Search:

[Advanced Search]



Cycle 3 Accepted IXPE GO Program Abstracts

Proposal Number: 3001
Proposal Type: REGULAR
PI Name: SERGEY TSYGANKOV
Title: EVOLVING ACCRETION GEOMETRY IN TRANSIENT X-RAY PULSARS
Abstract: Launch of IXPE opened a new era in studies of magnetized NSs and allowed to determine basic geometry parameters for several XRPs and magnetars. The activity of transient X-ray sky did not allow, however, to observe up to now any truly extreme XRP, i.e. one accreting at super-critical luminosities exceeding ~5x10^37 erg/s when the geometry of emission region is expected to change dramatically with the onset of an accretion column. Observing such a source would allow to test the theory behind the formation of the accretion columns, and thus refine models describing interaction of matter with extreme magnetic and radiation fields. The proposed program aims to address this shortcoming and will contribute to the understanding of XRPs in general and the legacy of the IXPE mission.

Proposal Number: 3003
Proposal Type: REGULAR
PI Name: PHILIP KAARET
Title: X-RAY POLARIZATION OF THE TEV BINARY LS I +61 303
Abstract: IXPE observations have provided new insights into particle acceleration in PWNe and blazars. A recent IXPE observation of a source in a novel class, TeV binaries, has lead to the detection of polarization and evidence that the magnetic field in the acceleration region is perpendicular to the axis of the shock cone produced by the interaction of the pulsar and companion star outflows. We propose IXPE observations of the only other feasible TeV binary that will enable us to determine the level of magnetic order and orientation of the magnetic field in the acceleration region. The results will provide new insights into relativistic shock acceleration.

Proposal Number: 3016
Proposal Type: REGULAR
PI Name: ROGER ROMANI
Title: A POLARIZATION PROBE OF THE CRAB PULSAR'S GEOMETRY
Abstract: Pulsars' high energy emission has long defied localization; polarization's sensitivity to the projected magnetic field is a key tool in this quest. While the Crab pulsar optical polarization has been well measured for decades, models have limited success in matching the sweeps. X-rays emit closer to the acceleration site with less de-polarization; initial IXPE Crab observations found several high polarization phase bins, differing substantially from the optical. Existing phase-resolved measurements are count-limited; deeper exposure is needed to really map the sweeps. We propose additional exposure to quadruple the Crab's IXPE S/N. Careful analysis of these data will reveal details of the polarization that could unlock the mysteries of the high energy emission zone.

Proposal Number: 3031
Proposal Type: REGULAR
PI Name: JAMES STEINER
Title: A TEST OF DISK-JET MISALIGNMENT AND BLACK HOLE SPIN MEASUREMENT FOR THE X-RAY BINARY H1743-322
Abstract: The BH microquasar H1743-322 is uniquely poised to deliver key insights into questions on putative misalignment between the binary orbital and BH spin axes. H1743 is a propitious source with recurrent transient activity, a high expected PD (owing both to its high inclination and its predicted low spin), and is one of the strongest and most prolific sources of QPOs. The leading model of QPO production requires significant misalignment, but this prediction hasn't been readily testable. An IXPE campaign of 320ks divided between two observations of H1743, one in a hard state and the other in a soft/thermal state, will enable a direct constraint on potential misalignment, testing the QPO mechanism. Moreover, this campaign will also produce an orthogonal constraint on H1743's spin.

Proposal Number: 3036
Proposal Type: REGULAR
PI Name: OLIVIER HERVET
Title: EVOLUTION OF X-RAY POLARIZATION AFTER STRONG FLARES: TESTING THE SCENARIO OF SUCCESSIVE RECOLLIMATION SHOCKS IN MRK 421
Abstract: We aim to probe the X-ray polarization of Mrk 421 for 15 days after a strong outburst. Based on a previous X-ray study of Mrk 421, we expect to see secondary flares attesting to the propagation of a perturbation through stationary recollimation shocks. From IXPE polarization evolution after a strong flare, helped with simultaneous low-frequency polarization data and multiwavelength (MWL) facilities such as Swift, Fermi-LAT, and VERITAS, we will deeply test this scenario. Any secondary flare observed, even if not directly linked to the recollimation shock scenario, will benefit from this simultaneous MWL coverage and provide unprecedented material to characterize blazars' variability. We expect a trigger rate of ~1/year.

Proposal Number: 3079
Proposal Type: REGULAR
PI Name: PHILIP KAARET
Title: THE MAGNETIC FIELD GEOMETRY IN THE EASTERN JET OF THE PEVATRON MICROQUASAR SS 433: KINETIC OR MAGNETIC JET?
Abstract: How jets dissipate the bulk of the energy supplied by the central engine is a fundamental question in astrophysics. The Galactic microquasar SS 433, uniquely accessible to spatially resolved observations, provides an excellent laboratory for studying the properties of the jet that produces the 100-pc scale lobes. The first IXPE observation revealed that the innermost eastern knot (e1) is highly polarized, with the magnetic field aligned along the jet axis. We propose an IXPE observation of the second eastern knot (e2) to investigate the spatial evolution of the magnetic field structure. By combining IXPE data on e1 and e2, we will, for the first time, map the magnetic field geometry across a microquasar jet and determine whether the jet is driven kinetically or magnetically.

Proposal Number: 3089
Proposal Type: REGULAR
PI Name: ALEXANDER SALGANIK
Title: SEARCHING FOR MULTI-COMPONENT POLARIZATION SIGNATURES IN THE WIND-FED X-RAY PULSAR 1E 1145.1-6141
Abstract: 1E 1145.1-6141 is a wind-fed high-mass X-ray binary hosting a persistent accretion-powered pulsar, making it an excellent target for X-ray polarimetry. Previous IXPE observations of wind-accreting systems have revealed energy-dependent polarization signatures, suggesting the coexistence of multiple components. We propose a 400 ks IXPE observation of the source near apastron to measure the pulse-phase- and energy-dependent polarization properties. Combined with archival NuSTAR spectroscopy, these data will enable joint spectro-polarimetric modeling to disentangle contributions from different components. The double-peaked pulse profile of the source in the IXPE band provides an opportunity to constrain pulsar s geometry, allowing direct comparison with the well-known orbital inclination.

Proposal Number: 3090
Proposal Type: REGULAR
PI Name: ALEXANDER SALGANIK
Title: THE FIRST POLARIMETRIC STUDY OF THE SYMBIOTIC X-RAY BINARY: GX 1+4
Abstract: We propose the first polarimetric study of the symbiotic X-ray binary GX 1+4 using IXPE. GX 1+4 is a unique symbiotic system with a neutron star (NS) accreting from the dense wind of an M6III red giant companion. The long 1160-day orbital period, symbiotic nature, and distinct accretion characteristics of the NS make it an ideal candidate for investigating the geometry of the accretion-powered pulsar. Through a 400 ks IXPE observation we aim to measure the polarization degree and angle with high precision, perform phase-resolved spectro-polarimetric analysis, and derive the geometric configuration of the pulsar. These observations will contribute significantly to our understanding of the physics of X-ray pulsars and the broader population of magnetized NSs.

Proposal Number: 3091
Proposal Type: REGULAR
PI Name: VITTORIA GIANOLLI
Title: A COMPLETE MAP OF THE X-RAY POLARIZATION OF NGC 4151: THE POLARIZATION PROPERTIES OF THE REFLECTION COMPONENT
Abstract: We propose to observe the Seyfert galaxy NGC 4151 in a low flux state with IXPE (900ks) and NuSTAR (75ks), with both observations triggered by a Swift monitoring (33ks). NGC 4151 is the first radio-quiet Active Galactic Nucleus with an X-ray polarization measurement of the corona. However, the polarization properties of the reflection component, from close and distant matter, are unconstrained. During its extended low flux states, the reflection component dominates over the primary emission, offering the best opportunity for a detailed characterization of the polarization properties of this component. This would allow us to achieve the first comprehensive characterization of the X-ray polarization properties of both the primary continuum and reflection component within a single source.

Proposal Number: 3092
Proposal Type: REGULAR
PI Name: VITTORIA GIANOLLI
Title: EXPLORING THE GEOMETRY OF THE HOT CORONA: THE IXPE VIEW OF NGC 5548
Abstract: We propose a 1.2 Ms IXPE observation of the radio-quiet Seyfert 1 galaxy NGC 5548 (MDP99 = 3%). Its proximity, brightness (F{2-10 keV} ~ 4e-11 erg/s/cm-2), well-studied X-ray properties, and current unobscured state make this archetypal Active Galactic Nucleus (AGN) an ideal target for X-ray polarization studies of the hot corona. Its spectrum is dominated by the primary continuum with minimal reflection contribution, ensuring that the observed polarization will directly trace the corona itself. Past IXPE studies favored radially extended coronal geometries over compact ones, but the sample is limited. Observing NGC 5548 offers the opportunity to obtain the second significant X-ray polarization measurement, providing a crucial step toward a comprehensive picture of this key AGN region.

Proposal Number: 3101
Proposal Type: REGULAR
PI Name: KARRI KOLJONEN
Title: IS MICROQUASAR GRS 1915+105 CURRENTLY IN A SUPER-EDDINGTON ACCRETION STATE?
Abstract: We propose an IXPE observation of GRS 1915+105 during its unusual obscured accretion state. Currently, GRS 1915+105 exhibits strong radio flaring and shares X-ray spectral properties similar to other X-ray binaries experiencing super-Eddington accretion rates (such as V404 Cyg, Cyg X-3, V4641 Sgr). These similarities strongly suggest super-Eddington accretion in GRS 1915+105, offering a rare opportunity to study this high accretion rate phase in detail. The potential detection of a high polarization degree would signify that the received emission is seen as scattered, in accordance with super-Eddington accretion. This discovery could hold profound implications for our understanding of black hole accretion processes and their impact on the surrounding environment.

Proposal Number: 3111
Proposal Type: REGULAR
PI Name: MELISSA EWING
Title: SEARCHING FOR RELATIVISTIC PRECESSION IN ACCRETING BLACK HOLES WITH X-RAY POLARIMETRY-TIMING
Abstract: We propose a 300 ks IXPE ToO observation of a black hole X-ray binary exhibiting a Type-C quasi-periodic oscillation (QPO) in its X-ray flux, alongside a simultaneous 20 ks NuSTAR exposure and three 1 ks Swift/XRT pointings. We will use IXPE to search for modulations in the PD and PA on the QPO period, definitively testing whether or not such QPOs are driven by relativistic nodal precession of the inner accretion flow. We will use NuSTAR to constrain the physical source parameters, and the Swift/XRT pointings to confirm the presence of a QPO before triggering. The source may be known or unknown, as long as it displays a confirmed Type-C QPO and its 2--8 keV IXPE count rate (estimated from MAXI) is projected to be ≥30 c/s. We request a 10 day lead time (medium priority).

Proposal Number: 3112
Proposal Type: REGULAR
PI Name: DMITRY PROKHOROV
Title: STUDYING TANGENTIAL MAGNETIC FIELDS IN THE YOUNG VELA JR. SNR VIA FILLER OBSERVATIONS
Abstract: We propose an additional 1 Ms of IXPE observations of the north-western region of Vela Jr and to accumulate these data over the three GO cycles. These observations will allow a study of polarized emission from Vela Jr. on par with that of RX J1713.7-3946, providing further insights into the transition of radial-to-tangential magnetic fields in SNRs. Given that only these two mentioned young SNRs in the Galaxy are known to have tangential magnetic fields near shocks thanks to the advent of IXPE, Vela Jr. - observable at any time with IXPE - is a suitable filler target.

Proposal Number: 3129
Proposal Type: REGULAR
PI Name: ALESSANDRO PAPITTO
Title: POLARIZED X-RAYS FROM ACCRETING MILLISECOND PULSARS: A PATHWAY TO THE EQUATION OF STATE OF NEUTRON STARS
Abstract: Modelling the waveform of the X-ray pulse of accreting ms pulsars (AMSP) to constrain the equation of state of neutron stars requires an extremely high number of counts to break the degeneracy between the many parameters that shape it. IXPE observations of an AMSP recently discovered polarised X-ray emission at a degree of ~2% but could not detect spin phase-resolved variability. Here, we propose a longer 900-ks-long ToO observation of the next outburst of an AMSP to constrain the binary inclination and the spot latitude to within a few degrees. This information will serve as a key prior in the fit of the waveform observed by instruments with a larger effective area (e.g. NuSTAR, XMM-Newton) and constrain the mass and the radius of these neutron stars with an accuracy of a few per cent.

Proposal Number: 3133
Proposal Type: REGULAR
PI Name: STEFANO SILVESTRI
Title: TRACING THE EFFECTS OF ENVIRONMENT ON THE X-RAY POLARIZATION PROPERTIES OF SNR WITH RCW86
Abstract: RCW86 is a young (~1800yr) supernova remnant (SNR) expanding in a diverse environment with the south-western region expanding slowly against the wall of a self-blown cavity, and the north-eastern expanding fasterbeyond or still inside such cavity, in a less dense region. Environmental conditions as well as age are known to influence the magnetic field properties at the shock front. In X-rays, slower expanding shock fronts in dense matter have been associated with tangential magnetic fields and lower polarization degrees, while faster and more diffuse are all radial and highly coherent. We propose a 1Ms observation of the NE region of RCW86 to compare it with the SW and see if different ambient condition lead to different magnetic field properties, regardless of age.

Proposal Number: 3134
Proposal Type: REGULAR
PI Name: VADIM KRAVTSOV
Title: ORIGIN OF ORBITAL VARIABILITY IN THE X-RAY POLARIZATION OF CYG X-1
Abstract: We propose two 250 ks IXPE observations of Cyg X-1 to investigate the origin of its recently discovered orbital variability in X-ray polarization. Cyg X-1 is one of only two black hole X-ray binaries known to exhibit such modulation, which may arise from changes in the disk orientation, scattering in the stellar wind or bow shock, or reflection from the companion star. The new observations will provide complete coverage of two orbits, enabling phase-resolved polarimetric analysis with high statistical significance for the first time. This program will allow us to discriminate between competing physical models and subtract the variable component from the total observed polarization, resulting in more robust estimates of the remaining coronal/disk polarized emission.

Proposal Number: 3140
Proposal Type: LARGE
PI Name: FRANCESCO URSINI
Title: X-RAY POLARIMETRY OF THE HIGHLY ACCRETING SEYFERT ARK 564
Abstract: We propose an IXPE and NuSTAR observation of the narrow-line Seyfert 1 galaxy Ark 564, one of the X-ray brightest high accretion rate AGN. IXPE observations of moderately accreting Seyferts to date point to radially extended slab or wedge-like coronae, yet the high-Eddington regime is still unexplored. A 2 Ms IXPE exposure of Ark 564 will allow polarization to be measured at a few percent level (MDP ~ 2.5%), sufficient to discriminate between competing models for the Comptonizing medium geometry. A simultaneous NuSTAR 100 ks exposure will provide independent constraints on the coronal temperature and the reflection component, ensuring a physically self-consistent interpretation. This campaign will deliver the first robust measurement of X-ray polarization in a highly accreting Seyfert.

Proposal Number: 3156
Proposal Type: REGULAR
PI Name: ROBERTO TAVERNA
Title: PHASE-RESOLVED X-RAY POLARIMETRY OF THE PERSISTENT MAGNETAR 1E 1841 045
Abstract: We propose a 700 ks IXPE observation of the persistent magnetar 1E 1841 045. A previous 300 ks IXPE pointing revealed a clear energy-dependent polarization signal, increasing with photon energy from 15% up to 60% (at 7 8 keV). This was interpreted as the first evidence that the hard X-ray tail, dominant above 10 keV in magnetars, is strongly polarized. However, the observation lacked sufficient statistics for phase-resolved polarimetric analysis. This proposal leverages 1E 1841 045, the only bright magnetar with a hard tail already present in the IXPE band, to enable the first phase-resolved X-ray polarimetric study of such a component. The results would provide critical insights into the physical origin of the hard tail and help to validate or rule out magnetospheric models.

Proposal Number: 3171
Proposal Type: REGULAR
PI Name: MANEL ERRANDO
Title: IXPE OBSERVATIONS OF THE NEXT OUTBURST OF THE NAKED-EYE RECURRENT NOVA T CORONA BOREALIS
Abstract: T Corona Borealis, a recurrent nova, is set to experience a thermonuclear ignition event before 2026. During its last nova event in 1946, it reached a visible magnitude of 3.0, becoming visible to the naked eye. The X-ray flux is expected to peak above 1E-9 erg cm-2 s-1 in the IXPE band. We propose an observation campaign of T CrB with IXPE to cover the initial and late stages of the nova event evolution. This strategy aims to provide X-ray polarization measurements with MDP_99 of ~3%. It will enable us to capture the initial shock interactions of the nova ejecta with the red giant donor, along with the transition to the characteristic thermal emission of the late super-soft state.

Proposal Number: 3175
Proposal Type: REGULAR
PI Name: LUIGI PACCIANI
Title: X-RAY AND BROAD BAND POLARIMETRIC STUDY OF THE PECULIAR HSP BLAZAR 1ES 1959+650
Abstract: The structure of Magnetic field of the blazar Mkn 421 and the other High Synchtrotron Peaked (HSP) blazars observed with IXPE is one of the main results obtained with IXPE the so far. IXPE Results show a magnetic field almost perpendicular to the jet direction, with the exception of 1ES 1959+650 (z=0.047). For this source the magnetic field was found to be almost orthogonal to the jet axis and the polarization degree around 5-7% for the first two observations, while for the other three, the magnetic field in the region probed in X-ray with IXPE, the magnetic field was found to be almost parallel to the jet axis. We propose to observe this source again during the IXPE cycle 3, to disentangle among the proposed scenarios for the polarized emission of the source.

Proposal Number: 3185
Proposal Type: REGULAR
PI Name: VLADISLAV LOKTEV
Title: ENERGY-DEPENDENT POLARIZATION IN 4U 1538-52: A FOLLOW-UP INVESTIGATION OF A UNIQUE WIND-FED X-RAY PULSAR
Abstract: Recent IXPE observations of the wind-fed X-ray pulsar 4U 1538-52 revealed unprecedented energy-dependent polarization properties, with a near 70 degrees polarization angle switch between low (2-3 keV) and high (4-8 keV) energy bands which is also varies with the pulse phase. This behavior differs from the 90 derees switch observed in the similar system Vela X-1 and challenges standard vacuum birefringence models that predict energy-independent polarization. The first observations provided insufficient photon statistics for definitive conclusions about this unique phenomenon. We propose 360 ks of additional IXPE observations to confirm these extraordinary properties that require individual theoretical treatment for this one-of-a-kind system.

Proposal Number: 3207
Proposal Type: REGULAR
PI Name: SUDIP CHAKRABORTY
Title: PROBING THE TRANSIENT OBSCURED BLACK HOLE X-RAY BINARIES WITH SPECTRO-POLARIMETRY
Abstract: We propose IXPE (150 ks) and NuSTAR (20 ks) observations of a transient obscured black hole binary during outburst. These systems, likely obscured by Compton-thick winds from super-Eddington accretion, show strong absorption and reflection features. Spectro-polarimetry will constrain the geometry of the obscurer. These observations will help us derive similarities between these galactic super-Eddington objects viewed at higher inclinations, to extragalactic ULXs viewed at lesser inclinations along the wind cone.

Proposal Number: 3208
Proposal Type: REGULAR
PI Name: HERMAN MARSHALL
Title: INVESTIGATING HER X-1 USING IXPE AND XRISM
Abstract: We propose to conduct new \ixpe\ observations of Her X-1 in order to 1) address the origin of the secular spin axis changes and measure crust-core coupling, 2) improve the body of data needed for pulsar beam modeling, and 3) examine how an X-ray spectral feature depends on pulsar orientation. The proposed observations of Her X-1 should provide a data set addressing an IXPE Legacy Project.

Proposal Number: 3213
Proposal Type: REGULAR
PI Name: ALESSANDRO DI MARCO
Title: STUDYING THE ACCRETION DISK CORONA GEOMETRY IN THE DIPPING SOURCE XB 1254 690
Abstract: Accreting weakly magnetized NSs in LMXBs exhibits remarkable physical phenomenology with X-ray emission originating near the NS from the accretion inflow in the inner disk region, where boundary/spreading layers are expected. An optically thin accretion disk corona (ADC) extending above the disk can also be present, but its nature and geometry are not yet fully understood. Hints of such a corona have been reported in some highly inclined sources. We are proposing to investigate the dipping source XB 1254-690, aiming to verify the presence of the ADC thanks to possible variations in the polarimetric properties related to time and/or flux (e.g., during dips). This study could allow us to probe for the first time the presence of ADC and its optical depth and geometry.

Proposal Number: 3215
Proposal Type: LARGE
PI Name: GEORGE YOUNES
Title: DEEP IXPE POLARIMETRY OF RADIO-LOUD MAGNETAR 1E 1547.0-5408: A LEGACY TEST OF VACUUM BIREFRINGENCE AND VACUUM RESONANCE
Abstract: We propose a 1.5 Ms IXPE observation of the radio-loud magnetar 1E 1547.0-5408, building on a 0.5 Ms observation that revealed extraordinary polarization properties; phase-resolved polarization degrees in the 2 3 keV band reaching 80% and a polarization angle modulation following a rotating vector model, both highly suggestive of vacuum birefringence (VB) influence on the outgoing surface X-rays. A sharp energy dependence suggestive of vacuum resonance (VR) is also observed. With 2 Ms exposure, we will substantially improve these results, resolve the polarization spectrum in finer bins, and establish beyond any reasonable doubt the presence of VB. This dataset will deliver the first definitive tests of QED VB and VR in astrophysical setting, providing a mission-defining IXPE legacy result.

Proposal Number: 3220
Proposal Type: REGULAR
PI Name: ANUVAB BANERJEE
Title: DECIPHERING PARTICLE ACCELERATION MECHANISMS IN HIGH-SYNCHROTRON PEAKED BLAZAR USING POLARIMETRY
Abstract: High-synchrotron peaked (HSP) blazars are key to testing particle acceleration in relativistic jets. Magnetic reconnection predicts coherent, multi-band polarization, while diffusive shock acceleration (DSA) yields turbulent, band-dependent signatures. We propose IXPE polarimetry of a bright HSP blazar, with simultaneous optical and radio data, to distinguish these scenarios. Month-long monitoring of polarization degree and angle will reveal whether X-ray polarization shows smooth, correlated rotations (reconnection) or stochastic, uncorrelated variability (DSA). The results will directly constrain jet magnetic fields and high-energy acceleration processes in blazars.

Proposal Number: 3224
Proposal Type: LARGE
PI Name: STEVEN EHLERT
Title: CONSTRAINING PARTICLE ACCELERATION MECHANISMS IN BLAZARS VIA HIGH-CADENCE IXPE OBSERVATIONS
Abstract: We propose a long term IXPE polarization monitoring program of the blazar Markarian 501 (Mrk 501), performing 20 observations of 100 ks each over the course of the entire Cycle year approximately two weeks apart. Each of these IXPE observations will be coordinated with supporting optical and radio polarization observations using a variety of ground based telescopes. We will use the medium and long-term polarization behavior of Mrk 501 in the X-ray, optical, and radio to definitively identify the particle acceleration mechanism within the jet. This observation program is also optimally designed to catch Mrk 501 in atypical polarization or flux states as they occur and place new constraints as to the time scales over which the jet structure varies.

Proposal Number: 3226
Proposal Type: REGULAR
PI Name: MAITREYA KUNDU
Title: DISTINGUISHING COMPETING JET MODELS THROUGH OPTICAL--X-RAY POLARIZATION CONNECTION IN THE HSP BLAZAR 1ES 0502+675
Abstract: We propose a 350 ks IXPE observation of the high synchrotron-peaked blazar 1ES 0502+675, jointly with Swift, NuSTAR, and coordinated optical polarimetry, and TeV coverage from VERITAS. With its synchrotron peak in the 2 8 keV band, this source offers a clean probe of the high-energy synchrotron regime. IXPE will measure X-ray polarization degree and angle, while optical X-ray polarization will test cross-band coherence, distinguishing competing jet models. Swift and NuSTAR will provide broad X-ray spectral coverage, and VERITAS will constrain the Comptonized emission, together yielding strong constraints on jet magnetic geometry, particle acceleration, and synchrotron Compton connections.

Proposal Number: 3234
Proposal Type: REGULAR
PI Name: CHIEN-TING CHEN
Title: THE FIRST X-RAY POLARIZATION MEASUREMENT OF THE POLAR-SCATTERED SEYFERT 1 GALAXY FAIRALL 51
Abstract: We propose a 1 Ms observation of the polar-scattered Seyfert 1 (S1) galaxy Fairall 51 accompanied by a Swift/XR campaign consisting of 20 2-ks snapshots. For one of the highest optically polarized S1 galaxies ever observed, we aim to conduct the first ever measurement of its X-ray polarization and to study its connection to the optical/UV wavebands. Through this relation, we can draw estimates on the geometry of the torus and absorbers in the vicinity of the source. A simultaneous Swift observation will be beneficial to conduct a spectro-polarimetric analysis with the presence of complex absorption and scattering component. This will help us better understand the geometry and processes in polar-scattered S1 objects, which is crucial in enhancing our understanding of AGN.

Proposal Number: 3238
Proposal Type: REGULAR
PI Name: MAYUKH PAHARI
Title: TESTING THE EXTENDED CORONA MODEL TO UNDERSTAND THE RELATIVISTIC REFLECTION IN 1H 0707-495 THROUGH X-RAY POLARISATION
Abstract: X-ray polarimetry of the NLS1 galaxy 1H 0707-495 with IXPE will provide a unique probe of the inner disk and corona, supported by its relativistically broadened Fe K & L-alpha lines and dual X-ray emission origins. The main uncertainty lies in corona geometry: a compact lamppost near the black hole explains strong relativistic effects and short lags, while extended or double models over tens of gravitational radii predict different reflection and variability. Polarisation degree (PD), angle, and energy dependence distinguish these cases, with PD of 4 5% favouring the compact and PD of 9 12% supporting extended geometry. Observed X-ray spectral properties-based simulation shows ~4 5% MDP99 with 800 ks exposure, motivating our request for 800 ks IXPE observations.

Proposal Number: 3239
Proposal Type: REGULAR
PI Name: INDRANI PAL
Title: MCG 06 30 15 AS THE BENCHMARK AGN FOR IXPE
Abstract: MCG-06-30-15 is the archetypal nearby Seyfert 1 galaxy ($z$ = 0.0077) in which the first broad relativistic Fe K line was discovered, establishing it as the textbook laboratory for strong-gravity reflection. Its spectrum is dominated by a power-law continuum and a relativistic reflection component that varies only weakly compared to the continuum. This behavior motivated the light-bending model, in which a compact corona close to the black hole modulates the observed continuum while keeping the reflection nearly constant. However, this conclusion has so far rested only on spectral and timing modeling, not on direct geometric evidence. We propose a 1.2 Ms IXPE observation to test whether MCG-06-30-15 hosts a compact lamp-post corona or an extended slab/wedge structure.

Proposal Number: 3250
Proposal Type: REGULAR
PI Name: MANEL ERRANDO
Title: FIRST MEASUREMENT OF THE PLASMA MAGNETIZATION IN THE RADIATION ZONE OF HSP BLAZARS WITH IXPE AND TEV OBSERVATORIES
Abstract: We propose a 10-day multiwavelength campaign on a bright HSP blazar (Mrk 421 or Mrk 501) with simultaneous observations by IXPE, MAGIC, VERITAS, and optical polarimeters. The April 11 22, 2026 window is the only period when both sources are observable by all facilities, allowing advance planning while leaving the final target selection to just weeks before the campaign, based on which blazar is brightest in X-rays. This strategy maximizes the chance of capturing and characterizing X-ray polarization variability. Combined X-ray and TeV coverage will probe polarization dynamics, constrain the plasma magnetization, and deliver a decisive test of whether particle acceleration in blazar jets is powered by shocks or magnetic reconnection.

Proposal Number: 3252
Proposal Type: REGULAR
PI Name: SWATI RAVI
Title: ENERGY-DEPENDENT POLARIZATION ROTATION: TESTING GENERAL RELATIVISTIC DISK MODELS WITH IXPE
Abstract: We propose a 1.4 Ms triggered IXPE program, with contemporaneous NuSTAR and Swift coverage, to search for an energy-dependent rotation of the X-ray polarization angle in a black-hole X-ray binary. General relativistic models predict such swings in the disk-dominated soft state, with amplitudes of up to tens of degrees across 2 8 keV. Detecting this effect would provide a direct strong-field test of General Relativity and yield an independent probe of black-hole spin and inclination. By targeting a luminous soft-state transient during its decline and applying Bayesian analysis techniques, this program offers the strongest opportunity yet to reveal the predicted EVPA evolution.

Proposal Number: 3257
Proposal Type: REGULAR
PI Name: NAZMA ISLAM
Title: AN IXPE OBSERVATION OF THE BRIGHT INTERMEDIATE POLAR V1223 SGR
Abstract: The theoretical models for X-ray polarization in Intermediate Polars, a type of magnetic Cataclysmic Variables, expect a high polarization signatures via scattering from the accretion columns and reflection from the White Dwarf surface. We propose a 500 ks IXPE observation of the bright IP V1223 Sgr, with the objective of carrying out phase-averaged and pulse phase resolved polarimetric analysis. These results would be used to infer the geometry of the accretion column and the reflection component.

Proposal Number: 3258
Proposal Type: REGULAR
PI Name: EDWARD NATHAN
Title: TARGETTING THE RETURN OF THE BRIGHT GRS 1915+105
Abstract: We propose three ToO observations to observe GRS 1915+105 if it leaves it's current absorbed state and returns to it's pre-2019 levels. These ToOs will target three different states of the source: the 'chi' state, analogous to a canonical hard XRB state; a disc dominated state, analogous to a canonical soft XRB state; and a state where the source is showing exotic variability. Together they will help uncover the mystery of the accretion system around GRS 1915+105. Even taking the observations individually, the high flux levels of the source means it's a perfect poster child to study XRB accretion via polarisation in these states. GRS 1915+105 has long been a keystone for studying XRBs, and any observations in its absorbed state will be a legacy of science done with IXPE.

Proposal Number: 3260
Proposal Type: REGULAR
PI Name: RANDY LOBERGER
Title: A LEGACY STUDY OF CEN X-3 WITH IXPE: POLARIZATION AS A PROBE OF NEUTRON STAR PHYSICS
Abstract: Cen X-3 is an X-ray binary system where a pulsar orbits a massive O star, producing some of the brightest and most complex X-ray emission known. While theory predicts strong polarization from such systems, past IXPE observations found unexpectedly low values, suggesting that additional effects such as scattering in the accretion disk or heating of the pulsar s atmosphere may dilute the signal. Recent XRISM data further revealed distinct absorption and scattering features tied to orbital phase, highlighting the importance of the surrounding environment. We propose 470 ks of IXPE observations spanning multiple orbits to disentangle these contributions, combining phase-resolved polarimetry with simultaneous broadband NuSTAR spectra.

Proposal Number: 3261
Proposal Type: REGULAR
PI Name: DAVID BOGENSBERGER
Title: THE QUEST FOR DETECTING VARYING POLARIZATION DURING DIPS OF 4U 1916-053
Abstract: IXPE is providing a new window for probing the complex physics of high-energy processes occurring in the accretion flows around compact objects. Dips are routinely observed in the light curves of some X-ray binaries, which are caused by obscuration in the line of sight. During dips, some parts of the accretion flow are hidden, so any changes in the measured polarization can help constrain its geometric origin, and improve our understanding of the underlying physical processes. 4U 1916-053 is the ideal source for investigating such polarization changes, given its persistent bright flux and frequent, long-duration dips.