IXPE Target of Opportunity (ToO)

Please use the web form below to trigger an existing approved GO Target of Opportunity (ToO) program or to submit an unanticipated observation to be considered for Director's Discrency Time (DDT). Note that unanticipated ToO and DDT observation requests will, in general, not be considered for events or sources that could have been proposed for in GO programs. In particular, requests for observations of these type of sources and events not included in an approved GO program require special justification describing why the requested observation type could not have been proposed as a GO target. Current US law prevents us from accepting proposals from the PRC. No response will be made to requests providing a Chinese institution, email, or phone number.

IXPE ToO response: ToO observations with longer lead times are less intensive for the operations team and are more likely to be approved and successfully scheduled. A "fast" response ToO is defined as the observation beginning within 3 days of the request. These are particularly difficult to implement and are approved only for exceptional astrophysical events. Due to the timing of the IXPE planning cycle, ToO requests for observations beginning on a Thursday and submitted at least 10 days in advance (Monday morning) are easier to schedule and more likely to be approved. Observations of bright targets (0.5 Crab or brighter) must be limited in duration. Additional time may be needed for planning for bright sources since additional ground contacts may need to be scheduled.

IXPE should not be used just to measure the X-ray flux of a source. IXPE is intended to measure the polarization of X rays, which requires a large number of counts. It will help your proposal if you can estimate the level of polarization you expect to see from your source. In any case, you must estimate the Minimum Detectable Polarization (MDP) you expect to achieve with this observation. Both the source count rate and MDP can be estimated using WebPIMMS .

The ability to get data off the spacecraft is limited and this limits how long a bright source can be observed before we need to switch to a faint target. For example, the Crab can only be observed for 2 days before the on-board storage is filled (assuming it was empty at the start) and it will take up to a week to download the data. Therefore, proposers also need to estimate the source counting rate in the full IXPE band using WebPIMMS .

Please review the IXPE as run target list to see if your target has already been observed. Also check the IXPE Long Term Plan to see if an observation target is already planned.

Please check to see if your target is currently observable with IXPE using viewing.

IXPE data associated with ToO requests will have no exclusive use period and will be available via the public archive at the HEASARC nominally within one week of completion of the observation.

The decision to perform ToO or DDT observations will be made by the IXPE Principal Investigator or their official designee.