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Approved Legacy Science Programs

Below is a list of approved General Observer and DDT programs that address legacy science goals. Please note that legacy projects were not officially introduced until Cycle 3. If you are the PI of a program that you think is missing from the list, please contact the IXPE help desk.

  1. Deep observation of a rapidly rotating stellar-mass black hole in the soft state to search for EVPA rotation versus energy as predicted in General Relativity
    • Proposal #3252 (ToO), “Energy-Dependent Polarization Rotation: Testing General Relativistic Disk Models with IXPE”, observed GS 1354-64 for 450 ks (ObsID 05250399).
    • DDT on 4U 1957+115 for 690 ks in Cycle 2 (ObsID 04251199), for 580 ks in prime mission (ObsID 02006601).
  2. Deep observation of the Crab pulsar to constrain the emission zone geometry thereby advancing our understanding of the pulse emission mechanism.
    • Proposal #3016 (Multi-cycle), “A Polarization Probe of the Crab Pulsar's Geometry”, approved for 700 ks.
  3. Observation of a high accretion rate AGN to determine the Comptonizing medium geometry
    • Proposal #3140 (Large), “X-Ray Polarimetry of the Highly Accreting Seyfert Ark 564”, observed Ark 564 for 1.8 Ms (ObsID 05000199, 05006999).
    • Proposal #3239, "MCG 06 30 15 as the Benchmark AGN for IXPE", approved for 1.2 Ms.
  4. Studies of stellar-mass BH and NS X-ray transients through all outburst phases to measure the evolution of the accretion geometry
    • Proposal #1220 (ToO0, “X-Ray Polarization Across the Black-Hole Accretion States Swift J1727.8-1613”, observed for 202 ks (ObsID 03005801), 151 ks (ObsID 03006001), 67 ks (ObsID 03005701). Observed in prime mission for 37 ks (ObsID 02251001), 21 ks (ObsID 02251101), 19 ks (ObsID 02250901), 18 ks (ObsID 02251301), 18 ks (ObsID 02251201).
  5. Observation of a bright outburst of an accreting millisecond X-ray pulsar suitable for constraining the magnetic field geometry and improving constraints on the NS equation of state
    • Proposals #1116 (ToO), #2138 (ToO), #3129 (ToO), “Polarized X-Rays from Accreting Millisecond Pulsars: A Pathway to the Equation of State of Neutron Stars”, observed SRGA J144459.2-604207 for 550 ks in Cycle 1 (ObsID 03250101), observed SAX J1808.4-3658 for 918 ks in Cycle 2 (ObsID 04007699).
  6. Observation of magnetars, in quiescence or outburst, to search for definitive signatures of vacuum birefringence
    • DDT on new magnetar EP260628c for 200 ks in Cycle 3 (ObsID 05250701).
    • Proposal #3215 (Large), “Deep IXPE Polarimetry Of Radio-Loud Magnetar 1E 1547.0-5408: A Legacy Test of Vacuum Birefringence and Vacuum Resonance”, approved for 1.5 Ms. Proposal #2219, “Polarization Properties of the Persistent X-Ray Emission from the Radio-Loud Magnetar 1E 1547.0-5408”, observed 1E 1547.0-5408 for 500 ks (ObsID 04003801).
  7. Detection of neutron star free precession in additional accreting X-ray pulsars and extended campaigns to measure the coupling between the crust superfluid and the crust itself
    • Proposal #3208, Investigating Her X-1 Using IXPE And XRISM (ToO).

Please note that the abstracts of previously approved GO programs can be found here