Cycle 2 Observations Abstracts

Proposal Number: 2011
PI Last Name: Ajello
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 mechanism, the bulk Lorentz factor, and the emission process. We propose to observe with NuSTAR the 4 highest-redshift blazars ever detected by Fermi. We will complement the NuSTAR exposures with observations with Fermi, Swift, GROND 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: 2014
PI Last Name: An
Title: The Sed Of The Highest-Redshift Blazar: Probing Beamed Black Holes In The Early Universe
Abstract: While only three radio bright z> 5 massive (> 10^9 Msun) blazars (AGN with jets beamed at Earth) are known, estimates of their bulk Lorentz factors (Gamma) gave Gamma> 10. Thus beaming corrections implied several hundred blazars at z> 5, with important implications for the early growth and spin evolution of massive black holes. However, our new Fermi analysis gives smaller Gamma and high-z population. Tightening the measurement for the best and brightest of these sources, J0906+6930 (z=5.48), is our goal. We have assembled the other requisite SED components: the last missing piece is a sensitive hard X-ray spectrum. A 100-ks NuSTAR exposure suffices to measure or tightly bound the external Compton component flux and the relativistic Doppler factor for this highest redshift blazar source.

Proposal Number: 2023
PI Last Name: Ursini
Title: NuSTAR/XMM Monitoring Of The Broad-Line Radio Galaxy 3C 382
Abstract: We propose a joint NuSTAR/XMM monitoring of the broad-line radio galaxy (BLRG) 3C 382, consisting of 5x20 ks observations spaced by 10-15 days. 3C 382 is an ideal radio-loud source to obtain high sensitivity measurements over a broad (UV/hard X-rays) high-energy range, which will allow us to: 1) study the UV/X-ray spectrum of a BLRG with unprecedented accuracy and test physically motivated Comptonization models, 2) understand the origin of the puzzling reflection component, and 3) investigate the nature of the soft X-ray excess. These observations will allow for a direct comparison with radio-quiet Seyfert 1s, in particular with a similar, successful NuSTAR/XMM monitoring of NGC 4593.

Proposal Number: 2024
PI Last Name: Wong
Title: Completing A Missing Chapter In Hard X-Ray Of The M87 AGN
Abstract: M87 hosts a 3-6 billion solar mass black hole with an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands. However, four orders of magnitude of energy from ~10 keV to 100 MeV is missing from the central core, making it hard to distinguish high energy radiative and accelerating mechanisms. With the excellent sensitivity of NuSTAR, hard X-rays above 10 keV should readily be detected. We propose to constrain the unexplored hard X-ray emission of the high energy activities at the M87 nucleus region with NuSTAR. We will provide constraints on hard X-ray emission models with a jet or an accretion flow origin.

Proposal Number: 2030
PI Last Name: Temim
Title: Spectral Evolution Of Crushed Pulsar Wind Nebulae
Abstract: As a highly magnetic, rapidly rotating pulsar converts its spin-down energy into a wind of relativistic particles, a synchrotron-emitting pulsar wind nebula (PWN) is formed that can be observed across the electromagnetic spectrum. Since the PWNs relativistic particle population is eventually injected into the interstellar medium (ISM), constraining the nature of this particle spectrum and its evolution is particularly important for understanding the Galactic cosmic ray population and energy density. We propose NuSTAR observations of two evolved PWNe inside supernova remnants G327.1-1.1 and MSH 15-56, with the goal of constraining the properties of the PWNe and the particle injection spectra, and understanding the nature and evolution of the particle population that escapes into the ISM.

Proposal Number: 2041
PI Last Name: Sartori
Title: The Sudden Death Of A Quasar: A NuSTAR Autopsy Of The IC 2497 - Hanny's Voorwerp System
Abstract: Until ~200 kyr ago IC 2497 hosted a powerful 1e46 erg/s quasar. The quasar has since shut down and its photoionisation echo is preserved in the AGN photoionised cloud known as Hannys Voorwerp, which provides us information about the past state of the quasar. We can therefore study AGN variability, and its effect on the host galaxy, on previously inaccessible timescales. Existing Chandra, XMM and Suzaku observations show that the present-day quasar luminosity is at least 2 and perhaps as much as 4 orders of magnitude lower than in the past. However, the Suzaku observations at 15-30 keV are uncertain. To measure the present-day nuclear luminosity of IC 2497 and therefore the true magnitude of the quasar shutdown we need deep hard X-ray observations. NuSTAR is the best instrument for this.

Proposal Number: 2042
PI Last Name: Della Ceca
Title: Probing Concomitant Starburst-Agn Activity With NuSTAR
Abstract: The relative role of stellar emission and black-hole accretion, as mechanisms of energy production in the Universe, and their connection are hot topics of modern astrophysics. We propose 40 ksec NuSTAR observation of two ULIRGs (IRAS12032+1707 and IRAS12018+1941) to unveil their putative (from IR signatures), but optically elusive, AGN component. An X-ray investigation at E> 10 keV is probably the only way to directly measure the AGN intrinsic power in such objects. Moreover broad band X-ray data (from ~ 5 keV up to ~ 50 keV), complemented with the wealth of data at other wavelengths, will allow us to have hints on the physical condition of the circum-nuclear absorbing matter. NuSTAR is at the moment the only instrument able to perform this investigation at the flux level proposed here.

Proposal Number: 2048
PI Last Name: Balman
Title: Characterization Of The X-Ray Emission And Boundary Layers In Nonmagnetic Nova-Like Cataclysmic Variables
Abstract: We propose pointed observations of three nonmagnetic nova-like (NL) Cataclysmic Variables (CVs) for a total of 100 ks with the NuSTAR observatory. NLs are high state CVs, with wind outflows and are laboratories to study the effects of high accretion rate on accretion physics and boundary layers. We observed these NLs with SWIFT and found virialized hot plasma emission, not expected in the high state of steady-state disks. They can be characterised as advective hot flows (ADAF-like). Such hot flows and advective heating of WDs are puzzling and important for CV accretion which may influence evolution, and nova explosions. NuSTAR will further our insights on the X-ray emission from these hardest NL sources utilizing the highest sensitivity in the widest energy band.

Proposal Number: 2049
PI Last Name: Reeves
Title: The Hard X-Ray View Of The Prototype Disk Wind Quasar Pds 456
Abstract: PDS 456, the most luminous nearby AGN, is now recognised as the prototypical example of an ultra fast outflow. Indeed our 2013 XMM-Newton and NuSTAR campaign established the presence of a fast (0.3c), wide angle accretion disk wind, with the wind power sufficient to provide significant mechanical feedback into its host galaxy. Here we propose for a longer 180ks exposure of PDS456 with NuSTAR, which will reveal the true nature of the quasar at hard X-rays. The observations will also form part of a simultaneous multiwavelength campaign, encompassing approved XMM-Newton and HST/COS observations, as well as a likely PV phase observation with Astro-H. For the first time, we will obtain high resolution coverage of this important prototype disk wind over the entire UV to hard X-ray band.

Proposal Number: 2059
PI Last Name: Braito
Title: Monitoring The Extreme Changing Look AGN, ESO 323-G077
Abstract: ESO 323-G077 is a nearby, bright, Sey1 galaxy in which Chandra, XMM, Suzaku and Swift observations unveiled dramatic spectral variability on timescales as short as a month with the Nh varying from few x 10^22 cm^-2 to > 10^24 cm^-2. A Chandra observation already caught an uncovering of the source, while a short XMM observation revealed a highly ionised high-column density wind. ESO323-G077 is thus remarkably similar to NGC1365, the archetypical changing look AGN, as both show an Nh variable by two orders of magnitude and an ionised wind. With the proposed monitoring program (5x40ks) we aim to study:- i) the nature of the variable absorber in terms of its variability timescale and thus location relative to the X-ray source: ii) constrain for the first time the Nh of the Compton thick state

Proposal Number: 2066
PI Last Name: Tombesi
Title: Establishing The Quasar Mode Feedback With NuSTAR And XMM-Newton
Abstract: Recent Herschel observations have identified powerful large-scale molecular outflows in ultraluminous infrared galaxies, indicating that AGN feedback can indeed influence star formation and galaxy evolution. Theoretical models describing the formation of such large-scale outflows require a putative inner AGN accretion disk wind. We found the first evidence of such a wind in IRASF11119+3257, in the form of blue-shifted Fe XXV/XXVI absorption lines with velocity 0.25c. However, just one object does not allow to establish the validity of such mechanism. Here, we request simultaneous 150ks NuSTAR and 90ks XMM-Newton observations of the next most promising ULIRG, IRASF05189-2524, to characterize its disk wind and conclusively establish the mechanism of quasar mode feedback.

Proposal Number: 2069
PI Last Name: Walton
Title: Extreme Reflection In The Complex Narrow Line Seyfert 1 AGN PG 1535+547
Abstract: Previous X-ray observations of the nearby "complex" NLS1 PG1535+547 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, PG1535+547 has never been observed in the hard X-ray band. We request a coordinated broadband X-ray observation of this remarkable source with XMM-Newton and NuSTAR in order to robustly confirm the extreme reflection, and utilize the full potential of the latest reflection models to measure the BH spin and constrain the accretion geometry.

Proposal Number: 2070
PI Last Name: Grefenstette
Title: Observations Of An Occulted Active Region: Hunting For Particle Acceleration On The Sun
Abstract: This proposal is to investigate particle acceleration in the solar corona. We will observe an active region after the low-altitude X-ray bright loops rotate over the limb of the Sun, allowing us to directly observe the fainter X-ray emission from particle acceleration high in the solar corona. With our 20 ks (12 orbit) NuSTAR Target of Opportunity observation we will search for any emission that may be associated with Type III solar radio bursts (radio signatures of outward propagating electron beams) and coronal mass ejections (CMEs) associated with flares from the occulted region, and to investigate any high altitude emission from hot plasma that may be associated with the active region.

Proposal Number: 2072
PI Last Name: Brightman
Title: Can The Growth Rates Of Heavily Obscured Supermassive Black Holes Be Estimated From Their X-Ray Spectral Indices?
Abstract: We request a total of 105 ks of NuSTAR observing time in order to increase the exposures of two heavily obscured AGN, NGC 2960 (80 ks) and NGC 1386 (25 ks). These galaxies are sources of water megamaser emission from which robust black hole mass measurements have been made and comparison of Gamma and Eddington ratio can be performed where these quantities have been shown to be strongly correlated in unobscured AGN. However, these sources have far steeper Gamma values than any Eddington ratio would predict. Our proposed observations will reveal if this is an artifact of the low count nature of the existing data, or whether these sources are new and interesting outliers.

Proposal Number: 2074
PI Last Name: King
Title: Investigating The X-Ray Corona In The AGN Mrk 110
Abstract: We propose to observe Mrk 110 with NuSTAR for 200 ksec. We will characterize the spectral properties including reflection fraction, coronal height, and high-energy cutoff in this radio-quiet AGN. The aim is to compare it to radio-loud AGN, such as 3C 120, in order to understand what are the primary differences in the corona that may drive variations in jet production. In particular, Mrk 110, has the same mass and mass accretion rate as 3C 120, yet its jet is suppressed by nearly three orders of magnitude in the radio band. Characterizing the coronal geometry, temperature, and spin will allow exploration as to other mechanisms that may drive the radio dichotomy.

Proposal Number: 2075
PI Last Name: Enoto
Title: Hard X-Ray Timing Behaviors Of Magnetar Activities: Search For Evidence Of Toroidal Field In Sgr 1900+14
Abstract: The non-thermal hard X-rays of magnetars are a crucial key to understand their magnetic activities,or even a unique way to access the toroidal magnetic field hidden inside a stelar interior. A new signature of stellar free precision has been suggested from two sources 4U 0142+61 and 1E 1547.0-5408. This can be interpreted as a distortion of stellar shape due to the extremely strong toroidal field of magnetars. However, the results are only limited to Suzaku observations from a few sources. It is hence imperative to confirm whether such a signature does exists in other magnetars from NuSTAR observations. We propose a 120 ks observation of a prolific soft gamma repeater SGR 1900+14 which hard X-ray timing and spectral nature has yet to be investigated in detail.

Proposal Number: 2087
PI Last Name: Williams
Title: Testing The Limits Of Particle Acceleration In An Extreme TeV Blazar With NuSTAR
Abstract: We propose NuSTAR observations, coordinated with spectral coverage from the infrared to very-high-energy (VHE) gamma rays, of the extreme high-synchrotron-peaked (HSP) blazar 1ES 0502+675. Extreme HSP blazars represent the apparent limiting case for particle acceleration in blazar jets, with emission in the hard X-ray and VHE gamma-ray regimes. These observations will advance our understanding of particle acceleration in extreme HSPs, as well as blazars more generally, and will also lay the foundation for using 1ES 0502+675 as a gamma-ray probe to study gamma-ray and cosmic ray propagation effects.

Proposal Number: 2088
PI Last Name: Gelfand
Title: The Initial Spin Period Of Psr J1930+1852 In Pwn G54.1+0.3
Abstract: How neutron stars are created during a core-collapse supernova is poorly understood. Since its surface magnetic field strength and initial spin period are determined during the explosion, measuring these properties is critical for understanding the underlying physical mechanisms. While a neutron stars surface magnetic field strength can be estimated from its spin-down properties, currently the best way of determining its initial spin period is by modeling the properties of the pulsar wind nebula (PWN) powered by its rotational energy. Our analysis of a new LOFAR observation of PWN G54.1+0.3, coupled with our recent modeling of this source, suggest the associated pulsar PSR J1930+1852 is born with a spin period of P 0 ~65 ms - which we will test with the requested NuSTAR observation.

Proposal Number: 2090
PI Last Name: Tomsick
Title: Determining The Nature Of The Brightest Serendipitous NuSTAR Source
Abstract: In our systematic search for serendipitous sources (serendips) in the NuSTAR data, we have found a very bright (7.5 mCrab in the 2-10 keV band) serendip (J0923 s1) near the edge of one of the NuSTAR fields of view. The source has been previously detected in the soft X-ray band, but its nature is unknown. Based on its X-ray spectrum, its optical counterpart, and its long-term variability (as seen by MAXI), it must be Galactic, and, while some of its properties are suggestive of a magnetic Cataclysmic Variable, other properties cause problems with this interpretation. One interesting possibility is that it may be an accreting black hole with a high temperature disk. We propose NuSTAR and XMM-Newton observations to determine the nature of J0923 s1.

Proposal Number: 2099
PI Last Name: Tortosa
Title: Constraining The X-Ray Emitting Mechanism In AGN Via Simultaneous Swift/NuSTAR Observations
Abstract: We propose NuSTAR observations of the three brightest AGN, MCG+8-11-11 (100 ks), MCG-2-58-22 (100 ks) and NGC 6814 (150 ks) not yet observed by NuSTAR. The primary goal of these observations is to investigate the Comptonization mechanisms. Taking advantage of the already awarded Swift UVOT+XRT observations, we propose to observe them simultaneously. Simultaneous data from UV to hard X-ray are essential to understand the link between the UV thermal emission from the disk and the Compton scattered radiation from the hot corona. Only a handful of AGN observed with NuSTAR have simultaneous, high sensitivity UV/soft X-ray coverage, and/or a good measurement of the coronal parameters. The brightness and hard spectral slopes make the proposed sources great candidates to enrich this sample.

Proposal Number: 2100
PI Last Name: Torrejon
Title: 4U2206+54: Is It Really An Accreting Magnetar?
Abstract: We propose to obtain, for the first time, a continuous, well exposed spectrum of the accreting magnetar candidate 4U2206+54, beyond 20 keV. This will allow to detect and characterise unam- biguously a previously claimed cyclotron line at 29 keV or disprove its existence definitely. Both outcomes are exciting. The first one would rule out the system as a magnetar. The very pronounced NS spin decay will need then a different explanation. This will certainly challenge current theories as only magnetobraking is thought to be effective enough. The second one, in turn, will support the magnetar scenario, helping to establish and characterize the newly proposed class of wind accreting magnetars.

Proposal Number: 2105
PI Last Name: Kreikenbohm
Title: The Nature Of The Soft Excess In The Radio And Gamma-Ray Loud Nls1 Pks 2004-447
Abstract: X-ray emission in excess of the intrinsic power law below 2 keV is a typical feature of radio-quiet active galactic nuclei (AGN). It has now been observed in a few sources of the newly-discovered class of radio-loud and gamma-ray emitting narrow-line Seyfert 1 (gamma-NLS1) galaxies. But the nature of this component in radio-loud AGN is not clear. Very recently, we found tentative evidence for the presence of a variable soft excess in the gamma-NLS1 galaxy PKS 2004-447 (Kreikenbohm et al. 2015, A&A, in press). Here, we propose a target-of-opportunity observation to study this peculiar component in this key source for the class of gamma-NLS1 galaxies. The unique joint NuSTAR-XMM-Newton program allows for the first reliable detection of the soft excess in this source.

Proposal Number: 2113
PI Last Name: Lohfink
Title: Exploring The Corona Of Mrk 926
Abstract: We propose to observe Mrk 926 for 35 ks with XMM and 100 ks with NuSTAR to explore the Comptonization spectrum of this bright Seyfert 1 galaxy. Previous analyses of non-simultaneous observations have found a lower limit of the high energy cut-off of 510 keV, bringing it in disagreement by the temperature limit set by run-away pair production. With the proposed observations we will test, whether Mrk 926s spectrum is consistent with thermal Comptonization or not. If it is, we can study its Comptonization spectrum from the UV to the hard X-rays and would obtain key information on the properties of coronae typical for Seyferts. However, if we find that the temperature is inconsistent with thermal Comptonization, we can use this dataset to understand which other process could be responsible.

Proposal Number: 2120
PI Last Name: Ricci
Title: Understanding The Peculiar X-Ray Spectrum Of 2Masx J09254750+6927532 With NuSTAR
Abstract: We propose here a 40ks NuSTAR observation of a very peculiar source found during our broad-band X-ray spectroscopical study of Swift/BAT AGN, which shows optical broad lines, a very flat 2-10 keV continuum and a large ratio between the 14-150 keV and the 2-10 keV fluxes. The 0.3-200 keV spectrum of this source could be explained by two statistically indistinguishable models: Compton-thick obscuration or by a dominant contribution of light-bended reflection from the innermost part of the accretion disk. The NuSTAR observation will allow to shed light on the nature of the X-ray emission in this object, and to constrain the main spectral parameters.

Proposal Number: 2125
PI Last Name: Margutti
Title: Continued NuSTAR Monitoring Of The Unprecedented Metamorphosis Of Sn2014C
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 program 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: 2128
PI Last Name: Zoghbi
Title: The Geometry Of The X-Ray Source In Ngc 7314 With Spectroscopy And Reverberation
Abstract: NuSTAR s unprecedented energy coverage has been providing many black hole spin measurements in AGN. Most of them are at the high end of black hole spin, where strong relativistic effects are present. In NGC 7314, the iron line shape from spectroscopy and reverberation is narrow, suggesting a low black hole spin and possibly either a truncated disk or an illuminating source that is distant from the disk. The current low energy data (< 10 keV) do not constrain the reflection spectrum to specify this. Here, we propose to observe x for 100 ks with NuSTAR and 60 ks with XMM in order to measure both the relativistic broadening and reverberation. The two will allow us to localize the X-ray source and test for truncations. A truncated disk would have implications on accretion theory.

Proposal Number: 2130
PI Last Name: Orio
Title: The Structure Of The Magnetic Accretion Column In Intermediate Polars
Abstract: We propose to obtain the first hard X-ray imaging observation of the intermediate polar EX Hya, which will allow us to explore the high energy spectrum. Previous non-imaging observations did not allow to subtract the contamination of the close cluster of galaxies Abell 3528. The hard X-ray spectrum will be used to determine the shock temperature and the shock height, thus obtaining the white dwarf mass and reflection signatures from the magnetic accretion column. The proposed study has broad implications for our understanding of magnetic accretion and plasma cooling mechanisms.

Proposal Number: 2133
PI Last Name: Ricci
Title: Compton-Thick Accretion In The Local Universe With NuSTAR
Abstract: Heavily obscured accretion is believed to represent an extremely important phase in the growth of supermassive black holes, and to play an important role in shaping the observed spectrum of the Cosmic X-ray Background. So far however, only a small number of Compton-thick AGN are known. Our group recently carried out a detailed study of ~830 Swift/BAT AGN, finding CT absorption in 55 objects. We propose here to observe 28 local CT AGN with NuSTAR, with the aim of accurately constraining their column density and luminosity. This will allow us to sample the low and high-luminosity bins of CT accretion, as well as the NH> 5e24 cm^-2 range. With this we will study the luminosity-function of CT AGN, and the evolution of CT material with the physical characteristics of the accreting system.

Proposal Number: 2135
PI Last Name: Kong
Title: X-Ray Emissions Of An Ultra-Compact Gamma-Ray Millisecond Pulsar Binary Candidate
Abstract: We propose to observe the ultra-compact gamma-ray millisecond pulsar (MSP) candidate, 2FGL J1653.6-0159 jointly with NuSTAR and XMM. The Fermi source has a candidate X-ray counterpart from Chandra data and its X-ray and gamma-ray properties are consistent with known gamma-ray pulsars. The source is also found to have a 75-min orbital period in optical data and possibly in a Chandra observation. We propose to use NuSTAR and XMM to search for the orbital X-ray modulation. Moreover, the high quality energy spectra will allow us to study the spectral properties and phase resolved spectra to constrain the system geometry. A NuSTAR observation will further constrain the X-ray emission mechanisms and enables a comparison with other well-known systems.

Proposal Number: 2140
PI Last Name: Degenaar
Title: An Accretion Disk Wind At Low Eddington Rate
Abstract: According to the current paradigm, accretion onto black holes and neutron stars is associated with two types of outflows that are mutually exclusive. At > E-2 of the Eddington limit, disk winds are detected through narrow X-ray absorption features, whereas at lower mass-accretion rates radio jets are seen. However, our AO1 NuSTAR observation of the neutron star low-mass X-ray binary IGR J17062-6143 revealed a ~3-4 sigma narrow absorption line at ~6.85 keV. This provides the very first evidence that disk winds can be launched at merely ~E-3 of Eddington, and may co-exist with a radio jet. We propose for a 75 ks NuSTAR observation and a supporting 70 ks XMM observation to solidify this measurement, which would change our current views of inflow-outflow coupling in accreting compact objects.

Proposal Number: 2142
PI Last Name: Fuerst
Title: Cyclotron Lines In Transient Pulsars I: Probing The B-Field
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 proposed 3 ToO observations at fluxes of 20mCrab, 100mCrab, and 200mCrab of a known CRSF source in outburst to study its behavior as function of luminosity. NuSTAR is the only instrument to be able to measure the energy with the necessary precision and at the same time allows us to study the CRSF profile. These measurements will inform physical models of the line forming processes and constrain the accretion physics and geometry close to the neutron star. In a parallel proposal we ask to observe a CRSF candidate to discover new CRSF sources.

Proposal Number: 2143
PI Last Name: Piconcelli
Title: Revealing The Origin Of The Reflection-Dominated Spectrum Of ESO 138-G1
Abstract: We propose here a 50 ks NuSTAR observation to collect the first spectrum above 10 keV of the reflection-dominated Seyfert 2 galaxy ESO138-G1. A 130 ks XMM spectrum can be explained by reflection from a Compton-thin medium without any contribution from a transmitted primary continuum, unless piercing through a heavily Compton-thick screen. The latter scenario requires the absorber to be inhomogenous, its Nh along the line of sight being much larger than the average Nh integrated over all lines-of-sight through the torus. We aim to unambiguously confirm the Compton-thick nature of ESO138-G1 by measuring these two Nh values and, thus, get insights into the physical properties of the circumnuclear gas. NuSTAR is the only X-ray telescope capable to perform the proposed study.

Proposal Number: 2144
PI Last Name: Fabian
Title: The Pair Constraint On Coronal Temperatures In Seyfert 1 Galaxies
Abstract: We propose to observe a sample of 5 bright Seyfert 1 AGN for 100 ks each to explore their coronal properties, especially the high energy cut-off. This will provide an increase of one third over the existing number of NuSTAR constrained cut-offs, i.e. coronal temperatures. Theoretically, there is a maximum coronal temperature, dependent on the radiative compactness and the geometry of the corona, above which runaway pair production stops a further temperature increase. Existing measurements suggest that coronae have temperatures up to this limit but are insufficient to determine for example the geometry.

Proposal Number: 2145
PI Last Name: Papitto
Title: Hunting For Transitional Ms Pulsars With NuSTAR
Abstract: Three ms pulsars have recently shown swings between an accretion (X-ray) and a rotation-powered (radio) pulsar state, demonstrating that transitions between these two states can be observed over timescales as short as a few weeks. We propose a NuSTAR 80 ks ToO observation aimed at studying the accretion state of one of these transitional millisecond pulsar, detecting X-ray accretion powered pulsations, and characterizing its X-ray variability up to 80 keV. Candidates are restricted to black widows and redbacks, systems that are in an evolutionary phase that makes them good candidates to observe a transition. Enlarging the number of transitional ms pulsars is crucial to test binary evolution theories, and to study the disk-field interaction over a large range of mass accretion rates.

Proposal Number: 2151
PI Last Name: Siemiginowska
Title: Pioneering Hard X-Ray Band Observations Of Young Radio Sources With NuSTAR
Abstract: This project will provide the first hard X-ray observations of the youngest (< 250 years old) known radio sources and establish their high energy properties. Theoretical models predict that young radio sources should be strong X-ray emitters, but they have never been observed above ~10 keV. The proposed NuSTAR observations of two young sources from a class of Compact Symmetric Objects will complement our existing Chandra and XMM data and allow us to put strong constraints on their intrinsic absorption, disentangle emission processes contributing to their SED and derive physical properties of radio sources at the time of the initial jet formation. Among the X-ray telescopes operating at energies > 10 keV, only NuSTAR has capabilities required to study these young radio sources.

Proposal Number: 2154
PI Last Name: Maccarone
Title: The Mass-Temperature Relation In Accreting White Dwarfs
Abstract: We propose NuSTAR observations of the cataclysmic variable BZ UMa. This object is an outlier in the relation between white dwarf dynamical mass and accretion flow temperature in past work. The relation can potentially be used to estimate white dwarf masses, but notably fails for the two lowest mass white dwarfs in the sample. BZ UMa has the more reliable dynamical mass estimate of the two, and is thus the key source for testing the relation.

Proposal Number: 2155
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: 2158
PI Last Name: Tendulkar
Title: Intra-Binary Shock And Energetics Of Transitional Binary Candidate Psr J2339 0533
Abstract: In the past two years, three pulsar binaries have shown surprising back-and-forth transitions between an accreting low mass X-ray binary (LMXB) state and a non-accreting radio millisecond pulsar (MSP) state. These transitional MSPs (tMSPs) overturned the idea that accretion in an LMXB switches off permanently in a single occurence during pulsar recycling, but it is unclear how/why the transitions happen. PSR J2339-0533 is a likely tMSP with spin and orbit parameters very similar to the known tMSPs and shows signs of intermittent accretion, orbital period and lightcurve variations. These signs suggest that PSR J2339-0533 may imminently transition into an LMXB. With 150-ks NuSTAR and 100-ks XMM observations, we propose to establish the pre-transition properties, critical for future work.

Proposal Number: 2171
PI Last Name: Mathur
Title: Unexplored Parameter Space Of Flat-Spectrum Radio-Loud Narrow-Line Seyfert-1 Galaxies And The Disk-Jet Connection
Abstract: Flat-spectrum radio-loud narrow line Seyfert 1 galaxies (F-RLNLS1s) define a newly discovered class of AGNs that appears to occupy a distinct locus in the parameter space of AGNs. They add a third dimension to the eigenvector-1 defined by black hole mass and accretion rate, with inclusion of BH spin. In models of scale-invariant disk-jet emission, radio emission defines the jet power while X-ray emission defines the accretion disk emission. The observed properties of F-RLNLS1s appear to defy this universality. The NuSTAR energy range of 3--79 keV is of particular interest as we expect it to reveal the physics of the disk-jet connection by probing accretion disk emission as well as relativistic jet emission. We propose NuSTAR observations of 3 F-RLNLS1s, 2 of which are gamma-ray loud.

Proposal Number: 2172
PI Last Name: Garcia
Title: Reflection Spectroscopy Of The Seyfert 1.5 AGN ESO 362-G18
Abstract: We propose simultaneous 100 ks XMM-Newton and NuSTAR observations of the Seyfert 1.5 galaxy ESO 362-G18 for the purpose of making a detailed study of the spectrum of radiation reflected from the inner accretion disk. Our chief aim is to constrain both the spin of the black hole and the properties of the corona that illuminates the disk. The combination of NuSTARs high-sensitivity in the hard X-ray band, the soft-band coverage of XMM-Newton, and our state-of-the-art relativistic reflection models will allow us to break degeneracies between different possible scenarios, and impose tight constraints on the accretion geometry and black hole spin of this bright AGN.

Proposal Number: 2174
PI Last Name: Risaliti
Title: Measuring Coronal Properties Of Two High Redshift, Luminous Quasars
Abstract: We propose NuSTAR and XMM joint observations of two quasars at z=2.36 and z=3.37, with the main goal of measuring the high-energy cutoffs of their X-ray emission. Only recently the high S/N NuSTAR spectra allowed precise measurements of these parameters for the brightest local AGN, finding cutoff energies above 100~keV. Here we demonstrate that the same estimates are possible also for the brightest high-z quasars, if (and only if) the whole 0.5-80~keV band is observed. The scientific outcome is of great value: we will be able to test whether the same physical conditions hold in quasars at luminosities $> $100 times higher than those probed so far in the nearby Universe. An important additional scientific goal will be the study of the X-ray absorption by the intervening IGM.

Proposal Number: 2181
PI Last Name: Yukita
Title: The Hard X-Ray Pulsar Candidate That May Dominate M31 At E> 25 Kev: NuSTAR-XMM Observations Of The M31 Bulge
Abstract: During our AO1 NuSTAR observation of the M31 bulge, we identified for the first time the counterpart to the single bright Swift source, Swift J0042.6+4112, that dominates M31s emission at E> 25 keV. We propose new simultaneous observations with NuSTAR and XMM-Newton one year later to (A) properly constrain the simultaneous 0.5-80 keV spectrum of this source with higher S/N and by removing ambiguities due to its significant E< 10 keV variability and (B) look for variability in its hard X-ray emission since AO1. We will also monitor ~30 X-ray binaries in the field, one of the richest local environments for old stellar populations outside the Galaxy, to provide better constraints on the nature of the resolved point sources (i.e., black hole binaries vs. neutron star binaries).

Proposal Number: 2185
PI Last Name: Paneque
Title: Extensive Multi-Frequency Monitoring Of The Classical TeV Blazars Mrk 421 And Mrk 501
Abstract: Multi-year and multi-frequency monitoring of the classical TeV blazars Mrk 421 and Mrk 501 is an important resource in the effort to understand the physics of relativistic jets. These objects are among the very small number of sources whose broadband SED can be characterized simultaneously by the currently existing instruments. We request NuSTAR observations as a part of two planned campaigns in 2016 and 2017 on these two objects. Only NuSTAR is sensitive enough to provide time-resolved hard X-ray spectroscopy on the short timescale over which the proposed targets vary. NuSTAR is therefore ideally suited to complement the UV and soft X-ray observations with Swift, and the VHE gamma-ray observations with MAGIC and VERITAS, in constraining the rapid variability of the targets broadband SED.

Proposal Number: 2186
PI Last Name: Bachetti
Title: Timing And Spectral Studies Of The Ultraluminous X-Ray Sources In M82.
Abstract: The galaxy M82 harbors two of the most spectacular ultraluminous X-ray sources (ULXs), off-nuclear point sources exceeding the Eddington limit for a typical stellar remnant black hole. M82 X-1 reaches Lx> ~10^41 erg/s, and its one of the best candidate intermediate mass black holes (IMBH). M82 X-2, reaching Lx> ~10^40 erg/s, was found to be powered by a pulsar, at 100 times the Eddington luminosity, by NuSTAR. This proposal complements an accepted Chandra program and aims at detecting these two sources in different spectral states. Thanks to the combined work of Chandra and NuSTAR, we will be able to disentangle the spectra of the two ULXs, unresolved in NuSTAR, but constrain the hard X-ray spectrum, invisible to Chandra, and investigate the nature of these two intriguing objects.

Proposal Number: 2187
PI Last Name: Nelson
Title: A Reflection On Symbiotic Stars - Using Reflected X-Rays To Constrain Properties Of The White Dwarf And Accretion Disk
Abstract: Building on successful NuSTAR observations of other accreting white dwarfs, we propose to observe RT Cru and V648 Car - two hard X-ray bright symbiotic stars. Our primary goal is to determine the white dwarf mass and accretion rate. These quantities have important implications for the frequency of nova outbursts and therefore the long term evolution of the white dwarfs in these systems. Although in principle X-ray spectra of CVs and symbiotic stars encode information about the white dwarf mass, the effects of reflection from the white dwarf surface must be taken into account to fully realize this potential. Only NuSTAR has the sensitivity above 10 keV to detect and assess the importance of reflection while independently measuring the intrinsic spectral shape in our target sources.

Proposal Number: 2196
PI Last Name: Harrison
Title: The Bright Hard State Of A Transient Black Hole Binary - Is The Accretion Disk Truncated?
Abstract: We propose to undertake a 50 ks NuSTAR target-of-opportunity observation of a new or known black hole transient during a bright, hard outburst phase. The goals of this program are to 1) measure the spin of the black hole via the Fe K-alpha line and broadband disk reflection spectrum, 2) test an apparent anti-correlation between winds and jets in soft and hard states by making a sensitive search for winds in a hard state. A network of ground-based observatories, and X-ray monitoring will support this observation. The NuSTAR-only program proposed here is designed to complement our approved XMM-Newton+NuSTAR campaign (PI: Harrison) to cover sources that are not visible to XMM-Newton during outburst.

Proposal Number: 2205
PI Last Name: Gastaldello
Title: The NuSTAR View Of The Shocked Region In Abell 754
Abstract: We propose a NuSTAR observation of the shocked region of the merging cluster Abell 754. It is the closest confirmed shock and it is in a position where the X-ray emission is still relatively bright. This will allow us to fully exploit the potential of NuSTAR of constraining hot temperatures allowing a series of tests of the ICM physics, in particular constraining the thermal conductivity.

Proposal Number: 2218
PI Last Name: Sokoloski
Title: Su Lyn: A Hard X-Ray Bright Symbiotic Star Hiding In Plain Sight
Abstract: Symbiotic stars, in which a white dwarf (WD) accretes from a red giant, produce some type Ia supernovae, provide a unique window into low-mass binary stellar evolution, and offer tests for theories of accretion and jets. But despite their importance, the Galactic population of symbiotics is wildly uncertain. We propose a 40 ks NuSTAR observation of a special source --- SU Lyn --- to reveal the properties of a hard-to-find but possibly dominant type of symbiotic. Because the WD in SU Lyn is powered by accretion alone rather than quasi-steady shell burning, it reveals itself more through hard X-rays than optical line emission. Characterizing its fundamental parameters and emission properties will help us craft the optimal search strategy for the elusive accretion-powered symbiotic stars.

Proposal Number: 2220
PI Last Name: Younes
Title: Uv To Hard X-Ray Properties Of The Radiatively Inefficient Low Luminosity AGN Ngc 3998 And Ngc 4579
Abstract: LLAGN likely have radiatively-inefficient accretion flows (RIAFs) where at least the inner accretion disk is a spherical plasma while the outer regions may be in a standard geometrically-thin accretion disk. We propose to observe two of the brightest LLAGN with NuSTAR and XMM-Newton. The NuSTAR data will provide, for the first time, coverage of these sources up to 50 keV, and the NuSTAR+XMM-Newton broad band spectrum will allow for the measurement (or placing stringent constraints) on the high energy cutoff in these sources, allowing for a comparison to luminous AGN. Using the XMM-Newton OM, these data will provide simultaneous UV-X-ray SED that can be fit to RIAF models. All this will add to the growing number of NuSTAR AGN and extend the hard X-ray properties to very low Eddington rates.

Proposal Number: 2222
PI Last Name: Cackett
Title: How Does The Accretion Disk Evolve With State In Gx 349+2?
Abstract: Neutron star low-mass X-ray binaries display significant spectral and timing variability, and get classified based their characteristic variability behavior. However, there is still not a clear picture as to what drives this variability. Timing properties suggest it may be due to changes in the radius of the inner accretion disk. Unfortunately, continuum modeling of neutron star LMXBs is especially degenerate, and thus hard to draw from. However, spectroscopy of the broad iron line and reflection spectrum provide a powerful tool to constrain the inner disk radius. Here, we propose an 80 ks observation of GX 349+2 to investigate spectral changes through the full set of spectral states. The broadband sensitivity make NuSTAR ideal for such a study.

Proposal Number: 2225
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 optically bright or Fermi-detected nova outburst. The recent 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: 2226
PI Last Name: Hamaguchi
Title: Colliding Wind X-Ray Emission From The Massive Binary Wr140 Around 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 variable density and on particle acceleration. Joint NuSTAR and XMM-Newton observation of WR 140 in AO14 discovered an extremely hard X-ray component, which can originate either from a kT ~13 keV plasma or inverse-Compton scattering. WR 140 will experience its periastron passage in 2016 Dec., a critical time when the WWC emission changes dramatically. We propose joint NuSTAR and XMM-Newton observations of WR 140 at key phases around periastron in AO15, to determine the origin of this component and answer questions about the abrupt X-ray flux decrease.

Proposal Number: 2227
PI Last Name: Brenneman
Title: Illuminating The Disk/Corona/Jet Connection In Nls1 Galaxies
Abstract: We propose a 200-ks NuSTAR observation of the radio-loud narrow line Seyfert 1 galaxy PMN J0948+0022, to be executed contemporaneously with an 80-ks XMM-Newton observation. The high accretion rate and rapid variability of NLS1s make them ideal candidates in which to observe the disk/corona system, but there are only a small handful of radio-loud members of this population. The broadband X-ray and optical/UV spectra we obtain, along with information from existing Fermi and radio campaigns, will allow us to address some of the key questions regarding the physics of jet formation in this critical sample, such as the physical conditions under which a jet can be launched, the relation of the jet to the putative corona in AGN, and correlations with the inner accretion flow.

Proposal Number: 2230
PI Last Name: Hemphill
Title: Is The Cyclotron Line Energy Of 4U 1538-522 Increasing Over Time?
Abstract: We propose a NuSTAR observation of the high-mass X-ray binary 4U 1538-522, with the aim of constraining the evolution with time energy of its cyclotron resonance scattering feature (CRSF). With the discovery by Staubert et al. (2014) of a secular decrease in the CRSF energy of Her X-1, 4U 1538-522 is the most promising candidate for a second source exhibiting a similar trend, as the 2012 Suzaku observation of 4U 1538-522 finds a CRSF energy that is ~1.5 keV higher than the energy measured by RXTE between 1996 and 2004. A NuSTAR observation would determine conclusively whether this represents a secular trend or a temporary shift in the CRSF energy, in addition to obtaining the most precise measurement of the hard X-ray spectrum to date.

Proposal Number: 2231
PI Last Name: Vignali
Title: Ngc 2785, A Heavily Compton-Thick AGN Candidate In A Star-Forming Galaxy In The Backyard
Abstract: We propose a 70 ks NuSTAR observation of NGC 2785, a Type 2 AGN hosted in a star-forming galaxy at z=0.009. The source was marginally detected (~3.5 sigma) at hard X-ray energies by a careful analysis of the 54-month Swift/BAT data. The intrinsic X-ray luminosity, derived from both the [OIII] emission line and the mid-IR AGN emission, is much higher than that measured from the 10 ks Swift/XRT pointed observation. The most likely explanation for these results and for the high BAT/XRT flux ratio is that the source is a heavily Compton-thick AGN. NuSTAR represents the most efficient way to shed definite light on this source.

Proposal Number: 2235
PI Last Name: Grefenstette
Title: Hunting For The Source Of Variability In The Stellar Mass Black Hole Lmc X-1
Abstract: We propose a 40 ks NuSTAR observation of the black hole binary LMC X-1, of two persistently emitting stellar mass black holes that are close enough to allow high quality spectroscopic analysis. We will search for the origin of the (~ks) variability in the non-thermal continuum and thermal disk emission in the "high/soft" state of the source. We have also identified a variable absorption feature associated with ionized plasma. Previous observations with other satellites could not observe this feature or have limited observations of the source. Crucially, we do not yet have coverage over the full orbit with high quality, broadband X-ray data that NuSTAR will provide can simultaneously constrain the emission from the accretion disk, the non-thermal continuum, and the disk reflection spectrum.

Proposal Number: 2238
PI Last Name: Hamaguchi
Title: Monitoring The Extremely Hard Spectral Slope Of Eta Carinae Around Apastron
Abstract: Eta Carinae is an extremely massive binary system whose strong winds produce a variety of high X-ray activities. Earlier INTEGRAL and Suzaku observations of the star suggested non-thermal emission from high energy particles above 10 keV, which might be related to the Fermi GeV gamma-ray source. Joint NuSTAR and XMM-Newton observations of the star near periastron in 2014 did not confirm this emission, but another joint observation in 2015 July at the orbital phase 0.17 detected a clear excess component above 17 keV. This result may suggest shock acceleration or extreme shock heating by the wind colliding shock, which is important for cosmic ray origin or stellar evolution theory. We propose a deep NuSTAR observation of the star near apastron to understand the nature of this component.

Proposal Number: 2246
PI Last Name: Gotthelf
Title: The Energetic Magnetar In Hess J1713-381/Ctb 37B
Abstract: The 3.82s AXP in the SNR CTB 37B is among the youngest and most energetic magnetars, with a spin-down power up to 7.4E34 erg/s. A recent NuSTAR observation reveals hard X-ray emission above 10 keV. We propose to measure its hard spectrum with sufficient accuracy to apply the Beloborodov e-/e+ outflow model and to characterize its > 10 keV pulsed emission, to study the emission geometry. We also propose to continue monitoring its spin-down rate, which varies by a factor of 2. The most energetic magnetars are SGRs, and a marked increase in their spin-down torque often precedes an outburst. By analogy with SGR/AXP 1E 1547.0-5408, the magnetar with the largest spin-down power, and most similar to the AXP in CTB 37B, we may be observing the behavior of an SGR before it outburst.

Proposal Number: 2247
PI Last Name: Bhattacharyya
Title: Broadband X-Ray Spectral And Timing Study Of Cygnus X-1 And Grs 1915+105
Abstract: X-ray spectral/timing properties of BHXBs can provide information about black hole spin, strong gravity regime and accretion-ejection mechanism. But this information can be reliable only if broadband spectral components can be identified, systematics in relativistic line shape can be reduced and timing properties can be connected to spectral properties. Our proposed 80 ks of NuSTAR observations of BHXBs Cygnus X-1 and GRS 1915+105, and contemporaneous ASTROSAT observations using our guaranteed time, will for the first time achieve a spectral/timing characterization above 10 keV at a level similar to what could be achieved with joint observations with a CCD and RXTE/PCA below 10 keV. This proposal relies on the broadband sensitivity of NuSTAR and the uniquely large area of ASTROSAT/LAXPC.

Proposal Number: 2251
PI Last Name: Schirmer
Title: Probing The Faded AGN Of The Lowest Redshift Lyman-Alpha Blobs
Abstract: Lyman-alpha blobs (LABs) are luminous extended emission line regions at high redshift. Their ionization sources remain mostly mysterious, and obscured AGN are thought to be responsible in many cases. Recently, we have discovered LABs at redshifts z=0.3, existing 7 billion years later in the Universe than previously known. Our Chandra data show that the embedded AGN are very weak, and that they must have faded by 3-4 orders of magnitude in the last 10,000-100,000 years. Such transient AGN and episodic duty cycles naturally explain the apparent ionization deficits in LABs because of the delayed escape of the resonant Lyman-alpha photons. With short NUSTAR observations we will show that these AGN are indeed weak and not deeply obscured, solving a long-standing puzzle in galaxy evolution.

Proposal Number: 2252
PI Last Name: Rivers
Title: Testing For Relativistic Reflection In Ngc 1052
Abstract: We propose a 60 ks NuSTAR observation of NGC 1052 with simultaneous XMM-Newton coverage in order to accurately model the reflection features in this source. NGC 1052 is a LINER with a low Eddington rate that has shown hints of a broad Fe Ka line but no Compton reflection hump in the past. A short NuSTAR observation of the source, indicated that there may indeed be Compton reflection in this source and a harder continuum than previously thought. Unfortunately, lack of statistics and low resolution in the Fe K bandpass of the current data negate the possibility of a robust measurement. A longer broadband observation will allow us to robustly measure the reflection signatures and simultaneous XMM coverage will allow us to carefully and consistently test for relativistic reflection.

Proposal Number: 2257
PI Last Name: Matzeu
Title: Solving The Origin Of The Hard X-Ray Excess In The Narrow Lined Seyfert 1,Ton S180
Abstract: The origin of the hard X-ray excess in AGN is the subject of active debate. Recent studies have suggested the presence of a hard excess in a significant fraction of Type I AGN, possibly due to partial covering by Compton thick matter. This finding appears at odds with the standard AGN Unified Model, where such obscuration would only be predicted in type II AGN. Here we propose a joint 120 ks NuSTAR and 30 ks XMM-Newton observation of the luminous NLS1 galaxy TON S180, where a strong hard excess was reported in a previous Suzaku observation. With the proposed observations we will differentiate between a hard excess caused by a partially covering absorber, or by relativistically blurred reflection. We will also discriminate between competing scenarios of the energy dependent time lags.

Proposal Number: 2262
PI Last Name: Kargaltsev
Title: Hard X-Ray Portrait Of Ls 5039
Abstract: The number of high-mass gamma-ray binaries (HMGBs) has been increasing in recent years, yet we are still far from understanding the nature of these systems. In all but one case we still cannot differentiate between a neutron star (NS) and a black hole (BH). We propose NuSTAR observation of the gamma-ray binary LS 5039 over entire orbital period to obtain a complete spectral and temporal portrait of this archetypal HMGB. The high-S/N spectral and high-resolution timing data, will allow us to search for NS or BH signatures in hard X-rays.

Proposal Number: 2263
PI Last Name: Wik
Title: What A Shock! Constraining The Heating Mechanism In Abell 665
Abstract: Mergers between galaxy clusters inject energy into the intracluster medium, which both heats up the gas and accelerates relativistic particles. In the massive cluster Abell 665, both processes are occurring, evidenced by a radio halo and a newly discovered shock front. We propose to characterize the heating mechanism of the electrons by measuring the temperature profile behind the shock, which can distinguish between instant heating or delayed equilibration. Such measurements are extremely difficult for other observatories due to the high temperatures involved: we have pioneered a method combining Chandra and NuSTAR data to do this, and the shock in A665 is the best target for such a test. We will also constrain non-thermal IC emission in A665 for the first time.

Proposal Number: 2266
PI Last Name: Rana
Title: Probing Reflection In A Dwarf Nova Ss Cygni Using Joint NuSTAR And XMM Data
Abstract: We propose for a joint observation of SS~Cyg in its optical quiescence and outburst states with NuSTAR and XMM with the aim of having first robust detection of reflection component, commonly observed in binaries and AGNs. Presence of such component have been inferred via detection of Fe 6.4 keV line, however no direct detection till date. We will fit the phase averaged spectra to derive reflection amplitude. These measurements will help verify theoretical ideas like presence of central hole in disk, main contributing site for the reflection during the two states and also to study response of the system to varying accretion conditions.

Proposal Number: 2270
PI Last Name: Lopez
Title: NuSTAR Observations Of The Energetic Pwn N157B
Abstract: We propose to observe the pulsar wind nebula N157B in the Large Magellanic Cloud for 100 ks with NuSTAR. N157B hosts the fastest and most energetic young pulsar PSR J0537-6910, and it has a similar spin-down energy loss rate as the Crab. We aim to detect, disentangle, and characterize the hard X-ray emission (> 8 keV) from the PWN and the PSR and to compare its properties to other PWN and PSRs. We will search for spectral breaks in the hard X-rays as well as measure the braking index which was shown to be anomalously high during monitoring with RXTE. The super-star cluster R136 will be serendipitously imaged off axis, and we expect it will be detected up to > 20 keV. We will model this emission as well to explore whether it arises from e.g., colliding wind binaries.

Proposal Number: 2279
PI Last Name: Steiner
Title: Revealing The Compact Object In Ngc 300 X-1
Abstract: Our goal is to test the nature of the compact object in NGC 300 X-1, one of only a trio of likely Wolf-Rayet, black hole systems using NuSTAR and XMM-Newton. As a primary challenge, we will test whether a neutron star model is compatible with the observations. If, as expected, we confirm that the compact primary must be a black hole, then we will analyze its spin as a function of mass and inclination. NuSTAR will firmly anchor the Compton component thereby allowing us to accurately disentangle the Compton and thermal emission. Without high-energy coverage, no meaningful constraint is possible. Accordingly, this science is uniquely feasible using NuSTAR and XMM-Newton in concert.

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