Proposal Number: 12013
PI Name: JOEL COLEY
Title: PROBING INTRABINARY EMISSION IN THE REDBACK CANDIDATE 4FGL J2054.2+6904 WITH NUSTAR
Abstract: We propose an 97 ks NuSTAR observation of the redback millisecond pulsar candidate 4FGL J2054.2+6904 spanning 6 cycles of its 7.47 hr optical modulation derived with ZTF. Our aim is to constrain the size of the binary orbit, discriminate between IBS emission and emission from the magnetosphere of the pulsar and search for a spectral break that will constrain the magnetic parameters of the millisecond pulsar. Our program will discriminate between a traditional redback and long-period redback classification of J2054, which is crucial in understanding the MSP population.

Proposal Number: 12021
PI Name: VITTORIA GIANOLLI
Title: PHYSICS AND GEOMETRY OF THE HOT X-RAY CORONA IN THE ARCHETYPAL TYPE-1 SEYFERT GALAXY NGC 5548
Abstract: We propose a 100 ks NuSTAR observation of the radio-quiet Type-1 Seyfert galaxy NGC 5548, to be performed simultaneously with the awarded IXPE (1.2 Ms) and XMM Newton (42 ks) observations. Its proximity, X-ray brightness, and current unobscured state make it an ideal target to probe the physics and geometry of the hot X-ray corona. The spectrum is dominated by the primary continuum with a constant reflection component. The NuSTAR observation is essential to constrain the high-energy cutoff and Compton reflection, enabling a robust spectro-polarimetric interpretation of the IXPE data and discrimination between competing coronal geometries.

Proposal Number: 12023
PI Name: TRACEY TURNER
Title: A CLEAR VIEW OF X-RAY REFLECTION IN MCG-2-58-22
Abstract: NuSTAR with XRISM provides high resolution spectra of the Fe K-band with broad continuum constraints encompassing the high-energy Compton hump - for a complete picture of the X-ray reflector. MCG-2-58-22 is a bright 'bare' Seyfert 1 nucleus, offering a rare, clear view of reprocessing from the inner disk. Existing data indicate fluid conditions - varying between Compton-thick and thin states for the inner disk reflector. XRISM Resolve offers an exquisitely sensitive probe of the physical state of the inner disk via measurement of Fe Ka1 and Ka2 and Fe Kb. A joint 100 ks observation using NuSTAR with XRISM for this `bare' AGN will allow leveraging of the Compton Hump and Fe K line together to obtain unprecedented constraints on the column density of the reflecting/scattering gas.

Proposal Number: 12027
PI Name: SCOTT HAGEN
Title: UNDERSTANDING AGN STRUCTURE AND VARIABILITY WITH FAIRALL 9: A MULTIWAVELENGTH LEGACY EXPERIMENT WITH NUSTAR, XMM AND HST
Abstract: Fairall 9 is one of the brightest local unobscured AGN, with a recent intensive optical/UV/X-ray monitoring campaign giving a unique insight into the structure of the central engine. However, the missing piece of the puzzle is how the inner flow links to the broad line region and/or inner disc winds. To address this HST recently awarded 34 orbits in Cycle 33 to map their structure. However, AGN emit over a broad bandpass, so to understand the ionising spectrum additionally requires data in the soft and hard X-rays. We propose 2x30ks NuSTAR+XMM observations during the HST campaign to fully characterise the spectral energy distribution. This is critical to fully leverage the science from a unique legacy dataset, providing the stepping stone for understanding AGN structure across cosmic time.

Proposal Number: 12028
PI Name: MURRAY BRIGHTMAN
Title: NUSTAR AND XMM-NEWTON TARGET OF OPPORTUNITY OBSERVATION OF A NEW TRANSIENT ULX
Abstract: Ultraluminous X-ray sources (ULXs) are our best laboratories for studying extreme super-Eddington accretion. Most studies of these objects are of relatively persistent sources, however there is growing evidence to suggest a large fraction of these sources are transient. We propose a 50-ks NuSTAR and 12-ks XMM-Newton target of opportunity (ToO) observation of a new transient ultraluminous X-ray source (ULX) that will be identified by searching through new Swift/XRT observations for serendipitous detections. These data will provide a high-quality broadband X-ray spectrum to characterize the source's emission components, and search for pulsations, ultrafast outflows and/or cyclotron lines.

Proposal Number: 12029
PI Name: STEPHEN WALKER
Title: NUSTAR OBSERVATIONS OF THE RADIO RELIC IN THE TOOTHBRUSH CLUSTER
Abstract: The Toothbrush galaxy cluster challenges our understanding of shock heating of the intracluster medium (ICM). While the Toothbrush radio relic indicates a very strong shock of Mach number 2.8, the temperature jump across the shock observed with Chandra gives an upper limit of just 1.5. One possibility is that the high and spatially variable galactic column density in the direction of the Toothbrush cluster, which lies near the galactic plane, has biased the Chandra temperature measurements. Only with NuStar's high energy bandpass can the temperature of the ICM be probed in a way that is insensitive to such variations in galactic column. This will allow us to accurately determine the pre- and post-shock temperature of the ICM, and the X-ray derived Mach number.

Proposal Number: 12032
PI Name: EUGENIO BOTTACINI
Title: THE PHYSICS OF SUPERMASSIVE BLACK HOLES ENCODED IN SPECTRAL LINES
Abstract: Theory predicts that the merger process of supermassive black holes is a fundamental process in cosmology. Such events will be directly detectable by future gravitational-wave observatories. However, to date it is already possible to observe through spectral lines supermassive black hole pairs that are the precursors of merger events. We propose a NuSTAR observation to probe such a system and to characterize it through its spectrum.

Proposal Number: 12033
PI Name: MARINA ORIO
Title: THE POWERFUL SHOCKS IN A SYMBIOTIC NOVA OUTBURST
Abstract: The outbursts of symbiotic novae are the ideal laboratory to study the ubiquitous phenomenon of powerful astrophysical shocks. In the initial explosion, particles are accelerated and there is always copious flux in the range of a few GeV. Surprisingly, the X-rays - and in one case also the gamma-rays in the range of few TeV - rise days later. The relative times of peaks in the different wavelengths depend on the interplay between the density of the red giant wind and the distance from the red giant or Mira companion. By monitoring the evolution of the shocks, many physical parameters can be derived, including elemental abundances. NuSTAR has the unique capacity to determine the initial shock temperature, constraining the spectral fits, and it may detect even the non-thermal hard X-rays.

Proposal Number: 12035
PI Name: SIBASISH LAHA
Title: REAL-TIME JET FORMATION AND MAGNETIC-FIELD ALIGNMENT, WITH A ``COOLING" CORONA IN A POST-CHANGING-LOOK AGN
Abstract: 1ES~1927+654 is an enigmatic changing look active galaxy (CL-AGN) which has shown violent behavior in UV, optical and X-rays from 2017-2021, followed by a unique event of jet formation. Contemporaneous to the jet formation, (1)radio polarization observations show strong signatures of Magnetic field alignment along the jet axis and (2) Snapshots of NuSTAR observations (May 2023- Oct 2025) have detected a ``cooling" corona and (3) NuSTAR spectra show an emergence of a new broad ionized Fe emission line at ~7 keV. We propose to observe this interesting source with NuSTAR with two snapshots of 150 ks exposure (=300ks Total) in 2026 separated by 6 months, to study (A) the evolution of `cooling' coronal temperature and (B) the evolution of the newly emerging broad Fe-K emission line.

Proposal Number: 12036
PI Name: ALESSANDRO DI MARCO
Title: STUDYING THE ACCRETION DISK CORONA GEOMETRY IN THE DIPPING SOURCE XB 1254-690
Abstract: Accreting neutron stars (NSs) in low-mass X-ray binaries (LMXBs) with a weak magnetic field are characterized by an accretion disk extending close to the NS and by a boundary/spreading layer where the inflowing matter comes to rest on the NS surface; the bulk of the accretion energy release takes place in these innermost regions. The presence of an extended accretion disk corona (ADC) and/or a disk wind (DW) has been clearly established in some NS LMXBs seen from high inclinations. We propose to observe XB 1254-690, one of the systems in which the central emissions are partially obscured by matter in the outer disk regions that periodically cross our line of sight (causing the so-called dips), providing a unique opportunity to study the ADC and the DW components and their geometry.

Proposal Number: 12039
PI Name: AARON PEARLMAN
Title: TARGET-OF-OPPORTUNITY NUSTAR OBSERVATIONS OF HIGH-B RADIO PULSARS: SEARCHING FOR MAGNETAR METAMORPHOSES
Abstract: We propose for a 150~ks (50 ks x 3) NuSTAR observational program to investigate magnetar-like behavior in high-magnetic field rotation-powered pulsars following timing glitches. Using near-daily radio monitoring observations with CHIME/Pulsar, we will trigger NuSTAR observations within ~48 hours of a glitch; the broadband coverage of NuSTAR will probe the presence of a power law tail (hard X-rays), a key signature of magnetars. The proposed observational cadence will track the evolution of the power law tail throughout the outburst and test the consistency with magnetospheric cooling scenarios in magnetars. The detection of the hard X-ray component will solidify the connection between high magnetic field rotation-powered pulsars and magnetars, unifying the neutron star zoo.

Proposal Number: 12040
PI Name: SHUO ZHANG
Title: INVESTIGATING PEAK X-RAY EMISSION FROM GALACTIC CENTER MOLECULAR CLOUD BRIDGE: STORYTELLER OF A PAST SGR A* OUTBURST
Abstract: After two decades of X-ray brightening, Bridge has become the brightest molecular cloud in the Galactic center, due to X-ray reflection of a past Sgr A* outburst. It is the only molecular cloud that will allow us to investigate the full profile of a Sgr A* illumination event. Bridge cloud has reached its peak X-ray luminosity, but a narrow-peak and flat-peak variability scenarios cannot be told apart by current data. A 100 ks simultaneous NuSTAR and XMM-Newton observation will efficiently distinguish between the two scenarios. Characterizing past Sgr A⋆ outbursts is a necessary step towards understanding the physical mechanisms that triggered major outbursts from a quiescent supermassive black hole.

Proposal Number: 12041
PI Name: SHUO ZHANG
Title: JOINT NUSTAR AND EHT PROBE OF SGR A*: FLARES, BLACK HOLE SHADOWS AND A NEW HARD X-RAY SOURCE
Abstract: Following successful joint NuSTAR/Chandra/EHT observation campaigns during 2017-2018 and 2021-2025, we propose a 100 ks NuSTAR exposure to overlap with the EHT observation window in spring 2027 during NuSTAR AO Cycle 12. Our primary science goals include: 1) Detect bright X-ray flares, determine flare start/stop time and X-ray variability during a flare to feed to the EHT analysis; 2) Enlarge the existing NuSTAR Sgr A* flare sample by detecting and characterizing new flares and test the trend that brighter X-ray flares have harder spectra than fainter flares. A secondary science goal is to monitor a new hard X-ray source newly revealed by archival NuSTAR data, which is located only 1 pc from Sgr A*.

Proposal Number: 12052
PI Name: ALEXANDER SALGANIK
Title: NUSTAR OBSERVATIONS OF X PERSEI IN A HISTORICALLY LOW-LUMINOSITY STATE
Abstract: X Persei is a persistent Be/X-ray binary that, following a sequence of recurrent high-flux episodes, has entered a historically faint and long-lived low-luminosity plateau. We propose a NuSTAR observation of X Persei in this state, at an X-ray luminosity of ~10^34 erg s^-1, providing a unique probe of the accretion-powered emission region at extremely low accretion rates. NuSTAR s sensitivity above 10 keV will allow us to test whether the hard X-ray hump persists in this regime and to measure its spectral shape. Broad-band spectroscopy and energy-resolved pulse profiles will constrain the temperature, optical depth, and geometry of the emission region, and track changes in the beam pattern and pulsed fraction across 3 79 keV.

Proposal Number: 12059
PI Name: MOAZ ABDELMAGUID
Title: A NUSTAR STUDY OF THE GALACTIC PEVATRON LHAASO J0249+6022
Abstract: Determining the origin of ultra-high-energy (UHE; $E_\gamma > 100$ TeV) $\gamma$-ray emission is a key step toward identifying the Galactic systems capable of accelerating particles to PeV energies. We propose a 100 ks \textit{NuSTAR} observation of the region surrounding PSR J0248+6021, associated with the UHE $\gamma$-ray source LHAASO J0249+6022.~A recent Fermi-LAT analysis suggest a GeV-TeV $\gamma$-ray spectrum that favors a pulsar wind nebula (PWN) interpretation for the emission. Existing X-ray data is limited to a short ($\sim$ 7 ks) Swift-XRT observation, insufficient to meaningfully constrain extended nebular emission and do not probe the high-energy synchrotron component.~\textit{NuSTAR s} broadband coverage enables a direct search for a compact X-ray PWN, allowing us to charac

Proposal Number: 12061
PI Name: KAYA MORI
Title: UNTANGLING X-RAY KNOTS FORMED BY THE PEVATRON MICROQUASAR SS 433
Abstract: The microquasar SS 433 and its surrounding nebula W50, powered by bipolar jets from the compact object, exhibit four non-thermal X-ray knots in the eastern and western TeV gamma-ray lobes. While the inner knots are identified as the primary sites of PeV particle acceleration, the outer knots (e2 and w2) show peculiar X-ray morphologies and their spectral evolution indicates distinct formation mechanisms involving magnetic-field amplification and particle re-acceleration. Our proposed NuSTAR and XMM observations will complete a broadband and multi-epoch X-ray survey of all non-thermal knots, aiming to (1) detect their hard X-ray extensions, (2) constrain the maximum particle energies with H.E.S.S TeV data and (3) confirm the putative X-ray variability in e2 suggested by archival X-day data.

Proposal Number: 12071
PI Name: ALESSANDRO PECA
Title: PROBING VARIABILITY AND TORUS STRUCTURE IN DUAL COMPTON-THICK AGN
Abstract: We propose a joint NuSTAR and XMM-Newton campaign to study short timescale (3 epochs over 12 months) X-ray variability in MCG+04-48-002 and NGC6921, a bright Compton-thick (CT; NH>1e24 cm-2) dual AGN system. This target is unique as the only known dual AGN system in which both nuclei are CT (or near-CT) and spatially resolvable by NuSTAR (projected 25.3 kpc; ~90'' at z=0.014). Archival data show years-long NH and flux variability in MCG+04-48-002, while NGC6921 shows flux variability with stable NH. Our campaign will probe month-scale variability to constrain NH and intrinsic flux changes, 6.4 keV Fe Ka behavior, and the geometry of the obscuring material, enabling the first hard X-ray variability study of a resolved dual CT AGN and, in turn, a direct comparison with isolated CT AGN.

Proposal Number: 12076
PI Name: JIACHEN JIANG
Title: MEASURING THE BLACK HOLE SPIN OF GRO J1655-40 WITH NUSTAR AND SWIFT
Abstract: The proposed observations aim to resolve the inconsistent black hole spin measurements for GRO J1655-40 by obtaining simultaneous NuSTAR and Swift observations during its next outburst. We will target three spectral states to apply both continuum-fitting and disk reflection methods. NuSTAR's high-energy data will enable precise reflection modeling, free from the calibration issues that plagued past studies, while Swift provides crucial soft X-ray coverage. This will yield a robust, self-consistent spin measurement, test disk-orbit alignment, and advance our understanding of accretion physics in strong gravity.

Proposal Number: 12078
PI Name: JIACHEN JIANG
Title: STUDYING THE VERY HIGH STATE OF BLACK HOLE TRANSIENTS USING RELATIVISTIC SPECTROSCOPY
Abstract: We propose a 30 ks NuSTAR ToO observation of a black hole X-ray binary in the very high state. With this observation, we will combine the two leading relativistic spectroscopy methods, relativistic reflection and continuum fitting, to make two simultaneous, independent measurements of the spin of the central BH. This combined approach is more powerful than either method applied individually, and has great potential for expanding our knowledge of BH formation and growth, accretion physics and strong gravity. In addition, an extended disk reflection model with a variable density parameter for the surface of the disk will be considered particularly.

Proposal Number: 12080
PI Name: ROBERTO SERAFINELLI
Title: INVESTIGATING THE MOST OBSCURED STATES OF THE CHANGING-OBSCURATION SEYFERT GALAXY ESO 323-G77
Abstract: ESO 323-G77 is a nearby Seyfert galaxy with extreme, recurrent line-of-sight absorption changes. Prior NuSTAR data sampled only Compton-thin states, though they revealed a stable Compton-thick reflector. However, hard X-ray coverage of the most obscured phases (log NH/cm^-2>23.6) is still missing. We request a 100 ks NuSTAR observation triggered by weekly Swift-XRT monitoring to catch the source in its highest-obscuration state. NuSTAR will constrain the >10 keV transmitted continuum and Compton hump, measuring the reflector column and geometry. Swift will also deliver a long-baseline PSD of hardness-ratio variability to test an f^-1 (pink-noise) trend, predicted by chaotic cold accretion models.

Proposal Number: 12083
PI Name: RAFFAELLA MARGUTTI
Title: NUSTAR+XRT PROMPT OBSERVATIONS OF THE MOST NEARBY STRONGLY-INTERACTING SN SHOCKS
Abstract: Recent observations have revolutionized our understanding of mass loss in evolved massive stars: contrary to theoretical expectations, observations revealed a rich phenomenology, with the ejection of shells of material in the years before explosion. The physical mechanism behind impulsive mass ejections synchronized with core-collapse is unclear. Building on the recent success with SNe 2023ixf and 2024ggi, we propose a coordinated XRT-NuSTAR effort to constrain the early evolution of the broad-band X-ray spectrum of 1 young nearby (d<20 Mpc) or X-ray bright (Fx>5x10^-14 erg/s/cm2) strongly interacting SN and enable progress. These observations will characterize the innermost circumstellar medium at times when the radio emission is completely absorbed, revealing the most extreme mass loss

Proposal Number: 12084
PI Name: RISHANK DIWAN
Title: COMPLETING THE HARD X-RAY SURVEY OF TEV GALACTIC SOURCES
Abstract: Very high-energy (VHE) astronomy is currently blooming, trying to shed light on the nature of Galactic PeVatrons. Apart from the pointed observations by Air Cherenkov Arrays, a new generation of Water Cherenkov Observatories (HAWC and LHAASO) is surveying the VHE Northern sky. Most TeV sources in their catalogues are extended and complex, demanding a multiwavelength study. NuSTAR s imaging can help localize hard X-ray emission, measure spectral slopes/absorption, and distinguish compact non-thermal components from diffuse background. We propose to go over all Galactic TeV sources in their most recent catalogues that have not yet been observed by NuSTAR but fit within its field of view. We ask for six 20ks observations.

Proposal Number: 12087
PI Name: KA-WAH WONG
Title: HARD X-RAYS FROM A GAMMA-RAY EMITTING FR0 RADIO GALAXY
Abstract: Most active galactic nuclei (AGNs) in the local Universe are low-luminosity AGNs (LLAGNs), generally associated with radiatively inefficient accretion flows (RIAFs). Fanaroff-Riley type 0 (FR0) radio galaxies, identified over the past decade, represent a major population of LLAGNs but remain much less studied than radio galaxies with prominent jets. We propose to study the brightest FR0 in X-rays, Tol 1326-379, which is also the first FR0 detected in gamma-rays. Multiwavelength studies suggest a jet origin for the X-rays, but a significant RIAF contribution cannot be excluded. The lack of hard X-ray coverage above 10 keV currently limits model discrimination. With NuSTAR s sensitivity, we will determine whether the hard X-rays originate from the jet or the accretion flow.

Proposal Number: 12088
PI Name: PRAGATI PRADHAN
Title: INVESTIGATING THE HARD X-RAY SPECTRA OF THREE SYMBIOTIC X-RAY BINARIES WITH NEWLY DISCOVERED SPIN PERIODS
Abstract: Symbiotic X-ray binaries(SyXBs)hosting a low mass K/M giants and neutron stars are quite rare owing to the short life of the red giant branch and the probability of survival of the companion star post supernova. SyXBs are therefore unique probes of binary evolution and constraining the X-ray emission mechanism, spin period, magnetic field is crucial in understanding the evolution. We request 40ks observation with NuSTAR and 20ks with XMM for three such SyXBs (1RXS J180431.1- 273932, 2XMM J174016.0-290337, IGR J17586-2129) with confirmed spin periods to constrain the broadband spectrum for the first time and compare it against the spectra of other high mass X-ray binaries with large magnetic fields. We will also constrain their broadband pulse profiles for the first time.

Proposal Number: 12090
PI Name: QI FENG
Title: SEARCHING FOR NEUTRINO-EMITTING BLAZARS IN HARD X-RAY BAND
Abstract: We propose NuSTAR target-of-opportunity (ToO) observations of a candidate neutrino-emitting blazar, triggered by the combination of an IceCube neutrino alert and detections of a spatially coincident blazar by Fermi-LAT and Swift-XRT. We request 40 ks of initial NuSTAR observation within 24 hours, on a best-effort basis, after the trigger. If the hard-X-ray flux from the initial observation is > 1.5 x 10^-12 erg cm^-2 s^-1 and X-ray variability is observed by Swift-XRT, we request another 40 ks of follow-up NuSTAR observations to characterize the low-flux state.

Proposal Number: 12092
PI Name: PRAGATI PRADHAN
Title: INVESTIGATING THE 11-YEAR ACCRETION MOOD SWINGS IN IGR J16320-4751
Abstract: We propose a 70 ks NuSTAR observation of the super-slow pulsar IGR J16320-4751. Past observations (INTEGRAL 2004, NuSTAR 2015) suggest an 11-year accretion regime cycle, making this NuSTAR cycle an ideal time to revisit the system. Through spectro-timing analysis, we will explore long-term regime changes (~11 years) driven by pulse period evolution and/or magnetic field reconfiguration. We will also study short-term (minutes to hours) change in accretion regime (propeller regime, quasi-spherical accretion, and spherical accretion) brought by local wind density fluctuations. Cyclotron studies can constrain the debated magnetic field (7 keV or 14 keV).

Proposal Number: 12095
PI Name: ROSS SILVER
Title: HUNTING FOR HIDDEN COMPTON-THICK AGN WITH AI
Abstract: The X-ray spectral analysis of new Compton thick (CT-) active galactic nuclei (AGN) represents a fundamental step to understand the physics of the obscuring material surrounding accreting super-massive black holes. However, at the present day, CT-AGN remain extremely hard to detect. Implementing a previously successful machine learning algorithm, we propose to target 5 low-redshift candidate CT-AGN from the WISE AGN catalog for 30-35 ks of NuSTAR and 25-30 ks of XMM-Newton time each. This analysis will help determine the true intrinsic fraction of CT-AGN in the local universe and their contribution to the Cosmic X-ray Background (CXB).

Proposal Number: 12096
PI Name: RAFFAELLA MARGUTTI
Title: DETECTING THE FIRST HARD X-RAYS FROM COMPACT-OBJECT MERGER AFTERGLOWS
Abstract: Hard X-rays from neutron star (NS) merger afterglows have yet to be detected. We propose to perform a systematic, deep search for hard X-rays from NS mergers with NuSTAR. These NuSTAR observations will be enhanced by approved coordinated follow-up across the electromagnetic spectrum, and will shed light on the nature and structure of relativistic outflows launched by NS-bearing mergers.

Proposal Number: 12097
PI Name: FAN ZOU
Title: FIRST CORONA-TEMPERATURE MEASUREMENTS OF MASSIVE BLACK HOLES IN DWARF GALAXIES
Abstract: We propose a total of 300 ks NuSTAR and 30 ks joint XMM exposures for two broad-line active galactic nuclei (AGNs) in dwarf galaxies. Our goal is to measure the corona temperatures of dwarf AGNs, which have smaller black holes compared to massive galaxies. The temperatures will be inferred from their X-ray spectral cutoff energies. Theoretically, the temperature is regulated by pair production; at a given luminosity, the maximum corona temperature allowed should be cooler in smaller black holes. We will examine if our targets in the dwarf-galaxy regime indeed follow this scenario. These observations will place the first robust constraints on coronal temperatures in dwarf AGNs and will thus improve our understanding of the physics of X-ray emission from less massive AGNs.

Proposal Number: 12102
PI Name: MATTHEW LUNDY
Title: THE END OF THE BLAZAR SEQUENCE: UNDERSTANDING THE LIMITS AND IMPACT THE MOST ENERGETIC ACCELERATORS
Abstract: Blazars host powerful relativistic jets, and the most powerful of these jets belong to a small class of TeV source known as eHBLs. Here, we propose an extensive campaign to measure the synchrotron peak frequency of eight remaining eHBLs without NuSTAR observations. Characterizing the synchrotron emission will allow us to decode the spectra at TeV energies, and understand why eHBLs seem to defy conventional understanding and require model parameters in tension with other multi-wavelength observations. It will also allow for the additional modeling of subdominant hadronic components hidden just under the powerful leptonic emission present in this source class.

Proposal Number: 12106
PI Name: XIURUI ZHAO
Title: A DYNAMIC VIEW OF AGN CORONAE WITH NUSTAR
Abstract: The hard X-ray emission of active galactic nuclei (AGN) originates from compact coronae whose physical nature remains uncertain. Recent NuSTAR observations of the bright type-1 AGN Mrk 509 revealed a dramatic decrease in coronal temperature at nearly constant luminosity, challenging standard hybrid thermal non-thermal coronal models. We propose coordinated NuSTAR and Swift monitoring of Mrk 509 across normal and faint flux states to track the coupled evolution of coronal temperature, compactness, and disk reflection. These observations will critically test hybrid corona predictions and distinguish them from emerging bulk Comptonization models, providing a dynamic view of AGN coronae and new constraints on their electron properties.

Proposal Number: 12110
PI Name: XIURUI ZHAO
Title: SYSTEMATICALLY PROBING THE PHYSICS OF AGN CORONAE USING A HIGH-Z, HIGH LUMINOSITY QUASARS
Abstract: The physical nature of AGN coronae remains poorly understood, particularly their electron energy distribution and heating mechanism. Recent NuSTAR observations of a small sample of high-redshift, high-luminosity quasars reveal systematically low coronal temperatures, inconsistent with purely pair-regulated models and suggestive of a significant non-thermal electron component. We propose joint NuSTAR and XMM-Newton observations of four carefully selected, non-lensed, radio-quiet quasars at high-z. Cosmological redshifting enables precise measurements of coronal cutoffs thus the coronal physical properties. This program will double the current clean sample of luminous quasars with well-measured coronal properties and provide decisive tests of hybrid versus purely thermal corona model.

Proposal Number: 12111
PI Name: SAYANTAN BHATTACHARYA
Title: HARD X-RAY ORBITAL PHASE RESOLVED SPECTROSCOPY OF THE GAMMA-RAY BINARY LS I+61 303 WITH NUSTAR
Abstract: LS I +61 303 is a gamma-ray binary that exhibits strong orbital flux modulation from radio to TeV energies, yet the physical origin of its hard X-ray emission remains poorly understood. Competing models invoke either synchrotron radiation from shock-accelerated particles in a pulsar-wind interaction or alternative non-thermal processes, which predict distinct spectral behavior above 15 20 keV. We propose four orbital phase resolved NuSTAR observations of LS I +61 303, each of 35 ks, sampling key phases across the 26.5-day orbit. These observations will measure the evolution of the hard X-ray continuum and search for spectral curvature or high-energy cutoffs in the 10-70~keV band. The resulting constraints will directly test the particle acceleration and cooling scenario.

Proposal Number: 12115
PI Name: RANDALL ROJAS
Title: SOLVING THE MYSTERY OF ABELL S1063 WITH NUSTAR: MERGING OR RELAXED CLUSTER?
Abstract: Since the Big Bang, the most energetic events in the Universe are the merging of two or more galaxy clusters. Mergers drive shock fronts and turbulence that heat the gas and accelerate electrons, which result in X-ray and radio features. Understanding the role of mergers in the evolution of galaxy clusters is crucial for our comprehension of large-scale structure and dark matter. In this proposal, we seek to investigate the merger status of Abell S1063. The high sensitivity of NuSTAR will allow us to probe the thermodynamic properties and potential shock fronts. Measurements of the giant radio halo present in Abell S1063 alongside NuSTAR's ability to probe the high energy non-thermal regime will provide constraints on inverse Compton scattering and the average magnetic field strength.

Proposal Number: 12120
PI Name: HIROMASA SUZUKI
Title: FRESH PARTICLE ACCELERATION IN THE 4000 YR SUPERNOVA REMNANT PUPPIS A
Abstract: Recent XRISM observations suggest that Puppis A provides an excellent environment for studying particle acceleration physics in middle-aged remnants and reflected shocks. We propose a 70 ks NuSTAR observation pointing toward the hard X-ray enhanced region of Puppis A. The hint of non-thermal emission found by XRISM naturally drives us to observe it with NuSTAR. The proposed NuSTAR observation will allow us to easily distinguish the synchrotron emission associated with a reflected shock from non-thermal bremsstrahlung in a shock-cloud interacting region. With the accurate hard X-ray spectral shape, in combination with the thermal X-ray and multi-wavelength data, we will be able to advance the understanding of the microphysics of shock acceleration in middle-aged remnants.

Proposal Number: 12121
PI Name: DANIEL WILKINS
Title: A DETAILED STUDY OF THE VARIABLE ULTRAFAST OUTFLOW IN I ZWICKY 1 WITH NUSTAR, ALONGSIDE XRISM AND XMM
Abstract: We propose a 250ks NuSTAR observation of the AGN I Zw 1, to be executed simultaneously with approved XRISM and XMM-Newton observations scheduled for June 2026. This observation will add to a legacy dataset that will measure the detailed structure and constrain the driving mechanism of of the highly-variable ultrafast outflow (UFO) that is observed. UFOs are likely an efficient channel of AGN feedback. Including broadband spectroscopy with NuSTAR will enable a comprehensive analysis of the broadband X-ray spectrum, probing not just the UFO but the structure of the corona and inner accretion disk when the UFO is launched, and will provide the required broadband SED data for accurate photoionization modeling of the UFO.

Proposal Number: 12124
PI Name: DHEERAJ PASHAM
Title: NUSTAR OBSERVATIONS OF ULTRA-LONG X-RAY TRANSIENTS DISCOVERED BY EINSTEIN PROBE
Abstract: Ultra-long X-ray transients unveiled by Einstein Probe hint at a revolutionary new frontier in high-energy astrophysics. These enigmatic explosions, with hours--days long plateaus defy conventional GRB behavior. They may hide powerful relativistic jets, shock interactions, or exotic accretion physics. We propose NuSTAR ToO follow-up observations of a future such event to capture its hard X-ray (3 79 keV) signatures--measuring spectral cutoffs and rapid variability--to unravel their true nature. The requested NuSTAR observations will be complemented with our approved multi-wavelength observations to constrain progenitor models and energetics, offering new insights into these novel enigmatic high-energy events.

Proposal Number: 12126
PI Name: ROBERTO SORIA
Title: BRIDGING THE SOFT AND HARD BANDS: NUSTAR FOLLOW-UP OF X-RAY BINARIES TO BE DISCOVERED BY EINSTEIN PROBE
Abstract: The Einstein Probe (EP) is rapidly expanding the sample of faint X-ray transients, yet understanding the nature of these sources requires information beyond the soft X-ray band. We propose a NuSTAR Target of Opportunity program to unveil the accretion physics of these new discoveries. We propose to use NuSTAR to do follow-up observations of faint X-ray binary candidates that will be discovered by EP during Cycle 12. By leveraging NuSTAR's hard X-ray coverage, we will identify the nature of these new candidates and accurately characterize their accretion physics

Proposal Number: 12136
PI Name: GIANLUCA ISRAEL
Title: ASSESSING THE NATURE OF A NEWLY (RE)DISCOVERED X-RAY PULSATOR
Abstract: In the last 10 years, several data-mining projects aimed at the search for periodic timing signals were carried out in X-ray archives and resulted in the discovery of more than a hundred new pulsators in the 0.1-10keV X-ray band. The obtained sample is expected to be dominated by spin and orbital periods of cataclysmic variables and other binary systems for which the nature of the accreting object is unknown. In this proposal, we ask for joint NuSTAR and XMM-Newton follow-up observations of one pulsator, the properties of which stand out with respect to those of the bulk of the sample and suggest the presence of an accreting neutron star in a rare binary system. The requested observations will allow us to unambiguously assess its nature.

Proposal Number: 12139
PI Name: RICCARDO MIDDEI
Title: THE BEAST IN ESO511-G030 IS AWAKE: A GOLDEN OPPORTUNITY TO LINK ACCRETION STATE AND HOT CORONAE
Abstract: The NuSTAR/XMM-Newton observations conducted in 2019 observed ESO 511-G030 in an unprecedented low-flux state, with L/L_Edd~1*10^-3. Since then, continuous monitoring with Swift has revealed a steady increase in flux in both the X-ray and UV bands, with the source recently reaching L/L_Edd~2%, consistent with its previously known high-flux state. The proposed joint NuSTAR/XMM-Newton observation will enable us to characterize the emission spectrum in this high-flux regime and, for the first time, compare it with the rich archival dataset from 2019. This presents a unique opportunity to track the evolution of the hot coronae across two distinct Eddington regimes, differing by a factor of ~10, and to explore its connection with the accretion disk.

Proposal Number: 12142
PI Name: JAEGEUN PARK
Title: HARD X-RAY CHARACTERIZATION OF MSH 11-62: CLUES TO ITS EVOLUTION
Abstract: Diverse morphologies and TeV-faint systems imply incomplete understanding of magnetic fields and evolution. Constraining PWN evolution is essential for linking present-day X-ray spectra and morphology to the injected particle population and transport history. MSH 11-62 is a young, energetic PWN with no TeV counterpart, implying a high magnetic field (B) that suppresses inverse-Compton emission. Our reanalysis of archival Chandra and NuSTAR data shows curvature: a cooling break at ~3 keV and a possible exponential cutoff at ~21 keV (p=0.04). We propose an 80 ks NuSTAR observation to confirm the cutoff and measure electron maximum energy. Break+cutoff fits with a multi-zone model will constrain B and flow speed, allowing us to reconstruct the evolution history.

Proposal Number: 12145
PI Name: HANEUL JEONG
Title: NUSTAR CONFIRMATION OF THE DRIVING PULSAR FOR SNR G337.2+0.1 AND HESS J1634-472
Abstract: HESS J1634-472 shows conflicting age indicators: radio data suggest a young system (~1.5 kyr), while its low X-ray-to-TeV flux ratio and large VHE extent favor an evolved PWN (~10 kyr). AX J1635.9-4719, the potential X-ray counterpart of HESS J1634-472, exhibits a compact, hard X-ray source and a candidate 20.83 Hz pulsation in archival NuSTAR data, though obscuration and off-axis conditions prevent confirmation. We request a 50 ks on-axis NuSTAR observation to confirm the pulsation and measure the spin-down parameters needed to resolve the age discrepancy and identify the TeV engine, providing a decisive test of PWN evolution models and the energy injection history. Given the heavy absorption and short period, NuSTAR offers the only viable means to reveal the central engine.

Proposal Number: 12147
PI Name: RICCARDO MIDDEI
Title: NUSTAR AND MULTI-ENERGY SPECTRAL AND POLARIMETRIC OBSERVATIONS OF A FLARING HSP BLAZAR
Abstract: We propose a ToO observation with NuSTAR (40 ks) of a high synchrotron peaked (HSP) blazar during a TeV flare. The requested ToO observation lies in the context of an already secured multiwavelength spectro-polarimetric observational campaign (radio, optical, X-rays, TeV-$\gamma$-rays). Precise estimates of the photon index (alpha) and the curvature parameter (beta) are a key ingredients for a robust spectro-polarimetric analysis, and the narrow operating band (2-8 keV) of the Imaging X-ray Explorer (IXPE) is not suitable for delivering the actual spectral shape of the source. Thanks to its unrivaled bandpass, NuSTAR is best suited} to model the curved spectrum of an HSP source and to track its spectral variability down to a few ks timescales.

Proposal Number: 12155
PI Name: MASAHIRO TSUJIMOTO
Title: ESTABLISHING A NEW CLASS OF BINARIES FOR A MISSING POPULATION WITH HARD X-RAY SPECTROSCOPY
Abstract: Binary evolution is one of the most fundamental ingredients in astronomy. Binaries consisting of a high-mass star and a compact object represent an important milestone in binary evolution. gCas and its analogs are likely the long-sought missing population of Be+WD binaries, although an alternative interpretation exists. Recently, a strong case for the Be+WD interpretation has been made by explaining their anomalous X-ray spectrum based on a physical model of accreting WD binaries. The validity of this model is best illustrated by the estimate of M_WD consistent with optical spectroscopic measurement. The dispute can be resolved by applying the same test to the full sample. We propose a NuSTAR observation of zTau and deremine M_WD with an accuracy of 0.1 Mo.

Proposal Number: 12158
PI Name: ANDREA GOKUS
Title: PROBING TEV BLAZAR ENGINES WITH HARD X-RAYS AHEAD OF THE CTAO ERA
Abstract: We propose NuSTAR observations of three bright TeV blazar candidates that have a very high chance to be detected by the upcoming Cherenkov Telescope Array Observatory (CTAO). Observations in the hard X-ray band are crucial to meaningfully constrain the physical parameters of the particle populations and provide predictions for the very-high energy emission expected to be seen with CTAO. We request a total of 97 ks of observing time with NuSTAR, which is the only flying instrument covering the X-ray emission above 10 keV and sensitive enough for our targets.

Proposal Number: 12162
PI Name: MOAZ ABDELMAGUID
Title: A NUSTAR INVESTIGATION OF THE GEV-BRIGHT, TEV-QUIET PWN IN SNR G292.0+1.8
Abstract: TeV emission from pulsar wind nebulae (PWNe) provides a direct observational signature of particle acceleration to the highest energies and is commonly observed in systems powered by young, high spin-down pulsars. However, the PWN in SNR~G292.0+1.8 stands out as a notable exception.~Despite being powered by a young ($\tau_{ch} <$ 3 kyr) \& energetic ($\dot{E} > 10^{37}\,\mathrm{erg\,s^{-1}}$) pulsar, and bright at GeV energies, it remains undetected at TeV energies.~This behavior sets it apart from other Galactic PWNe with similar ages and spin-down powers and raises a fundamental question when and under what conditions do PWNe become efficient TeV emitters? We propose a 50 ks \textit{NuSTAR} observation to study its X-ray emission, providing a critical link between its highest energy ele

Proposal Number: 12163
PI Name: AXEL ARBET-ENGELS
Title: PROBING EXTREME PARTICLE ENERGIZATION IN THE JET OF MRK501 WITH NUSTAR, X-RAY POLARIZATION AND TEV MEASUREMENTS
Abstract: High-synchrotron-peaked blazars (HSPs) are the most extreme AGNs in our universe. They display a synchrotron emission reaching 100keV, and a gamma-ray component peaking beyond 100GeV. This implies particles at the TeV scale in the jet. The processes bringing particles to such extreme energies remains to date an open question. The advent of X-ray polarization with IXPE has provided a completely new window to test acceleration models. We request NuSTAR observations of the HSP Mrk501 during an IXPE large program approved for the IXPE G.O. Cycle 3. The observations will be supported by a dense multiwavelength coverage, in particular above 100GeV with MAGIC. The proposed campaign will provide the most extensive view of spectral and polarization properties in a HSP at the highest energies.

Proposal Number: 12164
PI Name: TOLGA GUVER
Title: INVESTIGATING THE TEMPORAL AND SPECTRAL STATE OF HIGH MASS X-RAY BINARY 4U 2206+54
Abstract: We propose a 60ks NuSTAR observation of the high-mass X-ray binary 4U 2206+54, which hosts one of the slowest rotating neutron stars. Following a prolonged spin-down phase that reached approximately 5700s in 2015, the pulsar transitioned to spin-up, with the period decreasing to about 5200s by 2020, indicating a high-torque state with an average spin-up rate of 1.2x10^{-13} Hz s^{-1}. However, the current rotational state remains uncertain, as it is unclear whether the pulsar has maintained this trend or undergone another torque reversal. This observation will measure the current spin period with high precision while probing the accretion flow properties. We will constrain the limits for a cyclotron feature around 30 keV to determine the magnetic field strength.

Proposal Number: 12165
PI Name: CHANHO KIM
Title: PRECISE MEASUREMENT OF THE HARD X-RAY SPECTRUM OF THE PWN OF PSR J1400-6325: CONSTRAINING THE PWN EVOLUTION
Abstract: PSR J1400-6325 (spin-down power of 5e37 erg/s) is compelling because its SNR shell provides an independent age constraint for evolutionary modeling. Archival Chandra+NuSTAR data and the reported INTEGRAL flux suggest a curved synchrotron spectrum with breaks at energies ~2.9 keV and ~10 keV, but the current >10 keV statistics are insufficient to firmly establish the high-energy break implied by the INTEGRAL measurement. We propose a 50 ks NuSTAR observation to bridge soft X-rays and INTEGRAL and confirm the break above 10 keV, enabling multi-zone modeling of the transport and cooling history. We will use pulse-gated spectroscopy to isolate the nebula. These data will allow tests of shock-acceleration and PWN evolution theories within a multi-zone evolutionary PWN modeling framework.

Proposal Number: 12166
PI Name: XAVIER RODRIGUES
Title: CONSTRAINING A LEADING CANDIDATE SOURCE OF THE FIRST UHE NEUTRINO
Abstract: Blazar PKS 0605-085 is a leading candidate source of the first UHE neutrino ever detected. We show that 40 ks observations with NuSTAR would have unique potential to discriminate between robust model predictions, constraining the source s nature as an UHE neutrino emitter. We propose an analysis pipeline to measure the spectral index in a currently unconstrained frequency range. If the data supports the UHE scenario, the results would indicate the discovery of the first UHE neutrino source. If it supports a leptonic scenario, we will be uniquely able to exclude the source as the origin of the first UHE neutrino event, with crucial consequences for its interpretation.

Proposal Number: 12167
PI Name: AKOS BOGDAN
Title: MAPPING THE EXTREME PHYSICS OF ABELL 370 WITH NUSTAR
Abstract: We propose a 140 ks NuSTAR observation of Abell 370, one of the hottest and most luminous merging clusters, to probe how a major collision channels gravitational energy into heat and cosmic rays. Utilizing 2 Ms deep Chandra imaging, NuSTAR will target the shock/edge sectors and radio halo region, measuring temperatures with less than 10% uncertainty and delivering a decisive merger energy budget when combined with Chandra density jumps. These data will test how electrons are heated at shocks and will detect or place stringent limits on inverse-Compton emission, directly constraining the relativistic particle population and cluster magnetic field.

Proposal Number: 12169
PI Name: LAURA BORRELLI
Title: COMPLETING THE NUSTAR WISSHFUL PROGRAM: X-RAY CORONAE AND WINDS IN QUASARS AT COSMIC NOON
Abstract: We propose coordinated NuSTAR observations (780ks in total) of four luminous, high-redshift quasars (z ~ 3) from the XMM WISSHFUL program - among the most luminous and rapidly accreting known - to systematically study coronal properties and their connection to nuclear winds. By leveraging such deep XMM and NuSTAR observations, we will precisely measure high-energy cut-offs, which is crucial for understanding pair-production mechanisms and potential non-thermal coronae and constrain the continuum close to the UFO absorption features, which is critical to determine their significance and properties, and to investigate the link between the nuclear winds and accretion properties in an almost unexplored regime of redshift, luminosity and accretion rate.

Proposal Number: 12172
PI Name: RUEDIGER STAUBERT
Title: UNDERSTANDING THE COMPLEX COSMIC MACHINE HER X-1 BY FOLLOWING VARIATIONS IN THE CYCLOTRON LINE ENERGY
Abstract: It is proposed to study the cyclotron line energy Ec in Her X-1. A long-term decay of Ec by 5 keV over 20 yrs ended 2012, followed by a stable value at 37.5 keV until 2020. Since February 2020, out of six further NuSTAR observations three values are significantly below this stable value . We take this as a new phenomenon in Her X-1: originally perceived as erratic variability of Ec, there is now an indication of a possible periodic variation. We believe that the variations are related to the evolution of the magnetic field configuration at the accretion mounds in the polar regions of the neutron star. We propose to further follow the evolution of Ec with a high cadence: observe Her X-1 during every Main-On for 30 ks each, throughout Cycle-12 (that is 10 observations, in total 300 ks).

Proposal Number: 12179
PI Name: DANIEL STERN
Title: COMPTON-THICK QUASARS FROM EROSITA
Abstract: We propose 20 ks NuSTAR observations of seven candidate Compton-thick quasars selected as bright, extremely hard extragalactic X-ray sources by eROSITA. Our candidates, which reside at 0.101e44 erg/s, classifying them as Compton-thick quasars. Of the currently known X-ray confirmed Compton-thick AGN, only one is of comparable intrinsic luminosity.

Proposal Number: 12181
PI Name: DOMINIC WALTON
Title: DETERMINING THE LONG-TERM SPIN EVOLUTION OF NGC5907 ULX1
Abstract: Following a series of remarkable discoveries, we now know that some of the most luminous members of the ULX population are actually powered by highly super-Eddington pulsars, making them the most extreme sustained accretors known. NGC5907 ULX1 stands out as the most luminous of these ULX pulsars, peaking at Lx~1e41 erg/s. Since emerging from the latest of its low-flux states (likely related to the propeller regime), ULX1 is clearly spinning too fast for an extrapolation of the literature model for its long-term spin evolution. Here we seek to obtain a second measurement of Pspin from this latest period of activity to determine the current secular spin-up. This will provide information on how this model for the spin evolution, which provides key B-field constraints, should be revised.

Proposal Number: 12182
PI Name: JOSEPH NEILSEN
Title: X-RAY JETS & BH SHADOWS: NUSTAR, EHT, CHANDRA, SWIFT, AND HST ON M87
Abstract: With a large, well-studied jet and the second largest event horizon on the sky, the radio galaxy M87 is one of the primary targets for the Event Horizon Telescope, but the origin of its jet and its long-term variability remain unclear. A 2026 EHT "movie campaign" will test the dynamical link between the BH shadow and the evolving jet. We propose follow-up in the year after the movie campaign, where NuSTAR observations (2x50 ks) with 10x1 ks Swift will be essential for tracking the long-term high-energy variability of near-horizon plasma, diagnosing particle heating and acceleration, and interpreting models of the accretion flow. Our data will place the movie campaign in the context of decadal variability of M87's X-ray jet.

Proposal Number: 12183
PI Name: VAIDEHI PALIYA
Title: X-RAYING THE FIRST TEV-DETECTED FLAT SPECTRUM RADIO QUASAR
Abstract: We propose to observe a rare TeV-emitting flat-spectrum radio quasar (FSRQ), S5 1027+74, jointly with NuSTAR and Swift for 40 ksec and 10 ksec, respectively. We will reproduce the broadband SED using state-of-the-art leptonic and hadronic emission models to derive the most accurate estimates of the jet's physical parameters. We will also unravel the origin of the third SED bump peaking at multi-TeV energies, a feature never detected from any other FSRQs. The high-quality NuSTAR and Swift observations will also allow us to compare the broadband properties of the target with other FSRQs detected above 100 GeV.

Proposal Number: 12185
PI Name: BRIAN GREFENSTETTE
Title: GS 1826-238 RETURNS TO THE HARD STATE (OR DOES IT?)
Abstract: We propose a NuSTAR observation to constrain the hard X-ray spectrum of GS 1826-238, the Clocked Burster that earned its name by producing regular Type I X-ray bursts roughly every 6-hrs. In 2014 the source underwent a slow transition from a traditional atoll state to a banana state and was studied with NuSTAR both in stray light and in focused observations. The Type I X-ray bursts during the soft state were less frequent, and narrower, than the hard state bursts. In 2025 the soft X-ray flux measured by MAXI dropped and the source has been intermittently detected by the Swift-BAT again, possibility indicating a transition back to a hard state. We propose a 40-ks NuSTAR observation to investigate the hard X-ray behavior of this new state of a historical source.

Proposal Number: 12190
PI Name: MAXIME PARRA
Title: BRIDGING THE GAP BETWEEN HOT AND COLD OUTFLOWS IN A TRANSIENT BH X-RAY BINARY WITH BROADBAND X-RAY SPECTROSCOPY
Abstract: Accreting black holes (BH) are powerful X-ray emitters with episodic outbursts, and eject particles through jets and winds. Recent X-ray and Optical/Infrared (OIR) observations revealed hot and cold wind components by detecting narrow absorption lines from BH transients. We request three 50ks XMM+NuSTAR ToOs of 1 intermediate-inclination BH transient with only OIR wind detections, in bright hard, bright soft, and decaying hard states, to complement dedicated programs with XRISM and multi-wavelength coverage. As a first attempt to obtain a global picture of the BH wind dynamic, we aim to 1) determine how hot, warm and cold winds evolve in different spectral states, 2) elucidate the wind launching mechanism(s), and 3) search for diffuse X-ray emission produced by energetic particle outflows

Proposal Number: 12191
PI Name: GEORGE YOUNES
Title: BROADBAND SPECTRAL-POLARIMETRIC STUDY OF THE RADIO-LOUD MAGNETAR 1E 1547.0-5408
Abstract: We propose a 50 ks NuSTAR and 10 ks Swift-XRT observations of the radio-loud magnetar 1E 1547.0-5408 to be obtained (quasi-)simultaneously to an approved 1.5 Ms IXPE Large Program. The primary goal is to provide the broadband spectral context required to interpret IXPE polarization measurements in terms of distinct emission components. By enabling a robust decomposition of the soft and hard X-ray spectrum, these observations will allow us to characterize the polarization degree and angle of both the dominant thermal emission and the secondary soft component observed above ~4-5 keV. This coordinated dataset will yield a physically informed spectral polarimetric view of one of the most highly polarized magnetars known.

Proposal Number: 12194
PI Name: ANUVAB BANERJEE
Title: LIVING ON THE EDGE: AN EXTREME BL LAC IN HARD X-RAYS
Abstract: Extreme high-peaked BL Lac objects (EHBLs) are a rare subclass of blazars with synchrotron peaks above 10^17 Hz, making them key probes of extreme particle acceleration, extragalactic background light (EBL) attenuation, and possible connections to ultra-high-energy cosmic rays. Despite their importance, their hard X-ray properties especially the transition between the synchrotron and inverse-Compton components remain poorly constrained. We propose a NuSTAR observation of an extreme EHBL to extend synchrotron measurements to the highest accessible energies, identify spectral curvature or cutoffs, and constrain the maximum particle energies prior to radiative cooling.

Proposal Number: 12195
PI Name: JOOYUN WOO
Title: UNUSUAL SUSPECTS: AN X-RAY SEARCH FOR THE HIDDEN CORNERS OF THE PEVATRON ZOO
Abstract: The recent discovery of ~50 ultra-high-energy (UHE; >100 TeV) gamma-ray sources and neutrino emission in the Galactic Plane provided the first compelling evidence of Galactic PeVtrons: accelerators of the most energetic cosmic rays with energies >10^15 eV. Most UHE sources remain unidentified due to the limited angular resolution of UHE telescopes and the lack of multiwavelength data. We propose NuSTAR and XMM observations of 4 unidentified PeVatron candidates whose UHE emission originates from "unusual" types of accelerators. Our multiwavelength exploration of these PeVatrons, empowered by NuSTAR and XMM-Newton's synergy in broadband X-ray spectro-imaging capabilities, will reveal their nature, particle acceleration mechanisms, and surrounding environments.

Proposal Number: 12202
PI Name: ANTONINO D'AI
Title: UNVEILING THE HARD X-RAY ENGINE AND FE K ULTRA-FAST OUTFLOW OF THE PECULIAR BLACK HOLE CANDIDATE MAXI J1810-222
Abstract: Since 2018, the BHC MAXI J1810-222 has defied classification with a years-long outburst and complex "looping" state transitions. NICER observations revealed a state-dependent outflow (v>0.05c). However, the high-energy window remains unexplored. Re-analysis of a shallow 18 ks archival NuSTAR observation hints at a highly ionized Fe K wind (v∼0.1c) with residuals at 7.5 8.0 keV. We propose a 60 ks NuSTAR observation to guarantee high-impact science regardless of the spectral state. In the soft state, we will definitively constrain the blue-shifted Fe lines to test wind driving models. In the hard state, we will obtain the first high-quality broadband spectrum to constrain outflows, reflection geometry, and timing features.

Proposal Number: 12208
PI Name: LORENZO DUCCI
Title: SAMPLING THE ORBIT OF THE ACCRETING PULSAR A0538-66 WITH HARD X-RAY MONITORING
Abstract: A0538-66 is a Be/X-ray binary characterised by fast flares lasting ~2-50 s, with a peak luminosity near 4E38 erg/s (0.2-12 keV), and a dynamic range up to ~1000 on timescales of few seconds. Recently, it has also shown a super-Eddington outburst exceeding 1E39 erg/s. Its extreme behaviour is unique among Be/XRBs and is likely linked to its fast spin period (69 ms), high orbital eccentricity (e=0.7), and the still-unknown properties of the pulsar magnetic field. All previous hard X-ray observations with NuSTAR were taken near periastron, leaving the spectral and timing evolution over the full 16.6-day orbit unexplored. We therefore propose a monitoring program consisting of ten 20 ks visits to sample the orbit uniformly, to clarify the mechanisms behind the extreme variability of A0538-66.

Proposal Number: 12209
PI Name: FELIX FUERST
Title: CONTINUED SPIN-TRACKING OF THE NEUTRON STAR ULX NGC7793 P13 WITH NUSTAR
Abstract: NGC 7793 P13 is one of the best targets among the ultra-luminous X-ray pulsars (ULXPs) to study how accretion works in the super-Eddington regime. When P13 is X-ray bright, it shows strong X-ray pulsations with a long-term spin-up trend. In 2020 and 2021 the source was in an off-state but the spin-up continued, showing a disconnect between observed flux and transferred angular momentum in this system. The source is currently in a high state, providing us withthe best opportunity to follow the pulse period evolution during 2026 and 2027. We therefore propose to continue the successful campaign over the last 9 years to monitor the pulse period of P13 throughout cycle-12 with 2 50 ks observations.

Proposal Number: 12213
PI Name: MIRKO KRUMPE
Title: SEARCH FOR AN X-RAY COUNTERPART OF A HIGH FLUENCE FAST RADIO BURST REPEATER
Abstract: We propose one NuSTAR ToO of a fast radio burst (FRB) repeaters during phases of strong radio activity with hyperluminous fluence bursts. The ToO consists of 3 x 30 ks, providing fully synchronized radio and X-ray coverage. We will pursue two key objectives: (i) to determine whether the X-ray emission from the new FRB repeaters aligns with predictions from magnetar progenitor models, and (ii) to constrain the uniformity of X-ray-to-radio characteristics across the sample. The results will be directly compared to those of SGR 1935+2154, the only known Galactic magnetar to have shown simultaneous X-ray and radio emission. This dataset will provide crucial observational constraints on the still-mysterious nature of FRB repeaters and will help eliminate several competing theoretical models.

Proposal Number: 12214
PI Name: DANIEL WIK
Title: TRIANGULUM AUSTRALIS: UNCOVERING A MERGER IN AN OBSCURE(D) GALAXY CLUSTER
Abstract: The Triangulum Australis galaxy cluster is one of the hottest systems in the nearby universe, but its study has been hampered by its position near the Galactic plane where spatially variable absorption has obscured characterization of its temperature structure. Even so, evidence for an ongoing merger is apparent, including a disturbed X-ray morphology, a bright radio halo, and a surface brightness edge of unclear nature. NuSTAR's high energy sensitivity can overcome the challenges of absorption to map the cluster's temperature distribution, determining whether the edge is a shock or cold front, uncovering the overall merger dynamics, and placing the most accurate constraint on inverse Compton emission related to the radio halo.

Proposal Number: 12223
PI Name: AYSEGUL TUMER
Title: SHOCK FRONT AND INVERSE COMPTON SEARCH ACROSS THE DOUBLE RADIO RELICS OF MACS J1752.0+4440
Abstract: We propose a 200 ks NuSTAR data to study a post first core passage merger MACS J1752.0+4440. This galaxy cluster hosts one of the 12 known double radio relics in the universe. NuSTAR is the best instrument to confirm and constrain strong shock fronts thanks to it great sensitivity at hard X-ray band. Since these structures are generally observed in cluster outskirts, their faint nature and the scattered light background of NuSTAR make it difficult to constrain the inverse Compton (IC) emission. Radio relics of this cluster are enclosed within the field of view of NuSTAR, as well as the central bright intracluster emission. With this proposal, we aim to study the shock features that are indicated by relics, the cluster temperature structure, and search for IC emission.

Proposal Number: 12224
PI Name: AAFIA ANSAR MOHIDEEN
Title: ARE THERE BEXRBS LURKING AMONG LUMINOUS LONE BE STARS?
Abstract: Be stars, with circumstellar decretion disks have been increasingly posited to have hidden companions. In X-rays, they are mostly studied as BeXRBs which have thus far shown predominantly transient behaviour with their extremely luminous outbursts. However, recent research has shown that persistent X-ray emission at low luminosities outside of outburst is the default. The low luminosity end of the distribution of High Mass X-ray Binaries is thus populated by low luminosity BeXRBs. The luminosity distribution of Be stars on the other hand shows a handful of luminous systems which overlap in luminosity with the least luminous BeXRBs. We propose for follow-up of hitherto known to be isolated Be stars which populate this overlap region in luminosity, with 60ks of NuSTAR observations each.

Proposal Number: 12226
PI Name: CHRISTIAN NORSETH
Title: 3C 438: CONSTRAINING A SHOCK IN ONE OF THE HOTTEST CLUSTERS IN THE UNIVERSE
Abstract: 3C 438 is one of the hottest galaxy clusters and is undergoing a major merger with multiple surface brightness discontinuities in the ICM. Chandra observations suggest a strong shock and extremely hot gas, but temperatures are poorly constrained at such high energies. NuSTAR s hard band sensitivity will enable robust constraints on the hot gas and, when combined with Chandra surface brightness maps, will better characterize the temperature structure, constrain the temperature jump and Mach number across the shock, and place limits on the magnetic field strength through an IC search. These observations will provide a clearer picture of the processes operating in a hot, dynamically active system, improve the reliability of X-ray temperatures, and strengthen their use as cosmological probes.

Proposal Number: 12227
PI Name: AAFIA ANSAR MOHIDEEN
Title: ESTABLISHING LOW LUMINOSITY ACCRETION: A SURVEY OF GALACTIC BEXRBS
Abstract: We propose for 15-50ks low luminosity observations of 12 BeXRBs in the Western Galactic hemisphere, to build a volume complete X-ray luminosity function in the hard X-rays to complement the eROSITA survey (which has reached down to luminosities of 1e32 erg/s in the soft band). Of the 12 sources, 8 have persistent eROSITA X-ray detections, and are candidates for stable accretion at low luminosities. The remaining four have at most only one detection in soft X-rays outside of outburst, and are candidates to exhibit the propeller phenomenon. These observations are crucial for constraints in the B-P space on the elusive propeller phenomenon and to establish the prevalence of stable accretion outside of outburst.

Proposal Number: 12228
PI Name: JON MILLER
Title: DISK WIND EVOLUTION IN STELLAR-MASS BLACK HOLES
Abstract: Despite numerous campaigns over more than two decades, we have yet to trace the evolution of an accretion disk wind in a stellar-mass black hole over an order of magnitude in the inferred mass accretion rate. As a result, simple questions remain. Do mass outflow rates correlate with inflow rates? Do changes in wind strength really suggest quenching, or do winds merely become too highly ionized to detect? The combination of NuSTAR and XRISM is uniquely able to measure the evolution of disk winds across a broad range in accretion rates and ionizations. We request a series of three joint NuSTAR and XRISM observations (20 ks, 30 ks, 50 ks) of a stellar-mass black hole in outburst. Only known sources with previous disk wind detections will be targeted.

Proposal Number: 12230
PI Name: ELIAS KAMMOUN
Title: A DEEP LOOK AT THE HEART OF THE MOST LUMINOUS QUASAR
Abstract: We propose deep simultaneous NuSTAR and XMM observations of the z=3.96 quasar SMSSJ0529, the most luminous known non-jetted quasar with extreme Eddington ratio ~6 19. Recent GRAVITY+ observations revealed powerful outflows from its BLR, motivating a broadband X-ray study to measure the intrinsic coronal continuum in this super-Eddington regime. Swift data show a flat spectrum, but soft-band degeneracies allow either hard unabsorbed or steep absorbed spectra. We will robustly measure the photon index, absorption-corrected L2 10 keV, and constrain (or limit) the coronal temperature. This tests cool-corona expectations from pair regulation at high compactness and calibrates the X-ray bolometric correction in extreme accretion, providing essential context for rapid SMBH growth at high-z.

Proposal Number: 12232
PI Name: INDRANI PAL
Title: INVESTIGATING THE ORIGIN OF EXTREME REFLECTION IN TWO SUPER-EDDINGTON NARROW LINE SEYFERT GALAXIES
Abstract: The nature of the accretion disk in super-Eddington AGN differs significantly from that in lower accretion rate systems, with radiation pressure causing the disk to become geometrically thick. In such cases, X-ray reflection from the slim disk can dominate over the primary coronal emission. Additionally, strong ionized outflows in these sources may suppress the direct continuum, further enhancing the observed reflection features. We propose simultaneous NuSTAR and XMM-Newton observations of two super-Eddington AGN to investigate their reflection-dominated spectra. Through broadband X-ray reflection spectroscopy, we aim to characterize the reflection spectrum of these super-Eddington AGN.

Proposal Number: 12235
PI Name: JENNIFER SOKOLOSKI
Title: A HARD X-RAY VIEW OF THE BRIGHTEST NOVA THIS CENTURY
Abstract: The goal of this ToO proposal is to use high S/N hard X-ray spectra from NuSTAR and Swift during an eruption of the symbiotic recurrent nova T CrB to test two models for GeV and TeV emission from such events. We will determine whether novae in symbiotic binaries produce multiple gamma-ray shocks that traverse and probe different portions of the ejecta and circumbinary medium. The strength of non-thermal X-ray emission will also constrain the origin of gamma-rays. T CrB, which may experience a nova during Cycle 12, is ideal for this test, the results of which have implications for the physics of particle acceleration in shocks, high-energy emission from eruptive transients, and mass transfer in wide binaries. Projects with this objective were approved but not triggered in Cycles 9 -- 11.

Proposal Number: 12237
PI Name: JOEL COLEY
Title: PROBING THE ACCRETION WAKE IN THE SUPERGIANT X-RAY BINARY XTE J1855-026 WITH NUSTAR AND XMM-NEWTON
Abstract: We propose contemporaneous 40 ks+40 ks NuSTAR+XMM-Newton observations of the wind-fed Supergiant X-ray binary XTE J1855-026 to test the hypothesis that the enhanced absorption column density at late orbital phases is driven by an accretion wake. With the first NuSTAR observation of J11855, we will take advantage of its excellent timing and spectral resolution to measure the first high S/N broad band spectrum of the source and search for CRSFs to directly probe the magnetic field of the ~360.1 s neutron star. Extending our analysis to the soft bandpass with XMM-Newton, we will measure changes in its absorption column density and Fe fluorescent lines to test the hypothesis that the enhanced absorption at late orbital phases is driven by a wake.

Proposal Number: 12239
PI Name: YUEXIN ZHANG
Title: CAN POWER COLOR "HUE" EFFICIENTLY CAPTURE THE NEXT TRANSITION IN GX 339-4 WITH NUSTAR-SWIFT?
Abstract: We propose a 60-ks NuSTAR ToO with joint Swift/XRT observations of the black hole X-ray binary (BHXRB) GX 339-4 during its short-lived intermediate state (IMS) transition. The corona emission dominates the spectrum over a timescale of weeks in the low-hard state monitored by an approved 36x2-ks HXMT trigger, followed by a transition to the IMS. Our predicted monitoring will, for the first time, apply the power color method in real time, and precisely and efficiently follow the next fast hard-to-soft IMS transition in GX 339-4. During this transition, the change of the QPO frequency/type and spectral state will reveal the fast changes in the geometry of the innermost region.

Proposal Number: 12240
PI Name: DANIEL STERN
Title: NUSTAR FOLLOW-UP OF EXTREME WISE VARIABLE AGN
Abstract: We request 20 ks NuSTAR observations of four AGN that presented extreme mid-IR variability during the WISE mission. The targets were selected from an analysis of the mid-IR light curves of robust active galactic nuclei (AGN) candidates from the WISE AGN Catalog, and were spectroscopically confirmed as AGN. The mid-IR light curves show a diversity of morphologies, including sources that appear to have turned off and flaring sources. Optical spectroscopy typically reveals type-2 AGN, and optical light curves generally show minimal variability. The targets appear to be a combination of obscured changing-look AGN and tidal disruption events. This program will characterize the current accretion state of these sources.

Proposal Number: 12242
PI Name: JAMES STEINER
Title: STRUCTURE IN THE QUIESCENT EMISSION OF THE DORMANT TITAN A0620-00
Abstract: A0620-00 is the closest known black hole X-ray binary and in its discovery outburst in 1975 reached an unequaled 50 Crab X-ray brightness. In the decades since, it has remained in a deep quiescence, several micro-Crab bright. The quiescent emission of A0620-00 has never been studied in the hard X-rays. NuSTAR's unique hard X-ray sensitivity provides the only means by which we may use X-rays to clearly distinguish the emission mechanism of this quiescent black hole, and potentially place constraint on the size of a presumably quite truncated accretion disk.

Proposal Number: 12244
PI Name: ALESSIO MARINO
Title: CONNECTING JETS AND ACCRETION FLOWS IN TRANSIENT BLACK HOLE LMXBS WITH NUSTAR AND MEERKAT
Abstract: Stellar-mass black holes in low-mass X-ray binaries launch powerful jets, yet the physical mechanisms linking the jet production and emission to the structure of the underlying accretion flow remain unclear. In particular, key questions such as how the inner disc geometry and coronal properties influence jet power and collimation are to this day mostly unanswered. We propose two 60 ks NuSTAR Target-of-Opportunity campaigns, each with three observations, to capture the evolving accretion flow of a black hole low-mass X-ray binary during an outburst. These observations will be coordinated with weekly MeerKAT monitoring, enabling a direct, time-resolved comparison between hard X-ray and radio jet properties.

Proposal Number: 12247
PI Name: LORENZO MARRA
Title: PROBING THE HARD X-RAY TAIL OF THE MAGNETAR 1E 1841-045 WITH NUSTAR AND IXPE
Abstract: We propose a 50 ks NuSTAR observation of the persistent magnetar 1E 1841-045, coordinated with an approved 700 ks IXPE GO Cycle 3 program, to enable a broadband and phase-resolved characterization of its hard X-ray emission. 1E 1841-045 is unique among magnetars in exhibiting a hard power-law tail that becomes significant already at 6 keV and dominates the emission above 10 keV. NuSTAR s sensitivity and spectral coverage are essential to isolate this component, measure its spectral parameters, and track their evolution over the neutron star rotational cycle. The proposed observation will provide the broadband spectral constraints required to interpret the contemporaneous IXPE polarization measurements and associate the polarization properties to specific emission components.

Proposal Number: 12252
PI Name: YASH BHARGAVA
Title: CONSTRAINING THE DISK-JET CONNECTION OF LMXB AQL X-1 USING JOINT NUSTAR AND MULTI-WAVELENGTH OBSERVATIONS
Abstract: Aquila X-1 (Aql X-1) is a recurrent transient neutron star binary exhibiting well-defined spectral state transitions and variable radio emission during outburst, making it a well-suited laboratory to study disk-jet coupling. We propose 100 ks monitoring observations of Aql X-1 during its next outburst with NuSTAR to probe the transition from hard to soft state providing the first NuSTAR observations of this phase. This study will trace evolution of corona and reflection facilitating measurement of key physical parameters. We request 5 ks Swift observations for soft X-ray and UV coverage enabling broadband spectral modeling to disentangle disk and jet contributions. Coordinated VLA, ATCA, and Gemini observations will enable a comprehensive multi-wavelength study of disk-jet coupling.

Proposal Number: 12256
PI Name: ELIAS KAMMOUN
Title: HARD X-RAY LEVERAGE FOR XRISM: NUSTAR ON 3C 390.3
Abstract: We request a 50-ks NuSTAR observation of the bright broad-line radio galaxy 3C390.3, scheduled contemporaneously with a 170-ks XRISM/Resolve pointing in late April 2026. NuSTAR will anchor the hard-X-ray continuum and high-energy cutoff (Ecut) in the XRISM epoch and quantify the weak-reflection state. With Ecut constrained, we will fit finite-column reprocessing models to the Compton hump to test whether the dominant reflector is Compton-thin or near/Compton-thick, turning "weak reflection" into a physical constraint on the cold reprocessor and coronal illumination geometry.

Proposal Number: 12265
PI Name: FEDERICO FOGANTINI
Title: UNCOVERING THE MAGNETIC FIELD OF THE ECLIPSING HMXB IGR~J17252--3616
Abstract: {\bf We request a 260~ks \nustar{} observation of the eclipsing HMXB IGR~J17252$-$3616 to explicitly test magnetized wind-accretion models.} While the system's orbital and spin parameters are well-determined, the neutron star's magnetic field strength ($B$) remains unconstrained, preventing a physical solution to the accretion torque equation. Using archival \xmm{} spectroscopy to fix the continuum baseline, our simulations demonstrate that 260~ks is the statistical threshold required to distinguish weak cyclotron lines from continuum noise at the 99/% level. This observation serves as a definitive experiment: a detection directly measures $B$, while a non-detection statistically excludes the canonical $\sim 10^{12}$~G regime.

Proposal Number: 12266
PI Name: HARUKI KURAMOTO
Title: PROBING NON-THERMAL ACCELERATION IN STELLAR WINDS OF THE MASSIVE STAR-FORMING REGION RCW 38
Abstract: Massive star-forming regions (MSFRs) are likely major reservoirs of Galactic cosmic rays, potentially rivaling supernova remnants. While recent GeV-TeV gamma-ray detections support this, conclusive proof requires detecting non-thermal X-rays from colliding stellar winds. However, this signature has remained elusive due to severe thermal contamination in soft X-rays. We propose a 120 ks NuSTAR observation of RCW 38 to resolve this ambiguity. RCW 38 is the optimal target: it is extremely young (< 1 Myr) and free from supernova remnants, while being nearby (1.7 kpc) and rich in massive stars. Our simulations confirm that NuSTAR can robustly distinguish thermal from non-thermal emission (> 5 sigma), providing the first definitive test of particle acceleration in pure stellar cluster winds.

Proposal Number: 12267
PI Name: AKASH AGARWAL
Title: COMPARATIVE STUDY OF X-RAY EMISSION FROM DWARF NOVA RU PEG IN QUIESCENCE AND OUTBURST
Abstract: We propose a comparative study of the dwarf nova RU Peg to investigate its hard X-ray emission in quiescence and outburst. RU Peg has a massive (1.3 solar masses) white dwarf, leading to a high-temperature boundary layer emitting above 10 keV. NuSTAR s 3 79 keV coverage can constrain the shock temperature and detect reflection features. Comparing both states will test boundary-layer models, reveal how maximum shock temperature scales with accretion rate. The quiescent-state shock temperature will also provide an independent estimate of the white dwarf mass. Therefore, we request 40 ks exposure for each accretion state (quiescent and outburst) and hence total of 80 ks exposure.

Proposal Number: 12272
PI Name: BISWARAJ PALIT
Title: PROBING THE POST TRANSITION STATE OF MKN 590 WITH HARD X-RAYS
Abstract: Mrk 590 is a rare AGN that has undergone two changing-look (CL) transitions in the last fifty years, with the latest marked by a 20 increase in X-ray luminosity and the reappearance of broad optical emission lines and soft X-ray excess. We propose a 100 ks NuSTAR observation to study the X-ray coronal temperature and compactness at peak brightness, testing whether the source approaches the pair-production limit. Using the high S/N X-ray data and advanced torus models, we will constrain column density, covering factor, and geometry of the distant X-ray reprocessing gas. Furthermore, combined with contemporaneous multi-band data, this will yield the first broadband SED of Mkn 590 in its brightest state, providing key insights into the different accretion flow structures of CLAGN.

Proposal Number: 12273
PI Name: YUEXIN ZHANG
Title: A MULTI-DIMENSIONAL CAMPAIGN OF THE DISK WIND IN GRS 1915+105
Abstract: GRS~1915+105 is currently in a Compton-thick obscured state, during which the intrinsic accretion flow is largely hidden and polarization measurements are not feasible. Our approved IXPE and Chandra/HETG programs will trigger when the source emerges into a bright soft state with winds. NuSTAR provides the broadband hard X-ray coverage required to characterize the corona continuum and serves as the spectral anchor for the coordinated campaign. We propose a 40-ks NuSTAR ToO with joint Swift/XRT observations during Cycle 12. If GRS 1915+105 transitions into the soft state with a detectable disk wind, our observations will jointly constrain the broadband continuum, wind properties, and inner-disk geometry using complementary spectroscopic and polarimetric diagnostics.

Proposal Number: 12274
PI Name: MARCIN MARCULEWICZ
Title: THE MULTI-WAVELENGTH SPECTRAL ENERGY DISTRIBUTION OF THE LOW-MASS AGN NGC 4051
Abstract: A key question in AGN studies is the nature of the poorly understood accretion flow. NGC 4051 offers a rare opportunity to observe this process around a low-mass AGN, one of the brightest of its class. Its unique combination of variability, small black hole mass, and accessibility to monitoring makes it an ideal laboratory for testing models of the innermost structure of AGN. For this purpose, a 3-month multi-wavelength monitoring campaign of NGC 4051 will be undertaken, using broadband reverberation mapping. However, a critical open question is the role of X-rays in irradiating the accretion disk and the overall energy budget. NuSTAR's broad energy coverage and sensitivity are ideal for obtaining a high-quality X-ray spectrum, completing the broadband SED during the monitoring campaign.

Proposal Number: 12275
PI Name: KIRILL SOKOLOVSKY
Title: TRACING SHOCK DEVELOPMENT IN A NOVA
Abstract: We propose 3x50ks ToO observations of a new bright ($V<7.5$) nova likely to be detected in gamma-rays. The observations will trace the development of shocks within the nova ejecta, constrain the non-thermal particle acceleration and gamma-ray production mechanisms. We will put an upper limit on the particle acceleration efficiency by comparing thermal X-ray and optical to GeV luminosity and search for predicted non-thermal X-rays. Understanding nova shocks is relevant for other shock-powered transients: interacting supernovae, tidal disruption events, stellar mergers. NuSTAR is the only instrument capable of detecting hard X-rays from novae simultaneously with the GeV emission, making it critical to utilize this capability while Fermi continues operations.

Proposal Number: 12276
PI Name: INDRANI PAL
Title: A STATE-RESOLVED TEST OF RELATIVISTIC LIGHT-BENDING IN MCG-06-30-15 WITH NUSTAR AND XRISM
Abstract: We propose a coordinated NuSTAR+XRISM observation of MCG-06-30-15 designed to directly test the relativistic light-bending scenario through state-resolved hard X-ray spectroscopy. Leveraging NuSTAR's unique sensitivity to the Compton reflection hump and broadband spectral curvature, we will track how the coronal emission pattern evolves across distinct source flux states, while simultaneous XRISM observations will measure the corresponding disk response via Fe-K spectroscopy. Together, these data enable a controlled test of relativistic light-bending. In addition, an IXPE observation has been approved (private communication), providing an independent polarimetric constraint that, combined with simultaneous NuSTAR+XRISM spectroscopy, offers a complementary geometric test of the model.

Proposal Number: 12277
PI Name: MICHAEL KOSS
Title: PROBING BINARY-INDUCED HARD X-RAY EMISSION FROM THE CONFIRMED SMBH BINARY 4C +37.11 WITH NUSTAR
Abstract: We propose the first NuSTAR observation of 4C +37.11, the only confirmed supermassive black hole binary AGN with spatially resolved orbital motion. Numerical simulations predict that accretion in SMBH binaries can generate excess hard X-ray emission above 20 keV through shocks and heated mini-disks fed by circumbinary gas streams. We will test whether the X-ray spectrum follows a standard AGN power law or exhibits a significant hard excess. This observation provides a decisive test of binary accretion physics in a wide-separation SMBH binary and establishes a hard X-ray diagnostic that can be applied to unresolved binary AGN candidates identified by LSST and future time-domain surveys.

Proposal Number: 12279
PI Name: JAMES STEINER
Title: BLACK-HOLE X-RAY BINARY SPIN MEASUREMENT VIA THERMAL CONTINUUM FITTING
Abstract: Stellar-mass black holes (BHs) in X-ray transients undergo months-long outbursts during which they explore wide-ranging accretion rates and spectral-timing states. Following transitioning to the thermal/soft state, the BH undergoes a protracted thermal decline. The thermal/soft state contains modest contribution from nonthermal components; instead, most emission comes from the thermal accretion disk continuum. Accordingly, this state is the gold-standard for spin measurements via X-ray continuum fitting. We request 4x20ks NuSTAR observations during the thermal/soft state of up to 2 bright BH transients, with accompanying 4x5ks Swift data apiece. Sampling in 2-4 week intervals ensures data is in hand from the key thin-disk luminosity window in which continuum-fitting is most reliable.

Proposal Number: 12280
PI Name: VERA BERGER
Title: MILLISECOND MULTIWAVELENGTH VARIABILITY IN A BLACK HOLE TRANSIENT
Abstract: Until now, rapid X-ray/optical timing studies have been limited to the brightest systems and accretion states. proto-Lightspeed, a new CMOS high-speed optical photometer with sub-electron readout noise and frame rates up to 20,000 fps, opens a new parameter space to study black hole X-ray binaries (BH XRBs) at fainter fluxes and shorter timescales than ever before. We propose two 20 ks NuSTAR and XMM ToO observations (40 ks total per facility) with simultaneous proto-Lightspeed timing of BH XRBs. We will measure spectra, power spectra, and X-ray time lags to probe the structure of the corona and its potential connection to the jet on millisecond timescales.

Proposal Number: 12281
PI Name: OLEG KARGALTSEV
Title: EXPLORING THE HIGH-ENERGY PROPERTIES OF THE REMARKABLE LIGHTHOUSE NEBULA
Abstract: We propose a deep follow-up observation of the remarkable Lighthouse nebula - a unique relativistic plasma laboratory. The spectacular Lighthouse nebula offers a rare opportunity to study how the most energetic pulsar wind particles escape into the ambient ISM near the apex of the bowshock of the highly supersonic pulsar. The >7-arcmin-long structure is by far the brightest among its peers and the only one allowing for informative spatially-resolved spectroscopy constraining the injected particles SED, the physics of the particle beam magnetic field interaction, and leptonic cosmic ray propagation in ISM. The existing NuSTAR data enable reliable estimates of the spectral fit quality in the proposed longer observation which will be highly synergistic with the deep CXO and IXPE observations.

Proposal Number: 12284
PI Name: MATTHEW LUNDY
Title: UNCOVERING THE ORIGIN OF LONG-PERIOD RADIO TRANSIENTS THROUGH SIMULTANEOUS BROADBAND X-RAY OBSERVATIONS
Abstract: Long-period radio transients (LPTs) are a new class of radio sources with irregular outbursts, high linear polarizations and > 10^3 [s] periods. The nature of most of the 14 known LPTs is unknown. A serendipitous Chandra X-ray detection of ASKAP J1832-0911 during a radio outburst has led to a new, effective way to investigate the mysterious LPT phenomena through our proposed NuSTAR+XMM+Swift ToOs. Broadband X-ray spectral and timing data will allow us to determine the nature of LPTs speculated between old magnetars, exotic WD binaries or a new type of non-thermal sources. Our X-ray observation program, coordinated with ongoing radio monitoring, will greatly contribute to the frontier time-domain astrophysics driven by new large field of view radio observations.

Proposal Number: 12285
PI Name: AKASH AGARWAL
Title: INVESTIGATION OF COMPTON REFLECTION IN TWO INTRIGUING CATACLYSMIC VARIABLES: TX COL AND V426 OPH
Abstract: We propose the first NuSTAR observation of TX Col and V426 Oph, which show weak Fe 6.4 keV fluorescence lines (EW < 100 eV), a feature associated to reflection. Using NuSTAR s hard X-ray sensitivity (> 10 keV), we will directly measure the Compton reflection hump and the post-shock temperature, while XMM-Newton will constrain soft X-ray emission and absorption. Shock temperature measured with NuSTAR will allow precise white dwarf mass calculation. Amount of Compton reflection will reveal the shock height and viewing geometry, testing whether weak 6.4 keV line arises from tall shocks or other geometric effects in these highly variable systems. In addition, searching for periodicities in hard X-rays (> 10 keV) will provide additional insight into the accretion flow dynamics.

Proposal Number: 12295
PI Name: MICHAEL KOSS
Title: PROBING X-RAY WEAK AGN: NUSTAR OBSERVATIONS OF SUPER-SOFT EROSITA SOURCES WITHOUT HARD X-RAY DETECTIONS
Abstract: High-redshift quasars ($>6) exhibit steep X-ray spectra and X-ray weakness, similar to the X-ray faint AGN recently identified with JWST. We propose the first NuSTAR investigation of the brightest super-soft (0.2-0.5 keV) eROSITA-detected AGN that are undetected in hard X-rays (14-195 keV) by Swift/BAT. These sources may represent rare, low-redshift analogs of high-Eddington ratio quasars at cosmic dawn. Our pilot study targets three of the most extreme eROSITA-selected AGN (Gamma>3) to measure their hard X-ray slopes, search for high-energy cutoffs, and test for reflection signatures. NuSTAR observations will determine whether these AGN exhibit the same X-ray suppression and spectral steepness as high-z quasars, shedding light on the evolution of X-ray coronae across cosmic time.

Proposal Number: 12299
PI Name: EDWARD NATHAN
Title: OBSERVING H1743-322 IN THE HARD STATE OF ITS NEXT MAJOR OUTBURST
Abstract: H1743-322 is a well studied X-ray binary which spent many years undergoing small, `failed' outbursts, until 2018. Its current state is reminiscent of the state the source was in shortly before the major outburst in 2003, which was significantly more luminous and long lived. We propose a detailed, board-band NuSTAR observation, joint with XRISM, to capture a unique view of the source during a potential very bright outburst not seen for 20 years.

Proposal Number: 12305
PI Name: CHIEN-TING CHEN
Title: THE BROAD-BAND X-RAY SPECTRO-POLARIMETRIC MEASUREMENT OF THE POLAR-SCATTERED SEYFERT 1 GALAXY FAIRALL~51
Abstract: We propose 100 ks TOO NuSTAR observation of the polar-scattered Seyfert 1 (S1) galaxy Fairall 51 to be triggered by the confirmed schedule of IXPE observations. For one of the highest optically polarized S1 galaxies ever observed, we aim to conduct broad-band X-ray analysis with pre-approved XMM-Newton TOO to study the spectral property during the IXPE observation, which is crucial for interpreting the connection between X-ray and UV/Optical polarization. This will help us better understand the geometry and processes in polar-scattered S1 objects, which is crucial in enhancing our understanding of AGN.