A5004495261- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Mechanics and Biomechanics Studies
- Particle Detector Development and Performance
- High-pressure geophysics and materials
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Particle Accelerators and Free-Electron Lasers
- Radiation Detection and Scintillator Technologies
- Relativity and Gravitational Theory
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Nuclear Physics and Applications
- Galaxies: Formation, Evolution, Phenomena
- Adaptive optics and wavefront sensing
- Superconducting Materials and Applications
- Astro and Planetary Science
- Advanced X-ray Imaging Techniques
- Astrophysics and Star Formation Studies
- Medical Imaging Techniques and Applications
- Radio Astronomy Observations and Technology
University of California, Berkeley
2016-2025
Goddard Space Flight Center
2010-2024
Max Planck Institute for Extraterrestrial Physics
2024
University of California, San Diego
2000-2023
Universidad Católica Santo Domingo
2023
Berkeley College
2007-2023
Clemson University
2023
University of Maryland, College Park
2023
Kavli Institute for Particle Astrophysics and Cosmology
2023
Stanford University
2023
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...
The existing radio and X-ray flux correlation for Galactic black holes in the hard quiescent states relies on a sample which is mostly dominated by two sources (GX 339-4 V404 Cyg) observed single outburst. In this paper, we report series of observations recurrent hole GX with Australia Telescope Compact Array, Rossi Timing Explorer Swift satellites. With our new long term campaign, now have total 88 quasi-simultaneous during its state, covering seven outbursts over 15--year period. Our...
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...
Abstract The launch of NuSTAR and the increasing number binary black hole (BBH) mergers detected through gravitational wave observations have exponentially advanced our understanding BHs. Despite simplicity owed to being fully described by their mass angular momentum, BHs remained mysterious laboratories that probe most extreme environments in universe. While significant progress has been made recent decade, distribution spin not yet understood. In this work, we provide a systematic analysis...
We have discovered at x-ray and radio wavelengths large-scale moving jets from the microquasar XTE J1550-654. Plasma ejected near black hole traveled relativistic velocities for least four years. present direct evidence gradual deceleration in a jet. The broadband spectrum of is consistent with synchrotron emission high energy (up to 10 TeV) particles accelerated shock waves formed within ejecta or by interaction interstellar medium. J1550-654 offers unique opportunity study dynamical...
We report on simultaneous radio and X-ray observations of the black hole candidate XTE J1650-500 during course its 2001-2002 outburst. The scheduling allowed us to sample properties in different spectral states, namely, hard state, steep power-law thermal dominant according recent classification McClintock & Remillard. state is consistent with a compact jet dominating energy distribution at frequencies; however, current data suggest that contribution as direct synchrotron emission higher...
Precision astrometry at microarcsecond accuracy has applications for a wide range of astrophysical problems. This paper is study the science questions that can be addressed using an instrument with flexible scheduling delivers parallaxes about 4 μas on targets as faint V = 20, and differential 0.6 bright targets. The topics are drawn primarily from team key projects, selected in 2000, Space Interferometry Mission PlanetQuest (SIM PlanetQuest). We use capabilities this mission to illustrate...
We present the first systematic analysis of X-ray variability Sgr A* during Chandra Observatory's 2012 Visionary Project. With 38 High Energy Transmission Grating Spectrometer observations spaced an average 7 days apart, this unprecedented campaign enables detailed study emission from supermassive black hole at high spatial, spectral and timing resolution. In 3 Ms observations, we detect 39 flares A*, lasting a few hundred seconds to approximately 8 ks, ranging in 2–10 keV luminosity ∼1034...
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...
Abstract Here we study a 1–200 keV energy spectrum of the black hole binary Cygnus X-1 taken with NuSTAR and Suzaku . This is first report observation Cyg in intermediate state, was during part orbit where absorption due to companion’s stellar wind minimal. The includes multi-temperature thermal disk component, cutoff power-law relativistic nonrelativistic reflection components. Our initial fits publicly available constant density models ( relxill reflionx ) lead extremely high iron...
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...
ABSTRACT We present a phase-coherent timing solution for PSR J1640–4631, young 206 ms pulsar using X-ray observations taken with NuSTAR . Over this campaign, we have measured the braking index of J1640–4631 to be n = 3.15 ± 0.03. Using series simulations, argue that unusually high is not due noise, but intrinsic pulsar's spin-down. cannot, however, rule out contamination an unseen glitch recovery, although recovery timescale would longer than most yet observed. If eventually proven stable,...
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....
We present a high density disc reflection spectral analysis of sample 17 Seyfert 1 galaxies to study the inner densities at different black hole mass scales and accretion rates. All available XMM-Newton observations in archive are used. OM optical/UV band used estimate their find that 65% sources our show significantly higher than 1e15 cm^{-3}, which was assumed previous reflection-based analyses. The best-fit an anti-correlation with rate. High model can successfully explain soft excess...
MAXI J1820+070 (optical counterpart ASASSN-18ey) is a black hole candidate discovered through its recent very bright outburst. The low extinction column and long duration at high flux allow detailed measurements of the accretion process to be made. In this work, we compare evolution X-ray spectral timing properties initial hard state We show that inner disc, as measured by relativistic reflection, remains steady throughout period Nevertheless, subtle variability observed, which well...
The hard X-ray emission in active galactic nuclei (AGN) and black hole binaries is thought to be produced by a hot cloud of electrons referred as the corona. This emission, commonly described power law with high-energy cutoff, suggestive Comptonization thermal electrons. While several hypotheses have been proposed explain origin, geometry, composition corona, we still lack clear understanding this fundamental component. NuSTAR has playing key role improving our knowledge coronæ thanks its...
Abstract We extend our recent work on black hole spin in X-ray binary systems to include an analysis of 189 archival NuSTAR observations from 24 sources. Using self-consistent data reduction pipelines, spectral models, and statistical techniques, we report unprecedented uniform sample 36 stellar-mass measurements based relativistic reflection. This treatment suggests that prior reports low spins a small number sources were generally erroneous: comprehensive finds those tend harbor holes with...
Context. The INTEGRAL hard X-ray observatory has revealed an emerging population of highly obscured binary systems through multi-wavelength observations. Previous studies have shown that many these sources are high-mass binaries hosting neutron stars orbiting around luminous and evolved companion stars.
We present NuSTAR observations of Vela X-1, a persistent, yet highly variable, neutron star high-mass X-ray binary (HMXB). Two were taken at similar orbital phases but separated by nearly year. They show very different 3-79 keV flux levels as well strong variability during each observation, covering almost one order magnitude in flux. These allow, for the first time ever, investigations on kilo-second time-scales how centroid energies cyclotron resonant scattering features (CRSFs) depend...
GX 339-4 has been one of the key sources for unravelling accretion ejection coupling in accreting stellar mass black holes. After a long period quiescence between 1999 and 2002, underwent series 4 outbursts that have intensively observed by many ground based observatories [radio, infrared(IR), optical] satellites (X-rays). Here, we present results these broad-band observational campaigns, focusing on optical-IR (OIR)/X-ray flux correlations over four outbursts. We found tight OIR/X-ray...
Galactic black hole binaries produce powerful outflows with emit over almost the entire electromagnetic spectrum. Here, we report first detection Herschel observatory of a variable far-infrared source associated compact jets transient GX 339-4 during decay its recent 2010-2011 outburst, after transition to hard state. We also outline results very sensitive radio observations conducted Australia Telescope Compact Array, along series near-infrared, optical (OIR) and X-ray observations,...
We report on the results of spectral fits made to a NuSTAR observation black hole GRS 1915+105 in "plateau" state. This state is special interest because it similar "low/hard" seen other holes, especially that compact, steady jets are launched this phase. The 3-79 keV bandpass NuSTAR, and its ability obtain moderate-resolution spectra free from distortions such as photon pile-up, extremely well suited studies disk reflection X-ray binaries. In only 15 ks net exposure, an extraordinarily...
We present a scheme to determine the spectral state of canonical black hole Cyg X-1 using data from previous and current X-ray all sky monitors (RXTE-ASM, Swift-BAT, MAXI, Fermi-GBM). State determinations hard/intermediate soft agree better than 10% between different monitors, facilitating determination its context for any observation source, potentially over lifetimes individual monitors. A separation hard intermediate state, which strongly differ in their shape short-term timing behavior,...
With frequent flaring activity of its relativistic jets, Cygnus X‐3 (Cyg X‐3) is one the most active microquasars and only Galactic black hole candidate with confirmed high‐energy γ‐ray emission, thanks to detections by Fermi Large Area Telescope (Fermi/LAT) AGILE. In 2011, Cyg was observed transit a soft X‐ray state, which known be associated emission. We present results multiwavelength campaign covering quenched when radio emission from at weakest spectrum very soft. A giant (∼20 Jy)...