Windows on the universe: the ERA of multi-messenger astrophysics

The Universe is the ultimate laboratory, and we can now probe it as never before through several powerful and diverse windows - electromagnetic waves, high-energy particles, and gravitational waves. Each of these windows provides a different view. Together they reveal a detailed picture of the Universe that will allow us to study matter, energy, and the cosmos in fundamentally new ways. The "Windows on the Universe" Multi-Messenger Astrophysics (WoU-MMA) program identifies three categories of messengers - electromagnetic waves, high-energy particles including neutrinos and cosmic rays, and gravitational waves. The goals of WoU-MMA are to build the capabilities and accelerate the synergy between observations and theory to realize integrated, multi-messenger astrophysical explorations of the Universe. The WoU-MMA program welcomes proposals in any area of research supported through the participating divisions that address at least one of the following criteria:

• Coordination: Activities to coordinate observations involving more than one messenger.
• Observations: Observations of astrophysical objects or phenomena that are potentially sources of more than one messenger.
• Interpretation: Theory, experiment, simulations and other activities to understand or interpret observations of astrophysical objects that are sources of more than onemessenger.

Competitive proposals will accelerate the progress in multi-messenger astrophysics and advance the community activities that have been developed during the initial five-year period of the WoU-MMA program. These build on observational and analysis capabilities at the intersection of the explorations enabled by each of the three windows. Efforts to integrate research communities to develop full interoperability between the three windows, and to develop a skilled new workforce in this field, are also encouraged. Proposals should be submitted to the relevant programs listed below (see Related Programs). The WoU-MMA program is not intended to replace existing programs that make awards that involve experimental or theoretical efforts related to each of the three messengers. Rather, the WoU-MMA program is meant to fund awards that have significant components of multi-messenger astrophysics. Priority will be given to proposals for dedicated efforts that significantly advance the WoU-MMA goals. A proposal that is requesting consideration within the context of WoU-MMA should begin the title with the identifying acronym "WoU-MMA:". PIs should ask for consideration and review as a WoU-MMA proposal only if the proposal addresses at least one of the criteria listed above. Proposals marked for consideration by the WoU-MMA program that do not address at least one of these criteria will be reviewed solely within the participating program(s) to which they were submitted. Supplement requests to existing awards within a program that address one of the above criteria will also be considered.