R. Di Stefano
A5055029969- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Astrophysics and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- History and Developments in Astronomy
- Particle physics theoretical and experimental studies
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Adaptive optics and wavefront sensing
- Advanced X-ray Imaging Techniques
- Cosmology and Gravitation Theories
- Relativity and Gravitational Theory
- Black Holes and Theoretical Physics
- Atomic and Subatomic Physics Research
- Neutrino Physics Research
- Mechanics and Biomechanics Studies
- Particle Accelerators and Free-Electron Lasers
- Quantum Chromodynamics and Particle Interactions
- High-pressure geophysics and materials
Center for Astrophysics Harvard & Smithsonian
2016-2025
Harvard University
1997-2022
Istituto Nazionale di Fisica Nucleare, Sezione di Napoli
2015-2022
Università degli studi di Cassino e del Lazio Meridionale
2015-2021
Smithsonian Astrophysical Observatory
2004-2021
National Institute of Optics
2015
Harvard University Press
2014
Community Farm Alliance
2004-2009
SELEX Sistemi Integrati
2007-2009
Tufts University
2000-2008
We present the first results of Fermilab Muon g-2 Experiment for positive muon magnetic anomaly $a_\mu \equiv (g_\mu-2)/2$. The is determined from precision measurements two angular frequencies. Intensity variation high-energy positrons decays directly encodes difference frequency $\omega_a$ between spin-precession and cyclotron frequencies polarized muons in a storage ring. ring field measured using nuclear resonance probes calibrated terms equivalent proton spin precession...
A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of exciting science opportunities next decade. The Large Synoptic Survey Telescope (LSST) have an effective aperture 6.7 meters and imaging camera field view 9.6 deg^2, be devoted ten-year 20,000 deg^2 south +15 deg. Each pointing imaged 2000 times fifteen second exposures six broad from 0.35 1.1 microns, total point-source depth r~27.5. LSST Science Book describes basic...
Abstract We compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, common proper motion, etc. Each observational technique is sensitive to companions across a narrow parameter space orbital periods P and mass ratios q = <?CDATA ${M}_{\mathrm{comp}}$?> / M 1 . After combining the samples from various surveys correcting for their respective selection effects, we find that properties O-type B-type main-sequence (MS)...
We report results from searches for new physics with low-energy electronic recoil data recorded the XENON1T detector. With an exposure of 0.65 tonne-years and unprecedentedly low background rate 76±2stat events/(tonne×year×keV) between 1 30 keV, enable one most sensitive solar axions, enhanced neutrino magnetic moment using neutrinos, bosonic dark matter. An excess over known backgrounds is observed at energies prominent 2 3 keV. The axion model has a 3.4σ significance, three-dimensional 90%...
XENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict experimental background and project sensitivity to weakly interacting massive particles (WIMPs). The expected average differential rate in energy region interest, corresponding (1, 13) keV (4, 50) for electronic nuclear recoils, amounts $12.3 \pm 0.6$ (keV y)$^{-1}$ $(2.2\pm 0.5)\times 10^{-3}$ y)$^{-1}$,...
We report on a blinded analysis of low-energy electronic-recoil data from the first science run XENONnT dark matter experiment. Novel subsystems and increased 5.9 tonne liquid xenon target reduced background in (1, 30) keV search region to $(15.8 \pm 1.3)$ events/(tonne$\times$year$\times$keV), lowest ever achieved detector $\sim$5 times lower than XENON1T. With an exposure 1.16 tonne-years, we observe no excess above set stringent new limits solar axions, enhanced neutrino magnetic moment,...
The Muon g-2 Experiment at Fermi National Accelerator Laboratory (FNAL) has measured the muon anomalous precession frequency $ω_a$ to an uncertainty of 434 parts per billion (ppb), statistical, and 56 ppb, systematic, with data collected in four storage ring configurations during its first physics run 2018. When combined a precision measurement magnetic field experiment's ring, determines anomaly $a_μ({\rm FNAL}) = 116\,592\,040(54) \times 10^{-11}$ (0.46 ppm). This article describes...
We have re-examined a scenario for the evolution of binary system, initially comprising neutron star and low-mass giant ending as wide containing radio pulsar white dwarf in nearly circular orbit. The is driven by nuclear giant, which results stable transfer much or all envelope to star. angular momentum associated with transferred mass may spin up high rotation rates, yielding 'recycled' pulsar; dwarf, had been core progenitor, remains fossil relic giant. This provides unique test theory...
In the single-degenerate scenario for Type Ia supernovae (SNe Ia), a white dwarf (WD) must gain significant amount of matter from companion star. Because accreted mass carries angular momentum, WD is likely to achieve fast spin periods, which can increase critical mass, Mcrit, needed explosion. When Mcrit higher than maximum achieved by WD, central regions down before it explode. This introduces super-Chandrasekhar explosions, and delay between completion time Matter ejected binary during...
The Fermi National Accelerator Laboratory has measured the anomalous precession frequency $a^{}_\mu = (g^{}_\mu-2)/2$ of muon to a combined precision 0.46 parts per million with data collected during its first physics run in 2018. This paper documents measurement magnetic field storage ring. is monitored by nuclear resonance systems and calibrated terms equivalent proton spin spherical water sample at 34.7$^\circ$C. weighted distribution resulting $\tilde{\omega}'^{}_p$, denominator ratio...
We report on a search for nuclear recoil signals from solar $^8$B neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold 2.6 keV to 1.6 keV. develop variety of novel techniques limit resulting increase backgrounds near threshold. No significant neutrino-like excess is found an exposure 0.6 t $\times$ y. For first time, we use non-detection constrain light yield 1-2 recoils liquid xenon, as well non-standard neutrino-quark interactions. Finally,...
In a canonical model, the progenitors of Type Ia supernovae (SNe Ia) are accreting, nuclear-burning white dwarfs (NBWDs), which explode when dwarf reaches Chandrasekhar mass, MC. Such massive NBWDs hot (kT ∼ 100 eV), luminous (L 1038 erg s−1), and potentially observable as supersoft X-ray sources (SSSs). During past several years, surveys for soft in external galaxies have been conducted. This paper shows that results falsify hypothesis large fraction presently SSSs. The data also place...
Nearly 150 massive black hole binary (MBHB) candidates at sub-pc orbital separations have been reported in recent literature. Nevertheless, the definitive detection of even a single such object remains elusive. If least one holes is accreting, light emitted from its accretion disc will be lensed by other for inclinations near to line sight. This self-lensing could provide unique signature compact MBHB systems. We show that, MBHBs with masses range 106–1010 M⊙ and periods less than ∼10 yr,...
Abstract Xenon dual-phase time projection chambers designed to search for weakly interacting massive particles have so far shown a relative energy resolution which degrades with above $$\sim $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>∼</mml:mo></mml:math> 200 keV due the saturation effects. This has limited their sensitivity in rare events like neutrinoless double-beta decay of $$^{136} \hbox {Xe}$$...
The selection of low-radioactive construction materials is the utmost importance for rare-event searches and thus critical to XENONnT experiment. Results an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, 222 Rn emanation measurements. Furthermore, cleanliness procedures applied remove or mitigate surface contamination detector described. Screening results, used as inputs a Monte Carlo simulation, predict...
One of the most mysterious astrophysical states is common envelope (CE) phase binary evolution, in which two stars are enshrouded by shed one them. Interactions between and shrinks orbit. The CE can lead to mergers or a subsequent interactions. Mergers may involve any combination compact objects and/or stars. Some involving white dwarfs, produce Type Ia supernovae, while merging neutron yield gamma-ray bursts, all kinds gravitational radiation. Since CEs arise from variety different initial...
Abstract The Vera C. Rubin Legacy Survey of Space and Time (LSST) holds the potential to revolutionize time domain astrophysics, reaching completely unexplored areas Universe mapping variability scales from minutes a decade. To prepare maximize LSST data for exploration transient variable Universe, one four pillars science, Transient Variable Stars Science Collaboration, eight Collaborations, has identified research interest requirements, paths enable them. While our roadmap is...
view Abstract Citations (142) References (64) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Formation and Evolution of Luminous Supersoft X-Ray Sources Rappaport, S. ; Di Stefano, R. Smith, J. D. supersoft X-ray sources, with characteristic luminosities approximately 1038 ergs/s temperatures, kT, 35 eV, have been established as a new distinct class source through recent Roentgen Satellite (ROSAT) observations. Several possible physical models proposed for...
We report on \chandra observations of the central region M31. By combining eight ACIS-I taken between 1999 and 2001, we have identified 204 X-ray sources within $\sim 17'\times17'$ M31, with a detection limit 2\times10^{35}$\lum. Of these sources, 22 are globular clusters, 2 supernova remnants, 9 planetary nebula, as supersoft sources. comparing individual images, about 50% variable time scales months. also found 13 transients, light curves showing variety shapes. extracted energy spectra 20...
In order for a white dwarf (WD) to achieve the Chandrasekhar mass, MC, and explode as Type Ia supernova (SNIa), it must interact with another star, either accreting matter from or merging it. The failure identify class classes of binaries which produce SNeIa is long-standing "progenitor problem." Its solution required if we are utilize full potential elucidate basic cosmological physical principles. single-degenerate models, WD accretes burns at high rates. Nuclear-burning dwarfs (NBWDs)...
The detections of both X-ray and radio emission from the cluster G1 in M31 have provided strong support for existing dynamical evidence an intermediate mass black hole (IMBH) 1.8 +/- 0.5 x 10^4 solar masses at center. However, given relatively low significance astrometric accuracy detection, non-simultaneity measurements, this identification required further confirmation. Here we present deep, high angular resolution, strictly simultaneous observations G1. While (L_X = 1.74^{+0.53}_{-0.44}...