A5004176408- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Laser-Plasma Interactions and Diagnostics
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Magnetic confinement fusion research
- High-pressure geophysics and materials
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- High-Velocity Impact and Material Behavior
- Pulsars and Gravitational Waves Research
- Energetic Materials and Combustion
- Electromagnetic Launch and Propulsion Technology
- Solar Radiation and Photovoltaics
- Inertial Sensor and Navigation
- Ionosphere and magnetosphere dynamics
- Oceanographic and Atmospheric Processes
- Atmospheric Ozone and Climate
- Nuclear physics research studies
- Laser-induced spectroscopy and plasma
Los Alamos National Laboratory
2015-2024
University of California, Santa Barbara
2017
Los Alamos National Security (United States)
2013
Boston University
1999-2008
Los Alamos Medical Center
1995-2008
University of Minnesota System
2008
University of Wisconsin System
2008
Utrecht University
2008
Joyce Foundation
2004
Computational Physics (United States)
1997-2002
Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors thermodynamic radiative properties, on which depend, matter under extreme conditions found in sun. Current are agreement with inferences, suggests, example, that disagreement between predicted observed fluxes neutrinos sun is not caused by errors models. However, GONG data reveal subtle models, such as an excess sound speed just beneath convection...
The γ Doradus stars are a newly discovered class of gravity-mode pulsators that lie just at or beyond the red edge δ Scuti instability strip. We present results calculations predict pulsation high-order g-modes with periods between 0.4 and 3 days, as observed in these stars. pulsations driven by modulation radiative flux convection base deep envelope zone. Pulsation is predicted only for models temperatures zone ~200,000 ~480,000 K. estimated shear dissipation due to turbulent viscosity...
Global Oscillation Network Group data reveal that the internal structure of sun can be well represented by a calibrated standard model. However, immediately beneath convection zone and at edge energy-generating core, sound-speed variation is somewhat smoother in than it This could consequence chemical inhomogeneity too severe model, perhaps owing to inaccurate modeling gravitational settling or neglected macroscopic motion may present sun. Accurate knowledge sun's enables inferences made...
Observations of the pulsations stars can be used to infer their interior structure and test theoretical models. The main-sequence γ Doradus (Dor) δ Scuti (Sct) with masses 1.2–2.5 M☉ are particularly useful for these studies. Dor pulsate in high-order g-modes periods order 1 day, driven by convective blocking at base envelope convection zone. Sct low-order g- p-modes 2 hr, κ mechanism operating He ii ionization Theory predicts an overlap region Hertzsprung–Russell diagram between instability...
Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure evolution for large sample solar-type stars in field. We perform uniform analysis 22 brightest asteroseismic targets highest signal-to-noise ratio observed 1 month each during first year mission, we quantify precision relative accuracy determinations radius, mass, age that are possible using various methods. present...
Kepler observations of the star HD 187091 (KIC 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with superimposed set oscillations forming beating pattern in phase brightenings. Spectroscopic that this is binary highly eccentric orbit, e = 0.83. We are able to match and radial velocities nearly face-on (i 55) model which caused by tidal distortion irradiation identical A stars during their close periastron passage. The...
Recently the number of main-sequence and subgiant stars exhibiting solar-like oscillations that are resolved into individual mode frequencies has increased dramatically. While only a few such data sets were available for detailed modeling just decade ago, Kepler mission produced suitable observations hundreds new targets. This rapid expansion in observational capacity been accompanied by shift analysis strategies to yield uniform derived stellar properties more quickly easily. We use...
We present Kepler photometry and ground based spectroscopy of KIC 4544587, a short-period eccentric eclipsing binary system with self-excited pressure gravity modes, tidally excited influenced p rapid apsidal motion 182 y per cycle. The primary secondary components 4544587 reside within the delta Scuti gamma Dor instability region Hurtzsprung-Russell diagram, respectively. By applying modelling software PHOEBE to prewhitened photometric data radial velocity obtained using William Herschel...
We present a new, publicly available, set of Los Alamos OPLIB opacity tables for the elements hydrogen through zinc. Our are computed using ATOMIC and plasma modeling code, make use atomic structure calculations that fine-structure detail all considered. equation-of-state (EOS) model, known as ChemEOS, is based on minimization free energy in chemical picture appears to be reasonable robust approach determining state populations over wide range temperatures densities. In this paper we discuss...
We present the discovery of TOI-197.01, first transiting planet identified by Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology host star is possible. TOI-197 (HIP116158) a bright (V=8.2 mag), spectroscopically classified subgiant oscillates with an average frequency about 430 muHz and displays clear signature mixed modes. The oscillation amplitude confirms that redder TESS bandpass compared to Kepler has small effect on oscillations, supporting expected yield thousands...
view Abstract Citations (176) References (94) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Oscillations of Solar Models with Internal Element Diffusion Cox, Arthur N. ; Guzik, Joyce A. Kidman, Russell B. Data on the evolution a solar model are presented which include effects diffusive processes that lead to partial sorting elements depth. The two models and without diffusion. diffusion process gravitational settling, composition gradient diffusion, thermal...
Visual classification of over 10 000 stars in the Kepler data base has revealed a class with almost monoperiodic light variations and characteristic beating. A subset these have larger amplitude asymmetric curves variation maximum brightness than minimum brightness. The beating is mostly result two dominant, closely spaced frequencies. third group shows multiple low frequencies comparable amplitudes. All three types star fall region Hertzsprung–Russell diagram where γ Dor are found we...
The light curves of 2768 stars with effective temperatures and surface gravities placing them near the gamma Doradus/delta Scuti instability region were observed as part Kepler Guest Observer program from Cycles 1 through 5. analyzed in a uniform manner to search for Doradus, delta Scuti, hybrid star pulsations. pulsations extend asteroseismology slightly more massive (1.4 2.5 solar masses) than our Sun. We find 207 84 32 candidate stars. Many these are cooler red edge Doradus strip...
Recent solar photospheric abundance analyses (by Asplund et al. and Lodders) revise the C, N, O, Ne, Ar abundances downward by 0.15-0.2 dex compared to previous determinations Grevesse & Sauval. The of Fe other elements are reduced smaller amounts, 0.05-0.1 dex. With these revisions, Z/X decreases 0.0165 (or 0.0177, according Lodders), Z ~0.0122 0.0133, Lodders). A number papers (by, e.g., Basu Antia, Montalban al., Bahcall Pinsonneault, Turck-Chièze Antia Basu) report that models evolved...
Solar models using the new lower abundances of Asplund et al. or Caffau do not agree as well with helioseismic inferences that use higher Grevesse & Noels Sauval abundances. Adopting leads to sound-speed discrepancies up 1.4% below base convection zone (CZ) compared less than 0.4% old abundances; a CZ is too shallow; and helium abundance low. Here we briefly review recent attempts restore agreement, evaluate three changes models: early mass loss, accretion low-Z material, convective...
Eclipsing binaries (EBs) are unique targets for measuring precise stellar properties and can be used to constrain evolution models. In particular, it is possible measure masses radii of both components a double-lined spectroscopic EB at the percent level. Since advent high-precision photometric space missions (MOST, CoRoT, Kepler , BRITE, TESS), use pulsation infer interiors dynamics constitutes revolution studies low-mass stars. The mission has led discovery thousands classical pulsators...
Abstract We present a set of 1194 Type-1 Rosseland-mean opacity tables for four different metallicity mixtures. These new Los Alamos OPLIB atomic radiative are an order magnitude larger in number than any previous table release, and span regimes where have not existed. For example, the expands range to Z = 10 −6 0.2, which allows improved accuracy opacities at low high metallicity, increases density −4 0.1 enhance drawn from interpolations across neighboring metallicities, adds entries...
Deneb, the prototype Alpha Cygni variable, is a bright A2 Ia supergiant which shows irregular variability with 12-day quasi-period, presumed to be caused by pulsations. At 2023 AAVSO Annual Meeting we discussed radial velocity and photometry data from several sources showing that variations begin abruptly at an arbitrary phase, damp out after cycles, resume intervals of around 75 days. Additional more frequent time sampling longer series were needed verify existence precision 75-day...
We calculate solar models including dark matter (DM) weakly-interacting massive particles (WIMPs) of mass 5-50 GeV and test these against helioseismic constraints on sound speed, convection zone depth, helium abundance, small separations low-degree p-modes. Our main conclusion is that both direct detection experiments particle accelerators may be complemented by using the Sun as a probe for WIMP DM in range. The most sensitive to this has suppressed annihilations large spin-dependent elastic...
Aims. Our goal is to test the newly developed OPLIB opacity tables from Los Alamos National Laboratory and check their influence on pulsation properties of B-type stars.
A sequence search method was developed for searching regular frequency spacing in delta Scuti stars by visual inspection and algorithmic search. The sample contains 90 observed CoRoT. An example is given to represent the inspection. algorithm (SSA) described detail. data treatment of CoRoT light curves, criteria filtering spacings derived two methods (three approaches: VI, SSA FT) are each target. Echelle diagrams presented 77 targets, which at least one identified. Comparing shifts between...
The NASA Kepler and follow-on K2 mission (2009–2018) left a legacy of data discoveries, finding thousands exoplanets, also obtaining high-precision long time-series for hundreds stars, including many types pulsating variables. Here we highlight few the ongoing discoveries from on δ Scuti variables, which are core hydrogen-burning stars about twice mass Sun. We discuss unsolved problems surrounding properties variability in these progress enabled by using pulsations to infer their interior...
In this paper, we present the first theoretical γ Doradus instability strip. We find that our model strip agrees very well with previously established, observationally based, of Handler & Shobbrook. stress, as do Guzik et al., convection zone depth plays major role in determination Once becomes too deep or shallow, no longer allows for pulsational instability. Our Dor is bounded by ~6850 and 7360 K at red blue edge, respectively, on zero-age main sequence ~6560 7000 approximately 2 mag more...
view Abstract Citations (52) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Comparison between Mass-losing and Standard Solar Models Guzik, Joyce A. ; Willson, L. Brunish, Wendee M. The effects of main-sequence mass loss on the evolution, interior structure, surface composition sun are studied. Modeling results presented for three mass-losing solar models initial two solar, plus a standard one comparison model. It is shown that can be...
view Abstract Citations (78) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Using Solar p-Modes to Determine the Convection Zone Depth and Constrain Diffusion-produced Composition Gradients Guzik, Joyce A. ; Cox, Arthur N. Low- intermediate-degree solar p-mode frequencies, which are sensitive structure near bottom of convection zone, used find zone depth constrain size shape composition gradients produced by diffusive settling helium heavier...