The IXPE (Imaging X-ray Polarimetry Explorer) GO (General Observer) Program solicits proposals for investigations in any area of astrophysics (not constrained to IXPE’s prime science areas). IXPE Cycle 4 observations will commence on or about 1 February 2027, and continue for a nominal period of 12 months. Individuals may submit proposals for observations that will advance the IXPE mission science return. Observing proposals may be for "standard", "Target-of-Opportunity (ToO)", “Large Program (LP)” or “Multi-cycle” observations. For ToO observations, IXPE anticipates executing approximately 1 high (observations begin within 9 days of trigger) and 7 medium (observations begin between 9 days and 4 weeks of trigger) priority triggers in this GO cycle, hence proposers must strongly justify the response time required to meet the scientific objectives.

A new joint observing program with the European Space Agency’s (ESA)/NASA X-ray Multi-Mirror Mission (XMM)-Newton X-ray observatory was added to IXPE GO Cycle 4. New Text is in bold. See Section 9 of D.3 Combined General Investigator General Observer Program. The due date for IXPE Cycle 4 Phase-1 Proposals (submitted via the Astrophysics Research Knowledgebase Remote Proposal System (ARK RPS)) remains 17 September 2026.

Please direct programmatic questions concerning IXPE to Hashima Hasan at hhasan@nasa.gov, and technical questions to Kavitha Arur at kavitha.arur@nasa.gov.