Brian W. Grefenstette
A5062928530- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Particle Detector Development and Performance
- Galaxies: Formation, Evolution, Phenomena
- Lightning and Electromagnetic Phenomena
- High-pressure geophysics and materials
- Ionosphere and magnetosphere dynamics
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Advanced X-ray Imaging Techniques
- Dark Matter and Cosmic Phenomena
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Astronomy and Astrophysical Research
- Mechanics and Biomechanics Studies
- Advanced Semiconductor Detectors and Materials
- Nuclear Physics and Applications
- Solar Radiation and Photovoltaics
- Astro and Planetary Science
- Geophysics and Gravity Measurements
- Particle Accelerators and Free-Electron Lasers
- CCD and CMOS Imaging Sensors
California Institute of Technology
2015-2024
Space Micro (United States)
2021
European Space Astronomy Centre
2018-2021
Université de Toulouse
2013
Université Toulouse III - Paul Sabatier
2013
University of California, Santa Cruz
2008-2010
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
ABSTRACT We report the detection of coherent pulsations from ultraluminous X-ray source (ULX) NGC 7793 P13. The ≈0.42 s nearly sinusoidal were initially discovered in broadband observations using XMM-Newton and NuSTAR taken 2016. subsequently also found archival data 2013 2014. significant (≫5 σ ) demonstrates that compact object P13 is a neutron star, given observed peak luminosity ≈10 40 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>erg</mml:mi>...
We present the calibration of Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. used Crab as primary effective area calibrator and constructed a piece-wise linear spline function to modify vignetting response. The achieved residuals for all off-axis angles energies, compared assumed spectrum, are typically better than ±2% up 40 keV 5%–10% above due limited counting statistics. An empirical adjustment theoretical two-dimensional point-spread (PSF) was found using several strong...
With the first direct detection of merging black holes in 2015, era gravitational wave (GW) astrophysics began. A complete picture compact object mergers, however, requires an electromagnetic (EM) counterpart. We report ultraviolet (UV) and X-ray observations by Swift Nuclear Spectroscopic Telescope ARray (NuSTAR) EM counterpart binary neutron star merger GW170817. The bright, rapidly fading emission indicates a high mass ($\approx0.03$ solar masses) wind-driven outflow with moderate...
We report the discovery of 3.76 s pulsations from a new burst source near Sgr A* observed by NuSTAR observatory. The strong signal SGR J1745−29 presents complex pulse profile modulated with pulsed fraction 27% ± 3% in 3–10 keV band. Two observations spaced nine days apart yield spin-down rate =(6.5 1.4) × 10−12. This implies magnetic field B = 1.6 1014 G, power =5 1033 erg s−1, and characteristic age P/2 =9 103 yr for rotating dipole model. However, current may be erratic, especially during...
The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, most detections being either of low significance or controversial. Background and contamination uncertainties present in the data non-focusing observatories result lower sensitivity to IC a greater chance false detection. We 266ks NuSTAR observations Bullet cluster, detected 3-30 keV. NuSTAR's unprecedented focusing capability largely...
We present two complementary NuSTAR x-ray searches for keV-scale dark matter decaying to mono-energetic photons in the Milky Way halo. In first, we utilize known intensity pattern of unfocused stray light across detector planes -- dominant source from diffuse sources separate astrophysical emission internal instrument backgrounds using ${\sim}$7-Ms/detector deep blank-sky exposures. second, an updated parametric model full background, allowing us leverage statistical power independent...
We present NuSTAR observations of the nearby SN 2023ixf in M101 (d=6.9 Mpc) which provide earliest hard X-ray detection a non-relativistic stellar explosion to date at $\delta t\approx$4-d and t\approx$11-d. The spectra are well described by hot thermal bremsstrahlung continuum with $T>25 \rm{keV}$ shining through thick neutral medium hydrogen column that decreases time (initial $N_{\rm{Hint}}=2.6\times 10^{23} \rm{cm^{-2}}$). A prominent Fe K$\alpha$ emission line is clearly detected,...
The High Energy X-ray Probe (HEX-P) is a proposed NASA probe-class mission that combines the power of high angular resolution with broad bandpass to provide necessary leap in capabilities address important astrophysical questions next decade. HEX-P achieves breakthrough performance by combining technologies developed experienced international partners. To meet science goals, payload consists suite co-aligned telescopes designed cover 0.2–80 keV bandpass. Telescope (HET) has an effective 2–80...
We report the results of a multi-band observing campaign on famous blazar 3C 279 conducted during phase increased activity from 2013 December to 2014 April, including first observations it with NuSTAR. The $\gamma$-ray emission source measured by Fermi-LAT showed multiple distinct flares reaching highest flux level in this object since beginning Fermi mission, $F(E > 100\,{\rm MeV})$ $10^{-5}$ photons cm$^{-2}$ s$^{-1}$, and doubling time scale as short 2 hours. spectrum one was very hard,...
We present multi-wavelength observations of SN 2014C during the first 500 days. These represent solid detection a young extragalactic stripped-envelope out to high-energy X-rays ~40 keV. shows ordinary explosion parameters (Ek ~ 1.8 × 1051 erg and Mej 1.7 M⊙). However, over an ~1 year timescale, evolved from hydrogen-poor supernova into strongly interacting, hydrogen-rich supernova, violating traditional classification scheme type-I versus type-II SNe. Signatures shock interaction with dense...
The black hole binary Cygnus X-1 was observed in late-2012 with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage over ~1-300 keV range. source soft state a multi-temperature blackbody, power-law, reflection components along absorption from highly ionized material system. high throughput of NuSTAR allows for very quality measurement complex iron line region as well rest component. is clearly broadened well-described by relativistic blurring model, an...
Stellar metals shine toward our eyes only Taking a different look at familiar star may still yield surprises. Boggs et al. trained the x-ray vision of NuSTAR observatory on well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce titanium isotope, 44 Ti, whose radioactive decay yields hard emission lines. All associated with 44Ti appears to be from material moving us, none away. This implies that explosion was not symmetric. These findings help explain mechanics and...
We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in hard state. This is first time this state has been observed Cyg with NuSTAR, which enables us to study reflection broadband spectra unprecedented detail. confirm that iron line cannot be fit a combination narrow lines absorption features, instead requiring relativistically blurred profile from companion wind. use models García et al. simultaneously measure black...
We present the results of NuSTAR and XMM-Newton observations two ultraluminous X-ray sources (ULX) NGC 1313 X-1 X-2. The combined spectral bandpass satellites enables us to produce first spectrum between 0.3 30 keV, while X-2 is not significantly detected by above 10 keV. data demonstrate that has a clear cutoff whose presence was only marginally detectable with previous observations. This rules out interpretation as black hole in standard low/hard state, it deeper than predicted for...
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
The distribution of elements produced in the inner-most layers a supernova explosion is key diagnostic for studying collapse massive stars. Here we present results 2.4 Ms \textit{NuSTAR} observing campaign aimed at remnant Cassiopeia A (Cas A). We perform spatially-resolved spectroscopic analyses $^{44}$Ti ejecta which use to determine Doppler shift and thus three-dimensional (3D) velocities ejecta. find an initial mass 1.54 $\pm$ 0.21 $\times 10^{-4}$ M$_{\odot}$ has day average momentum...
Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most X-ray Sources (ULXs) accretors of stellar mass rather than sub-Eddington intermediate black holes. An important prediction theories supercritical is existence powerful outflows moderately ionized gas at mildly relativistic speeds. In practice, spectral resolution gratings such as RGS onboard XMM-Newton required resolve their observational...
We present results from the coordinated broadband X-ray observations of extreme ultraluminous source Holmberg IX X-1 performed by NuSTAR, XMM-Newton and Suzaku in late 2012. These provide first high-quality spectra above 10 keV to date, extending coverage this remarkable up ~30 keV. Broadband were undertaken at two epochs, between which exhibited both flux strong spectral variability, increasing luminosity Lx = (1.90+/-0.03)e40 erg/s (3.35+/-0.03)e40 erg/s. Neither epoch exhibits a spectrum...
The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity 200 keV 10 GeV energy range with wide field of view, good spectral resolution, polarization sensitivity. Therefore, key study astrophysical objects have unique signatures gamma-ray regime, such as neutron star mergers, supernovae, flaring active galactic nuclei....
Abstract We present the first extensive radio to γ -ray observations of a fast-rising blue optical transient, AT 2018cow, over its ∼100 days. 2018cow rose few days peak luminosity L pk ∼ 4 × 10 44 erg s −1 , exceeding that superluminous supernovae (SNe), before declining as ∝ t −2 . Initial spectra at δt ≲ 15 were mostly featureless and indicated large expansion velocities v 0.1 c temperatures reaching T 3 K. Later revealed persistent optically thick photosphere emergence H He emission...
We present a summary of data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) terrestrial gamma ray flash (TGF) catalog. describe RHESSI search algorithm and discuss its limitations due to design emphasis on cleanliness rather than completeness. This has identified 820 TGFs between March 2002 February 2008. Radiation damage detectors resulted in decreased sensitivity after early 2006 corresponding decrease number years 2006–2008. Prior this, average rate occurrence was...