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Notes on TOO Proposals

In Cycle 1, target of opportunity (TOO) proposals for unpredictable events occurring in known objects are allowed. However, Generic TOO proposals - where the identity of the target is not known in advance (such as for "a nearby supernova") - are not allowed.

In cases where the object itself is unknown until the event happens, requests for observations can be submitted after the fact. Such "real time-TOO requests" are outside the normal proposal process. If granted, there will be no exclusive use period for the realtime TOO data.

We anticipate that a total of up to 10% of XRISM Cycle 1 observing time will be made available for proposals to observe TOOs.

It is the responsibility of the PI of an accepted TOO proposal to alert the XRISM team when the trigger conditions for their accepted TOO have been satisfied. The turnaround time is 48 hours - that is, TOO observations can generally start as early as 48 hours after notification.

Please note that untriggered or unscheduled TOOs do not carry over into Cycle 2.

Here are some rules specific to Cycle 1 TOO proposals.

  • TOO and non-TOO observations cannot be mixed in a single proposal. There is a check box on the RPS form to indicate if it is a TOO proposa.
  • Triggering criteria must be clearly specified. That is, an explicit descriptions must be given regarding what astrophysical events or conditions, when met, should lead to the observations being carried out. It is recommended that a brief summary be given in the RPS form, possibly with further details in the scientific justification.
  • TOO proposals can list up to 10 specific targets for potential observations. One target form per object must be completed, including the trigger criterion. It is allowed to request observations of a subset of the candidate targets, even if all happened to satisfy the triggering criteria with a cycle. This (called the maximum number of trigtgers, or max-trigger) must be specified on the RPS form.
    • One possible reason is to specify a smaller max-trigger to stay within the 600 ks limit that a proposal can request. In a TOO proposal, the simple sum of all the exposure times can exceed 600 ks, as long as the sum of any combination of max-trigger exposure times do not exceed 600 ks. For example, it is permissible to list 10 candidates of 150 ks per target, if and only if max-trigger is 4 or fewer.
  • The proposers must estimate the probability that the proposed investigation will be carried out during Cycle 1.
    • What we request is the proposal-wide trigger probability, not target-by-target trigger probability, except in single target TOO proposal where the two are identical.
    • For multi-trigger proposals, this should be the probability of at least one target being observed.
    • Note that untriggered TOO proposals will not be carried over to future cycles.
  • The proposers must also supply the "exposure expectation value." This is the amount of time to be charged for the TOO proposal in constructing the overall observing proposal.
    • For a single-target TOO proposal with exposure time t and trigger probability p, this is simply t x p.
    • If there are n candidates, all with same exposure time t and the same target-by-target trigger probability p, with max-trigger of 1, then enter t x [1-(1-p)n].
    • When all the exposure time values are identical, this can be generalized, without too much effort, to cases with multiple triggers and/or when the trigger probability for each target is different. In this case, the expectation value does not depend on the specific target for which the proposal is triggered.
    • In the most general case of n (less than or equall to 10) candidate targets with exposure times of ti (where i goes from 1 to n) with m (less than or equal to 10) triggers, the proposers must estimate the probability pi,j that the target i is observed using the j-th trigger (where j goes from 1 to m), then sum ti x pi,j over the appropriate ranges of i and j. Note that the ordering of the visibility windows can influence pi,j - an object with lower overall trigger probability might be observed earlier if it has a visibility window early within the Cycle 1 period.


Any questions regarding the XRISM proposal tools can be submitted to our XRISM helpdesk. You can access our helpdesk by using HEASARC's Feedback form , or click the "HELP" icon to the left.