Proposal Number: 6027
PI Name: SAM KRUCKER
Title: NUSTAR OBSERVATIONS OF QUIETEST X-RAY SUN: CORONAL HEATING AND AXIONS
Abstract: We propose to take the ultimate NuSTAR observations of the quiet Sun during the minimum of the solar cycle. These observations, collected at close to 100 0vetime, will be used for the deepest-ever search for X-ray bremsstrahlung signatures to investigate the key question of coronal heating, and they will additionally allow us to search for an axion conversion signal. With solar activity being currently at a minimum and activity expected to pick up again in 2021, the proposed observations are time-critical.

Proposal Number: 6030
PI Name: RUEDIGER STAUBERT
Title: MAGNETIC FIELD VARIATION IN NEUTRON STARS: IS THERE ANOTHER CHANGE IN THE CYCLOTRON LINE ENERGY IN HER X-1?
Abstract: It is proposed to study the evolution of the cyclotron line energy Ec in Her X-1. The long-term decay of Ec was confirmed by a precise measurement by NuSTAR in 2015, establishing a decay by 5 keV over 20 yrs. Further observations (2016-2019) have provided evidence that the decay has ended with a stable line energy since at 37.5 keV. What happens next: will we see a further decay or a new increase, similar to the one in 1990-1993? Based on the idea, that the observed variations are related to the evolution of the magnetic field configuration at the accretion mounds in the polar regions of the neutron star, it had been speculated that a new increase might happen, once Ec had reached a level similar to its discovery. It is therefore proposed to observe Her X-1 again for 30 ksec.

Proposal Number: 6039
PI Name: JON MILLER
Title: MRK 817: A KEY TO AGN EVOLUTION AND ACCRETION GEOMETRY
Abstract: Markarian 817 is a Seyfert-1 AGN that has been observed to increase in X-ray flux by 1.5 orders of magnitude over decades. The conditions and geometry at work in the inner accretion flow in this source have not been studied in detail, though they may hold important clues to changing-look AGN, broad absorption line quasars (BALQSOs), and massive black hole accretion in general. Aspects of the UV and X-ray light curves from this source also raise fundamental questions. We propose to observe Mrk 817 for 120 ks in Cycle 6, to better understand the relationship between the corona and the disk, whether or not the inner disk is visible, and the role of geometry in shaping radiation and mechanical feedback in this important source.

Proposal Number: 6044
PI Name: STEFANO BIANCHI
Title: BUILDING SUBWAYS: THE NUSTAR LINE
Abstract: A Large Program (1.58 Ms) has been granted in XMM-Newton AO18 and 27 orbits have been awarded in HST Cycle 27 to study Supermassive Black Hole Winds in X-rays (SUBWAYS), designed to provide direct support on feedback models by deriving constraints on the energetics and duty cycle of Ultra-Fast Outflows (UFOs) in Active Galactic Nuclei. We ask now for NuSTAR observations of the 20 SUBWAYS sources (630 ks) without archival NuSTAR data. The availability of NuSTAR data above 10 keV is crucial for the objectives of SUBWAYS, and will maximise the outcome of this ambitious Large Program. The proposed observations represent a fundamental step to maintain NuSTAR science upfront during the next decade in the physically motivated investigation of multi-phase outflows.

Proposal Number: 6045
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: 6051
PI Name: RALF BALLHAUSEN
Title: HOW MANY ACCRETION COLUMNS DO WE SEE IN GX 301-2?
Abstract: GX 301-2 is a known Cyclotron Resonant Scattering Feature (CRSF) source but was only recently shown to exhibit not only one but two CRSFs at ~35 keV and ~50 keV. The non-harmonic spacing of the CRSFs and their different pulse-phase evolution make the system particularly interesting. Fuerst et al. (2018) suggest a scenario, where both CRSFs are formed at different locations inside one accretion column. We propose an 80 ks observation at a luminosity five times higher than used by Fuerst et al. (2018) to directly test their hypothesis that the observed CRSF behavior can be explained with a single accretion column. We will measure energy shifts and the pulse-phase evolution of both CRSFs to within 6% and compare our results to predictions of the single column model for higher luminosities.

Proposal Number: 6053
PI Name: JORDAN EAGLE
Title: 2FHL J1745.1--3035: A NEW EFFICIENT GALACTIC ACCELERATOR
Abstract: Very high energy (VHE, >50 GeV) gamma-rays provide a direct view of some of the most extreme environments in our Galaxy and are an excellent probe of non-thermal astrophysical processes. Studies of the non-thermal Galactic source population are essential to understand where and how the bulk of cosmic rays are accelerated in our Galaxy. We propose a NuSTAR observation of an intriguing VHE source, 2FHL J1745.1-3035, a candidate highly-energetic pulsar wind nebula with an extremely hard spectrum both in the 0.5-10 keV and in the >50 GeV energy range. Thanks to NuSTAR s unique capabilities, we will be able to characterize the age, energetics and emission mechanisms of this extreme VHE object.

Proposal Number: 6054
PI Name: GIORGIO LANZUISI
Title: WITNESSING THE BLOW-OUT PHASE IN THE CHANGING LOOK LOCAL QSO 2MASS 0918+2117
Abstract: 2MASS 0918+2117 is a type 1.5 QSO at z=0.149. It was found to be unobscured in 2000 by Chandra, obscured by Compton Thick material in 2003 by XMM and unobscured again by XMM in 2005, when there is evidence (at 3sigma) of an absorption feature at 7 keV, indicating a disk wind with velocity of vout=0.13c, with poorly constrained physical parameters. A faster wind (vout=0.3-0.4c) may be present at 10 keV, at the limit of the XMM response. These evidences suggest that the source was caught in an obscuration and following blow-out phase, in which powerful AGN-driven winds sweep away the obscuring material around the SMBH. We propose to observe the source for 60ks with Nustar (plus 50ks XMM) to fully characterize the wind at all energies, or study the absorber if the obscuration is recurrent.

Proposal Number: 6058
PI Name: KRISTEN DAGE
Title: COMPLETE SPECTRAL CHARACTERISATION OF A NEWLY DISCOVERED ULX
Abstract: A new ultra-luminous X-ray source in the edge-on spiral galaxy was recently discovered to have X-ray luminosities in excess of 10^40 erg/s. The spectrum is very hard (Gamma~1.4) with no soft excess and shows a possible evidence of a state change over subsequent observations. The hardness of this spectrum implies it is likely a pulsating ULX. The proposed data would establish the nature of the spectrum at high-energy regimes only observable by NuSTAR, as well as determine whether the spectrum has evolved since the source was last observed. Lastly, the data would be utilized to search for pulsations, possibly adding this source to the small sample of confirmed pulsating ULXs, and making it the only one to be discovered in an edge-on spiral galaxy.

Proposal Number: 6061
PI Name: XIN LIU
Title: X-RAY SPECTRUM OF A PERIODIC QUASAR FROM THE DARK ENERGY SURVEY: TESTING THE BINARY BLACK HOLE HYPOTHESIS
Abstract: We propose joint NuSTAR--XMM-Newton observations of a periodically variable quasar recently found from the Dark Energy Survey (DES). The target is unique because its periodicity is highly significant and robust thanks to the sensitive DES imaging and a ~20-yr long time baseline by combining DES with SDSS. The high sensitivity and long baseline are both crucial to rejecting false positives caused by quasars stochastic red noise variability. The proposed X-ray observations will test and distinguish two generic but different sets of models of circumbinary accretion disk simulations (a central cavity vs. minidisks), which predict dramatically different X-ray fluxes. The results will provide an independent and complementary test for the binary black hole hypothesis to explain the periodicity.

Proposal Number: 6070
PI Name: LUIGI GALLO
Title: DOES MRK 79 HAVE AN INTERMEDIATE SPIN BLACK HOLE?
Abstract: Robust measurements of black hole spin in supermassive black holes that are not rapidly rotating is difficult because of selection effects and technical challenges. We propose to observe the bright Seyfert 1 galaxy, Mrk 79, with NuSTAR and XMM, to confirm or correct the existing measured spin parameter of a*~0.7, which is based on multi-epoch XMM and Suzaku observations. Though measurements from the multi-epoch analysis are precise, some parameters (e.g. photon index and reflection fraction) appear unusual when compared with typical AGN values. The sensitivity above 10 keV provided with NuSTAR will let us directly constrain the primary continuum and Compton hump. This will result in more accurate measurements of the model parameters and a tighter constraint of the black hole spin parameter

Proposal Number: 6074
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: 6075
PI Name: JON MILLER
Title: A DOUBLE-PEAKED FE K LINE AND TRUNCATED DISK IN MRK 279
Abstract: Relativistic reflection from the inner disk is often controversial, since extremely skewed features could also be due to complex continua or complex absorption. Clearly double-peaked Fe K lines are more robust, as they can only be shaped by relativistic Doppler shifts; however, these line profiles are extremely rare. Analysis of a very recent NuSTAR snapshot observation of the Seyfert-1 Mrk 279 reveals such a line profile. It likely traces a signficant evolution in the inner accretion flow, and may signal that the disk is truncated. We request 300 ks of exposure on Mrk 279 during NuSTAR Cycle 6, to study the nature and evolution of the accretion flow in Mrk 279 and to place relativistic disk reflection on firmer ground.

Proposal Number: 6081
PI Name: MICHAEL KOSS
Title: MIRROR, MIRROR, ON THE WALL: CONSTRAINING REFLECTION IN THE BRIGHTEST COMPTON THICK AGN ABOVE 10 KEV
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. The peak variability periods also match unveiling events found with NuSTAR. We propose a volume limited variability study of the nearest and brightest CT AGN that have only been observed with NuSTAR a single time. These observations will test the frequency of variability in CT AGN, double the available NuSTAR data for CTs with multiple observations, and test whether the >10 keV variability is related to changes in column density or accretion luminosity.

Proposal Number: 6086
PI Name: ENRICO BOZZO
Title: UNVEILING THE NATURE OF NEWLY DISCOVERED INTEGRAL SOURCES WITH NUSTAR AND XMM
Abstract: We propose to carry out a 30 ks-long combined NuSTAR+XMM observation of any newly discovered INTEGRAL transient during the next observational cycle. As discussed in the proposal, these simultaneous high sensitivity broad-band data provide the most useful mean to unveil the nature of the transient and their timely scheduling is crucial to collect data from the source while it is still active in X-rays (typical outbursts of these unknown transients last from a week to about 10 days).

Proposal Number: 6087
PI Name: STEPHEN WALKER
Title: NUSTAR OBSERVATIONS OF THE STRONG SHOCK IN THE MERGING CLUSTER SPT-CLJ2031-4037
Abstract: Galaxy cluster mergers are the most energetic events in the Universe since the Big Bang. In these mergers, a significant fraction of this kinetic energy is transfered into heating the intracluster medium (ICM) through shocks. In only a handful of merging clusters have clear, high Mach number shocks (M>2.0) been identified. A new high Mach number shock (M=2.5) has been identified in a newly discovered merging cluster (SPT-CLJ2031) found by the South Pole Telescope and observed by Chandra and XMM. Here we propose a 230ks NuStar observation of the cluster to accurately measure the post-shock temperature, which is too high to be constrained by any other X-ray observatory, providing an invaluable probe of the physics of ICM heating.

Proposal Number: 6089
PI Name: ELIAS KAMMOUN
Title: THE CORONAL PROPERTIES OF AN EXCEPTIONALLY LUMINOUS QUASAR AT Z = 0.821
Abstract: High luminosity quasars are unique laboratories to test our understanding of X-ray coronae in AGN. We propose joint XMM-Newton and NuSTAR observations of a luminous, optically-selected, non-jetted quasar at z=0.821. Our main goal is to measure the high-energy cutoff in its X-ray spectrum, hence constraining, in the framework of Comptonization models, its coronal temperature and optical depth. This will allow us to test whether the same physical conditions hold in quasars at luminosities and masses 100 times higher than those probed in so far in the nearby Universe, exploring the unknown X-ray properties of the quasar population at intermediate redshifts (z = 0.1-1), constituting half the age of the Universe.

Proposal Number: 6091
PI Name: JON MILLER
Title: A LOOK INTO THE HEART OF A TIDAL DISRUPTION WITH NUSTAR
Abstract: X-rays probe fundamental aspects of tidal disruption events (TDE). We request a rapid 50 ks TOO observation of a TDE with a Seyfert-like flux in the NuSTAR band during Cycle 6. This flux and exposure will enable sensitive searches for the QPOs, disk reflection, winds, and reverberation that have been detected in prior TDEs. These tools can reveal the nature of nascent disks, super-Eddington disks, and inflow--outflow coupling. Studies of TDEs benefit from leveraging the best abilities of different observatories; the team is well positioned to support this program using Chandra, XMM-Newton, Swift, and HST.

Proposal Number: 6092
PI Name: JOHN TOMSICK
Title: WHITE DWARF MASSES FOR CATACLYSMIC VARIABLES WITH VERY HARD ENERGY SPECTRA
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 depends on the mass of the WD. By obtaining high-quality hard X-ray spectra, it is possible to measure the temperature and constrain 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 20-100 keV INTEGRAL survey good candidates for having more 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: 6096
PI Name: SHOBITA SATYAPAL
Title: THE MOST LUMINOUS AGN IN A TRULY BULGELESS DISK GALAXY? THE \NUSTAR\ VIEW OF NGC 4178
Abstract: Whereas supermassive black holes (SMBHs) are found in essentially every galactic bulge, very few SMBHs are known in purely bulgeless galaxies. As classical galactic bulges are typically only formed through galaxy interactions or mergers, identifying such a population is crucial to our understanding of the origins of SMBHs and the secular pathways for their growth. However, to date, there are only a handful of confirmed SMBHs in galaxies with no evidence for {\it any} bulge known in the Universe. We propose to observe for 50 ks the nearby (d=16.8 Mpc) bulgeless disk galaxy NGC 4178, which is optically classified as a star forming galaxy but shows prominent high ionization mid-infrared [NeV] emission thus far exclusively associated in extragalactic sources with AGNs. While {\it Chandra} obs

Proposal Number: 6108
PI Name: XIAOYANG CHEN
Title: IDENTIFYING A FADING AGN ASSOCIATED WITH AN EXTREME OUTFLOW IN A ULIRG AT Z=0.5
Abstract: Massive large-scale outflows are generally considered as the indicators that AGN can severely affect their host galaxies. Recently a ULIRG at z=0.49, J0916a, was found with one of the most powerful galaxy-scale outflow at z<1.6. However, the central AGN activity estimated from MIR luminosity of AGN torus is relatively weak. One possible scenario is that currently the AGN is in a fading status, while the outflow reflects a historical effect of the central engine. We propose a NuSTAR observation for J0916a to directly constrain the current AGN activity. If J0916a is actually weak in hard X-ray, it would be the first fading AGN detected in ULIRGs as well as the highest-z fading AGN. The result is helpful to understand the cumulative effect of AGN s feedback on the host galaxy.

Proposal Number: 6109
PI Name: DANIEL WIK
Title: ACCURATE GALAXY CLUSTER TEMPERATURES: A LEGACY DATASET WITH CHANDRA, XMM, AND XRISM
Abstract: Galaxy clusters are the most massive virialized objects in the universe, and their growth over cosmic time is sensitive to the underlying cosmology. Cluster cosmology requires accurate mass measurements, which generally depend on temperature measurements. Unfortunately, the main sources for X-ray temperatures are Chandra and XMM, which systematically disagree with each other. The hard band sensitivity of NuSTAR, however, has the potential to resolve this discrepancy and reduce the error budget on cluster-derived cosmological parameters. We propose deep observations of 4 low redshift, relaxed clusters, with extensive XMM and Chandra (and future XRISM) data, where both calibration and physical differences can be assessed in the simplest possible systems.

Proposal Number: 6110
PI Name: DANIEL WIK
Title: ACCURATE TEMPERATURES AND INVERSE COMPTON IN ABELL 2319
Abstract: Since the first non-thermal detections of inverse Compton (IC) emission in galaxy clusters at hard X-ray energies, we have yet to unambiguously confirm IC in follow-up observations. A claim of large IC fluxes from Abell 2319, a massive nearby merging cluster, make it the next best chance of confirming a previous IC detection with NuSTAR. Additionally, recently available Chandra and XMM data indicate similar, but inconsistent, temperature variations, potentially due to calibration differences and/or Galactic column density variations. However, both issues can be avoided with NuSTAR's harder energy band, yielding a more accurate temperature map of A2319. We will definitively confirm or refute the previously estimated IC flux and constrain the high kT makeup of this dynamic cluster.

Proposal Number: 6121
PI Name: VICTOR DOROSHENKO
Title: FOLLOW-UP OF X-RAY BINARIES DISCOVERED BY EROSITA
Abstract: The eRosita X-ray survey started last year is expected to discover several millions of new sources and double the number of known Galactic X-ray binaries (XRBs). This will help to clarify several long-standing questions related to numbers, origin, and evolution of XRBs and massive stars in general, and accretion physics in low-luminosity XRBs. To fully realise this potential, follow-up observations in X-ray and other bands are, however, essential. Here we propose to start the exploration of this new dataset with NuSTAR follow-up of up to four select High mass X-ray binary (HMXB) candidates discovered by eRosita within current Cycle 6 period with the aim to confirm identifications, and study their broadband X-ray properties in detail.

Proposal Number: 6122
PI Name: ANIRBAN DUTTA
Title: INVESTIGATING COMPTON REFLECTION FOR TWO ASYNCHRONOUS MAGNETIC CVS CD IND AND PALOMA USING JOINT NUSTAR XMM OBSERVATION
Abstract: Broadband X-ray spectra of polars and intermediate polars consist of multitemperature thermal plasma component,its reflection from white dwarf & 6.4 keV Fe fluorescence emission line. We propose simultaneous NuSTAR-XMM observation of CD Ind (an asynchronous polar) and Paloma (a special IP evolving from IP to polar)for the first time to robustly detect the reflection hump and resolve the 6.4 keV Fe fluorescence line. These observations will help us in having an idea of the geometry of accretion process. Also, we will determine the shock temperature to estimate the mass of WD and perform emission line spectroscopy to determine the temperature and density profile of the post-shock region. For both the sources, we request 50 ks of NuSTAR (Total 100 ks) & 25 ks of XMM observation (Total 50 ks).

Proposal Number: 6123
PI Name: ANDREA MARINUCCI
Title: HARD X-RAY SPECTRAL FEATURES OF THE LUMINOUS QUASAR RBS 1055
Abstract: An observation of the luminous quasar RBS 1055 is requested, for a net observing time of 250 ks. We aim at studying the yet poorly investigated emission of this object in the hard X-rays, which exhibits very interesting spectral features in the existing XMM and Swift-BAT data. Recent XMM observations of RBS 1055 show an intense Fe Ka emission line, one of the few ever detected at these luminosities. This is the most promising candidate for studying the Compton reflection parameters in very luminous quasars. Furthermore, the proposed NuSTAR observation will lead to a very accurate measurement of a high energy curvature of the primary continuum, which have been obtained so far only in three other sources with redshift z>0.4.

Proposal Number: 6131
PI Name: GABRIELE PONTI
Title: THE MOTION OF SGR A*'S NIR SOURCE DURING X-RAY FLARES
Abstract: We propose two long (143 ks) continuous NuSTAR exposures to cover 8 nights of VLTI-Gravity+(XMM-or-Chandra) observations of Sgr A*. The required exposure time of Gravity, XMM and Chandra have 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: 6133
PI Name: RALF BALLHAUSEN
Title: TRACING SPECTRAL TRANSITIONS TOWARD LOW LUMINOSITIES IN NEUTRON STAR HIGH MASS X-RAY BINARIES
Abstract: High-energy radiation from highly-magnetized neutron stars at very low luminosities (<1e35 erg/s) has so far only been observed with NuSTAR in two sources, A 0353+26 and GX 304-1, which both have CRSFs above 45keV. The spectral shape at these low mass accretion rates is fundamentally different compared to higher luminosities and in particular, the formation of high-energy radiation is still an open question. The available data are, however, very incomplete, because such observations can only be performed for nearby sources. We therefore propose a 100ks ToO of a low luminosity HMXB but with intermediate CRSF energy to study the dependence of the high-energy radiation with magnetic field and improve our understanding of radiative transfer in magnetized plasmas.

Proposal Number: 6141
PI Name: ALESSIA TORTOSA
Title: X-RAY STUDY OF EXTREME ACCRETION ONTO SUPERMASSIVE BLACK HOLES WITH NUSTAR
Abstract: Hereby we propose an X-ray study of super-Eddington AGN by observing three of them with NuSTAR : PG 0953+414 (70ks), NGC 4748 (80ks) and PG0026+129 (140ks). These object are part of the best sample available, SEAMBHs, in which all the objects have the black hole masses estimated by reverberation mapping. The use of the mass estimated by reverberation mapping makes the estimation of the Eddington ratio extremely reliable. These sources are the ones of this sample with the highest 2-10 keV flux that have not been observed by NuSTAR . The aim of these observations is to better understand the behavior of the primary power-law and the reprocessed radiation in the regime of extreme accretion, as well as the property of soft-excess and/or the outflows.

Proposal Number: 6149
PI Name: KAYA MORI
Title: A NEUTRON STAR ULTRA-COMPACT X-RAY BINARY WITH THE SHORTEST KNOWN ORBITAL PERIOD?
Abstract: An ultra-compact X-ray binary (UCXB) candidate with potentially the shortest known orbital period of 10.2 minutes was serendipitously discovered in the Galactic Bulge. Its only available X-ray spectra from a 2010 XMM observation and radio/IR observations suggest that the source may be the first direct impact NS binary with no accretion disk or (less likely) an intermediate polar. The proposed NuSTAR+XMM observations will confirm the period signal, search for a NS spin period and identify the source by a combination of broad-band X-ray spectroscopy and Fe line diagnostics. Given its short orbital period, the source may be one of the few UCXBs detectable by the future LISA gravitational wave observatory and suggests a possibility of finding more UCXBs in the Bulge.

Proposal Number: 6150
PI Name: FELICIA KRAUSS
Title: UNDERSTANDING THE HARD X-RAY EMISSION IN THE BLAZAR PKS 2005-489
Abstract: We propose to observe the low-redshift blazar PKS 2005-489 for 60 ksec with NuSTAR to investigate a peculiar hard X-ray feature. The hard X-ray feature could point to an additional jet component or an elusive hadronic component. It is unclear whether this feature is seen in all flux states, as no previous NuSTAR observations of this source exist.

Proposal Number: 6152
PI Name: DANIEL KYNOCH
Title: DETERMINING THE X-RAY SPECTRUM OF A LUMINOUS, HIGH-REDSHIFT SWIFT-BAT AGN
Abstract: Blazars are a class of active galaxies with a relativistic jet pointed towards us. High-redshift blazars can be used to probe the early Universe and investigate supermassive black hole growth over cosmic time. By determining the frequency and luminosity of the high-energy, inverse-Compton (IC) peak in their spectral energy distributions, key physical properties of the jet can be inferred. With increasing luminosity and redshift, the IC peak shifts down into the hard X-ray band, making high-z blazars ideal targets for NuSTAR observations. We propose an observation of the z = 3.29 blazar SWIFT J0909.0+0358, one of the most luminous objects in the Swift-BAT 105-month catalog. We aim to parameterise the source's IC peak and obtain a better characterisation of its unusually hard X-ray spectrum.

Proposal Number: 6156
PI Name: FELICIA KRAUSS
Title: BLAZAR X-RAYS AND NEUTRINOS: INVESTIGATING THE MOST PROMISING ICECUBE NEUTRINO ALERTS
Abstract: We propose to perform up to two 40 ksec ToO follow-up observations of X-ray luminous blazars that we identify in association with two separate "gold" quality IceCube high-energy neutrino alerts. These alerts are likely to be astrophysical neutrinos. 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.

Proposal Number: 6158
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 seven 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: 6159
PI Name: SOPHIA WADDELL
Title: CHARACTERISING THE HARD X-RAY VARIABILITY OF THE SEYFERT 1.2 GALAXY MCG +04-22-042
Abstract: MCG +04-22-042 is a Seyfert 1.2 AGN which shows evidence of significant hard X-ray variability. Curiously, previous analyses of the Swift BAT and a short NuSTAR observation suggest that the source shows increased variability at high energies (above 20keV) than at lower energies. Archival data also suggest that the spectrum appears harder when the source is brighter. These behaviours have been observed in radio loud AGN, but are extremely atypical for radio quiet, type-1 AGN. We propose to monitor the hard X-ray flux of this source using 3x40ks observations of the source throughout AO6. NuSTAR can uniquely provide the opportunity to study the source on short and long timescales across a wide energy range,and permit the search for spectral changes associated with the variability.

Proposal Number: 6163
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: Supermassive black holes (SMBHs) are believed to exist in the nuclei of almost all massive galaxies. SMBHs play crucial roles in galaxy evolution through merger, accretion and feedback processes such as jets and outflows. Given one of the largest apparent angular size, Sgr A* is an ideal target for the Event Horizon Telescope (EHT) to image the dark "shadow" caused by gravitational light bending and photon capture close to the event horizon. Simultaneous X-ray observations are vital to monitor variability of Sgr A* and to constrain the total energy budget during EHT observation. Therefore, we propose a 100 ks NuSTAR exposure to overlap with the EHT observation window. A 100 ks exposure which will allow us to capture at least one Sgr A* X-ray flare above 20 keV, unique for NuSTAR.

Proposal Number: 6164
PI Name: KIRILL SOKOLOVSKY
Title: UNDERSTANDING THE GAMMA-RAY PRODUCTION MECHANISM IN NOVA SHOCKS
Abstract: We propose a 60ks observation for one new GeV bright nova to explore the particle acceleration and gamma-ray production mechanisms. We will constrain the particle acceleration efficiency by comparing thermal X-ray to GeV luminosity and search for predicted non-thermal X-rays. Understanding shocks in novae is relevant for other shock-powered transients including Type IIn supernovae, tidal disruption events and stellar mergers. NuSTAR is the only instrument capable of detecting X-rays from novae simultaneously with the GeV emission (the lower energy X-rays accessible to other focusing instruments are hidden by the nova shell at these times). The observations should be conducted now to take advantage of the simultaneous operations with Fermi/LAT.

Proposal Number: 6165
PI Name: MIRKO KRUMPE
Title: RARE AND DRAMATIC FLUX DROPS IN EROSITA AGN: ACCRETION OR LINE-OF-SIGHT OBSCURATION CHANGES?
Abstract: eROSITA, successfully launched in mid-2019, will perform multiple all-sky X-ray surveys. Monitoring roughly half a million AGN/quasars, eROSITA will identify rare, accretion depletion events as they occur. NuSTAR observations are needed to distinguish depletion from heavy obscuration events. In case of a depletion event we will explore how the X-ray corona respond to a sudden, major drop in accretion rate. In the case of the line of sight obscuration event, we will determine the amount of absorption. Thus, we propose four ToOs of 70 ks each.

Proposal Number: 6166
PI Name: ANDREA GOKUS
Title: GAMMA-RAY FLARES FROM SUPERMASSIVE BLACK HOLES AT HIGH REDSHIFT
Abstract: We propose a 100 ks ToO observation of a high-redshift (z>=3) blazar during a gamma-ray flare detected by Fermi/LAT. Only 12 high-redshift blazars have been detected in gamma-rays. These objects are the most luminous and massive objects in the Universe, which allow to study the formation of active galactic nuclei in the early Universe. Because the high-energy hump of their SED peaks in the MeV range, X-ray and gamma-ray data is needed to constrain the hump's shape. We propose to get high-sensitivity X-ray data during enhanced gamma-ray activity of a blazar at high redshift. The data will be complemented by triggered radio observations. The resulting multiwavelength data set will yield important knowledge on the behaviour of flaring MeV blazars for future MeV telescopes.

Proposal Number: 6167
PI Name: GIULIA MIGLIORI
Title: BEYOND THE 10 KEV WALL: UNVEILING THE HIGH-ENERGY OUTPUT OF YOUNG RADIO SOURCES WITH NUSTAR AND FERMI
Abstract: We propose NuSTAR observations of NGC6328 (z=0.014) and NGC3894 (z=0.0108), the only two CSOs(young radio sources) which are also confirmed gamma-ray (>0.1 GeV) emitters by Fermi-LAT. The joint modeling of the broadband X-ray and gamma-ray bands will be an asset to establish the nature of the X-ray emission and disentangle the non-thermal radiative output from the accretion related components. This is key to understand the initial conditions of the growing source, its following evolution, and the nature of the feedback with the host galaxy. Among the current X-ray telescopes operating at energies >10 keV, only NuSTAR has the capabilities required to detect and study our targets.

Proposal Number: 6171
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 2021. 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: 6174
PI Name: AMY FURNISS
Title: DEFINING THE SPECTRAL TRANSITION BETWEEN SYNCHROTRON AND INVERSE-COMPTON EMISSION IN THE ISP BLAZAR 3C 66A
Abstract: The NuSTAR telescope is currently the only instrument with the capability to define the spectral change between the synchrotron and inverse-Compton emission for a rare class of very-high-energy gamma-ray emitting blazars. This transition occurs in the 1-100 keV energy range. Of the seven blazars of this type so far known, we target one ideal candidate where NuSTAR observations will be the most fruitful, 3C 66A. The NuSTAR observations will be augmented with observations by Swift-UVOT, Swift-XRT, Fermi-LAT, and VERITAS to cover the optical to VHE spectrum and provide unprecedented constraint of the relatively unique emission mechanism at work within the source. For this program, the standard service Swift snapshots collected simultaneous with NuSTAR observations are sufficient.

Proposal Number: 6179
PI Name: PRAGATI PRADHAN
Title: CHARACTERIZING THE HARD X-RAY SPECTRUM OF SFXT IGR J17391-3021 WITH NUSTAR
Abstract: Supergiant Fast X-ray Transients (SFXTs) are a subset of HMXBs showing sporadic outbursts that've fascinated X-ray community and many theories attempt to explain their erratic behaviour.The most direct way to disentangle these theories is to estimate magnetic field of SFXTs through cyclotron resonant scattering features (CRSFs).We propose first NuSTAR observation of SFXT IGR J17391-3021 for 40ks during its outburst at periastron to confirm hints of CRSF at 30keV seen by INTEGRAL and Suzaku. We will also study hard X-ray properties of IGR J17391-3021 in the context of other SFXTs and superslow pulsars.In an unlikely event of quiescence at periastron, we will characterize the quiescence spectrum of IGR J17391-3021 with greatest accuracy yet made possible by large area of FPMs.

Proposal Number: 6181
PI Name: NAZMA ISLAM
Title: UNRAVELLING THE ENIGMATIC SUPER-ORBITAL MODULATION OBSERVED IN 4U 1538-52
Abstract: The puzzling variety of super-orbital modulations seen in the long term light-curves of Supergiant High Mass X-ray binaries (sgHMXBs), opens up new questions on the stellar wind interaction with a highly magnetised neutron star. We propose a joint 40 ks NuSTAR + 10 ks NICER observation of the persistent sgHMXB 4U 1538-52 at its super-orbital maximum and minimum to conclusively understand the mechanisms driving these flux modulations. The results of energy resolved pulsation studies, pulse phase resolved spectroscopic study of photon indices, absorption column density and cyclotron lines will be used to differentiate or constrain the various models explaining these super-orbital modulations.

Proposal Number: 6189
PI Name: YAHERLYN DIAZ
Title: STUDYING THE ENVIRONMET OF LOW LUMINOSITY AGN
Abstract: Recent observations point out that Low-luminosity active galactic nuclei, such LINERs and low power Seyfert galaxies, might have a different torus configuration compared to more powerful AGNs. The shape of the Compton hump observed above 10 KeV is an excellent tool to study the geometry and the physical features of the reflector. The purpose of this proposal is study a low powered (L/LEdd sim 10^-5) Seyfert galaxy NGC 5033, to study the characteristics of the material surrounding the SMBH. We ask for observations with NuSTAR and XMM-Newton to study the relation between the accretion rate and properties of the reflector (torus covering fraction and column density) and to compare with existing, similar quality data of a LINER with equal black hole mass and accretion rate.

Proposal Number: 6195
PI Name: JOANNA KURASZKIEWICZ
Title: WHAT FRACTION OF POWERFUL RADIO GALAXIES IS COMPTON-THICK IN X-RAYS ?
Abstract: The total accretion luminosity in the Universe is a key parameter for cosmology, but despite decades of study, the fraction hidden behind obscuring material is unknown. A Chandra survey of luminous, high-redshift, radio-loud 3CRR AGN found that narrow-line radio galaxies (NLRGs) have 10-1000 times lower X-ray luminosities than quasars of the same radio luminosity. If obscuration causes the X-ray weakness, 500f luminous AGN are obscured, 25% are Compton-Thick (CT), and typical AGN surveys miss much of the accretion luminosity. The alternative hypothesis is a new population of X-ray-weak AGN. Either scenario is important for cosmology, and we propose NuSTAR observations of three CT candidates to distinguish between them.

Proposal Number: 6196
PI Name: SCOTT WOLK
Title: THE HIGH ENERGY SIGNATURE OF MAGNETISM IN RHO OPH A
Abstract: Periodically pulsed X-ray emission from the nearby B2 star Rho Oph A have been discovered along with a variable magnetic field and strongly modulated radio emission. All these observations fit in a model of an oblique magnetic rotator, where, alternatively, the magnetic poles and their radio emission point towards the Earth. In this proposal we request to use NuSTAR and XMM-Newton to monitor Rho Oph A for about two rotational periods (total exposure ~140 ks) in order to clarify the link between X-rays, radio emission and magnetism which requires us to firmly characterize its high energy (> 10 keV) emission. The hard X-ray spectrum will provide a clear signature of non-thermal emission and a better knowledge of the auroral emission and particle acceleration in magnetic B stars.

Proposal Number: 6197
PI Name: DOMINIC WALTON
Title: TESTING THE CONNECTION BETWEEN THE ULTRALUMINOUS X-RAY SOURCES HOLMBERG IX X-1 AND NGC1313 X-1
Abstract: Multi-epoch broadband spectroscopy of the ultraluminous X-ray source (ULX) NGC1313 X-1 has revealed unusual spectral variability. When fit with accretion disk models, the data show two distinct groups in the L-T plane, each of which exhibits its own positive L-T correlation. Understanding this behaviour is likely key to understanding the structure of super-Eddington accretion flows. Holmberg IX X-1 also shows some evidence for this behaviour, but there is currently only one broadband observation in the high-flux regime, meaning this cannot yet be firmly established. This proposal aims to take a series of 4 XMM+NuSTAR observations (each 25+50ks) of Holmberg IX X-1 in its high-flux state in order to determine whether it does show the same unusual behaviour as NGC1313 X-1.

Proposal Number: 6207
PI Name: JEROEN HOMAN
Title: SUPER-EDDINGTON ACCRETION IN CIR X-1: A ULX CONNECTION
Abstract: Cir X-1 is one of the few galactic X-ray binaries that has entered ULX territory (Lx>1e39 erg/s). It provides a unique bridge between the near-/super-Eddington Z sources and ULXs. Archival data suggest that on its way to becoming a ULX Cir X-1 develops a strong outflow that affects the measured temperatures of the continuum components. After a long relatively quiet period, Cir X-1 has become persistently active again, allowing us to investigate this behavior with modern instrumentation. We request 3 NuSTAR/NICER observations (75/45 ks total) near peaks of the source's X-ray cycles, to probe its mildly super-Eddington regime. Our goal is to better understand inflows/outflows in X-ray binaries as they become super-Eddington and to establish a connection to the phenomenology of ULX spectra.

Proposal Number: 6209
PI Name: GEORGIOS VASILOPOULOS
Title: FOLLOW-UP MAJOR OUTBURSTS FROM HARD X-RAY TRANSIENTS IN THE MAGELLANIC CLOUDS
Abstract: The Magellanic Clouds (MCs) harbor a large sample of Be/X-ray binaries (BeXRBs) at a moderate and well known distance with low Galactic foreground absorption. We propose 3 ToO observations (100 ks total time) of new or unexplored BeXRBs in the MCs during super-Eddington outbursts. Our goal is to study their spectral and temporal properties to gain insight onto super-Eddington accretion.

Proposal Number: 6210
PI Name: AYSEGUL TUMER
Title: PRE-MERGER DYNAMICS OF ABELL 3395
Abstract: Clusters of galaxies are the largest virialized objects in the universe. Since the unknown physics lies at high energy phenomena and the mergers of these objects are the most energetic events in the universe, they are inherently interesting. Shocks and turbulence driven by these mergers as well as their interaction with cosmic web structures are yet to be understood, and our knowledge of the pre-merger dynamics is limited. We propose to observe the cluster Abell 3395, which is at a pre-merger state. We aim to obtain the first observational evidence of the interaction between shock heated regions and intercluster filaments, as well as to unveil the dynamics of the merger. NuSTAR's high sensitivity at hard X-ray energy band will enable precise measurements of high temperature regions.

Proposal Number: 6212
PI Name: LUIGI COSTAMANTE
Title: FINDING THE SYNCHROTRON PEAK OF NEW EXTREME-TEV BL LACS
Abstract: We propose to observe 4 new extreme-TeV BL Lacs characterized by a hard X-ray spectrum below 10 keV, thus indicating a synchrotron peak in the SED above 8-10 keV. Extreme-TeV BL Lacs are a new type of BL Lacs with the highest gamma-ray peak energy in the whole blazar class, above 1-10 TeV. The origin of such extreme emission is not yet understood, but to discriminate between different scenarios the precise knowledge of the synchrotron peak is essential. NuSTAR is the only instrument capable of determining the peak energy and luminosity of the synchrotron emission in these sources. The total requested time of 200 ks is sufficient to reveal the possible curvature of the spectrum in all objects, at their typical flux levels.

Proposal Number: 6213
PI Name: MATTEO BACHETTI
Title: BROADBAND TIMING OF THE ULTRALUMINOUS X-RAY SOURCES IN M82: ORBITAL DECAY, QPOS, AND MORE.
Abstract: The galaxy M82 harbors two notable ultraluminous X-ray sources (ULX): M82 X-2, the archetipal pulsating ultraluminous X-ray source (PULX), and M82 X-1, a IMBH candidate. The extreme luminosity of ULXs, and the observation of strong winds from these sources, suggests that these sources are undergoing strongly super-Eddington accretion. The supply of matter that powers these accreting systems is likely to come from Roche Lobe overflow from a more massive companion star, and should produce changes of orbital period observable in time scales of ~years. This program aims at detecting this orbital period derivative through pulsar timing in M82 X-2, and study in detail the quasi-periodic oscillations from both ULXs.

Proposal Number: 6214
PI Name: SEAN PIKE
Title: A DEEPER LOOK FOR PULSATIONS FROM CIRCINUS ULX5
Abstract: We propose a 100 ks NuSTAR observation of Circinus ULX5 in the high-flux state, triggered by a Swift XRT monitoring campaign in order to search for transient pulsations. The source is a bright, variable ULX in the Circinus galaxy, which is well-isolated from the nucleus and other X-ray sources, making it a prime ULX for further study. Although short observations of the source have been previously carried out, this would be the first deep exposure by NuSTAR which would allow for detection of pulsations at pulse fractions significantly lower than were previously possible. Additionally, it will yield superior constraints on spectral models, particularly at high energies. This observation will build upon the field's current understanding of ULX demographics, variability, and spectral modeling.

Proposal Number: 6217
PI Name: MATTEO CERRUTI
Title: NUSTAR OBSERVATIONS OF A NEW VERY-HIGH-ENERGY QUASAR
Abstract: We propose to perform NuSTAR observations of a new very-high-energy (VHE; E > 100 GeV) quasar, detected in a gamma-ray flaring state with the MAGIC array of Cherenkov telescopes. NuSTAR observations will be coordinated to happen simultaneously with MAGIC and will be part of a multi-wavelength campaign from optical to VHE gamma-rays. The goal of the project is to obtain a simultaneous multi-wavelength coverage of a bright flare from a VHE quasar, putting constraints on the acceleration and radiation mechanisms in relativistic jets from super-massive black holes.

Proposal Number: 6218
PI Name: FRANCESCA CIVANO
Title: DEEP NUSTAR OBSERVATIONS OF THE JWST-NEP TIME DOMAIN FIELD: LONG TERM MONITORING
Abstract: The JWST Deep Time-Domain Field in the North Ecliptic Pole (NEP DTDF) is a GTO target that will have continuous visibility and 8-band deep imaging and grism spectra in the NIR by JWST. In the past few years, the NEP DTDF has grown into a comprehensive survey with deep radio to X-ray data, becoming the most promising new field for extragalactic studies and time-domain investigations. Given interesting results from Cycle 5 NuSTAR program, we request 780 ks for long term monitoring of the NEP DTDF, split into 4 epochs (spaced before and after JWST launch over 2 NuSTAR cycles), enabling studies of hard X-ray variability, 0.3-24 keV spectroscopy through simultaneous XMM observations, the faint end of the AGN luminosity function at >8 keV, the obscured AGN fraction, and a bright NLSy1 at z> 1.

Proposal Number: 6220
PI Name: MARCO AJELLO
Title: COMPTON THICK AGN WITH NUSTAR AND XMM-NEWTON
Abstract: The X-ray spectral analysis of Compton thick (CT-, i.e., having intrinsic obscuration NH>1E24 cm^-2) active galactic nuclei (AGN) is key to understand the physics of the obscuring material surrounding accreting supermassive black holes. We propose to target with a combined NuSTAR/XMM-Newton observation two candidate CT-AGN selected from the BAT 100-month survey. Thanks to the excellent count statistics, we will be able to constrain several spectral parameters (e.g., relative importance of the scattered component versus the direct one, geometry of the obscuring torus, equivalent width of the Iron emission line). This analysis will refine our knowledge of the selection function of CT-AGN, therefore helping us in determine the true intrinsic fraction of CT-AGN in the local Universe.

Proposal Number: 6221
PI Name: CHIEN-TING CHEN
Title: OBSCURED LOW-MASS AGNS WITH NUSTAR AND SPITZER IRS
Abstract: Current limitations of our knowledge of low-mass AGN hinder our understanding of massive black holes (mBHs) and primordial BH seeding. This is largely due to the lack of direct detections of X-ray obscured low-mass AGN caused by the limitations of optical AGN diagnostic lines in low-mass AGN. Here we propose to obtain 100ks of NuSTAR observations for a dwarf galaxy with high-ionization [OIV] and [NeV] detections in its Spitzer IRS spectrum. We will use the NuSTAR observations and multiwavelength data to establish a baseline for studying X-ray obscured low-mass AGN, which will provide key insights into the nature of obscuration and accretion for mBHs.

Proposal Number: 6222
PI Name: ANDREA SANNA
Title: REVEALING ACCRETING MILLISECOND X-RAY PULSARS WITH SIMULTANEOUS NUSTAR AND NICER OBSERVATIONS.
Abstract: We propose a ToO observation of Galactic X-ray transients aimed at discovering accreting millisecond X-ray pulsars. NuSTAR and NICER represent ideal observatories capable of fulfilling such goal, which will help increasing the knowledge of the evolutionary paths followed by NS, and possibly lead to breakthrough discoveries of extremely quickly rotating objects. We propose a 40 ks observations of newly discovered X-ray transients. Criteria set to maximise the probability of discovering new sources of this class, based on the X-ray flux (> 7 and 10 mCrab, in 2-10 and 20-40 keV energy bands, respectively), the spectral shape (a power law with index 1.5-2.5), and the absence of an alternative identification, will be used to trigger the proposed observations among newly discovered transients.

Proposal Number: 6223
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 7 local ULIRGs 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 observed outflows, and determine the global importance of AGN activity at the highest galaxy luminosities.

Proposal Number: 6224
PI Name: KAYA MORI
Title: NUSTAR HARD X-RAY SURVEY OF PULSAR WIND NEBULAE IN SYNERGY WITH TEV GAMMA-RAY TELESCOPES
Abstract: The proposal seeks a unique opportunity to collect legacy NuSTAR data and explore pulsar wind nebula (PWN) astrophysics at the deepest level through multi-wavelength SEDs, in synergy with the existing and near-future TeV gamma-ray telescopes. NuSTAR observations of 8 additional PWNe will complete the sampling of all 22 TeV-PWNe detectable by NuSTAR. Our targets includes PWNe detected by HAWC above 50 TeV, PWNe crushed by reverse SNR shocks, a young PWN in the Galactic Center and the archetype Vela nebula. Some of the nebulae may contain a hadronic outflow which produces TeV gamma-rays via interacting with the ISM or dense clouds. NuSTAR can probe sub-PeV electron populations through X-ray synchrotron spectra and allow us to perform spectro-imaging studies of PWNe above 10 keV.

Proposal Number: 6227
PI Name: RANDALL ROJAS
Title: CONSTRAINING THE NATURE OF DARK MATTER WITH CIZA 0107.7+5408
Abstract: Galaxy cluster mergers provide key insights into the way dark matter behaves. In rare cases, there can be a dissociative merger in which the baryonic matter and dark matter are separated noticeably, as is the case with the Bullet Cluster and CIZA0107.7+5408. Our objective is to constrain the self interacting dark matter (sigma_SIDM) cross section in CIZA0107 by using the methods first discussed in Markevitch et al. 2004 and applied in Randall et al. 2016. We will determine the temperature jump in a region where archival Chandra data suggests the presence of a shock front and use this to calculate the Mach number and gas merger velocity, which will be used to find sigma_SIDM in numerical simulations. We will also rule out this temperature spike being due to non-thermal emission.

Proposal Number: 6230
PI Name: NOEL KLINGLER
Title: NUSTAR STUDY OF PSR J1101-6101 AND ITS REMARKABLE NEBULA
Abstract: PSR J1101-6101 powers an INTEGRAL source and the remarkable Lighthouse pulsar wind nebula (PWN). J1101 belongs to the rare type of radio- and gamma-ray-quiet pulsars which tend to be bright in hard X-rays. We propose to investigate the pulsations and spectrum of the pulsar in hard X-rays. The contribution of the compact PWN is negligible above 8 keV, and below 8 keV we can account for it using CXO data. We will also spatially isolate and study the spectrum of the puzzling extended structure that earned the PWN its name. There are only a few such examples known, all around high-speed pulsars, strongly misaligned with pulsar velocities, and extending far beyond the bow shock boundaries. Probing one above 8 keV will aid the ongoing theoretical investigations to understand their origins.

Proposal Number: 6231
PI Name: NEVEN VULIC
Title: A NUSTAR-XMM VIEW OF THE RESOLVED X-RAY BINARY POPULATION IN THE FIREWORKS GALAXY (NGC 6946)
Abstract: What dictates the formation of luminous black hole (BH) versus neutron star (NS) X-ray binaries (XRBs)? Recent studies have shown that some ultraluminous X-ray sources in starburst and high specific star formation rate (sSFR) galaxies are pulsars, while low sSFR galaxies such as M31 have a dearth of accreting BHs. These discoveries have challenged our understanding of XRB evolution and the associated accretion processes. We request a 420 ks NuSTAR observation simultaneous with a 50 ks XMM-Newton observation of the starburst galaxy NGC 6946 (The Fireworks Galaxy) to characterize the accreting BH and NS populations and investigate the black hole fraction at luminosities below the NS Eddington limit.

Proposal Number: 6236
PI Name: MARY SAADE
Title: NUSTAR SURVEY OF CANDIDATE SUBPARSEC SMBH BINARIES
Abstract: Graham et al. (2015ab) reported the discovery of 111 optically periodic quasars. The most plausible mechanisms for the observed periodicity all involve a supermassive black hole (SMBH) binary at subparsec separation. Most theoretical models of close SMBH binaries predict them to have different X-ray spectra than single SMBH systems of the same total mass, generally being brighter and harder at X-ray energies. However, Chandra observations of a sample of seven such systems found them to have typical X-ray spectra in the observed 0.5-7 keV energy range (Saade et al. 2020). We propose to observe the five X-ray brightest periodic quasars with NuSTAR to test if the unusual X-ray spectra appear at higher energies, above 10 keV.

Proposal Number: 6238
PI Name: MARIANNE VESTERGAARD
Title: TOO OBSERVATIONS OF A RE-AWAKENING AGN: EXPLORING THE PHYSICS OF CHANGING-LOOK AGN
Abstract: After a 10-year break, Mrk 590 is rekindling its nuclear activity with a rise in X-ray flux! We wish to seize this rare opportunity to record, for the first time, the onset of AGN activity as it occurs since this can lead to significant insight on the long-standing issue of how AGNs are triggered and fueled. We ask to trigger up to 3 single-visit joint NuSTAR/Swift/XMM observations to determine if a standard thin accretion disk is being built up as the AGN turns on or if alternate physics are at play. Relatively inexpensive XMM exposures are needed to constrain any intrinsic absorption. The data are also ideal for testing the recent prediction that quasi-periodic eruptions can explain the flux changes seen for Mrk 590.

Proposal Number: 6239
PI Name: KENJI HAMAGUCHI
Title: CATCHING THE PEAK OF NON-THERMAL EMISSION FROM ETA CARINAE
Abstract: NuSTAR observations of the massive stellar binary system eta Carinae have provided definitive evidence for extremely hard, non-thermal X-ray emission. This emission probably originates from the inverse-Compton (IC) of seed stellar photons by GeV electrons produced by the wind-wind colliding (WWC) shock acceleration. The NuSTAR monitoring observations exhibit a continuous decline of the non-thermal flux ratio to the thermal flux through a binary orbit after the recovery, which was unexpected in the standard WWC shock acceleration models. This ratio is expected to be at a maximum during the next NuSTAR cycle. We propose 3 NuSTAR observations of eta Carinae to understand how the non-thermal emission recovers from the periastron decay and connects to the steady decline toward apastron.

Proposal Number: 6244
PI Name: MALLORY ROBERTS
Title: CATCHING THE TRANSITION OF THE HIGH B FIELD REDBACK PSR J2129-0429
Abstract: Redback millisecond pulsars serve as the link between radio millisecond pulsars and low-mass X-ray binaries, with several redbacks having transitioned from a radio pulsar state to an accretion state on timescales of months to years. PSR J2129-0429 is a gamma-ray and radio redback with an unusually high magnetic field (B ~ 1.8e9 G) and long pulse period (7.6 ms), suggesting it is relatively early in the recycling process. Observed changes in the color of the companion suggest it may transition to an LMXB state at any time, which would make it only the 4th redback to be observed transitioning. We propose to monitor the system with monthly Swift observations of ~ 3 ks in anticipation of a state change, at which point we would trigger an 100 ks NuStar TOO observation.

Proposal Number: 6245
PI Name: VALLIA ANTONIOU
Title: A HARD X-RAY LOOK OF A NEARBY BULGELESS SPIRAL GALAXY
Abstract: We propose 180ks NuSTAR observations of the spiral galaxy NGC2403, the most isolated of the 3 nearby morphologically analogous galaxies (3.2 Mpc) that hosts (a) a ULX source, NGC2403 X-1, with a black hole (BH) mass of 10-15 Mo; (b) a transient X-ray pulsar (Pspin = 18s) with one of the fastest observed decreased rates of Pspin; and (c) a substantial population of candidate Wolf-Rayet stars. The proposed observations (Lx,limit ~ 10^38 erg/s; 4-25 keV) will extend the non- uniform, across specific star-formation rate (sSFR), sample of galaxies used to derive the first scaling relations in the hard X-rays down to values of log(sSFR)~-10.4/yr. Two 45ks long supporting XMM observations will provide point source lists to localize and determine source characteristics in the NuSTAR observations.

Proposal Number: 6246
PI Name: KENJI HAMAGUCHI
Title: EXTREMELY HARD X-RAY EMISSION FROM WR140 AROUND APASTRON
Abstract: The wind-wind collision (WWC) in eccentric massive binary systems produces predictably variable shock-heated X-ray plasma. This collision provides an ideal laboratory for shock astrophysics, providing key constraints on how gas thermalizes at variable density and on particle acceleration. A series of NuSTAR observations of WR140 around periastron in 2016 has provided an interesting variation of the extremely hard X-ray component, which may originate from inverse-Compton scattering of stellar UV photons by particles accelerated at the WWC region. We propose one NuSTAR observation of WR140 around apastron to measure the intensity of the extremely hard X-ray component.

Proposal Number: 6247
PI Name: OLEG KARGALTSEV
Title: THE VELA PULSAR AND ITS PWN IN HARD X-RAYS
Abstract: Thanks to two decades of observations in soft X-rays, we have learned a lot about PWNe and pulsars powering them. Much less is known about the hard X-ray properties of PWNe and pulsars due to the limitations of hard X-ray instrumentation. The proposed observation of the famous nearby Vela PWN will, for the first time, resolve it in hard X-rays, providing an important addition to the small sample of PWNe observed by NuSTAR. Both the Vela pulsar and its PWN exhibit unusual spectral properties (multiple pulsed spectral components, very hard PWN spectrum) whose origin must be studied via sensitive observations. Hard X-ray measurements are critical because they bridge the optical/UV and GeV data on the pulsar and allow one to look for synchrotron cooling and maximum energy for the particle SED.

Proposal Number: 6248
PI Name: LEA MARCOTULLI
Title: CHASING THE MOST POWERFUL BLAZARS
Abstract: We request to observe 2 high redshift blazars with NuSTAR for a total of 50 ks. Detected in gamma-rays and by Swift-BAT, these sources are some of the most powerful of their class. We propose to observe it in the X-ray with NuSTAR, which will allow us to accurately measure the rising part of the inverse Compton (IC) spectrum up to 70 keV, expected to be very hard. Together with the LAT data, NuSTAR data will be fundamental to pinpointing the IC peak, determining the power of the jet, deriving the underlying electron population responsible for the emission and measuring the location of the emission region.

Proposal Number: 6250
PI Name: ANDREAS ZEZAS
Title: DEMOGRAPHICS OF THE COMPACT OBJECT POPULATIONS OF M81
Abstract: We propose two NuSTAR observations of the M81 disk that together with existing observations of its bulge will provide complete coverage of its X-ray binary populations down to luminosities of 10^38 erg/s. These observations together with a wealth of existing HST and multi-wavelength data will allow us to fully characterize its X-ray binary populations on the basis of their compact objects and donor stars. This will provide a complete picture of the demographics of the compact objects in a typical spiral galaxy and together with population synthesis models will allow us to constrain their formation and evolution paths.

Proposal Number: 6252
PI Name: PALLAVI PATIL
Title: UNVEILING THE NUCLEAR ENGINE OF A HEAVILY OBSCURED QUASAR WITH YOUNG RADIO JETS
Abstract: We propose a NuSTAR pilot study of a young, highly-reddened, ALMA CO-detected WISE AGN with recently-launched radio jets (extents ~ 8 kpc). Our key observational goals are to test the feasibility of X-ray observations, measure the accretion luminosity via spectral fits, and estimate the flux and obscuration of the intrinsic power-law for the target source. The direct measurements of the hard X-ray properties of this unique source that are possible only with NuSTAR will allow us to better constrain the energetics and conditions in the central engine during a critical, yet less understood stage of galaxy evolution. Ultimately, our goal is to pave the way for future X-ray studies targeting larger samples of this unique population of obscured quasars with nascent jets.

Proposal Number: 6253
PI Name: PETER BOORMAN
Title: VALIDATING A NEW AGN SELECTION AS A MEANS TO CONSTRUCT THE LOCAL CENSUS OF AGN
Abstract: To tackle some of the biggest ongoing questions regarding AGN activity and feedback, we are constructing a complete census of local Seyfert-luminosity AGN. The Local AGN Survey (LASr) is a multi-tiered selection of AGN designed to reveal all AGN in the local Universe, even in the presence of heavy obscuration. As a proof-of-concept, we propose 3x100ks NuSTAR observations of 3 previously-unknown Compton-thick AGN candidates to quantify the efficiency of our selection. Extensive simulations show that the requested exposure is sufficient to confirm the presence or lack of a heavily obscured AGN to high significance in each. The observations will test the robustness of the LASr selection and pave the way towards achieving it's primary goal: mitigating obscuration biases of AGN selection.

Proposal Number: 6259
PI Name: JESSIE DUNCAN
Title: COORDINATED NUSTAR OBSERVATION IN SUPPORT OF SIX EARTH-SIDE PARKER SOLAR PROBE PERIHELIA
Abstract: The goal of this proposal is to take advantage of opportunities for co-observation between NuSTAR and the Parker Solar Probe (PSP) during six of the PSP perihelia ocurring during NuSTAR GO Cycles 6 & 7. These Earth-facing perihelia provide compelling opportunities to combine NuSTAR s capability for highly sensitive remote X-ray observation with PSP s powerful suite of in-situ instruments. By arranging these co-observations, the capacity of NuSTAR and PSP will be used in tandem to examine connectivity between the corona and the inner heliosphere. Additionally, solar observations performed at these times will allow the NuSTAR observatory to continue to contribute to the rich, multi-instrument solar datasets achieved when the heliophysics community unites in support of each PSP perihelia.

Proposal Number: 6263
PI Name: SULOV CHALISE
Title: PROBING THE TORUS OF TWO POLAR SCATTERED SEYFERT 1 GALAXIES, MRK 1218 AND UGC 7064, 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 two Seyfert 1.9 galaxies, Mrk 1218 and UGC 7064 using the archival soft X_ray data and 75 ks of new NuSTAR observations each. These two sources, which are also polar-scattered Seyfert 1 galaxies (PSS), are the only two out of the known 12 PSS sources to not have any archival hard X-ray spectra. Thus, these observations would also complete the data and will allow us to study the torus of the whole PSS sample.