Brian W. Grefenstette
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View article: The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the X-Rays and Radio
The Most Luminous Known Fast Blue Optical Transient AT 2024wpp: Unprecedented Evolution and Properties in the X-Rays and Radio Open
We present X-ray (0.3–79 keV) and radio (0.25–203 GHz) observations of the most luminous fast blue optical transient (LFBOT) AT 2024wpp at z = 0.0868, spanning 2–280 days after first light. AT 2024wpp shows luminous ( L X ≈ 1.5 × 10 43 erg…
View article: NuSTAR as an Axion Helioscope
NuSTAR as an Axion Helioscope Open
We present a novel approach to investigating axions and axionlike particles by studying their potential conversion into x-rays within the Sun’s atmospheric magnetic field. Utilizing high-sensitivity data from the nuclear spectroscopic tele…
View article: A NuSTAR Study of Quasiperiodic Oscillations from the Ultraluminous X-Ray Sources in M82
A NuSTAR Study of Quasiperiodic Oscillations from the Ultraluminous X-Ray Sources in M82 Open
The study of quasiperiodic oscillations (QPOs) in X-ray binaries provides valuable insights into the physics of accretion around compact objects. The M82 galaxy hosts multiple ultraluminous X-ray sources, including two prominent ones—X-1 a…
View article: XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy<sup>*</sup>
XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy<sup>*</sup> Open
Green Pea galaxies are a class of compact, low-mass, low-metallicity star-forming galaxies in the relatively local Universe. They are believed to be analogs of high-redshift galaxies that reionized the Universe, and, indeed, the James Webb…
View article: Dinosaur in a Haystack: X-Ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper I)*
Dinosaur in a Haystack: X-Ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper I)* Open
We present the results from our extensive hard-to-soft X-ray (NuSTAR, Swift-XRT, XMM-Newton, Chandra) and meter-to-millimeter-wave radio (Giant Metrewave Radio Telescope, Very Large Array, NOEMA) monitoring campaign of the very nearby ( d …
View article: XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy
XMM-Newton Conclusively Identifies an Active Galactic Nucleus in a Green Pea Galaxy Open
Green Pea galaxies are a class of compact, low-mass, low-metallicity star-forming galaxies in the relatively local universe. They are believed to be analogues of high-redshift galaxies that re-ionised the universe and, indeed, the James We…
View article: Electromagnetic Follow-up to Gravitational Wave Events with the UltraViolet EXplorer (UVEX)
Electromagnetic Follow-up to Gravitational Wave Events with the UltraViolet EXplorer (UVEX) Open
The Ultraviolet Explorer (UVEX) is expected to fly in 2030 and will have the opportunity—and the rapid near/far-ultraviolet (UV) capabilities—to glean unprecedented insight into the bright UV emission present in kilonovae like that of AT 1…
View article: GX 340+0: In and Out of Focus
GX 340+0: In and Out of Focus Open
The Nuclear Spectroscopic Telescope Array (NuSTAR) enables detailed high-energy X-ray observations from 3--79 keV, but its performance can be constrained by telemetry saturation when observing bright sources, leading to reduced effective e…
View article: NuSTAR Observations of a Varying-flux Quasar in the Epoch of Reionization
NuSTAR Observations of a Varying-flux Quasar in the Epoch of Reionization Open
With enough X-ray flux to be detected in a 160 s scan by SRG/eROSITA, the z = 6.19 quasar CFHQS J142952+544717 is, by far, the most luminous X-ray source known at z > 6. We present deep (245 ks) NuSTAR observations of this source; with ∼18…
View article: NuSTAR observations of a varying-flux quasar in the Epoch of Reionization
NuSTAR observations of a varying-flux quasar in the Epoch of Reionization Open
With enough X-ray flux to be detected in a 160s scan by SRG/eROSITA, the $z = 6.19$ quasar CFHQS J142952+544717 is, by far, the most luminous X-ray source known at $z > 6$. We present deep (245 ks) NuSTAR observations of this source; with …
View article: The NuSTAR Local AGN N <sub>H</sub> Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe
The NuSTAR Local AGN N <sub>H</sub> Distribution Survey (NuLANDS). I. Toward a Truly Representative Column Density Distribution in the Local Universe Open
Hard X-ray-selected samples of active galactic nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion but are biased against objects obscured by Compton-thick gas column densities of N H > 10 24 cm −2 . To tack…
View article: The high energy X-ray probe (HEX-P): science overview
The high energy X-ray probe (HEX-P): science overview Open
To answer NASA’s call for a sensitive X-ray observatory in the 2030s, we present the High Energy X-ray Probe (HEX-P) mission concept. HEX-P is designed to provide the required capabilities to explore current scientific questions and make n…
View article: Dinosaur in a Haystack : X-ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper 1)
Dinosaur in a Haystack : X-ray View of the Entrails of SN 2023ixf and the Radio Afterglow of Its Interaction with the Medium Spawned by the Progenitor Star (Paper 1) Open
We present the results from our extensive hard-to-soft X-ray (NuSTAR, Swift-XRT, XMM-Newton, Chandra) and meter-to-mm wave radio (GMRT, VLA, NOEMA) monitoring campaign of the very nearby (d $=6.9$ Mpc) Type II SN2023ixf spanning $\approx$ …
View article: Spectrum and location of ongoing extreme particle acceleration in Cassiopeia A
Spectrum and location of ongoing extreme particle acceleration in Cassiopeia A Open
Young supernova remnants (SNRs) are believed to be the origin of energetic cosmic rays (CRs) below the "knee" of their spectrum at $\sim3$ petaelectronvolt (PeV, $10^{15}$ eV). Nevertheless, the precise location, duration, and operation of…
View article: The NuSTAR Local AGN $N_{\rm H}$ Distribution Survey (NuLANDS) I: Towards a Truly Representative Column Density Distribution in the Local Universe
The NuSTAR Local AGN $N_{\rm H}$ Distribution Survey (NuLANDS) I: Towards a Truly Representative Column Density Distribution in the Local Universe Open
Hard X-ray-selected samples of Active Galactic Nuclei (AGN) provide one of the cleanest views of supermassive black hole accretion, but are biased against objects obscured by Compton-thick gas column densities of $N_{\rm H}$ $>$ 10$^{24}$ …
View article: NuSTAR as an Axion Helioscope
NuSTAR as an Axion Helioscope Open
The nature of dark matter in the Universe is still an open question in astrophysics and cosmology. Axions and axionlike particles (ALPs) offer a compelling solution, and traditionally ground-based experiments have eagerly, but to date unsu…
View article: NuSTAR as an Axion Helioscope
NuSTAR as an Axion Helioscope Open
We present a novel approach to investigating axions and axion-like particles (ALPs) by studying their potential conversion into X-rays within the Sun's atmospheric magnetic field. Utilizing high-sensitivity data from the Nuclear Spectrosco…
View article: The high energy X-ray probe (HEX-P): instrument and mission profile
The high energy X-ray probe (HEX-P): instrument and mission profile Open
The High Energy X-ray Probe (HEX-P) is a proposed NASA probe-class mission that combines the power of high angular resolution with a broad X-ray bandpass to provide the necessary leap in capabilities to address the important astrophysical …
View article: The high energy X-ray probe (HEX-P): Resolving the nature of Sgr A* flares, compact object binaries and diffuse X-ray emission in the Galactic center and beyond
The high energy X-ray probe (HEX-P): Resolving the nature of Sgr A* flares, compact object binaries and diffuse X-ray emission in the Galactic center and beyond Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ( FWHM) and broad spectral coverage (0.2–80 keV) with an effective area far superior to current facilities’ (including XMM-Newton and NuSTAR ).…
View article: The high energy X-ray probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries
The high energy X-ray probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ( FWHM) and broad spectral coverage (0.2–80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to…
View article: The High Energy X-ray Probe (HEX-P): supernova remnants, pulsar wind nebulae, and nuclear astrophysics
The High Energy X-ray Probe (HEX-P): supernova remnants, pulsar wind nebulae, and nuclear astrophysics Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ( full width at half maximum) and broad spectral coverage (0.2–80 keV) with an effective area far superior to current facilities (including XMM…
View article: The high energy X-ray probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries
The high energy X-ray probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2–80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR)…
View article: Thermal Evolution of an Active Region through Quiet and Flaring Phases as Observed by NuSTAR XRT, and AIA
Thermal Evolution of an Active Region through Quiet and Flaring Phases as Observed by NuSTAR XRT, and AIA Open
Solar active regions contain a broad range of temperatures, with the thermal plasma distribution often observed to peak in the few millions of kelvin. Differential emission measure (DEM) analysis can allow instruments with diverse temperat…
View article: The High Energy X-ray Probe (HEX-P): Instrument and Mission Profile
The High Energy X-ray Probe (HEX-P): Instrument and Mission Profile Open
The High Energy X-ray Probe is a proposed NASA probe-class mission that combines the power of high angular resolution with a broad X-ray bandpass to provide the necessary leap in capabilities to address the important astrophysical question…
View article: The high energy X-ray probe: resolved X-ray populations in extragalactic environments
The high energy X-ray probe: resolved X-ray populations in extragalactic environments Open
We construct simulated galaxy data sets based on the High Energy X-ray Probe (HEX-P) mission concept to demonstrate the significant advances in galaxy science that will be yielded by the HEX-P observatory. The combination of high spatial r…
View article: The High Energy X-ray Probe: Resolved X-ray Populations in Extragalactic Environments
The High Energy X-ray Probe: Resolved X-ray Populations in Extragalactic Environments Open
We construct simulated galaxy data sets based on the High Energy X-ray Probe (HEX-P) mission concept to demonstrate the significant advances in galaxy science that will be yielded by the HEX-P observatory. The combination of high spatial r…
View article: The High Energy X-ray Probe (HEX-P): Supernova remnants, pulsar wind nebulae, and nuclear astrophysics
The High Energy X-ray Probe (HEX-P): Supernova remnants, pulsar wind nebulae, and nuclear astrophysics Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging ($<10"$ full width at half maximum) and broad spectral coverage (0.2--80 keV) with an effective area far superior to current facilities (includi…
View article: The High Energy X-ray Probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries
The High Energy X-ray Probe (HEX-P): Galactic PeVatrons, star clusters, superbubbles, microquasar jets, and gamma-ray binaries Open
HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10" FWHM) and broad spectral coverage (0.2-80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR)…
View article: Wavelet-based image decomposition method for NuSTAR stray light background studies
Wavelet-based image decomposition method for NuSTAR stray light background studies Open
The large side aperture of the NuSTAR telescope for unfocused photons (so-called stray light) is a known source of rich astrophysical information. To support many studies based on the NuSTAR stray light data, we present a fully automatic m…
View article: NuSTAR Observations of Abell 665 and 2146: Constraints on Non-Thermal Emission
NuSTAR Observations of Abell 665 and 2146: Constraints on Non-Thermal Emission Open
Observations from past missions such as RXTE and Beppo-SAX suggested the presence of inverse Compton (IC) scattering at hard X-ray energies within the intracluster medium of some massive galaxy clusters. In subsequent years, observations b…