A/ What information on GRBs the TeV community would like from GLAST ?
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What can GLAST provide to aid the TeV observatories in deciding whether to repoint (IACTs) ?

1/ How many GRBs do we expect to see with the LAT ?

  a/ how many photons do we expect above a few (tens of) GeV : how does this vary with Epeak ?
  Cf Nicola's results (prompt emission), in particular : 6 GRBs/yr with >10 photons above 100 GeV

  b/ this is model-dependent ; currently 2 modelisations (Nicola & Felix) are available
     -> in the long term, would it be interesting to review models and study the most
     optimistic one ? We may be questionned on the maximal detection rate we expect...

2/ What informations will be delivered ? How fast (prompt emission) ?

  a/ position : what accuracy ? Don't forget Swift.

  b/ fluence, spectral information (index, no cut-off ?) ?


1/2/ -> estimates of how frequently we expect to have the possibility of joint observations : probably not more than a few per year


3/a/ what information will be released at the end, particularly during the 1st year (no individual photons) ?

  b/ how can we use TeV data and how TeV observers can use LAT data ?
     how someone might in practice use the TeV and LAT data in a joint analysis ?

  c/ beyond 2008, will we have to formalize a bit more the GeV-TeV collaboration on GRBs, e.g. by submitting proposals to
     the GLAST Investigator program ?

Cf Minutes of GeV/TeV Symposium, SLAC Sept 2004 : "There will be no data rights awarded to successful GI proposals [...]
The TeV community will need to prepare for the GI program and should provide feedback to members of the SWG and GUC"

--> MWL group 


4/ CAL only events :

Can we propose a trigger mode where the LAT responds in some way to an alert from the GBM that a GRB has been detected ?
Namely if GBM trigger + no TKR trigger -> only use CAL triggers during a few minutes ?

Pros : - bigger FoV than the LAT (60 deg -> 110 deg)
         -> 2 or 3 times more GRBs observable by the LAT at ~GeV energies
         -> better follow-up of each GRB at ~GeV energies
Cons : - CAL only events have a bad PSF : does not matter, only spectral measurements are important here
       - what backgd rejection power do we need ?
       - consequence on onboard filter and trigger ?

--> analysis group


B/ What information related to GRBs GLAST would like from the TeV community ?
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1/ Sensitivity to GRBs ?

- HESS : 5sigma detection in 30s for a Crab-like source at Zenith and a 100-150 GeV threshold.

Remember also that :
                     + the threshold of an Cerenkov telescope is defined as the energy where the gamma count rate
is maximal, for a standard source spectrum like the Crab nebula. For instance many sub-100 GeV gammas can be detected by
the current IACT arrays like HESS. 
                     + next generation of IACTs will have a better threshold ; for instance in the case of HESS II (operationnal in
~2008, after the addition of a 28m diameter telescope to the four 13m diameter existing telescopes), people expect a 50 GeV threshold
with the full array and probably below with the single big telescope (but probably with less sensitivity...)

2/ Procedure of TeV response to alerts :

  a/ repointing fastness and strategy (IACTs) ?
    + slew capabilities  
    + do all telescope arrays react automatically to alerts (shift instructions) ?
    + do we want to define conditions and criteria for re-pointing (according to A/2/) ?
      e.g. repoint 1 or several telescopes, depending on the spectrum and fluence measured by the LAT, etc...
    + GRB follow up to search for delayed emission ?
  b/ detection strategy : is it possible to change the threshold at the trigger level ?

Cf Minutes of GeV/TeV Symposium, SLAC Sept 2004 : "More coordination is really needed in the TeV community. Right now each
experiment works rather independently and general policies and procedures for alerts are not well established and publicized"

-> Check with each IACT that repointing at GRBs will be as much guaranteed as possible (besides GRB observation will probably
take little of their time)

example: Julie told me VERITAS has a grant from Swift -> within VERITAS, the GRB proposal is guaranteed to get time from the TAC

3/ Try to get all TeV experiments (CANGAROO, HESS, MAGIC, VERITAS, Milagro, etc.) involved so as to maximize the sky coverage

--> MWL group

4/ data, Cf above A/3/