Brian W. Grefenstette - Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA

Brian W. Grefenstette
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Name
Brian W. Grefenstette
Affiliation
Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA
City
Pasadena
Country
United States

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Pub Categories

 
High Energy Astrophysical Phenomena (37)
 
Instrumentation and Methods for Astrophysics (7)
 
Solar and Stellar Astrophysics (5)
 
Astrophysics of Galaxies (2)
 
Cosmology and Nongalactic Astrophysics (1)
 
Physics - Atmospheric and Oceanic Physics (1)

Publications Authored By Brian W. Grefenstette

We present observations of the occulted active region AR12222 during the third {\em NuSTAR} solar campaign on 2014 December 11, with concurrent {\em SDO/}AIA and {\em FOXSI-2} sounding rocket observations. The active region produced a medium size solar flare one day before the observations, at $\sim18$UT on 2014 December 10, with the post-flare loops still visible at the time of {\em NuSTAR} observations. The time evolution of the source emission in the {\em SDO/}AIA $335\textrm{\AA}$ channel reveals the characteristics of an extreme-ultraviolet late phase event, caused by the continuous formation of new post-flare loops that arch higher and higher in the solar corona. Read More

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing high energy (3-79 keV) X-ray observatory operating for four years from low Earth orbit. The X-ray detector arrays are located on the spacecraft bus with the optics modules mounted on a flexible mast of 10.14m length. Read More

We present results from the the first campaign of dedicated solar observations undertaken by the \textit{Nuclear Spectroscopic Telescope ARray} ({\em NuSTAR}) hard X-ray telescope. Designed as an astrophysics mission, {\em NuSTAR} nonetheless has the capability of directly imaging the Sun at hard X-ray energies ($>$3~keV) with an increase in sensitivity of at least two magnitude compared to current non-focusing telescopes. In this paper we describe the scientific areas where \textit{NuSTAR} will make major improvements on existing solar measurements. Read More

The evolved, massive highly eccentric binary system, eta Carinae, underwent a periastron passage in the summer of 2014. We obtained two coordinated X-ray observations with XMM-Newton and NuSTAR during the elevated X-ray flux state and just before the X-ray minimum flux state around this passage. These NuSTAR observations clearly detected X-ray emission associated with eta Car extending up to ~50 keV for the first time. Read More

2015Oct
Affiliations: 1Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 2Jet Propulsion Laboratory, 3California Institute of Technology, Cahill Center for Astronomy and Astrophysics, 4Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 5Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 6Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 7Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 8Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 9Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 10Anton Pannekoek Institute for Astronomy, 11California Institute of Technology, Cahill Center for Astronomy and Astrophysics, 12California Institute of Technology, Cahill Center for Astronomy and Astrophysics, 13Jet Propulsion Laboratory, 14Jet Propulsion Laboratory, 15Rice University, Department of Physics and Astronomy, 16Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 17Georgia College, Department of Chemistry, Physics, and Astronomy, 18Jet Propulsion Laboratory, 19Jet Propulsion Laboratory, 20North-West University, Centre for Space Research, 21Technical University of Denmark, DTU Space, National Space Institute, 22Yale University, Department of Astronomy, 23Washington University in Saint Louis, Physics Department and McDonnell Center for the Space Sciences, 24University of Virginia, Department of Astronomy, 25MPI for Extraterrestrial Physics Garching, 26Durham University, Centre for Extragalactic Astronomy, Department of Physics, 27Jet Propulsion Laboratory, 28North Carolina State University, Department of Physics, 29Jet Propulsion Laboratory, 30Cambridge, Institute of Astronomy, UK, 31Penn State University, Department of Astronomy and Astrophysics, 32Jet Propulsion Laboratory, 33University of California, Berkeley, Department of Physics, 34ASI Science Data Center, Italy, 35California Institute of Technology, Cahill Center for Astronomy and Astrophysics, 36Cambridge, Institute of Astronomy, UK, 37Jet Propulsion Laboratory, 38Purdue University, Department of Physics and Astronomy, 39Texas Tech University, Physics Department, 40Nagoya University, Center for Experimental Studies, Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, 41University of Maryland, Physics Department, 42RIKEN, 43Univ. of Michigan in Ann Arbor, Astronomy Dept, 44Harvard-Smithsonian Center for Astrophysics, 45Istituto di Astrofisica e Planetologia Spaziali, INAF, 46Department of Astronomy/Steward Observatory, 47Lawrence Livermore National Laboratory, 48Jet Propulsion Laboratory, 49Department of Astronomy/Steward Observatory, 50NASA Goddard Space Flight Center, 51Tohoku University, Astronomical Institute, 52NASA Goddard Space Flight Center

This paper describes the Polarization Spectroscopic Telescope Array (PolSTAR), a mission proposed to NASA's 2014 Small Explorer (SMEX) announcement of opportunity. PolSTAR measures the linear polarization of 3-50 keV (requirement; goal: 2.5-70 keV) X-rays probing the behavior of matter, radiation and the very fabric of spacetime under the extreme conditions close to the event horizons of black holes, as well as in and around magnetars and neutron stars. Read More

The recent discovery by Bachetti et al. (2014) of a pulsar in M82 that can reach luminosities of up to 10^40 ergs s^-1, a factor of ~100 the Eddington luminosity for a 1.4 Msol compact object, poses a challenge for accretion physics. Read More

We present results from multi-wavelength simultaneous X-ray and radio observations of the black hole X-ray binary V404 Cyg in quiescence. Our coverage with NuSTAR provides the very first opportunity to study the X-ray spectrum of V404 Cyg at energies above 10 keV. The unabsorbed broad-band (0. Read More

We present results from a 244\,ks \textit{NuSTAR} observation of 3C\,273 obtained during a cross-calibration campaign with the \textit{Chandra}, \textit{INTEGRAL}, \textit{Suzaku}, \textit{Swift}, and \textit{XMM-Newton} observatories. We show that the spectrum, when fit with a power-law model using data from all observatories except \textit{INTEGRAL} over the 1--78\,keV band, leaves significant residuals in the \textit{NuSTAR} data between 30--78\,keV. The \nustar\ 3--78\,keV spectrum is well-described by an exponentially cutoff power-law ($\Gamma = 1. Read More

The black hole candidate XTE J1908+094 went into outburst for the first time since 2003 in October 2013. We report on an observation with the Nuclear Spectroscopic Telescope Array (NuSTAR) and monitoring observations with Swift during the outburst. NuSTAR caught the source in the soft state: the spectra show a broad relativistic iron line, and the light curves reveal a ~40 ks flare with the count rate peaking about 40% above the non-flare level and with significant spectral variation. Read More

We report the observation of two isolated clouds of positrons inside an active thunderstorm. These observations were made by the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, which flew on a Gulfstream V jet aircraft through the top of an active thunderstorm in August 2009. ADELE recorded two 511 keV gamma-ray count rate enhancements, 35 seconds apart, each lasting approximately 0. Read More

We report results from deep observations (~750 ks) of Tycho's supernova remnant (SNR) with NuSTAR. Using these data, we produce narrow-band images over several energy bands to identify the regions producing the hardest X-rays and to search for radioactive decay line emission from 44Ti. We find that the hardest (>10 keV) X-rays are concentrated in the southwest of Tycho, where recent Chandra observations have revealed high emissivity "stripes" associated with particles accelerated to the knee of the cosmic-ray spectrum. Read More

We present the calibration of the \textit{Nuclear Spectroscopic Telescope Array} (\nustar) X-ray satellite. We used the Crab as the primary effective area calibrator and constructed a piece-wise linear spline function to modify the vignetting response. The achieved residuals for all off-axis angles and energies, compared to the assumed spectrum, are typically better than $\pm 2$\% up to 40\,keV and 5--10\,\% above due to limited counting statistics. Read More

We present broadband (3 -- 78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power-law in this energy band, spatially resolved spectroscopy of the nebula finds a break at $\sim$9 keV in the spectral photon index of the torus structure with a steepening characterized by $\Delta\Gamma\sim0.25$. Read More

We present deep ($>$2.4 Ms) observations of the Cassiopeia A supernova remnant with {\it NuSTAR}, which operates in the 3--79 keV bandpass and is the first instrument capable of spatially resolving the remnant above 15 keV. We find that the emission is not entirely dominated by the forward shock nor by a smooth "bright ring" at the reverse shock. Read More

Timing of high-count rate sources with the NuSTAR Small Explorer Mission requires specialized analysis techniques. NuSTAR was primarily designed for spectroscopic observations of sources with relatively low count-rates rather than for timing analysis of bright objects. The instrumental dead time per event is relatively long (~2. Read More

2014Aug
Affiliations: 1Physics Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA, 2Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA, 3Department of Physics, McGill University, Montreal, Quebec, Canada, 4Department of Physics, McGill University, Montreal, Quebec, Canada, 5Department of Physics, McGill University, Montreal, Quebec, Canada, 6Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA, 7Space Sciences Laboratory, University of California, Berkeley, CA, USA, 8DTU Space, National Space Institute, Technical University of Denmark, Lyngby, Denmark, 9Physics Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA, 10Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA, 11Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA, 12Physics Department and Columbia Astrophysics Laboratory, Columbia University, New York, NY, USA, 13Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA, 14Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA, USA, 15Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA, USA, 16Physics Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA, 17Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, 18Goddard Space Flight Center, Greenbelt, MD, USA

We report on new broad band spectral and temporal observations of the magnetar 1E 2259+586, which is located in the supernova remnant CTB 109. Our data were obtained simultaneously with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift, and cover the energy range from 0.5-79 keV. Read More

We present the first images of the pulsar wind nebula (PWN) MSH 15-52 in the hard X-ray band (>8 keV), as measured with the Nuclear Spectroscopic Telescope Array (NuSTAR). Overall, the morphology of the PWN as measured by NuSTAR in the 3-7 keV band is similar to that seen in Chandra high-resolution imaging. However, the spatial extent decreases with energy, which we attribute to synchrotron energy losses as the particles move away from the shock. Read More

2014Mar
Affiliations: 1MIT, 2Berkeley, 3Caltech, 4Arizona, 5IRAP/Toulouse, 6IRAP/Toulouse, 7Berkeley, 8DTU Space, 9LLNL/Berkeley, 10Caltech, 11Columbia, 12Caltech, 13McGill, 14Michigan, 15MIT, 16Caltech, 17JPL/Caltech, 18NASA/GSFC, 19Erlangen-Nuremberg, 20NASA/GSFC

The low-mass X-ray binary Cen X-4 is the brightest and closest (<1.2 kpc) quiescent neutron star transient. Previous 0. Read More

The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, with most detections being either of low significance or controversial. Background and contamination uncertainties present in the data of non-focusing observatories result in lower sensitivity to IC emission and a greater chance of false detection. We present 266ks NuSTAR observations of the Bullet cluster, detected from 3-30 keV. Read More

Sagittarius A* harbors the supermassive black hole that lies at the dynamical center of our Galaxy. Sagittarius A* spends most of its time in a low luminosity emission state but flares frequently in the infrared and X-ray, increasing up to a few hundred fold in brightness for up to a few hours at a time. The physical processes giving rise to the X-ray flares are uncertain. Read More

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first focusing hard X-ray mission in orbit and operates in the 3-79 keV range. NuSTAR's sensitivity is roughly two orders of magnitude better than previous missions in this energy band thanks to its superb angular resolution. Since its launch in 2012 June, NuSTAR has performed excellently and observed many interesting sources including four magnetars, two rotation-powered pulsars and the cataclysmic variable AE Aquarii. Read More

We present results for two Ultraluminous X-ray Sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by $\sim$7 days. We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3--30 keV luminosities being $1. Read More

2013Nov
Affiliations: 1SRL, Caltech, Pasadena, CA, 2UMBC, Baltimore, MD, 3Remeis-Observatory & ECAP, Bamberg, Germany, 4SSL, UC Berkeley, Berkeley, CA, 5Universite de Toulouse, Toulouse, France, 6SSL, UC Berkeley, Berkeley, CA, 7DTU Space, Lyngby, Denmark, 8SSL, UC Berkeley, Berkeley, CA, 9SRL, Caltech, Pasadena, CA, 10, Columbia Astrophysics Lab, New York, NY, 11SRL, Caltech, Pasadena, CA, 12SRL, Caltech, Pasadena, CA, 13U Michigan, Ann Arbor, MI, 14JPL, Caltech, Pasadena, CA, 15SRL, Caltech, Pasadena, CA, 16NASA GSFC, Greenbelt, MD

We present NuSTAR observations of Vela X-1, a persistent, yet highly variable, neutron star high-mass X-ray binary (HMXB). Two observations were taken at similar orbital phases but separated by nearly a year. They show very different 3-79 keV flux levels as well as strong variability during each observation, covering almost one order of magnitude in flux. Read More

2013Oct
Affiliations: 1Istituto di Astrofisica e Planetologia Spaziali, INAF, 2Space Sciences Laboratory, University of California, Berkeley, 3Istituto di Astrofisica e Planetologia Spaziali, INAF, 4Physics Dept. and Institute for Particle Physics, University of California, Santa Cruz, 5Universitè de Toulouse, 6Universitè de Toulouse, 7Space Sciences Laboratory, University of California, Berkeley, 8DTU Space, Technical University of Denmark, 9Space Sciences Laboratory, University of California, Berkeley, 10Istituto di Astrofisica e Planetologia Spaziali, INAF, 11Cahill Center for Astronomy and Astrophysics, Caltech, 12Cahill Center for Astronomy and Astrophysics, Caltech, 13Columbia Astrophysics Laboratory, Columbia University, 14Cahill Center for Astronomy and Astrophysics, Caltech, 15Space Sciences Laboratory, University of California, Berkeley, 16European Space Astronomy Centre, 17Dept. of Astronomy, University of Michigan, 18CRESST and NASA/GSFC, 19Jet Propulsion Laboratory, Caltech, 20Istituto di Astrofisica e Planetologia Spaziali, INAF, 21Cahill Center for Astronomy and Astrophysics, Caltech, 22NASA/GSFC

The microquasar 1E1740.7-2942, also known as the "Great Annihilator", was observed by NuSTAR in the Summer of 2012. We have analyzed in detail two observations taken ~2 weeks apart, for which we measure hard and smooth spectra typical of the low/hard state. Read More

We report new spectral and temporal observations of the magnetar 1E 1841-045 in the Kes 73 supernova remnant obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR). Combined with new Swift and archival XMM-Newton and Chandra observations, the phase-averaged spectrum is well characterized by a blackbody plus double power-law model, in agreement with previous, multi-mission X-ray results. However, we are unable to reproduce the spectral results reported using Suzaku observations. Read More

2013Oct
Affiliations: 1SSL/UCB, 2MIT, 3Cambridge, 4Univ. of Michigan, 5Cambridge, 6Caltech, 7Univ. of Toulouse and CNRS, 8Univ. of Toulouse and CNRS, 9SSL/UCB, 10DTU Space, 11SSL/UCB and LLNL, 12Caltech, 13Caltech, 14Caltech, 15Columbia, 16Univ. of Michigan, 17Caltech, 18INAF-IAPS, 19CRESST, NASA/GSFC, and Univ. of Maryland, 20Holy Cross, 21JPL, 22Caltech, 23Dr. Karl-Remeis-Sternwarte and Erlangen Center for Astroparticle Physics, 24NASA/GSFC

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 the ~1-300 keV range. The source was in the soft state with a multi-temperature blackbody, power-law, and reflection components along with absorption from highly ionized material in the system. The high throughput of NuSTAR allows for a very high quality measurement of the complex iron line region as well as the rest of the reflection component. Read More

We present the results of NuSTAR and XMM-Newton observations of the two ultraluminous X-ray sources (ULX) NGC 1313 X-1 and X-2. The combined spectral bandpass of the two satellites enables us to produce the first spectrum of X-1 between 0.3 and 30 keV, while X-2 is not significantly detected by NuSTAR above 10 keV. Read More

2013Sep
Affiliations: 1Cahill Center for Astronomy and Astrophysics, 2Cahill Center for Astronomy and Astrophysics, 3Institut fuerr Astronomie und Astrophysik, Universitaat Tuebingen, 4Space Sciences Laboratory, University of California, 5Universite de Toulouse, UPS-OMP, 6Universite de Toulouse, UPS-OMP, 7Cahill Center for Astronomy and Astrophysics, 8Space Sciences Laboratory, University of California, 9DTU Space, National Space InstituteLynby, Denmark, 10DTU Space, National Space InstituteLynby, Denmark, 11Space Sciences Laboratory, University of California, 12Columbia Astrophysics Laboratory, Columbia University, 13Cahill Center for Astronomy and Astrophysics, 14Institut fuerr Astronomie und Astrophysik, Universitaat Tuebingen, 15Cahill Center for Astronomy and Astrophysics, 16CRESST and NASA Goddard Space Flight Center, 17Jet Propulsion Laboratory, California Institute of Technology, 18Cahill Center for Astronomy and Astrophysics, 19Dr. Karl-Remeis-Sternwarte, 20Center for Space Science and Technology, University of Maryland Baltimore County

Her X-1, one of the brightest and best studied X-ray binaries, shows a cyclotron resonant scattering feature (CRSF) near 37 keV. This makes it an ideal target for detailed study with the Nuclear Spectroscopic Telescope Array (NuSTAR), taking advantage of its excellent hard X-ray spectral resolution. We observed Her X-1 three times, coordinated with Suzaku, during one of the high flux intervals of its 35d super-orbital period. Read More

The NuSTAR hard X-ray telescope observed the transient Be/X-ray binary GS 0834-430 during its 2012 outburst - the first active state of this system observed in the past 19 years. We performed timing and spectral analysis, and measured the X-ray spectrum between 3-79keV with high statistical significance. We find the phase-averaged spectrum to be consistent with that observed in many other magnetized accreting pulsars. Read More

2013Jan

The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 13 June 2012, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates in the band from 3 -- 79 keV, extending the sensitivity of focusing far beyond the ~10 keV high-energy cutoff achieved by all previous X-ray satellites. The inherently low-background associated with concentrating the X-ray light enables NuSTAR to probe the hard X-ray sky with a more than one-hundred-fold improvement in sensitivity over the collimated or coded-mask instruments that have operated in this bandpass. Read More

The Nuclear Spectroscopic Telescope Array (NuSTAR) will be the first space mission to focus in the hard X-ray (5-80 keV) band. The NuSTAR instrument carries two co-aligned grazing incidence hard X-ray telescopes. Each NuSTAR focal plane consists of four 2 mm CdZnTe hybrid pixel detectors, each with an active collecting area of 2 cm x 2 cm. Read More

The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing hard X-ray (5 -- 80 keV) telescope to orbit. NuSTAR will offer a factor 50 -- 100 sensitivity improvement compared to previous collimated or coded mask imagers that have operated in this energy band. In addition, NuSTAR provides sub-arcminute imaging with good spectral resolution over a 12-arcminute field of view. Read More