Proposal Number: 7027
PI Name: SAM KRUCKER
Title: USING DISK-OCCULTATION TO STUDY NON-THERMAL PROCESSES IN SOLAR FLARES WITH NUSTAR AND SOLAR ORBITER/STIX
Abstract: The aim of this proposal is to search for X-ray bremsstrahlung signatures, produced by non-thermal electrons within solar flares, in the solar corona. We propose to use the solar disk as a natural occulter ( coronagraph ) to shield NuSTAR from the intense flare emission lower down and thus reveal the much fainter non-thermal signatures from the corona. To also capture the main flare emissions that are not visible to NuSTAR, we will use Solar Orbiter STIX hard X-ray observations taken from a different vantage point than Earth. The time frame for observing occulted flares is ideal in Cycle 7, as solar activity is rising with moderately bright flares that are most suitable for NuSTAR solar observations.

Proposal Number: 7036
PI Name: SHUO ZHANG
Title: UNVEILING THE NATURE OF A UNIQUE GALACTIC CENTER X-RAY FILAMENT XMM 0.173-0.413 USING NUSTAR AND MEERKAT
Abstract: The most unique and striking phenomenon in the Galactic center region is the existence of numerous radio and X-ray filaments. In 2019, MeerKAT discovered more than 100 radio filaments, which are associated with bi-polar radio bubbles. Only four of the known radio filaments have X-ray counterparts. Three of them have been thoroughly explored in the X-ray band, providing intriguing insights into the nature of Galactic center filaments, e.g. magnetic structures trapping GeV-TeV electrons produced by powerful particle accelerators. However, the most recently discovered one, XMM 0.173-0.413 has never been studied in the hard X-ray band. Therefore, here we propose a 120 ks NuSTAR observation of the unique filament XMM 0.173-0.413, aiming to reveal its origin using NuSTAR, Chandra and MeerKAT.

Proposal Number: 7037
PI Name: MURRAY BRIGHTMAN
Title: NUSTAR AND XMM-NEWTON OBSERVATIONS OF A NEWLY DISCOVERED ULX IN NGC 4045
Abstract: A new ULX in the galaxy NGC 4045 that reaches X-ray luminosities greater than 10^41 erg s^-1 was recently found, making it one of the most powerful ULXs discovered to date. DDT observations with NuSTAR revealed enticing candidate signals of an absorption line at 8.7 keV which could be the signature of an ultrafast outflow, the hallmark of super-Eddington accretion, and a potential pulsation signal, that could confirm the source as an neutron star accretor. However, neither of these were found to be significant in the 50-ks observation. Here we propose follow-up target of opportunity observations with NuSTAR and XMM-Newton in order to confirm these signals.

Proposal Number: 7039
PI Name: JOHN TOMSICK
Title: WHITE DWARF MASSES AND SPIN PERIODS FOR HARD X-RAY-SELECTED GALACTIC SOURCES
Abstract: The hard X-rays from accreting white dwarfs (WDs) in magnetic cataclysmic variables (CVs) are produced by shock-heating in the accretion column, and the measured temperature of the accreting material depends on the mass of the WD. Thus, with high-quality hard X-ray spectra, it is possible to determine the WD mass. An important question is whether the WD mass distribution extends up to the Chandrasekhar limit. The best place to look for high-mass WDs is among CVs with the hardest spectra, making CVs found in the hard X-ray INTEGRAL survey excellent candidates for having the most massive WDs. We propose NuSTAR and XMM observations of two IGR CVs. In addition to measuring the WD masses, the observations will be used to search for periodic signals expected to be seen at the WD rotation period.

Proposal Number: 7049
PI Name: FRANCESCO COTI ZELATI
Title: UNRAVELLING THE EMISSION MECHANISMS OF MAGNETARS: DEEP X-RAY OBSERVATIONS OF SGR 1830-0645 TOWARDS ITS QUIESCENCE
Abstract: Magnetars form a small group of isolated X-ray pulsars powered by the dissipation of their magnetic energy. The physical mechanism powering their activity is currently poorly understood. It is in particular debated whether the long-term evolution of their outbursts is due to the cooling of the stellar crust, and/or the untwisting of complex magnetic field structures in the magnetosphere. We propose joint observations with NuSTAR and XMM-Newton of the latest discovered magnetar in outburst, SGR 1830-0645, to map the thermal structures on its surface, test the model predictions for magnetar outbursts, and gain insights into the physics of magnetars' emission.

Proposal Number: 7050
PI Name: ANDREA MARINUCCI
Title: THE GEOMETRY OF THE HOT CORONA IN MCG-05-23-16 AND IC 4329A
Abstract: Observations the bright Seyfert galaxies MCG-05-23-16 and IC 4329A with NuSTAR and XMM for 80 ks are requested, simultaneously to their IXPE pointings. The two objects have been identified as high priority targets for IXPE in its first year of operations. X-ray polarimetry has the potentiality to provide constraints on their coronal geometry, but the polarimetric signal is partly degenerate with respect to the various geometrical and physical parameters of the accretion disk-corona system. To reduce such degeneracies and infer the geometrical shape of the corona it is vital to have simultaneous and independent constraints on a number of parameters (e.g. coronal temperature and optical depth, inner radius of the disk) which can only be provided by joint NuSTAR and XMM observations.

Proposal Number: 7051
PI Name: VALENTINA BRAITO
Title: AGN FEEDBACK IN ACTION: THE POWERFUL WIND IN IRASF05054+1718
Abstract: We propose simultaneous NuSTAR (80 ks) & XMM-Newton (60ks) observations of IRASF05054+1718, a local (z=0.0175) Seyfert2, which hosts a powerful disk wind and where there is evidence of quenching of starformation. In this source, Swift data detected a powerful and high-velocity (v~0.1c) wind. A short NuSTAR observation confirms the presence of the wind, but with a higher velocity (v~0.2c). Neither of the previous observations have the statistical quality needed to investigate the properties of the wind. Our aim is to confirm the disk wind at a higher statistical significance. The proposed program will allow us to: (a) measure for the first time the profile of the Fe-K absorption feature, (b) derive the energetics of the wind and (c) compare the inner disk wind with the large-scale outflow.

Proposal Number: 7052
PI Name: RALF BALLHAUSEN
Title: SEARCHING FOR NEW CYCLOTRON LINES IN TRANSIENT PULSARS
Abstract: Cyclotron resonant scattering features (CRSFs or cyclotron lines) are the only direct way to measure the B-field close to the surface of an accreting neutron star and probe the physics in the accretion column. Here we propose a 40ks ToO observation of a CRSF candidate source in outburst at a flux of 100mCrab or higher to discover new CRSF sources. The current sample of known CRSF sources underrepresents the huge parameter space of B-fields, luminosities and geometries and therefore any new discovery is valuable to provide insight in the physical conditions necessary to form an observable line. NuSTAR is the most sensitive instrument to date to discover new CRSFs and constrain their energy and profile.

Proposal Number: 7058
PI Name: MAI LIAO
Title: THE PHYSICAL ORIGIN OF THE HARD X-RAY EMISSION IN YOUNG RADIO AGN: JET OR CORONA?
Abstract: NuSTAR observations have detected high energy cutoff (Ec, a key characteristic feature of thermal coronal emission) in a number of regular radio galaxies (non-blazars), implying the corona but not the jet is dominating hard X-ray emission. It is essential to explore whether the hard X-ray emission in young radio AGN with compact jet is similarly dominated by coronal emission, and check if central disc-corona-jet system changes from the infant to the mature stage. We request 100ks exposure of the hard X-ray brightest young AGN Mrk 348. Compared with the archival 21ks exposure which yielded a probable but statistically insignificant Ec detection, our proposed exposure has a good chance to detect an Ec at statistically high confidence level, enabling us to confirm its X-ray emission origin.

Proposal Number: 7075
PI Name: ERIC SCHLEGEL
Title: ECLIPSING INTERMEDIATE POLARS WITH NUSTAR: SHORT & WIDE OR TALL & NARROW ACCRETION FOOTPRINTS?
Abstract: This proposal argues for use of NuSTAR to observe four deeply eclipsing intermediate polar (IP) cataclysmic variables (CV) to define their hard (20-60 keV) spectra. The available data on these systems only provide lower limits to the fitted temperatures of their hard spectral component. This hard component is expected to arise from the accretion shock in these systems. A recent study demonstrated that Compton reflection exists in these IPs implying that the post-shock accretion region is tall and narrow. A previous study argued that the accretion region could be short and wide. The NuSTAR data will be used to investigate the post-shock accretion region: is it short and wide or tall and narrow?

Proposal Number: 7080
PI Name: KAYA MORI
Title: BROAD-BAND X-RAY SURVEY OF A GALACTIC PEVATRON ACCELERATOR ASSOCIATED WITH THE MICROQUASAR SS433
Abstract: The long-awaited HAWC discovery of TeV gamma-ray emission from the eastern and western lobes of W50 nebula, powered by the microquasar SS433, was the first evidence that accreting X-ray binaries can efficiently accelerate particles to TeV-PeV energies, indicating a new class of Galactic PeVatrons. The proposed NuSTAR and XMM observations will complete a broad-band X-ray survey of the particle acceleration and jet termination sites of the W50/SS433 system. Spatially-resolved X-ray spectroscopy will resolve the non-thermal X-ray emission, characterize thermal X-ray knots in the western lobe and constrain the jet acceleration efficiency. Our multi-wavelength approach with the proposed observations will provide deep insights to this unique mini-AGN jet interacting with the W50 nebula.

Proposal Number: 7084
PI Name: ANDREW FABIAN
Title: A DEEP SPECTRAL-TIMING STUDY OF THE X-RAY BRIGHT AGN 1H 1934-063
Abstract: NuSTAR can make a transformational advance in our understanding of how luminous accreting black holes work through long observations of rapidly-variable, X-ray-bright AGN. This enables X-ray reverberation studies, already a commonplace feature of AGN, to proceed to the next level and follow the behavior of the powerful dynamic corona and map the accretion flow immediately next to the black hole, measuring both spin and mass of the black hole. We propose a 500ks NuSTAR observation of the X-ray brightest high variability NLS1 AGN 1H1934-063, with 260ks of XMM, to measure relativistic reflection and reverberation in 3 flux states.

Proposal Number: 7088
PI Name: MICHAEL NOWAK
Title: JOINT NUSTAR/EVENT HORIZON TELESCOPE OBSERVATIONS OF SUPERMASSIVE BLACK HOLE SYSTEMS
Abstract: The Event Horizon Telescope (EHT) is effectively an Earth-sized, interferometric mm-band array with 20 uas spatial resolution that is conducting ground-breaking observations of supermassive black hole systems. The mm emission region sizes resolved by EHT are consistent with those inferred from X-ray and gamma-ray variability studies. We propose NuSTAR (in conjunction with XMM and/or NICER) observations of up to 6 blazars during the Spring 2021 EHT campaign. The chosen systems are those targeted by EHT, in prime mission or calibration, for studying blazar jet launching. Our X-ray observations will provide exceptional quality spectra and timing capabilities in the 0.1 70 keV band. All of the selected targets have shown both long term and short term flaring variability.

Proposal Number: 7094
PI Name: RENEE LUDLAM
Title: UNDERSTANDING ACCRETION IN ULTRA-COMPACT X-RAY BINARIES: THE CASE OF 4U 0614+091
Abstract: Ultra-compact X-ray binaries (UCXBs) are a subclass of low-mass X-ray binaries that contain a degenerate stellar companion in a short orbit (< 80 mins). The accretion disk in these systems differ in chemical composition from typical LMXBs due to a lack of hydrogen and overabundance of higher Z elements. These systems exhibit multiple emission lines in their reflection spectrum from O and Fe. These multiple emission features offer the opportunity to learn more about the properties of the compact object and accretion disks in these systems. We request four 30 ks NuSTAR and joint 10 ks NICER observations of 4U 0614+091 to reveal the entire reflection spectrum in order to examine any changes in the reflection spectrum with intensity and enhance our understanding of accretion in these systems.

Proposal Number: 7098
PI Name: DANIEL STERN
Title: A PROTOTYPICAL HOTDOG AT AN ACCESSIBLE REDSHIFT
Abstract: We propose NuSTAR observations of the recently discovered, highly obscured AGN W1904+4853 at z=0.415, selected by the WISE mission. Its UV-to-IR spectral energy distribution, optical spectrum, luminosity, and Eddington ratio all resemble the properties of the hyperluminous Hot, Dust-Obscured Galaxy (HotDOG) population, which are almost exclusively at high redshift (z~2). However, the low redshift of W1904+4853 makes it accessible to detailed study. While previous X-ray studies of HotDOGs have relied on low SNR detections or stacking analyses, W1904+4853 should be well detected in 75 ks by NuSTAR, even if absorbed by N(H)>1e24/cm2 . The proposed data will enable X-ray spectral analysis of a prototypical example of this important population, likely caught in the AGN fast blow-out phase.

Proposal Number: 7102
PI Name: HONGJUN AN
Title: PROBING STRUCTURE OF INTRABINARY SHOCK USING THE HARD X-RAY ORBITAL LIGHT CURVE OF XSS J12270-4859
Abstract: In pulsar binaries, non-thermal emission that is produced in the intrabinary shock (IBS) dominates observed X-ray flux. In IBS formed by wind-wind interaction, particles emit synchrotron radiation which modulates orbitally due to viewing geometry. Hence, the system geometry, in particular the inclination, can be inferred by comparing X-ray light curves to an IBS model. However, detailed properties of IBS are not yet well known. It is often assumed that IBS is thin but in practice it can have a structure (thick). In the latter case, an IBS light curve may change with energy in the X-ray band. Here, we propose to observe the bright MSP binary XSS J12270-4859 with NuSTAR for 90ks in order to check to see if the source's light curve changes with energy, confirming a thick shock scenario.

Proposal Number: 7103
PI Name: ANN HORNSCHEMEIER
Title: THE BIRTH OF BLACK HOLES AND NEUTRON STARS IN STARBURSTS: A LEGACY FOR NUSTAR BUILDING ON A HST TREASURY PROGRAM
Abstract: Understanding the emission from X-ray binaries in high-redshift galaxies is of utmost importance to understanding the heating of the primordial IGM. This program, to observe five starbursting, High Mass X-ray Binary (HMXB)-dominated galaxies, for a total of 1.49 Ms with NuSTAR and 207 ks with XMM-Newton, will provide a representative sample of starburst galaxies for establishing the connection between the 12-25~keV emission arising from neutron star and black hole populations and their host galaxy properties that is highly relevant to high-z galaxies. We will double the number of HMXB-dominated galaxies with measured 0.5-30~keV Spectral Energy Distributions, so we may correctly interpret high-z galaxies' X-ray emission where we only sample the rest-frame hard X-ray emission.

Proposal Number: 7106
PI Name: RAFFAELLA MARGUTTI
Title: A BROAD-BAND X-RAY VIEW OF THE MOST EXTREME MASS-LOSS WITH NUSTAR+XMM
Abstract: Contrary to expectations from current stellar evolutionary models, recent observations uncovered the ejection of shells of material by massive stars in the years before the supernova (SN) explosion. The physical mechanism behind the impulsive mass ejection synchronized with the stellar core-collapse is unclear. Here we propose a coordinated XMM-NuSTAR effort to map the evolution of the broad-band X-ray spectrum of 1 nearby ($d<50$ Mpc) strongly interacting SN and enable progress. Our program has the immediate goal to characterize the medium around strongly interacting SN, which originate from stellar progenitors with the most extreme mass loss before explosion. This programs has the potential enlarge the very small sample of two strongly interacting SNe with broad-band X-ray detections.

Proposal Number: 7112
PI Name: YUHAN YAO
Title: NUSTAR OBSERVATIONS OF TIDAL DISRUPTION EVENTS
Abstract: A growing number of tidal disruption events (TDEs) are expected to be discovered by the ongoing Spektrum-Roentgen-Gamma (SRG) all-sky X-ray survey. We propose 2x40ks NuSTAR observations on two subgroups of SRG-discovered TDEs with hard X-ray emission. For non-relativistic TDEs with non-thermal X-ray emission, the observation will allow us to search for spectral features characteristic of relativistic reflection. For relativistic TDEs, this will provide the highest resolution hard X-ray spectrum ever obtained, shedding light on the power mechanism of TDE jets.

Proposal Number: 7113
PI Name: JOSEPH NEILSEN
Title: NUSTAR-NICER OBSERVATIONS OF BLACK HOLE TRANSIENTS
Abstract: With its excellent hard X-ray sensitivity, energy resolution, and timing, NuSTAR has revolutionized our view of BH accretion, particularly through studies of Compton scattering and relativistic reflection. But we still have yet to attain a fully self-consistent model of the accretion flow, in part because of the difficulty of constraining seed photons: thermal emission from cool, faint disks. With the launch of NICER in June 2017, we took a great step forward. NICER is to soft X-rays what NuSTAR is to hard X-rays, and together they can produce incredibly tight constraints on the geometry of the inner disk, corona, and their interactions. We propose 5x20 ks coordinated observations of a black hole transient with NuSTAR and NICER (5x10 ks) to exploit their groundbreaking capabilities.

Proposal Number: 7117
PI Name: ANDREAS ZOGLAUER
Title: MONITORING THE HARD X-RAY EVOLUTION OF THE YOUNG SNR G1.9+0.3 AND IMPROVING THE NUSTAR UPPER LIMITS OF ITS 44TI EMISSION
Abstract: With an age of roughly 110 years, G1.9+0.3 is the youngest known supernova remnant in the Milky Way. It is also one of the few remnants in our Galaxy whose evolution we can monitor and which show evidence for emission from the 44-Ti decay chain. We propose to observe G1.9+0.3 for 600 ks. This will allow us to identify changes of spectrum, flux, and morphology between the original NuSTAR observation from 2013 and now in the hard X-ray band. In addition, this observation will significantly improve the upper limits of the 44-Ti emission, and deeply probe the uncertainty range of a potential detection of 44-Ti by Chandra, and, in the case emission is confirmed, enable its characterization. With its unique hard X-ray capabilities, only NuSTAR can carry out these observations.

Proposal Number: 7134
PI Name: ALESSIA TORTOSA
Title: BROAD-BAND X-RAY STUDY OF A PECULIAR HYPER-EDDINGTON AGN: IRAS04416+1215
Abstract: We propose here a broadband X-ray study of a peculiar hyper-Eddington Active Galactic Nucleus, namely IRAS 04416+1215, by observing it simultaneously with NuSTAR (170ks) and XMM-Newton (40ks). IRAS 04416+1215 has one of the highest Eddington-ratio in the local Universe (λEdd=427), it represents a prototype for the elusive class of hyper-Eddington AGN. The aim of these simultaneous observations is to understand the behaviour of the primary power-law and the reprocessed radiation in the regime of extreme accretion, as well as the properties of soft-excess and the outflows. To this end, the combined large effective area of XMM-Newton and high sensitivity of NuSTAR at high energy are fundamental to constrain the spectral parameter of the proposed target.

Proposal Number: 7145
PI Name: ARASH BAHRAMIAN
Title: NATURE OF SUPER-ORBITAL MODULATION IN THE ONLY GALACTIC GLOBULAR CLUSTER ULTRA-COMPACT BH-XRB
Abstract: 47Tuc X9 is a candidate black hole XRB with a 28 min orbital period. This system is the faintest XRB to show a clear reflection hump, in addition to an unexplained ~week-long super-orbital modulation, during which the X-ray flux varies by a factor of 10. We ask for a 300 ks continuous observation to characterize spectral evolution linking the reflection hump and the super-orbital modulation. Detection of spectral variability in the reflection hump will indicate an accretion-induced origin for the modulation (e.g., repeating faint outbursts), while its absence would indicate a geometric origin (e.g., a preccessing warped accretion disk). Proving either of these scenarios have important implication on our understanding of nature and evolution of accreting black hole in globular clusters.

Proposal Number: 7148
PI Name: MATTEO BACHETTI
Title: TRACKING THE ORBITAL ADVANCE OF THE FIRST ULTRALUMINOUS PULSAR M82 X-2
Abstract: Ultraluminous x-ray sources (ULXs) are X-ray binaries radiating above the Eddington luminosity. An increasing sample of ULXs are known to be powered by accreting pulsars (PULXs), and it is currently unclear if their observed emission is amplified by strong radiation beaming or it denotes a genuine super-Eddington mass accretion rate. In the second case, the large mass transfer required is expected to produce detectable effects on the binary orbit, which were tentatively detected in past observations. In this program, we use pulsar timing to track the orbital evolution of the first discovered PULX, M82 X-2, producing a strong constraint on the mass transfer and finally discriminate between the beaming and the extreme super-Eddington models.

Proposal Number: 7153
PI Name: GEORGE PRIVON
Title: GAZING INTO THE INFERNO: EMBEDDED AGN IN LOCAL ULIRGS
Abstract: Ultraluminous infrared galaxies (ULIRGs; LIR > 10^12 Lsun) are the most intrinsically luminous galaxies in the low-redshift Universe, yet the power source of ULIRGs (AGN vs starburst) is still debated. We propose NuSTAR observations of the final 3 local ULIRGs in GOALS to, 1) establish the first complete, unbiased sample with which to assess (at E>10 keV) the role of BH accretion in powering these luminous systems, and 2) resolve significant disagreements in the AGN luminosities and obscuring columns for the individual systems. These observations will be used to perform detailed studies of individual systems, linking the AGN properties to ancillary data on, e.g. outflows, and determine the global importance of AGN activity at the highest galaxy luminosities.

Proposal Number: 7154
PI Name: GABRIELE PONTI
Title: THE MOTION OF SGR A*'S NIR SOURCE DURING X-RAY FLARES
Abstract: We propose a long (100 ks) continuous NuSTAR exposure in Summer 2021 to cover 3 con nights of VLTI-Gravity+Chandra observations of Sgr A*. The required exposure time of Gravity and Chandra has been already secured. The Gravity team has recently measured the astrometric motion of the near infrared (NIR) source during three bright NIR flux excursions of Sgr A*. Simultaneous NuSTAR+Gravity observations will allow us to understand the evolution of the radiative mechanism and to test whether, during bright X-ray flares, the NIR source will display similar circular orbital motions or whether it will be characterised by a dramatically different pattern, such as by linear motions, reminiscent of jet like ejections. This will provide us with a groundbreaking test of accretion physics.

Proposal Number: 7156
PI Name: XIAOYANG CHEN
Title: X-RAY VIEW OF A Z ~ 0.5 HYLIRG: SHARING EXTREME OUTFLOW AND STARBURST IN ONE PLACE
Abstract: ULIRGs/HyLIRGs are thought to represent the rapidly growing phase of massive galaxies before quenching of star formation by AGN-driven outflows. A HyLIRG, J1126 at z ~ 0.5, was found with the fastest ionized outflow among ULIRGs/AGNs at z < 1. However, the star formation in J1126 is vigorous with SFR over 1000 Msun/yr. In order to reveal the physical mechanism behind the puzzling co-existence of the extreme outflow and SFR, we try to constrain the dust covering factor (CF) using the intrinsic AGN X-ray luminosity with NuSTAR observation. A large CF could imply that the powerful wind is limited by a small opening angle and has not affected the main part of the nuclear starburst; while a CF similar to typical AGNs could suggest AGN wind is not effective in the quenching of star formation.

Proposal Number: 7160
PI Name: NAOMI TSUJI
Title: UNVEILING THE INJECTION PROBLEM OF DSA BY REVISITING HARD X-RAY COMPONENT IN SNR RXJ 1713.7-3946
Abstract: Previous observations with NuSTAR revealed near the outer edge of SNR RX J1713.7-3946 the presence of a region with an extremely hard spectrum. The measured photon index of 1 is incompatible with synchrotron radiation from accelerated electrons, implying the bremsstrahlung emission of sub-MeV electrons. We propose a follow-up observation of this hard component to precisely determine its extension and spectrum above 20 keV. This information would lead us to determine the nature (nonthermal or thermal) of the parent particles, presumably, shedding light on the injection process, one of the critical problems in diffusive shock acceleration theory.

Proposal Number: 7162
PI Name: ALAN MARSCHER
Title: MULTI-ENERGY X-RAY OBSERVATIONS OF IXPE BLAZAR TARGETS
Abstract: The investigators propose to observe up to 6 X-ray bright blazars plus the radio galaxy Cen A with NuSTAR during X-ray linear polarization measurements by the Imaging X-ray Polarimetry Explorer (IXPE). The 0.3-70 keV continuum spectrum derived from synchronous NuSTAR and Swift observations will allow modeling needed to interpret the IXPE polarization data. Comparison of millimeter-wave, optical, and X-ray polarization, and measurement of the mm/optical/UV/X-ray continuum spectra of the blazars and Cen A with NuSTAR, Swift, and ground-based telescopes, will provide data needed to determine the mechanism and location of the X-ray emission, which have yet to be determined conclusively. It will also test models for particle acceleration that produces high-energy emission in relativistic jets.

Proposal Number: 7163
PI Name: FELIX FUERST
Title: CONTINUED SPIN-TRACKING OF THE NEUTRON STAR ULX NGC7793 P13 WITH NUSTAR
Abstract: NGC 7793 P13 is an ideal target to study super-Eddington accretion in ultra-luminous X-ray pulsars (ULXPs), as it is an almost persistent source, with a relatively high flux and strong pulsations. Additionally, it is one of only two ULXPs for which the mass donor is known and the only one with a fully determined ephemeris. In 2020 P13 entered an off-state, from which it is currently re-emerging. This gives us the unique opportunity to study the accretion flow as the accretion geometry is changing, and will allow us to infer more physical parameter of the system, like the magnetic field. We therefore propose to observe P13 twice with NuSTAR during cycle-7, continuing the successful monitoring observations in the past.

Proposal Number: 7164
PI Name: FELICIA KRAUSS
Title: BLAZAR X-RAYS AND NEUTRINOS: INVESTIGATING THE MOST PROMISING ICECUBE NEUTRINO ALERTS
Abstract: We propose to perform two 40 ksec target of opportunity follow-up observations of X-ray luminous sources that we identify in association with two separate ``gold''-quality IceCube high-energy neutrino alerts, which have a likelihood of at least 70% to be astrophysical in origin. The first identification of an astrophysical source of high-energy neutrinos occurred in 2018, following IceCube-170922A and the BL~Lac-type blazar TXS 0506+056. X-ray follow-up of likely-cosmic neutrino alerts has thus proven its utility for identifying possible neutrino counterparts, and most importantly to measure the hadronic contribution to the high-energy emission. We aim to use this approach to identify more such sources and calculate their neutrino flux.

Proposal Number: 7165
PI Name: LUIGI GALLO
Title: MRK 1239: THE NATURE OF THE DISTANT X-RAY EMISSION IN A SEYFERT 1
Abstract: In the highly polarised NLS1 Mrk1239, the primary X-ray emission from the inner black hole region appears to be completely absorbed revealing the underlying host galaxy emission. This low energy emission-line spectrum was fitted with a combination of a collisionally ionised plasma and cold, optically thick reflected emission from the distant torus. With the highest sensitivity NuSTAR spectra, we will peer through the absorbing column to accurately determine the continuum model, the level of absorption, and the distant torus parameters. Constraining the torus parameters will allow us to utilize simultaneous XMM RGS data to determine the origin of the photoionised emission at low energies.

Proposal Number: 7170
PI Name: DANIEL STERN
Title: COMPTON-THICK AGN CANDIDATES FROM SPECTRUM-ROENTGEN GAMMA
Abstract: We propose NuSTAR observations of three AGN detected by ART-XC which are faint/undetected by eROSITA, implying heavy obscuration. Data from SRG only sets limits on their obscuring column density, thereby setting lower limits on their intrinsic flux and luminosity. The proposed observations will allow for detailed X-ray spectral analysis and characterization of these sources, and demonstrate the combined power of SRG+NuSTAR to measure the full distribution of AGN obscuring columns into the Compton-thick regime. This is a key ingredient for AGN population synthesis models and for understanding both the growth of supermassive black holes and their role in galaxy evolution.

Proposal Number: 7171
PI Name: FRANCESCO SALVESTRINI
Title: UNVEILING THE INTRINSIC X-RAY PROPERTIES OF THE 12 MICRON SY2 SAMPLE: TOWARDS A COMPLETE X-RAY COVERAGE
Abstract: The proposed observation of six obscured AGN are necessary to obtain a complete and uniform coverage of the X-ray emission for the sample of Seyfert-2 galaxies from the 12micron galaxy sample (12MGS). Coupled with the broad-band X-ray observations available for the remaining 12MGS AGN, the proposed observations will allow us to investigate the column density distribution at low redshift for a complete and unbiased AGN sample (because of its mid-IR selection) and to connect the accretion properties to those of the hosts by exploiting the unique multi-band characterization and coverage of the proposed sample.

Proposal Number: 7176
PI Name: CHONG GE
Title: EXPLORING THE ACCELERATION LIMIT OF THE PECULIAR SUPERNOVA REMNANT G106.3+2.7 WITH NUSTAR
Abstract: Supernova remnant (SNR) G106.3+2.7 is a PeVatron candidate with detected gammy-ray up to 100 TeV. It's in a unique environment beneficial to particle acceleration. This peculiar SNR is the first one detected with extended synchrotron-originated X-ray emission. The multiwavelength data indicates efficient particle acceleration in the SNR. We propose NuSTAR observations to probe the acceleration limit of this peculiar SNR, which will further help us to constrain the maximum proton energy and the velocity of blast wave in SNR. The knowledge of aforementioned information is crucially important for us to understand the acceleration mechanism and to solve the century puzzle of the origin of Galactic cosmic-rays.

Proposal Number: 7179
PI Name: MIRKO KRUMPE
Title: RARE AND DRAMATIC FLUX DROPS IN EROSITA-DETECTED AGN: CHANGES IN ACCRETION FLOW OR LINE-OF-SIGHT OBSCURATION?
Abstract: eROSITA is currently performing multiple all-sky X-ray surveys. Monitoring roughly 500 very bright AGN/quasars, eROSITA can identify rare, accretion shut-down events in these objects as they occur. NuSTAR observations are needed to distinguish shut-down from heavy occultation events. In case of a shut-down event, we will explore how the X-ray corona responds to a sudden, major drop in accretion rate. In the case of the line of sight occultation event, we will constrain cloud properties. The NuSTAR data are critical for the subsequent multi-wavelength follow-up strategy of already approved programs. Thus, we propose two ToOs of 100 ks each.

Proposal Number: 7183
PI Name: EKATERINA SOKOLOVA-LAPA
Title: ENERGY REDISTRIBUTION IN NEUTRON STAR ATMOSPHERES: CONSTRAINING THE HIGH-ENERGY EMISSION IN GX 304-1 IN DEEP QUIESCENCE
Abstract: A recent NuSTAR observation of GX 304−1 in quiescence (~1e34 erg/s) has shown evidence of a dramatic spectral transition, interpreted as a change of the emission region from an accretion column to the spot of an overheated atmosphere of a polar cap. However, the existing observation does not allow to study the high-energy region around the known cyclotron line due to its intermediate exposure and significant background contamination at high energies (above ∼40 keV). The high-energy emission is of particular importance for testing the existing low luminosity models and determining the surface magnetic field from the measured cyclotron line energy. We therefore propose an in-depth, 180 ks observation to firmly constrain the high-energy emission.

Proposal Number: 7192
PI Name: STEFANO MARCHESI
Title: A JOINT NUSTAR AND XMM-NEWTON MONITORING OF A CANDIDATE CHANGING-LOOK COMPTON THICK AGN
Abstract: Studies of heavily obscured active galactic nuclei (AGN) suggest that the torus that causes the obscuration is patchy, rather than uniform. The line-of-sight column density (NH_los) of the obscuring material should vary over weeks to months, but such an evidence has been observed only in a few X-ray detected AGN, due to lack of large samples of heavily obscured AGN with multi-epoch observations. We propose for a joint NuSTAR-XMM monitoring of NGC 1358, a nearby Compton thick (CT-) AGN with small torus covering factor and NH_los significantly larger than the torus average NH. Through this monitoring, we expect to measure significant variability in NH_los and detect a transition from CT- to Compton thin, thus improving our knowledge on the properties of the obscuring material surrounding AGN

Proposal Number: 7197
PI Name: MIHOKO YUKITA
Title: X-RAY BINARIES IN THE LOW-METALLICITY GALAXY NGC 4631
Abstract: We propose a joint NuSTAR and XMM observation of NGC4631 (d=7Mpc), a nearby metal-poor galaxy (Z/Z_sun ~ 0.2) with multiple luminous HMXBs. We will (1) examine the nature and accretion states of the HMXBs via color diagnostics, (2) measure the galaxy-integrated 0.3-30 keV spectrum to calibrate the bolometric correction for low metallicity galaxies, and (3) investigate the contribution of each bright source to this spectrum. As an ancillary science goal, we will search for the signature of inverse Compton emission from electrons accelerated in the magnetic field of the galaxy.

Proposal Number: 7200
PI Name: CHARLES KILPATRICK
Title: A SEARCH FOR THE FIRST X-RAY COUNTERPART TO AN EXTRAGALACTIC FRB
Abstract: Fast radio bursts (FRBs) are millisecond pulses discovered at radio wavelengths. The number of FRB detections has increased rapidly in the last year, culminating in the detection of bursts from a Galactic magnetar and the extragalactic source FRB180916, but the mechanism powering FRBs is still unknown. As the Galactic magnetar was detected at radio and hard X-ray wavelengths and theoretical models that associate these bursts with relatively long-lived (seconds to minutes) non-thermal radiation, X-ray follow up is the most promising avenue to explore the spectral energy distribution of FRB emission. We propose a 20 ks NuSTAR/XMM-Newton observation coordinated with CHIME of the periodic FRB180916 during one of its 'active' phases when one or more high fluence radio bursts are expected.

Proposal Number: 7205
PI Name: ELISA PRANDINI
Title: WHAT'S IN THE JET OF 1ES 1959+650? SOLVING THE MYSTERY WITH SIMULTANEOUS NUSTAR AND VHE OBSERVATIONS
Abstract: We propose to observe the blazar 1ES1959+650 for 21.5 ks with NuSTAR in the context of a multi-wavelength campaign involving Swift, XMM-Newton, Fermi, MAGIC and other radio and optical facilities. This unprecedented data sample will be used to study the simultaneous broad-band spectral energy distribution (SED) of the source, including for the first time both TeV energies and hard X-rays, which covers the two SED peaks. NuSTAR data are essential for constraining the synchrotron peak shape and position, and for studying the correlation with soft X-ray and TeV energies. The deep exposure will furthermore allow to study the temporal evolution. With the simultaneous observations will allow us to constrain the electron distribution in the jet and test emission models.

Proposal Number: 7206
PI Name: MICHAEL KOSS
Title: RESOLVING THE AGN BOLOMETRIC EMISSION
Abstract: Nearby powerful AGN provide the best way to understand the growth of supermassive black holes and their effect on galaxies. The Swift-BAT 105-month survey, with its all-sky coverage, provides the largest, most complete sample of local (z<0.1) powerful AGN. We propose 13 joint XMM/NuSTAR observations to complement an approved HST program that is observing 137 type 1 BAT AGN in the near ultraviolet (<3000 A) to accurately calibrate AGN bolometric luminosity. These results for the first time with 100 pc resolution of HST to measure the AGN emission are critical to determining the intrinsic scatter of the UV/X-ray relation for cosmological parameters and X-ray bolometric corrections, precisely measuring the Eddington ratio distribution of AGN and linking it to feedback and SFR.

Proposal Number: 7211
PI Name: GAYATHRI RAMAN
Title: BROADBAND SPECTRAL STUDIES OF THE X-RAY PULSAR - MXB 0656-072 DURING QUIESCENCE
Abstract: We propose 50 ks of Nustar observing time for the Be X-ray pulsar, MXB 0656-072 in order to characterize its spectrum and pulsation properties during quiescence. Quiescent observations of X-ray pulsars will provide insights into the process of accretion onto magnetized neutron stars at low mass accretion rates. Nustar, with its broadband capabilities and large photon collecting area will be ideally suited to uncover the hard X-ray quiescent properties of this pulsar.

Proposal Number: 7217
PI Name: FRANCESCO URSINI
Title: RAISING THE LUMINOSITY BAR: BROAD-BAND X-RAY VIEW OF THE MOST LUMINOUS UNOBSCURED QUASAR AT Z<0.1
Abstract: The high-energy emission of AGNs is mostly studied in nearby Seyferts. Bright QSOs, on the other hand, offer the opportunity to study accretion processes and AGN-driven winds in the less explored high luminosity regime. We propose a joint NuSTAR (200 ks) and XMM (100 ks) observation of HE 1029-1401, the most X-ray luminous AGN among local (z<0.1) unobscured, radio-quiet QSOs, and a very intriguing source showing a significant soft excess and a broad iron line. The unique joint capabilities of NuSTAR and XMM will allow us to constrain the properties of the X-ray corona, to assess the contribution of relativistic reflection, and to determine the nature of the soft excess. We will also be able to robustly search for X-ray winds, such as warm absorbers and more powerful ultra-fast outflows.

Proposal Number: 7218
PI Name: TAIKI KAWAMURO
Title: A HARD X-RAY SPECTRUM OF AN ACTIVE HEAVY-SEED MASS BH OF POX 52
Abstract: While future soft X-ray (0.5--2 keV) surveys are being designed to discover high-redshift (z > 9) heavy-seed mass black holes (hsBHs) with M_BH ~ 10^5 M_SUN, a rest-frame hard X-ray spectral model is crucial to understand how many hsBHs can be detected. Motivated by this, we propose a simultaneous 70-ksec NuSTAR and 20-ksec XMM-Newton observation to a local AGN in POX 52 with M_BH ~ 3x10^5 M_SUN and L_2-10 ~ 10^42 erg s^-1, resembling the future targets. While there are two expected X-ray models: (1) a power-law with low-energy cutoff like ultra-luminous X-ray sources and (2) one with high-energy cutoff and reflected emission like Seyfert galaxies, the superior sensitivity of NuSTAR above 10 keV will distinguish them and provide a reliable hard X-ray spectral template.

Proposal Number: 7219
PI Name: ROSS SILVER
Title: HUNTING FOR COMPTON-THICK AGN IN THE LOCAL UNIVERSE
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 previously successful selection criteria, we propose to target 2 low-redshift candidate CT-AGN from the Swift-BAT 150-month catalog with joint 50 ks NuSTAR and 30 ks XMM-Newton observations 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: 7221
PI Name: JEAN SOMALWAR
Title: TIDAL DISRUPTION EVENTS IN ACTIVE GALACTIC NUCLEI
Abstract: Tidal disruption events in AGN can drive bright, slowly evolving optical flares. The few known TDE candidates in AGN lack extensive multi-wavelength follow up. In particular, both hard and soft X-ray observations are key to understanding how a TDE impacts the AGN disk and its X-ray corona. For example, a TDE is predicted to drive super-Eddington inflows which can destroy the AGN corona and result in a dramatic reduction in soft emission. Also, the collision of diffuse stellar debris with the AGN disk can produce hard X-ray flares. We propose a pilot program of joint NuSTAR+Swift observations of the most promising optically selected TDE-AGN candidate found in our vigorous program to discover such events in optical time-domain surveys, to probe physical conditions in their innermost regions.

Proposal Number: 7228
PI Name: CLAUDIO RICCI
Title: UNDERSTANDING THE CONNECTION BETWEEN THE X-RAY CORONA AND THE NUCLEAR RADIO EMISSION IN AGN
Abstract: In order to understand the origin of the X-ray corona, and its connection to the radio emission in radio-quiet AGN, we propose here the joint study of the mm/X-ray variability of a radio-quiet AGN, using NuSTAR, XMM-Newton and ALMA to monitor the brightest unobscured AGN in the southern sky, IC4329A, observing it five times, once every two days over ten consecutive days. This is part of a large campaign that includes ALMA (10 obs., highest resolution), XMM-Newton (10), Swift (10) and NICER (20) observations, all of which have already been approved. The NuSTAR observations proposed here will be fundamental to infer the physical properties of the Comptonizing plasma (temperature and optical depth), and to study how they change with the submm emission produced by the electrons in the corona.

Proposal Number: 7230
PI Name: HENRIC KRAWCZYNSKI
Title: SMOKING GUN TESTS OF BLACK HOLE ACCRETION MODELS BASED ON NUSTAR, NICER, IXPE, AND XL-CALIBUR OBSERVATIONS OF CYG X-1
Abstract: We propose a joint observation campaign of the stellar mass black hole Cyg X-1 with the NuSTAR and NICER missions. The new feature of the proposed campaign are simultaneous linear X-ray polarization observations with NASA's Imaging X-ray Polarimetry Explorer (IXPE) and the balloon-borne XL-Calibur missions. The latter two missions deliver 2-8 keV (IXPE) and 15-75 keV (XL-Calibur) X-ray polarimetric coverage with unprecedented sensitivities for percent and sub-percent level polarization fractions. The proposed observations will give a legacy data set that can be used to put models to powerful tests based on the new polarization information. Immediate results are new and independent constraints on the inclination of the inner accretion disk and on the properties of the corona.

Proposal Number: 7234
PI Name: MCKINLEY BRUMBACK
Title: INVESTIGATING PULSATION TRANSIENCE IN SMC X-1 DURING SUPERORBITAL PERIOD EXCURSION
Abstract: The accreting pulsar SMC X-1 exhibits a superorbital cycle likely caused by a warped precessing accretion disk, which drives behaviors like pulsation transience and varying spectral obscuration levels. The superorbital cycle is typically ~55 days but has excursions, driven by instability in the disk geometry, where the period increases to 44 days. To date, there exists no broad-band spectral and timing coverage of superorbital excursion. This proposal asks for simultaneous NuSTAR and XMM observations to sample the upcoming 2022 excursion. The next excursion is not expected until 2030, meaning that we have a unique opportunity to use tomography to probe the fluctuating disk geometry and investigate the effect of excursion on obscuration levels, pulse shape, and pulsation transience.

Proposal Number: 7237
PI Name: JOSEPH NEILSEN
Title: X-RAY JETS & BH SHADOWS: NUSTAR, EHT, CHANDRA, AND SWIFT 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. In light of the great success of the 2017 campaign, we are eagerly planning for observations in 2022. To this end, we request 100 ks of NuSTAR time and 10x1 ks with Swift on M87 to be coordinated with Chandra. In addition to the potential tests of GR, coordinated X-ray/EHT observations offer an incredible opportunity: a chance to observe structures near the event horizon while tracking their high-energy variability. In synergy with Chandra, NuSTAR/Swift spectra of M87 (and multiwavelength SEDs) will place tight constraints on the energetics and acceleration of particles near the event horizon of this supermassive black hole.

Proposal Number: 7239
PI Name: TSUBASA TAMBA
Title: THREE-DIMENSIONAL VIEW OF THE MAGNETIZED ACCRETION FLOW ONTO CENTAURUS X-3
Abstract: We propose a 180 ks NuSTAR observation of the high mass X-ray binary Cen X-3. The duration covers two orbital periods of the system. Through the orbital- and pulse-phase resolved spectroscopy, it is possible to track variations of spectral parameters such as the photon index, CRSF line energy, and cut-off energy. Combined with Monte Carlo simulation, these spectral parameters can be connected with certain physical interpretations by simulating complex physical processes taking place in the accretion column, such as thermal bremsstrahlung, Comptonization, and magnetic field effects. The observation data with two successive orbits will also reveal long-term stability of surrounding photo-ionized plasma in the wind of the companion by examining spectral variations of the successive orbits.

Proposal Number: 7240
PI Name: MICHAEL KOSS
Title: USING VARIABILITY TO STUDY THE SIZE OF THE ABSORBER IN COMPTON-THICK AGN
Abstract: For more than 30 years, it has been assumed that a pc-scale torus produces a constant Compton reflection component in heavily obscured AGN. The 157-month Swift BAT processing has recently been finished and nearly all (87%, 14/16) of the brightest Compton-thick AGN are variable in the 20-50 keV band. We propose a variability study of 4 CT AGN with large NH variability detected in multi-epoch spectra showing changes from reflection to transmission dominated or Compton-thick to thin or vice versa, to place constraints on the size of the variable absorber. These observations will test the size and patchiness in the absorbing material that is the chief component of the AGN unified model.

Proposal Number: 7241
PI Name: SULOV CHALISE
Title: PROBING THE TORUS OF POLAR SCATTERED SEYFERT 1 GALAXY, MRK 1218, WITH NUSTAR
Abstract: Until recently, AGN unification models could not explain the presence of intermediate Seyfert galaxies. Recent developments have hinted towards the presence of a clumpy torus instead of the traditional "donut" torus as a solution. A good understanding of this torus is still lacking, especially on non-Seyfert 2 galaxies. We propose to study the torus structure of a Seyfert 1.9 galaxy, Mrk 1218, using the archival soft X_ray data and 75 ks of new NuSTAR observations each. This source, which is also a polar-scattered Seyfert 1 galaxies (PSS), is the only one out of the known 12 PSS sources to not have any archival or planned hard X-ray spectra. Thus, this observations would also complete the data and will allow us to study the torus of the whole PSS sample.

Proposal Number: 7242
PI Name: DOMINIC WALTON
Title: EXTREME REFLECTION IN THE RADIO QUIET QUASAR RBS 1124
Abstract: Previous X-ray observations of the RQ quasar RBS1124 show evidence for some of the strongest reflection from the accretion disc observed among local, Compton-thin AGN. The unusually high reflection fraction indicates an extreme accretion geometry in which the intrinsic continuum emission experiences strong gravitational light bending, resulting in an X-ray spectrum dominated by reflection. We request a coordinated broadband X-ray observation of this remarkable source with NuSTAR (150ks) and XMM (135ks). The quality of the data will enable us to robustly confirm the strong reflection, and utilize the full potential of the latest models to measure the black hole spin and constrain the coronal geometry, self-consistently accounting for both the strength and profile of the reflection.

Proposal Number: 7248
PI Name: AARRAN SHAW
Title: USING NUSTAR TO DEVELOP A NEW METHOD OF MEASURING WHITE DWARF MASSES
Abstract: One of the most fundamental parameters of any class of astronomical objects is mass. For binary systems, mass can be measured directly through measuring the radial velocities of the binary components, but this is heavily reliant on knowledge of binary inclination, which is often poorly constrained. This has resulted in the development of other, independent, methodologies of mass measurement such as the one shown in the recent NuSTAR Legacy survey of white dwarf masses in magnetic CVs. This proposal aims to answer the question whether X-rays are able to also probe the masses of non-magnetic CVs. This proposal requests a total of 125ks of NuSTAR observations of three CVs with well-constrained masses in order to study the relation between the X-ray continuum temperature and mass.

Proposal Number: 7250
PI Name: XIURUI ZHAO
Title: UNVEILING WITH NUSTAR THE MOST POWERFUL, HEAVILY OBSCURED QUASAR EVER DISCOVERED IN X-RAYS
Abstract: Active galactic nuclei (AGN), which represent the growing phase of supermassive black holes (SMBHs), allow us to study the accretion history of the SMBH. Population synthesis models predict that, at the peak of the global SMBH growth (z~1.5--3), nearly 50\% of all AGN should be Compton thick (CT). Discovery of CT-AGN at high-redshift is still a challenging task. Here, we propose to observe jointly with NuSTAR and XMM-Newton a bright CT-AGN candidate at redshift z=2.99, selected from the XMM serendipitous source catalog. The unabsorbed rest-frame 2-10 keV luminosity of the source is found to be Lx~5e46 erg/s, which potentially makes it the largest intrinsic luminosity quasar ever observed in X-rays, and currently the only CT-AGN candidate that is observable by NuSTAR at z>~3.

Proposal Number: 7259
PI Name: MISSAGH MEHDIPOUR
Title: TRACKING TRANSIENT OBSCURING OUTFLOWS IN AGN
Abstract: Obscuring outflows are remarkably different from the common warm-absorber outflows in AGN. They exhibit large columns of high-velocity gas close to the black hole. They shield much of the X-ray radiation, which can have important implications for the surrounding gas and the launching of outflows. Joint ToO observations with NuSTAR and XMM, triggered using Swift monitoring, have been instrumental for the new results on obscuration events to come into light. We propose to investigate a new event to help us address current questions regarding the obscuring outflows and broaden our understanding of these transient events in AGN. We request a ToO NuSTAR observation (50 ks) to be taken jointly with a XMM-Newton observation (50 ks), using weekly Swift monitoring of an AGN sample (93 ks in total).

Proposal Number: 7261
PI Name: GABRIELE MATZEU
Title: A NEW EXTREME COMPTON-THICK AGN CANDIDATE NGC 591
Abstract: A $150$\,ks \textit{NuSTAR} observation of the extreme candidate Compton-thick AGN \ngc ($z=0.0152$) is proposed. A previous \xmm snapshot of $12\,\rm ks$ revealed the presence of a very strong \feka emission line $EW=3.6_{-1.4}^{+1.1}\,\rm keV$. This suggests that this object is characterized by heavy obscuration and hence could be identified as an extreme Compton-thick AGN. With a \nustar observation we will obtain crucial information on its hard X-ray spectral properties and derive a robust constraint on the intrinsic column density ($\nh$). These measurements, will allow us to characterize in great details the properties of the strong \feka line and the physical properties of the torus with the ultimate goal of deriving a more physical picture of the innermost regions of highly obscure

Proposal Number: 7263
PI Name: ERIN KARA
Title: ACCRETION AND EJECTION IN NGC 1365 WITH NUSTAR AND CHANDRA/HETG
Abstract: NGC 1365 is a Seyfert 1.8 galaxy, known for transitioning quickly between AGN types, likely due to variable broad line region obscuration. In its Compton-thin state (which occurs ~72% of the time), NGC 1365 routinely shows the most robust evidence for an ionised outflow, through the detection of 4 separate iron absorption lines, associated with Fe XXV and Fe XXVI Kalpha and Kbeta. These lines are not resolved, and have never been detected with a high-resolution spectrograph, but near the beginning of NuSTAR Cycle 7, Chandra will observe NGC 1365 with high-energy transmission gratings for 300 ks, providing an unprecedented view of a low-velocity ionised wind. We request accompanying NuSTAR observations to constrain the continuum with hard X-rays, and to simultaneously probe the

Proposal Number: 7264
PI Name: IGOR ANDREONI
Title: WHERE IS THE "MISSING ENERGY" FROM THE CENTRAL ENGINE OF SUPERLUMINOUS SUPERNOVAE?
Abstract: Superluminous supernovae (SLSN) are a rare class of stellar explosions. Hydrogen-deficient SLSNe are believed to be powered by a central engine, a highly-magnetized neutron star, which pumps heat into the ejecta and generates bright optical emission. Several years after the explosion, the optical emission has faded, but the magnetar wind is still powerful. The majority of the radiation from the central engine is expected to leak out of the ejecta, making the source X-ray bright - the "smoking gun" signature of the magnetar wind. However, previous observations in the soft X-ray band (<10keV) could not detect such emission, giving rise to a "missing energy problem". We propose to use NuSTAR to search for the first evidence of magnetar central engine in the hard X-rays (>8keV).

Proposal Number: 7266
PI Name: BENJAMIN COUGHENOUR
Title: SPIN AND REFLECTION IN A BLACK HOLE TRANSIENT
Abstract: We propose a 50 ks NuSTAR TOO observation of a transient black hole (BH) source during outburst. Using Swift/XRT to determine the source state, we will trigger the NuSTAR observation when the source transitions from the hard state to its intermediate state. Modeling of reflection features in the source spectrum will be used to measure the BH spin, as well as constrain the environment of the innermost accretion disk. We will only target sources that have not yet been observed by NuSTAR during outburst, whether that means an entirely new BH candidate or a previously known BH source that has been in quiescence since the launch of NuSTAR. Examples of such sources include GRO J1655-40 and 4U 1543-475, allowing us to test different methods for measuring the black hole spin.

Proposal Number: 7271
PI Name: KA-WAH WONG
Title: NATURE OF HARD X-RAYS FROM GAMMA-RAY EMITTING LLAGNS
Abstract: Most of the AGNs in the local universe are low luminosity AGNs (LLAGNs). They are generally associated with radiatively inefficient accretion flows (RIAFs). We propose to study two of the few LLAGNs with detected gamma-ray emission, NGC 315 and NGC 4261. Multiwavelength studies suggest that the X-rays come from jets. However, it is also possible that the RIAF can contribute significantly to the X-rays. Unfortunately, hard X-ray spectrum above 10 keV is missing, making it hard to characterize the X-ray emission model. With the excellent sensitivity of NuSTAR, we will study the nature of the hard X-rays from these rare gamma-ray LLAGNs and will distinguish whether the hard X-rays come from jets or accretion flows.

Proposal Number: 7278
PI Name: DAVID PANEQUE
Title: UNRAVELLING THE COMPLEX AND EXTREME BEHAVIOURS IN THE CLASSICAL TEV BLAZARS MRK421 AND MRK501
Abstract: Owing to their brightness and proximity, Mrk421 and Mrk501 are among the blazars that can be studied with the greatest level of detail; and hence a sort of astrophysical laboratories to study the blazar phenomena. We request 4x20ks NuSTAR observations that would be taken simultaneously to various other instruments (including XMM and MAGIC). Only NuSTAR and XMM are sensitive enough to provide time-resolved hard and soft X-ray spectroscopy on the sub-hour timescales over which the proposed targets vary.The NuSTAR data would play an uniquely important role in the investigation of several important scientific questions, like the processes generating the flux variability, and the evaluation of whether the blazar emission is dominated by one zone or by multiple zones.

Proposal Number: 7279
PI Name: SUMAN BALA
Title: CONFIRMATION OF THE CYCLOTRON FEATURE IN 4U 1700-37
Abstract: We propose an 80 ks observation of the supergiant HMXB 4U 1700-37 to confirm the presence of a cyclotron line, search for pulsations, and study the accreting matter via flares. We aim to conclusively establish whether the compact object is a neutron star. We expect to confirm the putative 16 keV cyclotron line at high significance. We will rigorously test any distortions of the line profile and create a physical model of the accretion column. Spectro-temporal analysis of the source will yield valuable information about the accretion environment like density and clumpiness of the wind, accretion disk properties, or plasma instabilities in the accretion column. These data will boost our understanding of how characteristics of supergiant HMXBs depend on the properties of the compact object.

Proposal Number: 7281
PI Name: SOPHIA WADDELL
Title: PHYSICAL CONSTRAINTS FROM AGN X-RAY SPECTRA: A PILOT NUSTAR-XMM STUDY OF EROSITA-SELECTED SOURCES
Abstract: The eROSITA instrument on-board Spectrum-Roentgen-Gamma (SRG) has performed the first imaging all-sky survey in the hard X-ray (2-10keV) band. The final survey will be over 30 times deeper than previous hard X-ray surveys, yielding a large and very pure sample of AGN. Combining eROSITA data with observations from other multi-wavelength missions, a detailed picture of the AGN population can be constructed, including black hole mass, luminosity, and spectral shape. We propose simultaneous NuSTAR+XMM-Newton follow up observations of a group of hard X-ray selected AGN observed with eROSITA. This pilot study will demonstrate the power of joint NuSTAR and XMM observations to break degeneracies present in different spectral models, motivating future joint NuSTAR, XMM and eROSITA investigations.

Proposal Number: 7284
PI Name: OLEG KARGALTSEV
Title: MAGNETAR IN GAMMA-RAY BINARY LS~5039?
Abstract: LS 5039 is one of the few known high-mass gamma-ray binaries (HMGBs). Two widely discussed scenarios for HMGBs are (1) colliding winds of a young pulsar and a massive star and (2) accretion onto a black hole. In two HMGBs, with the largest orbital periods, young pulsars have been found in the radio but nothing is known about the compact object nature in HMGBs with shorter orbital periods (smaller eccentricities) perhaps due to differences in the SN explosion and the compact object progenitor. Suzaku and NuSTAR observations of LS 5039, which has the shortest orbital period among HMGBs, showed evidence of an unexpectedly slow (~9 s) pulsations indicative of a magnetar. New NuSTAR observation will either confirm or refute this tentative result which may hold key to the origin of magnetars.

Proposal Number: 7286
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 gold alert and detections of a spatially coincident blazar by Fermi-LAT and Swift-XRT. We request 40 ks of NuSTAR observations, limited to one trigger, scheduled as soon as possible after the trigger.

Proposal Number: 7287
PI Name: PRAGATI PRADHAN
Title: HARD X-RAY STUDIES OF THE ADC SOURCE, 4U 1822-37
Abstract: Among hundreds of LMXBs, only few are confirmed Accretion Disk Corona (ADC) sources in which X-rays from the compact object illuminate the disk and this heated gas form a corona above the disk. In such sources, the scattering in corona and variable disk rim cause eclipses and X-ray modulations. Taking advantage of large area of NuSTAR with broadband energy coverage and good spectral resolution, we propose 80 ks observation of ADC LMXB 4U 1822-37 (i)to perform orbital phase resolved spectroscopy and map such physical structures at various orbital phases, (ii)measure eclipse depth with energy to characterize coronal properties. Finally we will (iii)investigate the much-debated cyclotron line at 33 keV that imparts a very high magnetic field for 4U 1822-37 two orders higher than typical LMXBs

Proposal Number: 7291
PI Name: THOMAS CONNOR
Title: THE NUSTAR VIEW OF THE EPOCH OF REIONIZATION: HARD ENERGY INSIGHTS INTO THE DRIVERS OF EARLY QUASAR SUPERLUMINOSITY
Abstract: We propose to observe the z=6.18 quasar J1429+5447, recently found to have a rest-frame X-ray luminosity of L(2-10)=3E46 erg/s. This extreme luminosity is challenging to explain for a quasar seen only 900 million years after the Big Bang. If this luminosity is not intrinsic to the source but is instead a product of a favorable viewing angle (i.e., it is a blazar), then the tensions induced by this luminosity are eased. We propose to search for hard X-ray emission to characterize the blazar nature of this source. If a blazar, the source s existence would imply hundreds of other, similar quasars at early redshifts; if confirmed not to be a blazar, it is one of the universe's most extreme accretion systems.

Proposal Number: 7294
PI Name: AYSEGUL TUMER
Title: CL0217+70: A LATE STAGE GALAXY CLUSTER MERGER AND ITS TELL-TALE RADIO HALO
Abstract: Mergers of galaxy clusters are the most energetic events in the universe, driving shock and cold fronts, generating turbulence, and accelerating particles that create radio halos and relics. How and when radio halos are generated in a merger is poorly understood. Galaxy cluster CL 0217+70 is a remarkable, late-stage merger, with two or more radio relics and a well-studied radio halo, and recent Chandra observations have revealed edges in the gas that correspond to features in the halo--making it one of a handful known systems. However, the nature of the edges remain unclear. We propose a 180 ks observation with NuSTAR to determine if these edges are shock or cold fronts and their connection to the extended radio halo, as well as measure IC emission associated with the halo.

Proposal Number: 7295
PI Name: EILEEN MEYER
Title: THE FIRST HARD X-RAY MEASUREMENT OF A KPC-SCALE JET
Abstract: High-resolution imaging with Chandra and HST has revealed that many powerful jets emit strongly in the optical/UV and X-rays on kpc to Mpc scales. In the most powerful jets, the optical and X-ray have spectral properties which show they are not a continuation of the radio synchrotron emission. These extra high-energy emission components, despite dominating the energetic output, are currently unidentified. Understanding the emission mechanism in jets is the only way to get a proper accounting of the energy they carry and the impact on their environments. We propose to observe Pictor A, the only large-scale resolved jet target feasible for NuSTAR, to measure the hard X-ray spectrum to high accuracy in order to break degeneracies and constrain competing models for the emission mechanism.

Proposal Number: 7303
PI Name: GEORGE LANSBURY
Title: HIDDEN POWER: DOUBLING THE NUSTAR CENSUS OF BURIED TYPE 2 QUASARS
Abstract: The intrinsic column density (NH) distribution of quasars is poorly known. Many optically selected obscured quasars show indirect evidence of being heavily obscured, at or above the Compton-thick threshold. Such buried QSO2s are extremely challenging to study at X-ray energies of E < 10 keV. NuSTAR is unique in its ability to constrain NH for buried QSO2s, and thus reveal the hidden accretion power of these most extreme sources. Despite this, only five buried QSO2s have been detected with NuSTAR, with even fewer having sufficient counts for spectral modelling. The primary aim of this proposal is to double the number of NuSTAR-observed buried QSO2s with direct constraints on NH (at a precision of D log NH < 0.2), by observing five promising new targets, with a total exposure of 220 ks.