Proposal Number: 3005
PI Last Name: Nielsen
Title: OBSERVATION OF POSSIBLE CYCLOTRON RESONANCE SCATTERING FEATURE IN THE X-RAY PULSAR 2A 1822-371
Abstract: We propose to conduct a 30 ks observation with NuStar, which would give new insight into the strength of the magnetic field of the X-ray pulsar 2A 1822-371 and thus give insight into the geometry of this source. With this NuStar observation we will be able to confirm if this pulsar has a high magnetic field as observed in similar sources or if it has a lower magnetic field.

Proposal Number: 3009
PI Last Name: Bianchi
Title: THE NUSTAR-XMM MONITORING OF THE HIGH ACCRETION RATE SEYFERT 1 HE1143-1810
Abstract: We propose a joint NuSTAR/XMM monitoring of the high accretion rate Seyfert 1 HE 1143-1810 (L/Ledd>0.5), consisting of 5x20 ks observations spaced by 2-3 days. The source is an ideal candidate to obtain high sensitivity measurements over a broad (UV/hard X-rays) high-energy spectrum, which will allow us to: 1) study the UV/X-ray spectrum with the highest possible accuracy and test physically motivated Comptonization models, 2) investigate the nature of the soft X-ray excess, and 3) put firm conclusions on the reflection component. These observations will allow for a direct comparison with different sources, in particular with a similar, successful NuSTAR/XMM monitoring of NGC 4593 (L/Ledd<0.15).

Proposal Number: 3013
PI Last Name: Ghisellini
Title: THE MOST POWERFUL GAMMA RAY LOUD BLAZARS
Abstract: We propose to observe 4 blazars at z>2, detected in the gamma-rays by Fermi/LAT and in the soft X-rays, but not yet observed at energies larger than 10 keV. They are among the most powerful blazars and they host black holes whose masses exceed 1e9 Msun. The total requested time of 80 ks is sufficient to establish flux and slope of their X-ray continuum in order to estimate their total electromagnetic output and peak frequency, combined with the Fermi gamma-ray data. This will shed light on the jet-accretion relation, on the controversy about the blazar sequence at its high power extreme, and about the formation epoch of supermassive black holes in jetted quasars.

Proposal Number: 3015
PI Last Name: Marinucci
Title: LOCATING THE ABSORBING STRUCTURE IN NGC 1068 VIA HARD X-RAY MONITORING
Abstract: We propose four 50 ks NuSTAR observations of the Seyfert galaxy NGC 1068, the archetypal and one of the brightest Compton-thick Seyfert 2s. A flux excess above 20 keV was discovered by NuSTAR in the August 2014 observation, with respect to observations performed 20 months earlier, and 6 months later. This variability is ascribed to Compton-thick material (with column density NH>2.5 10^24 cm^-2 ) moving temporarily out from our line of sight, allowing the nuclear radiation to pierce through the circumnuclear absorbing material. NuSTAR is the only telescope in orbit that permits a search for such column density variations in this energy band. This monitoring program aims to estimate the distance of the variable absorber, to check if it is consistent with the pc-scale torus.

Proposal Number: 3018
PI Last Name: Sidoli
Title: CYCLOTRON LINES IN THE SFXT PULSAR IGRJ11215-5952
Abstract: Supergiant Fast X-ray Transients are massive X-ray binaries showing rare, sporadic and short outbursts that cannot be simply produced by Bondi-Hoyle accretion of supergiant wind onto the neutron star. At present, two competing scenarii have been proposed, involving magnetar-like neutron star magnetic fields (1e14 G) versus more typical values (1e12 G). IGRJ11215-5952 is the only SFXT with predictable outbursts, occurring every 165 days. This allows us to propose a NuSTAR observation (40 ks) during next outburst, to confirm the hint of a cyclotron line we found at 17 keV during a previous shorter NuSTAR pointing. This confirmation is of paramount importance to disentangle among the competing scenarii.

Proposal Number: 3028
PI Last Name: An
Title: UNDERSTANDING PARTICLE ACCELERATION AND TRANSPORT MECHANISM IN PWNE
Abstract: A pulsar wind nebula (PWN) is an extended structure surrounding a pulsar and is powered by the rotation energy of the central pulsar. The pulsar wind shocks against a surrounding medium, so that the particles accelerate, pitch angle scatter, and radiate in the PWN. Since particles are expected to be accelerated to very high energy ~100 TeV, the study of PWN X-ray spectra can illuminate the injected (accelerated) spectrum and transport of such particles. Here, we request a 70-ks NuSTAR observation of the TeV PWN 3C 58. Our prime goal is to measure the broadband spectral energy distribution (SED) of 3C 58 and to model the PWN emission for constraining the acceleration process in this PWN and to search the PWN spectrum for a Crab-like hard X-ray break.

Proposal Number: 3040
PI Last Name: Miller
Title: A NUSTAR SURVEY OF OBSCURED AGN IN THE LOCAL UNIVERSE
Abstract: We propose to use a complete, volume-limited sample of AGN to obtain an accurate measurement of the column density distribution of AGN in the local universe. At the same time, we will measure the volume emissivity of hard X-ray emission in the local universe, which can be an important component in ionization and feedback. The survey is modest, and reasonable exposure times have been estimated with the aid of the Swift/BAT 105-month catalog. NuSTAR has only observed a few sources from this sample, but we need only 420 ks to observe the remaining sources in a quasi-uniform manner.

Proposal Number: 3041
PI Last Name: Staubert
Title: MONITORING THE CYCLTRON LINEE ENERGY IN HERCULES X-1: FOLLOW THE LONG-TERM VARIABILITY
Abstract: We propose to continue the study of the long-term evolution of the cyclotron line energy Ecyc in Her X-1. The long-term decay of Ecyc between 1993 and 2012, was confirmed by NuSTAR observations, firmly establishing a decay by ~5 keV over the last 20 yrs. However, the last observing campaign in 2016, coordinated between NuSTAR and INTEGRAL has provided evidence that the decay has ended, in fact hinting at a possible increase, similar to the increase observed between 1990 and 1993. We had speculated that a new increase might happen, once Ecyc had reached a low level similar to the time at the discovery. We therefore propose to continue the monitoring of Her X-1 during Cycle-3 with two observations of 30 ks each: the first as soon as possible, the second half a year later.

Proposal Number: 3044
PI Last Name: Fabian
Title: THE PAIR CONSTRAINT ON CORONAL TEMPERATURES IN SEYFERT 1 GALAXIES
Abstract: What determines the coronal temperature in AGN is much debated. One plausible possibility is the Pair Thermostat, where heating drives the temperature up to the point at which electron-positron pairs are produced in significant quantity to control further temperature rise. Hybrid plasmas, in which most pairs are produced by a small nonthermal fraction, can lead to still lower coronal temperatures. We propose to use NuSTAR to observe 3 hard X-ray bright AGN with low temperatures (30-40 keV) measured by INTEGRAL in order to test this hypothesis. NuSTAR will give snapshot spectra of the objects, correct for relativistic reflection and be at much higher precision than Integral.

Proposal Number: 3045
PI Last Name: Sartori
Title: PROBING THE LIFECYCLE OF SUPERMASSIVE BLACK HOLES ON 10-100 KYR TIMESCALES
Abstract: We identified a sample of low-z galaxies with extended AGN photoionised clouds indicative of a powerful AGN, the Voorwerpjes (VP). Far-IR and X-ray data suggest that the current luminosity of some of these AGN is lower than what expected from the VP. This may signify that the AGN dropped in luminosity in the last 10-100 kyr, but the clouds remain lit up because of the travel time of the ionising photons. NuSTAR observations are the best probe of the current AGN state. We propose to observe 4 VP related galaxies with no hard X-ray data available, completing the investigation of the shut down AGN candidates sample. We will probe if the AGN are shutting down, and the magnitude of the drop in luminosity. With this sample we will study AGN variability on previously unreachable timescales.

Proposal Number: 3048
PI Last Name: Pavlov
Title: SPECTRAL AND TIMING PROPERTIES OF THE YOUNG, ENERGETIC PSR J1617-5055 IN HARD X-RAYS
Abstract: Observations of hard X-ray emission from rotation-powered pulsars are crucial for understanding the physics of pulsar magnetospheres. However, only a handful of brightest pulsars have been observed at these energies, and most of them have not been investigated in detail. To probe the magnetosphere of the young, energetic PSR J1617-5055, whose properties are drastically different from those of the best-investigated Crab pulsar, we propose a NuSTAR observation for phase-resolved spectroscopy and energy-resolved timing of pulsar radiation. Being bright in hard X-rays, this pulsar has a very underluminous pulsar wind nebula, which greatly facilitates NuSTAR data analysis.

Proposal Number: 3054
PI Last Name: Margutti
Title: DETAILED MAPPING OF EXTREME MASS LOSS WITH COORDINATED NUSTAR-XMM OBSERVATIONS
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 NuSTAR-XMM 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.

Proposal Number: 3057
PI Last Name: Park
Title: SPECTRAL NATURE OF THE QUIESCENT X-RAYS FROM SGR 0526-66
Abstract: Unlike most magnetars the soft Gamma-ray repeater (SGR) 0526-66 has been in a quiescent state for decades, and is projected within the boundary of a supernova remnant (SNR N49). This object represents a rare opportunity for the study of the long-term cooling and structural evolution of a magnetar after its conspicuous outbursts. The nature of the progenitor star to create a magnetar may also be studied directly through the host supernova remnant, if this SGR is physically associated with SNR N49. The origin of the X-ray emission in the quiescent state, a key component for such studies, is elusive. NuSTAR is a unique opportunity to reveal the spectral nature of 0526-66's X-ray emission, and thus we request a 50 ks NuSTAR observation of the quiescent state 0526-66.

Proposal Number: 3059
PI Last Name: Madsen
Title: CATCHING THE FLARING JET OF 3C 273
Abstract: The gamma-ray flaring of the jet in 3C273 is a rare event and seen just twice over the last 5 years. Only once before has a hard X-ray instrument been pointed at 3C273 during such a confirmed event, and we request 75ks to observe the impact of the bright jet state on the X-ray band. NuSTAR is the only observatory currently capable of probing the hard X-ray turnover with sufficient sensitivity during such a rare event, and the observation will provide unprecedented details on this complex transition region between AGN and jet, and perhaps once and for all solve the mystery of whether the curvature of the hard X-ray spectrum comes primarily from the accretion flow of the AGN component, or from a SSC+ERC jet.

Proposal Number: 3062
PI Last Name: Yamaguchi
Title: REVEALING THE ORIGIN OF THE THERMAL AND NONTHERMAL EMISSION FROM THE SUPERNOVA REMNANT W49B
Abstract: The supernova remnant (SNR) W49B is an extremely intriguing object in both thermal and nonthermal aspects. Regarding the former, recent Suzaku observations discovered an overionized plasma from this SNR, but its formation mechanism is still under debate. Regarding the latter, Fermi and HESS detected extremely luminous gamma-ray emission, but whether it originates from hadronic or leptonic processes is not conclusively determined. Here we propose a 100-ks NuSTAR observation of W49B to solve these important open issues through spatially-resolved spectral analysis in the hard X-ray band. The data will certainly provide deep insight into the SNR evolution and efficient cosmic-ray acceleration.

Proposal Number: 3069
PI Last Name: Margutti
Title: CONTINUED NUSTAR MONITORING OF THE UNPRECEDENTED METAMORPHOSIS OF SN2014C AT T>1000 DAYS SINCE EXPLOSION
Abstract: Mass loss in evolved massive stars is one of the least understood yet fundamental aspects of stellar evolution. HOW and WHEN do massive stars lose their H-envelopes? This central question motivates this proposal. We request a continuation of our successful NuSTAR campaign that led to the first detection of a H-poor extragalactic SN in the hard X-rays. We request NuSTAR observations to map the unique situation of the interaction of the H-stripped SN2014C with a H-rich shell ejected by its progenitor star, as part of our approved gamma-ray to radio follow up. Our goal is to complete the mapping of the density profile of the H-rich material at R>7d17 cm to determine its location and total mass, and hence the mass-loss history of the progenitor in the years before stellar death.

Proposal Number: 3070
PI Last Name: Miller
Title: NEUTRON STARS AND THEIR INNERMOST ACCRETION FLOWS
Abstract: We propose to observe the neutron star low-mass X-ray binaries and Atoll sources GX 3+1, 4U 0614+09, 4U 1735-44, 4U 1746-37, and 4U 1702-43, for 20 ks each. Our primary goal is to increase the number of neutron stars with clear, robust indications of relativistic reflection from the inner disk. These observations will also address the radial extent of the inner disk in Atoll sources, which likely accrete at a low Eddington fraction similar to the black hole low/hard state. Our final goal is to find examples of disks that extend very close to stellar surfaces in order to obtain limits on neutron star radii.

Proposal Number: 3080
PI Last Name: Garcia
Title: THE EVOLUTION OF THE ACCRETION DISK IN GX 339-4
Abstract: X-ray reflection spectroscopy is one of the most effective means of probing the strong-field region near an event horizon. Modeling a reflection spectrum, one can constrain the spin of a black hole, the degree of truncation of the inner disk, the inclination of the system, and other key parameters. We request 80 ks of NuSTAR time to trigger four observations of the black hole binary GX 339-4 during the rise of its next outburst. Our principal goal is to track the radius of the inner edge of the accretion disk in the hard state as a function of luminosity, as we have done before using RXTE data. Using NuSTAR advanced capabilities, we aim to resolve the gross discrepancies in published measurements of the inner disk radius.

Proposal Number: 3087
PI Last Name: Lamassa
Title: MODELING THE OBSCURATION AROUND EXTREME AGN NGC 4968
Abstract: NGC 4968, a nearby Seyfert 2 galaxy, has an extreme Fe K-alpha equivalent width (EW = ~2.5 keV), a hallmark of Compton-thick obscuration. Hints from the Chandra spectrum suggest this obscuration has a spherical covering geometry, which could possibly be fed by circumnuclear star formation. We request 2 20 ks NuSTAR observations, spaced >= 6 months apart, to measure the column density and geometry of the X-ray reprocessor, calculate the intrinsic X-ray luminosity and compare that with the mid-infrared emission, and to search for variability similar to that observed in NGC 1068, the prototypical Compton-thick AGN which also has an extreme Fe K-alpha EW. Evidence of variability would provide insight into the physics of the central engine and perhaps distance to the X-ray reprocessor.

Proposal Number: 3095
PI Last Name: Wong
Title: NATURE OF HARD X-RAYS FROM A TEV EMITTING RADIO GALAXY
Abstract: We propose to study one of the four FRI radio galaxies with detected TeV emission, PKS 0625-354. It hosts a billion solar mass black hole emitting at 0.2% Eddington luminosity, generally associated with a radiatively inefficient accretion flow (RIAF). It has been studied in radio to TeV bands, suggesting that the TeV and X-ray emission comes from a jet. 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 distinguish the X-ray emission model. With the excellent sensitivity of NuSTAR, we will study the nature of the hard X-rays from this rare TeV FRI radio galaxy and will provide constraints on hard X-ray emission models: do they have a jet or an accretion flow origin?

Proposal Number: 3096
PI Last Name: Kawamuro
Title: FIRST DETECTION OF BURIED ACTIVE GALACTIC NUCLEI IN EARLY STAGE OF GALAXY FORMATION: GREEN PEA GALAXIES
Abstract: We propose NuSTAR observations of two green pea galaxies (GPs) with an exposure of 20 ksec for each to detect hard X-ray emission as a direct AGN sign. GPs offer valuable opportunity to study the supermassive black hole (SMBH) growth in an early stage of the galaxy formation. Our goal is to investigate whether the AGN resides in such an immature galaxy. Observables ever obtained suggest that our targets can host a buried AGN. Weak optical high excitation lines and the absence of broad lines do not necessarily mean the absence of an AGN. As an alternative idea, these facts could suggest that the AGN is highly obscured if any. Also, the high X-ray luminosity to star formation rate ratios infer the presence. Thus, detecting less extincted hard X-rays is important to finally unveil the AGN.

Proposal Number: 3112
PI Last Name: Marinucci
Title: INVESTIGATING THE VARIABLE CORONAL ENVIRONMENT OF THE SEYFERT 1 GALAXY GRS 1734-292
Abstract: We propose an observation of the Seyfert 1 galaxy GRS 1734-292 with NuSTAR, 25 ks long. Our primary aim is to search for changes in the variable coronal environment of this source, which has recently shown one of the lowest high-energy cutoff in the NuSTAR era (Ec=53+11-8 keV: Tortosa et al., 2016). GRS 1734-292 is the perfect candidate for this goal: it is a bright Seyfert 1 galaxy which showed a variable primary continuum (both in spectral shape and in flux), on time scales of years. The comparison between past data and the hereby proposed observation will allow us to infer, with high accuracy, a variation in the physical parameters of the corona surrounding the accretion disk in GRS 1734-292.

Proposal Number: 3113
PI Last Name: Ota
Title: UNVEILING THE NATURE OF HARD X-RAY EXCESS IN A DISTANT GALAXY CLUSTER RX J1347.5-1145
Abstract: We propose to observe a merging galaxy cluster RX J1347.5-1145 at z=0.451 with NuSTAR to 1) distinguish between thermal and non-thermal origins of the excess hard component detected by Suzaku and 2) identify its peak position in hard X-rays. If the measured spectrum follows a power-law, we will achieve either the first detection of the non-thermal hard X-ray emission from galaxy clusters or the thermal emission in excess of 25 keV. If it is thermal, we will significantly improve both accuracy of gas temperature and limits on the magnetic field strength in this distant cluster. NuSTAR's hard X-ray spectroscopy and imaging capability are crucial for this study.

Proposal Number: 3115
PI Last Name: Lohfink
Title: EXPLORING THE HARD X-RAY SPECTRUM OF THE HIGH EDDINGTON BROAD-LINE RADIO GALAXY 3C 109
Abstract: The X-ray reflection spectrum from the inner parts of the accretion disk is one of the key sources of information about the structure of the innermost regions around the black hole. While it has provided us with valuable details in radio-quiet AGN, few radio-loud objects have been studied with similar detail. However these studies of the innermost regions are needed, as it is there that relativistic jets are thought to be launched. Here, we propose to study the reflection spectrum of the broad-line radio galaxy 3C 109. 3C 109 is a particularly interesting target as it is the only radio galaxy with an Eddington fraction exceeding unity. Our findings will be placed into context of studies of reflection in other radio-loud and radio-quiet sources.

Proposal Number: 3127
PI Last Name: Krucker
Title: USING DISK-OCCULATION TO STUDY NON-THERMAL PROCESSES IN SOLAR ACTIVE REGIONS
Abstract: The aim of this proposal is to search for X-ray bremsstrahlung signatures produced by non-thermal electrons in the solar corona within active regions. Such electrons are thought to be accelerated by the release of coronal magnetic energy. The X-ray signatures of these events are predicted to be one of the smoking guns to identify the heating mechanism of the solar corona. Here we propose to use the solar disk as a natural occulter to shield NuSTAR from the intense thermal soft X-rays and observe non-thermal signatures from the corona. With the requested 80 ks (25 orbits), we are confident that we will catch several occulted microflares/nanoflares with at least one event seen during the impulsive rise phase.

Proposal Number: 3131
PI Last Name: Zappacosta
Title: CONSTRAINING THE NON-LOCAL COMPTON THICK AGN FRACTION IN THE NUSTAR 8-24 KEV BAND
Abstract: Through a joint NuSTAR+XMM/Chandra spectroscopic analysis we have obtained the column density (Nh) distribution for a sample of 63 bright hard-band detected AGN selected in the NuSTAR survey fields. This is the most sensitive Compton Thick (CT) AGN search to date from a blind >10 keV sample. The two faintest candidates for being the most obscured AGN in the sample lack low-energy data and have Nh upper/lower limits consistent with being heavily obscured/CT. We are proposing a joint NuSTAR+XMM observation of these sources in order to complete the CT census. This will effectively double the observed fraction of CT AGN in our sample and will give us the opportunity to challenge X-ray Background population synthesis models directly aiming at the major contributors to the 20-30 keV peak.

Proposal Number: 3135
PI Last Name: Koljonen
Title: TESTING THE MAGNETIC FLUX PARADIGM WITH RADIO INTERMEDIATE QUASARS
Abstract: In this proposal, we seek to test the new magnetic flux paradigm for AGN jet production, which claims that the magnetic flux threading the black hole is the dominant factor determining the wide distribution of observed jet powers. We propose to constrain the black hole spin values of two radio intermediate quasars by using joint NuSTAR-XMM observations, and compare them to the jet magnetic flux measurements obtained via radio observations with the Very Long Baseline Array. The jet production efficiency in these sources is lower compared to powerful radio-loud quasars and we aim to find out, if this is due to their low black hole spin value, or them having failed to accumulate enough magnetic flux.

Proposal Number: 3136
PI Last Name: Tanaka
Title: A NUSTAR STUDY OF A HARD X-RAY EMISSION DISCOVERED IN THE SUPERNOVA REMNANT W44
Abstract: We propose a 50-ks NuSTAR observation of a hard X-ray emission in the supernova remnant W44 recently discovered by Suzaku. The Suzaku XIS spectrum of the emission is described by a power law with a photon index of 1.5. The hard spectrum is consistent with nonthermal bremsstrahlung either by electrons or protons. If this scenario is the case, we can probe low-energy particles accelerated in W44, which cannot be done in any other wavelengths. In the hard X-ray band, the power-law component becomes dominant over the thermal emission. Therefore, a NuSTAR observation is essential to determine the spectral slope and flux of the hard component and to disentangle possible emission mechanisms.

Proposal Number: 3138
PI Last Name: Walton
Title: TRACKING THE NEUTRON STAR ULX NGC7793 P13 WITH NUSTAR
Abstract: Following a series of remarkable recent discoveries, we now know that some of the most luminous members of the ultraluminous X-ray source (ULX) population are actually powered by apparently super-Eddington neutron star accretors. Three such systems are now known: M82 X-2, NGC7793 P13, and NGC5907 ULX1. Here we propose 2x75ks NuSTAR observations of P13 in order to extend our approved XMM-Newton program and track the evolution of the pulse period and the spectral properties of P13 across a full cycle of the 64d period exhibited by this source, and test its proposed orbital nature. Out of the three ULX pulsars currently known, the low absorption and lack of source confusion make P13 a key laboratory for such systems.

Proposal Number: 3145
PI Last Name: Walton
Title: MULTI-EPOCH BROADBAND X-RAY SPECTROSCOPY OF THE ULTRALUMINOUS X-RAY SOURCE NGC1313 X-1
Abstract: We request 5x75ks NuSTAR observations of the ultraluminous X-ray source (ULX) NGC1313 X-1 (375ks in total), to be coordinated with the very large XMM-Newton (750ks) and Chandra (500ks) follow-up programs our team has been awarded to study its extreme (~0.2-0.25c) outflow. The addition of NuSTAR observations to these programs will allow us to perform multi-epoch broadband spectroscopy, robustly determining the continuum and thus allowing us to better study the ionization structure and variability of this outflow, as well as undertaking broadband spectral variability studies for comparison with other ULXs. NGC1313 X-1 is the only source for which this is currently possible, so it is vital we take advantage of this unique opportunity.

Proposal Number: 3148
PI Last Name: Brenneman
Title: PROBING THE OBSCURING WIND, DISK AND CORONA IN NGC 3516
Abstract: We propose two 90-ks NuSTAR observations of NGC 3516 with a cadence of three weeks, to be executed contemporaneously with the already-scheduled 90-ks Chandra/LETGS observations in 2017. The NuSTAR data will enable tracking of broadband X-ray spectral and flux changes in this notoriously variable source and will also facilitate accurate modeling of its AGN continuum. This will significantly augment the science return of the Chandra observations, allowing more accurate and precise measurements of the properties of a new obscuring wind from this AGN as well as providing important insight into the driving mechanism(s) of AGN winds and their role in AGN/galaxy coevolution. The NuSTAR data will also yield the most accurate probe of the corona and reflection spectrum in this source.

Proposal Number: 3164
PI Last Name: Borghese
Title: THE FIRST HARD X-RAY OBSERVATION OF THE PUZZLING SOURCE 1E 161348-5055 TOWARDS THE QUIESCENT STATE
Abstract: 1E 161348-5055 (1E 161348), the source at the center of the supernova remnant RCW103, has defied any easy classification since its discovery. Because of its puzzling behavior (a long periodicity of 6.67 hr and a strong variability) it is challenging to interpret it within the standard neutron-star scenarios. On June 2016, 1E 161348 emitted a magnetar-like millisecond burst of hard X-rays accompanied with a factor ~ 100 brightening in the persistent soft X-ray emission. This recent episode suggests that 1E 161348 is an isolated magnetar with an incredibly slow spin period. We ask for a new 70 ks observation with NuSTAR to characterize the nature and phenomenology of this unique source while it recovers from its recent outburst.

Proposal Number: 3190
PI Last Name: Privon
Title: DO COMPTON-THICK AGN LURK IN HCN-ENHANCED LIRGS?
Abstract: Stars are widely understood to form from molecular gas, so knowledge of the molecular ISM is a key ingredient in understanding galaxy formation. Emission from the HCN molecule has been invoked both as a tracer of dense gas and of embedded AGN. We a pursuing a multi-wavelength campaign to understand the ISM and nuclear activity in local IR lumionus galaxies. We have identified starburst galaxies with HCN enhancements (relative to emission from HCO+) similar to those seen in AGN, suggesting they may host Compton-thick AGN. We reqeust NuSTAR observations of four targets to detect or put stringent upper limits (~1% of Lbol) on buried AGN. These data will be used to improve our understanding of the excitation of dense molecular gas tracers and test this proposed method of finding buried AGN.

Proposal Number: 3194
PI Last Name: Ward
Title: HARD X-RAY OBSERVATIONS OF GAMMA-RAY DETECTED SEYFERTS
Abstract: Gamma-ray Narrow Line Seyfert 1 s (NLS1) are a new class of AGN detected at GeV energies by Fermi which extend the domain of relativistic jets sources down to lower black hole masses. We have 8m Gemini near-IR spectra of some objects and estimated black hole masses from their Balmer and Paschen line profiles. We also now have VLT time (2017). We propose NuSTAR (with standard short SWIFT) observations of 3 gamma-ray NLS1s to build broad band SEDs which we will fit with our newly developed models for the jet and disc components. We will use the results to determine the relationship between the gamma-ray NLS1s, and the similarly high Eddington ratio flat spectrum gamma-ray radio quasars to determine how the jet properties relate to black hole mass.

Proposal Number: 3195
PI Last Name: Nelson
Title: UNDERSTANDING THE GAMMA-RAY PRODUCTION MECHANISM IN NOVA SHOCKS
Abstract: We request a 60 ks target-of-opportunity observation of the next gamma-ray-bright nova. The detection of gamma-rays from novae demonstrates that they are capable of accelerating particles to high energies. However, the site of particle acceleration, and the mechanism responsible for the gamma-ray emission, remains poorly understood. X-ray observations at E > 20 keV can probe the low-energy tail of the non-thermal emission that is detected by theFermi-LAT and provide important constraints on the physical conditions in the particle-accelerating shock. NuSTAR, with its unprecedented sensitivity above 10 keV, can therefore provide a unique probe of the shocks taking place in nova outbursts at early times.

Proposal Number: 3197
PI Last Name: Lanzuisi
Title: THE HIGH-ENERGY CUT-OFF IN HIGH-Z QSOS: A FIRST CUT
Abstract: We propose NuSTAR observations of two among the X-ray brightest (F_0.5-10 > 5 10^-13 ergs s^-1 cm^-2, L_2-10 > 10^45 ergs s^-1) radio-quiet QSOs at z > 1.8, complemented by a joint, short XMM-Newton exposure for one of them. Our total time request is 250ks with NuSTAR and 30ks with XMM-Newton. By looking at rest-frame energies up to ~ 200-300 keV, our goal is to measure unambiguously the presence of spectral cut-offs at rest-frame energies as high as E_c=500 keV. This is not possible for targets in the local Universe, where NuSTAR is just sensitive to E_c < 250 keV. Our sample is unique and will allow unprecedented measurements of E_c in distant AGN with such X-ray luminosities. Our program will prove for the first time whether there is a physical limit to the temperature of AGN

Proposal Number: 3200
PI Last Name: Miniutti
Title: EXPLORING THE JET-WIND CONNECTION IN MRK 231
Abstract: We propose for two 80 ks TOO observations of Mrk 231 with NuSTAR. We aim at obtaining two high quality NuSTAR X-ray spectra, one during a quiescent radio state, the other during a bright radio flare. Results from our previous radio and X-ray campaign show that low radio flux states are associated with the appearance of an X-ray ultra fast outflow (UFO) that is not detected during radio flares. This suggests that winds and jets could be mutually exclusive, as is the case in black hole X-ray binaries. We aim at confirming this behaviour with better statistics and at a different epoch to exclude chance coincidence. The resulting intermittent nature of UFOs in AGN, and the associated jet-wind anti-correlation will have an important impact on wind-driven AGN feedback models.

Proposal Number: 3209
PI Last Name: Neilsen
Title: GRAVITY, VARIABILITY, AND WINDS IN GRS 1915+105 WITH NUSTAR AND CHANDRA
Abstract: We propose 2 25 ks NuSTAR observations of the enigmatic microquasar GRS 1915+105 designed to study its accretion instabilities, ionized winds, Comptonization and reflection processes in coordination with our existing Chandra GTO program. With the ability to track the ionizing radiation field, wind absorption lines, and the behavior of the disk and corona simultaneously, NuSTAR is ideal for probing connections between inflows, outflows, and radiation with Chandra. Our previous work on winds and GRS 1915+105 with Chandra, Suzaku, and RXTE has provided numerous discoveries about the physics of accretion and ejection around stellar mass black holes. With this proposal, we aim to grow a legacy dataset and further our understanding of the extreme accretion physics of this remarkable source.

Proposal Number: 3216
PI Last Name: Powell
Title: WHAT IS CAUSING THE NEW, EXTREME VARIABILITY IN MRK 1018?
Abstract: We propose a 40 ksec observation of Mrk 1018, a `changing-look' AGN changing optical type to a Type 1.9 after 30 stable years of being a Type 1 (McElroy et al. 2016, Husemann et al. 2016). After dropping by an order of magnitude over the last two years, the optical continuum is now again on the rise, hinting at a return to increased accretion activity. We are monitoring Mrk 1018's ongoing extreme variability from the radio through X-ray, but new NuSTAR observation is critically needed to probe the innermost regions surrounding the accretion disk in order to further constrain scenarios that might account for these dramatic, rapid, and cross-spectrum changes.

Proposal Number: 3217
PI Last Name: Yukita
Title: MONITORING X-RAY BINARIES IN THE M31 BULGE WITH NUSTAR
Abstract: We propose three 40 ks observations to continue monitoring the M31 bulge, the region of the galaxy with highest source density, with NuSTAR. The previous NuSTAR observations detected ~ 30 bulge X-ray binary (XRB) systems, in one of the richest local environments for temporal and spectral monitoring of old stellar populations outside our own galaxy. We will provide better constraints on the nature of the resolved point sources (i.e., black hole (BH) binaries vs. neutron star (NS) binaries) by improving the signal-to-noise for the persistent sources and investigating variability to examine spectral transitions in BH and NS binaries to determine accretion states.

Proposal Number: 3220
PI Last Name: Gotthelf
Title: THE TRANSFORMATIVE YOUNG PULSAR PSR J1846-0258 IN SNR KES 75
Abstract: The discovery of magnetar-like activity from the young rotation-powered pulsar (RPP) in the supernova remnant (SNR) Kes 75 offers a unique opportunity to study the connection between RPPs and magnetars, their birth and early evolution. PSR J1846-0258 and its wind nebula also provide a unique window on shock acceleration physics taking place in some of the highest B-fields known in nature. We propose a joint NuSTAR/XMM-Newton observation of Kes 75 to characterize its hard X-ray emission in a critical energy band and search for a spectral break near ~10 keV, to help distinguish PWN from magnetar physics. For a transitionary object, this may indicate the emergence of a buried, magnetar strength field responsible for powering the rapid spin-down of the pulsar and its unusually energetic PWN

Proposal Number: 3224
PI Last Name: Steiner
Title: A NUSTAR & NICER LOOK AT COMPTONIZATION, REFLECTION, AND THERMAL EMISSION IN CYGNUS X-1
Abstract: Understanding the nature of the corona and disk-coronal interaction is a forefront challenge. While NuSTAR is the leading instrument at probing the high-energy spectral reflection component, NICER provides a complementary view of the thermal accretion disk. Both instruments handle bright sources without suffering from pileup effects. NICER is carrying out a monitoring program on Cyg X-1, the black-hole source for which disk and reflection components are most strongly intermingled, and with a disk that is cool and out of reach for NuSTAR alone. We ask for 6x20 ks NuSTAR observations of Cyg X-1 to be carried out at any time. NICER will work with NuSTAR to coordinate these observations and the NICER allotment is already approved.

Proposal Number: 3229
PI Last Name: Annuar
Title: A COMPLETE CENSUS OF THE COMPTON-THICK AGN POPULATION IN OUR COSMIC BACKYARD
Abstract: We propose for a total of 150 ks NuSTAR and 30 ks XMM-Newton observations to characterise the intrinsic power and obscuring properties of four of the nearest active galactic nuclei (AGN) to us. We are carrying out the first complete and direct measurement of the column density (N_H) distribution of AGN in a local volume-limited (D < 15 Mpc) AGN survey using primarily NuSTAR. Prior to our program, only 50% of the AGN had reliable obscuration measurements. We have recently improved this to 75%, and found a Compton-thick AGN fraction of at least 30%. This is higher than that directly measured in flux-limited AGN samples. NuSTAR observations of these four targets will be crucial in bringing the local N_H distribution of AGN to 100% completeness.

Proposal Number: 3231
PI Last Name: Mori
Title: NUSTAR HARD X-RAY PROBE INTO THE JOVIAN MAGNETOSPHERE IN SYNERGY WITH JUNO AND XMM-NEWTON
Abstract: Among the multi-wavelength observations coordinated with Juno, the NASA spacecraft orbiting Jupiter since July 2016, NuSTAR will make unique contributions to understanding non-thermal emission in the Jovian aurorae. Combined with Juno and XMM-Newton data (potentially with other telescopes such as Chandra and HST), the proposed NuSTAR observations provides a once-in-decades opportunity to explore (1) firm detection of hard X-ray emission from the aurorae above 7 keV, (2) comparison of the soft and hard X-ray morphology to probe potentially different X-ray emission mechanisms between the north and south poles, (3) detection of a sharp energy cutoff between 7 and 25 keV probing the maximum energy of accelerating electrons in the Jovian magnetosphere.

Proposal Number: 3237
PI Last Name: Kuraszkiewicz
Title: WHAT FRACTION OF POWERFUL RADIO GALAXIES IS COMPTON-THICK IN X-RAYS?
Abstract: A key unknown is how much of the accretion power in the universe is visible versus obscured. Our Chandra survey of luminous, radio-loud 3CRR AGN found that radio galaxies (RGs) have X-ray flux 10-1000 times lower than quasars of the same radio luminosity. The Unification hypothesis explains this as obscuration of the RGs with half of them being Compton thick (CT). However, the potential CT sources show relatively soft Chandra spectra, suggesting low obscuration and therefore low intrinsic luminosity. If obscuration causes the X-ray weakness, 50% of luminous AGN are obscured, and 25% are CT. The alternative is the existence of a new population of X-ray-weak AGN. We propose NuSTAR observations of six CT candidate high-redshift 3CRR radio galaxies to distinguish between these possibilities.

Proposal Number: 3240
PI Last Name: Scholz
Title: SEARCHING FOR MAGNETAR-LIKE X-RAY BURSTS FROM THE REPEATING FAST RADIO BURST
Abstract: Fast Radio Bursts (FRBs) are a new class of astrophysical transients whose origins are currently a mystery. Early this year, we reported on the subarcsecond localization and identification of the host galaxy of the first, and to date only, repeating FRB, FRB 121102 (Chatterjee et. al 2017). Some models, notably those involving magnetars, predict hard X-ray bursts along with FRBs which may be detectable with NuSTAR. The emission of radio bursts from FRB 121102 seem to be highly clustered in time. We therefore propose a 100 ks NuSTAR Target of Opportunity observation with coordinated radio telescope observations to be performed in the event that FRB 121102 enters a period of radio burst activity.

Proposal Number: 3243
PI Last Name: Lansbury
Title: THE HARDEST X-RAY SOURCE FOUND IN THE NUSTAR SERENDIPITOUS SURVEY: A DEEPER, BROADER LOOK
Abstract: Through our survey of all serendipitous sources detected with NuSTAR, we have found one source (J1506) which stands out in having the most extreme hard X-ray spectrum. The existing data suggest that J1506 is a Compton-thick (CT) AGN. There is currently a sparsity of such discoveries in the NuSTAR extragalactic surveys. In determining the nature of J1506 we are limited by: (1) the shallow depth of the off-axis (10.8ks) NuSTAR coverage, and (2) the lack of sensitive soft X-ray (<8keV) coverage. Here, we propose a deeper and broader-energy investigation using on-axis NuSTAR and XMM observations of 60ks and 30ks duration. These will dramatically improve the broad-band (~0.5-50keV) spectral constraints, detect iron line emission, and place stringent constraints on a merging companion galaxy.

Proposal Number: 3245
PI Last Name: Vincentelli
Title: GRS 1915+105 MULTI-WAVELENGTH FAST VARIABILITY
Abstract: In recent years, the study of the correlated X-ray/OIR fast variability in black-hole transients (BHTs) is showing more and more promising results. GRS 1915+105 was one of the first BHTs to be studied with a multi-wavelength approach, showing the first strong evidences for a disk-jet connection. As of today, only few X-ray-OIR simultaneous observations have been reported of this source. We therefore propose to participate with NuSTAR to an already approved multi-wavelength observing campaign to study the X-ray-IR fast variability, together with XMM-Newton and VLT, in order to cover the hard X-ray band. NuSTAR sensibility in the hard X-rays will be crucial to study the inflow-outflow connection without the accretion disc contamination.

Proposal Number: 3247
PI Last Name: Lanz
Title: MEASURING AGN LUMINOSITY IN THE EARLY STAGES OF TRANSITIONING IN IC860
Abstract: IC860 is a nearby IR-luminous early-type spiral with a unique set of properties: it is in the early stages of transition without clear signs of the triggering event for the transition, showing optical signatures of shocks and hosting an AGN-driven neutral wind and a compact core of molecular gas. New Hubble observations will trace the mass distribution in the neutral outflow. We propose to observe IC860 using NuSTAR for 70ks to measure the X-ray properties of its moderately to heavily obscured AGN and thereby gauge the relative mechanical and radiative powers applied by the AGN during this process, yielding insights into the role of AGN in driving outflows in transitioning galaxies.

Proposal Number: 3249
PI Last Name: Masini
Title: DISK MEGAMASERS IN LATE MERGERS. A CASE STUDY: NGC5765B
Abstract: We propose to observe NGC5765b with NuSTAR for 50 ks. NGC5765b is a recently discovered water disk megamaser, and candidate Compton-thick AGN in a close merger. In the X-ray band, only a short CHANDRA observation is available. The NuSTAR high-quality spectrum will constrain the X-ray spectral parameters of the source (e.g. photon index Gamma, column density NH, intrinsic luminosity Lx). Combining the latter with the precise BH mass derived from the maser kinematics, we will also obtain an accurate estimate of the Eddington ratio, LEdd.

Proposal Number: 3251
PI Last Name: Miller
Title: A NICER NUSTAR LOOK AT SERPENS X-1
Abstract: Numerous properties make Serpens X-1 the best candidate for constraints on the inner accretion flow and neutron star radius via disk reflection spectroscopy. We propose a joint NuSTAR (40 ks) and NICER observation of Serpens X-1, in order to obtain the best possible limits on the neutron star radius, the best measurements of the inner accretion flow, and to explore changes in the ionization of the disk with radius. The extraordinary sensitivity of NICER at and below 1 keV will be able to reveal relativistic Ne X and Fe L lines predicted by the prior NuSTAR exposure of Serpens X-1. We will maximize the return of these observations by utilizing new disk reflection models, optimized for neutron star X-ray binaries.

Proposal Number: 3258
PI Last Name: Marchesi
Title: COMPTON THICK AGN: THE PHYSICS BEHIND THE OBSCURATION
Abstract: The X-ray spectral analysis of Compton thick (CT-) active galactic nuclei (AGN) represents a fundamental step 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 volume-limited (z<0.03) sample. 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 and their contribution to the CXB.

Proposal Number: 3272
PI Last Name: Hamaguchi
Title: ON THE PATH OF UNDERSTANDING THE EXTREMELY HARD X-RAY COMPONENT OF ETA CARINAE
Abstract: The massive stellar binary system Eta Carinae drives strong shocks by the collision of winds from two stars. Our NuSTAR observations of Eta Carinae in 2015 and 2016 detected an extremely hard X-ray component over the thermal emission above 15 keV. The apparent absence of this component during the 2-10 keV X-ray minimum around periastron indicates that the source is located very close to the wind colliding region. This component may originate from inverse-Compton scattering of stellar UV by accelerated non-thermal particles and may be related to the Fermi GeV gamma-ray source. We propose a NuSTAR observation of the star in AO3 to monitor its variation when the gamma-ray emission above 10 GeV is expected to increase, and thus establish a crucial correlation between the two ranges.

Proposal Number: 3276
PI Last Name: Wik
Title: THE MERGER-MINIHALO CONNECTION IN THE OPHIUCHUS CLUSTER: A SMOKING GUN?
Abstract: The Ophiuchus cluster is the most massive galaxy cluster within 200 Mpc and it hosts a radio minihalo in its sloshing cool core, which one theoretical model predicts is the result of a minor merger, although the merging subcluster has never been clearly identified in any minihalo cluster. The minihalo is also thought to be the source of INTEGRAL-detected IC emission from the cluster. NuSTAR's hard band sensitivity and spatial resolving power makes it ideal for directly detecting the merging subcluster, for which there are hints at lower X-ray energies, but need confirmation due to complications with foreground absorption. It is also ideal for confirming the IC detection, which is critical given how controversial such detections have been in the past.

Proposal Number: 3279
PI Last Name: Paliya
Title: CHASING THE MOST POWERFUL BLAZARS
Abstract: MeV blazars, that have larger-than-average jet powers, accretion luminosities and black hole masses are best studied in the hard X-ray domain where they display extremely hard X-ray continua. Observations in this domain probe the acceleration & emission mechanisms, the bulk Lorentz factor. We propose to observe with NuSTAR the 4 highest-redshift that have ever been detected at gamma-rays and that do not have any observation between 10 keV and 100 MeV. We will complement the NuSTAR exposure with observations with Fermi, Swift, and SARA to obtain an high-quality simultaneous SED for all these sources. Moreover, optical spectroscopy will be performed for 3 targets lacking a kinematic measurement of the black hole mass. All this will greatly enhance our knowledge of this elusive source class.

Proposal Number: 3286
PI Last Name: Lobban
Title: SPECTRAL TIMING STUDIES OF IRAS 18325-5926
Abstract: Here we propose a simultaneous NuSTAR and XMM-Newton (100+50ks) observation of IRAS 18325-5926, a highly variable type-2 Seyfert galaxy and one of the very few with a claim of a broad FeK profile. Archival data have previously been insufficient to distinguish between a relativistically broadened Fe line and a blend of narrow Gaussians. However, we will be able to break the degeneracy thanks to the uninterrupted coverage of the NuSTAR bandpass extending well >10keV. Additionally, this source shows one of the clearest low-frequency lag-energy spectra to date with lags well defined up to 10keV. With NuSTAR we will extend our lag analysis up to >50keV, providing some of the most robust tests of Fourier-based inter-band time lag models to date.

Proposal Number: 3287
PI Last Name: Walton
Title: STRONG DISK REFLECTION IN THE SEYFERT 2 AGN IRAS 00521-7054
Abstract: Previous X-ray observations of the Seyfert 2 galaxy IRAS00521 show evidence for some of the strongest reflection from the accretion disk 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 a broadband X-ray spectrum dominated by reflection from the inner accretion disk. However, IRAS00521 has never been observed in the hard X-ray band. We request a coordinated broadband X-ray observation of this remarkable source with XMM (175ks) and NuSTAR (300ks). 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.

Proposal Number: 3288
PI Last Name: Hamaguchi
Title: EXTREMELY HARD X-RAY VARIATION OF WR140 AFTER PERIASTRON
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 various, shock densities and on particle acceleration. The campaign observation of WR 140 with NuSTAR and XMM around periastron in 2016 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 two joint NuSTAR and XMM observations of WR 140 in AO3 to monitor the variation of the extremely hard X-ray component during the flux decline after periastron.

Proposal Number: 3290
PI Last Name: Parkinson
Title: NUSTAR OBSERVATIONS OF SOFT GAMMA-RAY PULSARS
Abstract: Fermi has detected over 200 gamma-ray pulsars, but only a handful fall in the soft gamma-ray (emission peaking below 1 GeV) category. These tend to be single-pulsed, young, and extremely energetic, the archetypal example being PSR B1509-58. With the greatly improved sensitivity of Pass 8, Fermi is expected to detect increasing numbers of soft gamma-ray pulsars. We propose NuSTAR observations of 5 soft gamma-ray pulsar candidates. The unprecedented sensitivity of NuSTAR in the hard X-ray energy range, combined with existing soft X-ray and gamma-ray data (e.g. Chandra, XMM, and Fermi) will enable us to test and constrain models of high-energy pulsar emission over a range of parameters (e.g. viewing geometries, spind-down parameters).

Proposal Number: 3295
PI Last Name: Lin
Title: NUSTAR SURVEY OF BRIGHT X-RAY SOURCES IN M32
Abstract: X-ray binaries (XBs) in nearby galaxies have been studied for decades. However, their nature largely remains illusive, mainly due to the lack of hard X-ray coverage. With the extraordinary sensitivity of NuSTAR in hard X-rays, we propose a small NuSTAR survey of four luminous hard X-ray sources (Lx>2e38 erg/s) in M31. The observations will allow us to differentiate between black-hole XBs in the hard state and luminous neutron star (NS) low-mass XBs (LMXBs) by measuring the spectral shape in hard X-rays. The program is important for understanding the origin and evolution of LMXBs. It also allows us to identify supercritically accreting NSs and provides a valuable test for our recently discovered simple, yet effective, source identification method in the Chandra band.

Proposal Number: 3296
PI Last Name: Neilsen
Title: NUSTAR-NICER OBSERVATIONS OF BLACK HOLE TRANSIENTS
Abstract: With its excellent hard X-ray sensitivity, spectral resolution, and timing, NuSTAR has revolutionized our view of black hole 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 April 2017, we take a great step forward. NICER will be to soft X-rays what NuSTAR is to hard X-rays, and together they will 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 to exploit these groundbreaking capabilities.

Proposal Number: 3297
PI Last Name: Reynolds
Title: NUSTAR OBSERVATIONS OF AN NEW IP ASSOCIATED WITH A PNE
Abstract: Cataclysmic variables (CVs) are the most abundant class of X-ray binary system. We have recently discovered a new CV (intermediate polar) that is consistent with the position of the planetary nebula HaTr5. The discovery of a compact binary system in a planetary nebula comes with the promise of insight into common envelope physics and SN Ia progenitors if the binary mass is greater than Chandrasekhar. Herein, we propose to take advantage of the superior hard X-ray sensitivity of NuSTAR to measure the temperature of the accretion shock onto and constrain the mass of the white dwarf in this intriguing binary system.

Proposal Number: 3298
PI Last Name: Natalucci
Title: PROBING THE MAGNETIC FIELDS OF NEUTRON STARS IN SUPERGIANT FAST X-RAY TRANSIENTS
Abstract: The detection of cyclotron resonance absorption features in transient accreting HMXBs, also known as Supergiant Fast X-ray Transients (SFXT) is a powerful tool to unveil the processes driving their accretion modes. Our previous discoveries of cyclotron lines in the transients SAX J17544-2619 and IGR J16418-4532 with NuSTAR have motivated us to further study the role of magnetic fields in the extreme variability of these objects. For this purpose we ask to study two additional HMXB systems, selected by the available sample of SFXTs, for a a total exposure of 100~ks to be executed in AO3. These sources, SAX J1818.6-1703 and AX J1841.0-0536 show a dynamic range of variability of about 10^3 and may show bright flaring activity during a single exposure of 50ks.

Proposal Number: 3299
PI Last Name: Pavlov
Title: AR SCO: THE FIRST WHITE DWARF PULSAR
Abstract: A recent detection of pulsations with the 1.97 min period, modulated by the binary period of 3.56 hr, in the radio-IR-optical-UV synchrotron emission from the white dwarf (WD) - M-star binary AR Sco was the first discovery of a WD pulsar powered by WD spindown. Although it is clear that the detected emission is produced by relativistic particles, the acceleration mechanism and the sites of emission remain uncertain. To distinguish between different models for the WD-pulsar - M-star binary, X-ray observations are particularly useful, especially at energies above 10 keV. We propose a NuSTAR observation supplemented by a short XMM-Newton observation to investigate the X-ray spectrum and pulsations of AR Sco and infer a realistic model of this unique object.

Proposal Number: 3302
PI Last Name: Ricci
Title: PROBING THE GROWTH, OBSCURATION AND FEEDBACK OF SUPERMASSIVE BLACK HOLES IN THE FINAL STAGES OF GALAXY MERGERS
Abstract: Major gas-rich galaxy mergers play a significant role in galaxy evolution and SMBH growth. However, we still do not know exactly when and how in the last stages of the merger sequence the observed dramatic SMBH growth phase and its feedback on the environment start. Thanks to its unprecedented E>10 keV sensitivity and imaging capabilities, NuSTAR can strongly contribute to answer these questions. We propose to carry out ten observations of galaxies in the final stages of galaxy mergers which are known to host an AGN. The NuSTAR data will allow to infer the intrinsic luminosity and amount of obscuration in these AGN, and to understand whether feedback removes part of the obscuring material around coalescence.

Proposal Number: 3306
PI Last Name: Arevalo
Title: TRACKING ACCRETION POWER INTO THE LOW LUMINOSITY REGIME
Abstract: The accretion flow in AGN changes its structure when the accretion rate drops. High power AGN are softer when brighter while low-luminosity sources do the opposite. The transition point is not well known, largely because of the imprecise determination of the spectral slope, whose dynamic range is very small. What happens to the accretion flow at low rates is also not well understood, either a RIAF or a jet are possible. In this proposal we target three low accretion rate AGN to measure their spectral slope, and confirm or reject spectral curvature, which would point to a RIAF. The targets belong to a flux limited sample covering a wide range in accretion rates. They fill the mid-low L/L_Edd range, crucial to follow the evolution of the X-ray emission at the turning point.

Proposal Number: 3312
PI Last Name: Coley
Title: LMC P3: AN EXTREME PARTICLE ACCELERATOR
Abstract: We propose NuSTAR observations of the newly discovered gamma-ray (GR) binary LMC P3 simultaneous to our already approved XMM-Newton AO-16 observations. LMC P3 is 4x more luminous than similar systems in gamma-rays and 10x in X-ray and radio. This extreme behavior may be driven by a large spin-down power from the suspected pulsar, as well as a high UV photon seed density of the O5 III star, but the details of the high energy emission region remain perplexing. With the high spectral and temporal resolution of NuSTAR, we will probe the physical conditions of this emission region with the first high S/N spectrum above 10 keV, and search for signatures of a NS or BH. Our study of LMC P3, the first extra-galactic GR binary, is the first step towards characterizing the GR binary population.

Proposal Number: 3314
PI Last Name: Wik
Title: TOWARD A BETTER CENSUS OF BLACK HOLES AND NEUTRON STARS IN THE DISK OF M31
Abstract: The sensitivity and spatial resolving power of NuSTAR have allowed the study of individual neutron stars and black holes in other galaxies at hard energies for the first time, but they are nearly all more luminous than the population of sources probed in detail in the Milky Way. With a NuSTAR legacy survey of M31, we have finally detected sources at these lower luminosities, allowing a direct comparison of M31's neutron star and black hole accretors to the Milky Way's in the crucial window above 10 keV. We propose 4 additional pointings of M31 to double the number of >10^37 erg/s detected at hard energies to ensure the shape of the luminosity function is more robust to low number fluctuations. Also, we will classify the brightest sources, which is only possible with hard band data.

Proposal Number: 3318
PI Last Name: Castro
Title: A HARD (X-RAY) LOOK AT THE SW REGION OF SNR RCW 86
Abstract: That SNRs accelerate particles to CR energies is no longer in doubt, but there are many questions yet to be answered. We still lack detailed knowledge about the efficiency of the process of particle acceleration at SNR shocks, the effect of CR production on the evolution of SNRs, and the properties of magnetic fields in these systems and how these are amplified. In order to address these outstanding issues, we propose to observe the SW region of SNR RCW 86 with NuSTAR, with a 200 ks pointing (shown in Fig. 1). This will allow us to: (1) determine the morphology of the non-thermal X-ray emission in this region in the NuSTAR band, and contrast it to observations with XMM-Newton and Chandra, (2) constrain the spectral shape of the electron population that underlies the non-thermal emission.

Proposal Number: 3321
PI Last Name: Malkan
Title: OBSCURED ACCRETING MASSIVE BLACK HOLES: SURVEY OF THE COMPLETE SAMPLE OF X-RAY WEAK 12UM AGN
Abstract: To determine the population of heavily obscured AGN, we have searched the complete 12um Seyfert Galaxy sample for likely Compton-thick candidates. In it we identified 10 Seyfert 2's as candidates, with XMM 2-10keV flux at least 10 times weaker than predicted from their [OIII] line fluxes, and also not detected by BAT (except for one, weakly). NuSTAR observations of five of the candidates confirms that four are currently accreting at a much higher rate than XMM found. For a statistically robust measure of the volume density and other properties of Compton-thick AGN in the local Universe, we propose NuSTAR observations of the remaining 5 candidates to see how strongly their MBHs are accreting, if at all. Supplemented with spectropolarimetry at Keck, we will test torus unification models.

Proposal Number: 3322
PI Last Name: Homan
Title: WINDS AND REFLECTION FEATURES AT THE SUPPER-EDDINGTON LUMINOSITIES
Abstract: The properties of super-Eddington accretion flows onto neutron stars (NS) remain poorly understood. Recent NuSTAR observations of the super-Eddington Z source GX 5-1 suggest that significant changes occur in the reflection and wind properties at the highest luminosity end of NS LMXBs. Here we propose to observe GX 340+0, a close twin to GX 5-1, with NuSTAR and NICER, to obtain broadband spectra of unprecedented quality. These spectra will allow us to study the evolution of the source's continuum components and emission/absorption lines. Our main goal is to investigate 1) to what extent GX 340+0 shows the same divergent behavior as seen in GX 5-1 and 2) how its wind and reflection properties change along its Z track. We request three 25 ks NuSTAR observations, to be spaced ~1 day apart.