A5057478451- Stellar, planetary, and galactic studies
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Solar Radiation and Photovoltaics
- Geomagnetism and Paleomagnetism Studies
- Physics of Superconductivity and Magnetism
- Ionosphere and magnetosphere dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Planetary Science and Exploration
- Geophysics and Gravity Measurements
- Atomic and Subatomic Physics Research
- Gamma-ray bursts and supernovae
- Quantum, superfluid, helium dynamics
- Magnetic Properties and Applications
- Space Exploration and Technology
- Superconducting Materials and Applications
- Inertial Sensor and Navigation
- Rare-earth and actinide compounds
- Iron-based superconductors research
- Solar Thermal and Photovoltaic Systems
- Magnetic and transport properties of perovskites and related materials
- History and Developments in Astronomy
University of Sussex
2025
New Mexico State University
2015-2024
Weatherford College
2023
Institut d'Astrophysique Spatiale
2018
Max Planck Institute for Solar System Research
2005-2011
Max Planck Society
2006-2008
Boston College
2003-2005
University of Cambridge
1993-1996
University of Łódź
1993-1996
Lodz University of Technology
1992-1993
The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds A-F type stars. We present a first general characterization the pulsational behaviour stars as observed in light curves sample 750 candidate propose three main groups to describe variety pulsating stars: gamma Dor, delta Sct, and hybrid assign 63% our one groups, identify remaining part rotationally modulated/active stars, binaries, different spectral type, or that show no clear...
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...
ABSTRACT Given the potential of ensemble asteroseismology for understanding fundamental properties large numbers stars, it is critical to determine accuracy scaling relations on which these measurements are based. From several powerful validation techniques, all indications so far show that stellar radius estimates from asteroseismic accurate within a few percent. Eclipsing binary systems hosting at least one star with detectable solar-like oscillations constitute ideal test objects...
While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There two main hypotheses for of sunspots: monolithic model and cluster model. Local helioseismology only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do yet allow to probe internal with sufficient confidence distinguish between monolith models, development physically realistic sunspot models a priority...
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...
Red-giant stars are an incredible source of information for testing models stellar evolution, as asteroseismology has opened up a window into their interiors. Such insights direct result the unprecedented data from space missions Kepler and CoRoT well recent theoretical advances. Eclipsing binaries also fundamental astrophysical objects, when coupled with asteroseismology, would provide two independent methods to obtain masses radii exciting opportunities develop highly constrained models....
Various methods of helioseismology are used to study the subsurface properties sunspot in NOAA Active Region 9787. This was chosen because it is axisymmetric, shows little evolution during 20-28 January 2002, and observed continuously by MDI/SOHO instrument. (...) Wave travel times mode frequencies affected sunspot. In most cases, wave packets that propagate through have reduced times. At short distances, however, sign travel-time shifts appears depend sensitively on how data processed and,...
Among 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection remaining 4 is an observational bias or possibly evidence damping originates from tidal interactions. A careful analysis corresponding light curves shows modes with amplitudes are usually observed red giants would detected if they were present. observe depletion strongly associated short-period systems,...
The light curves of 252 B-star candidates in the Kepler data base are analyzed a similar fashion to that done by Balona et al. (2011) further characterize B star variability, increase sample variable stars for future study, and identify whose power spectra include particularly interesting features such as frequency groupings. Stars classified either constant emitters, $\beta$ Cep stars, slowly pulsating hybrid pulsators, binaries or dominated rotation (Bin/Rot), hot subdwarfs, white dwarfs....
Meridional flow is thought to play a very important role in the dynamics of solar convection zone; however, because its relatively small amplitude, precisely measuring it poses significant challenge. Here we present complete time–distance helioseismic analysis about 2 years ground-based Global Oscillation Network Group (GONG) Doppler data retrieve meridional circulation profile for modest latitudes an attempt corroborate results from other studies. We use empirical correction travel times...
Large-scale plasma flows in the Sun's convection zone likely play a major role solar dynamics on decadal timescales. In particular, quantifying meridional motions is critical ingredient for understanding cycle and transport of magnetic flux. Because signal such features can be quite small deep layers buried systematics or noise, true velocity profile has remained elusive. We perform time–distance helioseismology measurements several years worth Global Oscillation Network Group Doppler data....
The objective of this work is to determine what fraction red-giant (RG) stars shows photometric rotational modulation, and understand its origin. One the underlying questions role close binarity in population, standing upon fact that RGs short-period binary systems (<150 days or so) have been observed display strong modulation. We select a sample about 4500 relatively bright by Kepler, show 370 them (8%) Almost all oscillation amplitudes below median sample, while 30 are not oscillating at...
Eclipsing binaries (EBs) are unique benchmarks for stellar evolution. On the one hand, detached EBs hosting at least star with detectable solar-like oscillations constitute ideal test objects to calibrate asteroseismic measurements. other and surface activity of stars that belong offer information about evolution binary systems. This paper builds upon previous works dedicated red giant (RG) in -- 20 known systems so far discovered by NASA Kepler mission. Here we report discovery 16 RGs also...
Jupiter and Saturn played a major role in the formation evolution of Solar System. The internal structure gas giants was shaped during their birth process still contains traces this formation. A detailed description would be key for understanding physical properties, Equations State, high-pressure physics, effects rotation, heat transfer, interaction between interiors atmospheres, finally necessary step study extra solar planets.The measurement gravitational moments by space missions can...
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...
To recover the flow information encoded in travel-time data of time-distance helioseismology, accurate forward modeling and a robust inversion travel times are required. We accomplish this using three-dimensional finite-frequency sensitivity kernels for flows along with 2+1 dimensional (2+1D) optimally localized averaging (OLA) scheme. Travel measured by ridge filtering MDI full-disk Doppler corresponding Born computed these particular times. also utilize full noise covariance properties...
Inversions for local helioseismology are an important and necessary step obtaining three-dimensional maps of various physical quantities in the solar interior. Frequently, full inverse problems that one would like to solve prove intractable because computational constraints. Due enormous seismic data sets already exist those forthcoming, this is a problem needs be addressed. To end, we present very efficient linear inversion algorithm helioseismology. It based on subtractive optimally...
Abstract We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, second node JOVIAL network, which is mounted on Dunn Solar Telescope Sunspot, New Mexico. report 12 nights observations between 2018 May 4 and 30, representing a total about 80 hr. First, average zonal wind profile derived our compatible that cloud-tracking measurements performed Hubble Space images April Outer Planet...
ABSTRACT We present empirical phase curves of Jupiter from ∼0° to 140° as measured in multiple optical bandpasses by Cassini /Imaging Science Subsystem (ISS) during the Millennium flyby late 2000 early 2001. Phase are interest for studying energy balance and understanding scattering behavior planet an exoplanet analog. find that is significantly darker at partial phases than idealized Lambertian roughly 25% not well fit Jupiter-like atmospheric models across all wavelengths. provide analytic...
We combine Kepler photometry with ground-based spectra to present a comprehensive dynamical model of the double red giant eclipsing binary KIC 9246715. While two stars are very similar in mass (M1 = 2.171 [+0.006 / -0.008], M2 2.149 -0.008] Msun) and radius (R1 8.37 [+0.03 -0.07], R2 8.30 [+0.04 -0.03] Rsun), an asteroseismic analysis finds one main set solar-like oscillations unusually low-amplitude, wide modes. A second from other star may exist, but this marginal detection is extremely...
Abstract The solar meridional flow is a crucial ingredient in modern dynamo theory. Seismic estimates of this have, however, been contradictory deeper layers below about <?CDATA $0.9\,{R}_{\odot }$?> . Results from time−distance helioseismology have so far obtained using the ray approximation. Here, we perform inversions Born initial result similar to previously by Jackiewicz et al. kernels while same set GONG data and SOLA inversion technique. However, show that assumption uncorrelated...
The $κ$-mechanism has been successful in explaining the origin of observed oscillations many types "classical" pulsating variable stars. Here we examine quantitatively if that same process is prominent enough to excite potential global within Jupiter, whose energy flux powered by gravitational collapse rather than nuclear fusion. Additionally, whether external radiative forcing, i.e. starlight, could be a driver for hot Jupiters orbiting various main-sequence stars at defined orbital...