it gspot} allows only GRBs with an angular distance of $> 30^\circ$ from the Moon.
     91Telescope slewing in case of a GRB alert will be done
    9292without closing the camera lids, so that the camera could be
    93 flashed by the moon during such a movement. In principle
    94 a fast moon-flash shouldn't damage the PMTs, but the behaviour
     93flashed by the Moon during such movement. In principle,
     94a fast Moon flash should not damage the PMTs, but the behaviour
    9595of the camera and the Camera Control {\it La Guagua} must
    9696be 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.
     97to get even a short flash from the Moon, the Steering System, while slewing,
     98will have to follow a path around the Moon.
    10099
    101100\par
    102101
    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\%.
     102In December 2004, the shift in La Palma observed the Crab-Nebula even during half-moon.
     103During the observation, the nominal HV could be maintained while the currents were kept below
     1042\,$\mu$A. This means that only full-moon periods are not suitable for GRB-observations.
     105We want to stress the fact that observations at moon-time increase the chances to catch GRBs by 80\%.
    108106It is therefore mandatory that the shifters keep the camera in fully operational conditions with
    109107high-voltages switched on from the beginning of a half-moon night until the end.
    110108This includes periods where no other half-moon observations are scheduled.
    111 If no other data can be taken during the those periods, the telescope should be pointed
     109If no other data can be taken during those periods, the telescope should be pointed
    112110to a Northern direction, close to the zenith. This increases the probability to overlap
    113111with the FOV of \sw.
     
    115113\par
    116114
    117 Because of higher background with moon-light, we suggest to decrease the maximum zenith angle from
    118 $\theta_{max} = 70^\circ$ to $\theta_{max} = 65^\circ$, there.
     115In these conditions, because of higher background with moon-light, we suggest to decrease the maximum zenith angle from
     116$\theta_{max} = 70^\circ$ to $\theta_{max} = 65^\circ$.
    119117
    120118\subsection{Active Mirror Control Behaviour}
     
    142140\begin{itemize}
    143141\item In case of a repeated outbursts for a longer time period of direct observation.
    144 \item In the other case for having off-data at exactly the same sky location.
     142\item Or else, for having off-data at exactly the same sky location.
    145143\end{itemize}
    146144
  • trunk/MagicSoft/GRB-Proposal/Timing.tex

    r6272 r6550  
    88
    99Different models predict prompt and delayed HE $\gamma$-ray emission.
    10 Most of them predict HE photons parallel to the keV-MeV burst,
    11 but also delayed emission is possible.
     10Most of them predict HE photons to be simultaneous with the keV-MeV burst,
     11but also a delayed emission is possible.
    1212Our main goal should be to observe the GRB location as quickly as possible.
    1313However, in order to confirm or rule out different predictions,
     
    5353
    5454Based 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.
     55The 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}}
    5963(b) and (c) are the components which may be detectable by \ma and other ground based $\gamma$-ray detectors.
    6064
     
    6670\begin{equation}
    6771B_{min} \sim \frac{5\times10^{-2}}{\Gamma^{3}}\,
    68              \frac{\epsilon_{2ph}}{1TeV}\,
    69              \frac{t_{GRB}}{10s}\, G
     72             \frac{\epsilon_{2ph}}{1\,\mathrm{TeV}}\,
     73             \frac{t_{\mathrm{GRB}}}{10\,\mathrm{s}}\,\mathrm{G}
    7074\label{eq:minimal}
    7175\end{equation}
     
    7377If the magnetic field is much stronger than $B_{min}$,
    7478the delay of reprocessed photons may become observable.
    75 For this perpendicular case it can be calculated via the following asymptotic expression:
     79Taking into account only the components of $B$ orthogonal to the electron path,
     80the delay can be calculated via the following asymptotic expression:
    7681
    7782\begin{equation}
     
    8186
    8287For 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 shell
     88the duration time of GRB main pulse $t_{\mathrm{GRB}}=10^{2}\,\mathrm{s}$ and Lorentz factor of the GRB shell
    8489$\Gamma=10^{2}$, 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 $B_{\perp}=10\,Gauss$.\\
     90field perpendicular to electron's trajectory $B_{\perp}=0.1\,\mathrm{G}$,
     913.6 hours for $B_{\perp}=1.0\,\mathrm{G}$ and 17.3 hours for $B_{\perp}=10\,\mathrm{G}$.\\
    8792
    8893The observation of the delayed VHE emission and the time correlation will give informations
     
    95100constraints on model parameters of GRB sources.\\
    96101
    97 In the case of an \textcolor{red}{\bf Red Alarm}, we propose to take data for {\bf 5 hours}.
     102In case of a \textcolor{red}{\bf Red Alarm}, we propose to take data for {\bf 5 hours}.
    98103\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.
     104In case of a \textcolor{yellow}{\bf Yellow Alarm}, we propose to observe the source
     105from the time when it will become observable until {\bf 5 hours} after the GRB beginning.
    101106
    102107%%% Local Variables:
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