G. R. Davies
A5040126050- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- Spectroscopy and Quantum Chemical Studies
- Solar Radiation and Photovoltaics
- Service-Oriented Architecture and Web Services
- Climate variability and models
- Inertial Sensor and Navigation
- Calibration and Measurement Techniques
- Geophysics and Sensor Technology
- solar cell performance optimization
- Semantic Web and Ontologies
- Astronomical and nuclear sciences
- Ionosphere and magnetosphere dynamics
- Logic, Reasoning, and Knowledge
- Scientific Research and Discoveries
- Planetary Science and Exploration
University of Birmingham
2015-2024
Royal Astronomical Society
2024
Aarhus University
2014-2023
Université Paris Cité
2011-2017
Astrophysique, Instrumentation et Modélisation
2011-2017
Centre National de la Recherche Scientifique
2011-2017
Institut de Recherche sur les Lois Fondamentales de l'Univers
2011-2017
CEA Paris-Saclay
2011-2017
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2011-2017
The University of Sydney
2017
We report on the masses, sizes, and orbits of planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits 7 revealed by precise Doppler measurements host Based an analysis brightness measurements, along with high-resolution imaging spectroscopy, (for 11 stars) asteroseismology, we establish low false-positive probabilities (FPPs) for all transiting (41 have FPP under 1%), constrain their sizes masses. Most smaller than three...
Data Release 5 (DR5) of the Radial Velocity Experiment (RAVE) is fifth data release from a magnitude-limited (9< I < 12) survey stars randomly selected in southern hemisphere. The RAVE medium-resolution spectra ($R\sim7500$) covering Ca-triplet region (8410-8795\AA) span complete time frame start observations 2003 to their completion 2013. velocities 520,781 457,588 unique are presented, which 255,922 stellar have parallaxes and proper motions Tycho-Gaia astrometric solution (TGAS) Gaia DR1....
Rotation is expected to have an important influence on the structure and evolution of stars. However, mechanisms angular momentum transport in stars remain theoretically uncertain very complex take into account stellar models. To achieve a better understanding these processes, we desperately need observational constraints internal rotation stars, which until recently were restricted Sun. In this paper, report detection mixed modes - i.e. that behave both as g core p envelope spectrum early...
We present a study of 33 Kepler planet-candidate host stars for which asteroseismic observations have sufficiently high signal-to-noise ratio to allow extraction individual pulsation frequencies. implement new Bayesian scheme that is flexible in its input process oscillation frequencies, combinations them, and average parameters, derive robust fundamental properties these targets. Applying this grids evolutionary models yields stellar with median statistical uncertainties 1.2 per cent...
We use asteroseismic data from the Kepler satellite to determine fundamental stellar properties of 66 main-sequence targets observed for at least one full year by mission. distributed tens individual oscillation frequencies extracted time series each star among seven modelling teams who applied different methods radii, masses, and ages all stars in sample. Comparisons results reveal a good level agreement properties, which is remarkable considering variety codes, input physics analysis...
Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation variability can be studied for thousands stars. Because many these old field stars also have independently measured asteroseismic ages, measurements activity are particularly interesting the context age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at problem that this sample old-field is uniquely suited to...
Context : We still do not know which mechanisms are responsible for the transport of angular momentum inside stars. The recent detection mixed modes that contain signature rotation in spectra Kepler subgiants and red giants gives us opportunity to make progress on this issue. Aims: Our aim is probe radial dependance profiles a sample targets. For purpose, early particularly interesting targets because their rotational splittings more sensitive outside deeper core than case evolved...
Abstract Simulations predict that hot super-Earth sized exoplanets can have their envelopes stripped by photoevaporation, which would present itself as a lack of these exoplanets. However, this absence in the exoplanet population has escaped firm detection. Here we demonstrate, using asteroseismology on sample and candidates observed during Kepler mission that, while there is an abundance with low incident fluxes, none are found high fluxes. We do not find any radii between 2.2 3.8 Earth...
The Rossiter-McLaughlin effect observed for transiting exoplanets often requires prior knowledge of the stellar projected equatorial rotational velocity. This is usually provided by measuring broadening spectral lines, however this method has uncertainties as lines are also broadened velocity fields in photosphere known macroturbulence. We have estimated accurate values from asteroseismic analyses main sequence stars Kepler. frequency splittings detected solar-like oscillations these...
The chemical composition of stars hosting small exoplanets (with radii less than four Earth radii) appears to be more diverse that gas-giant hosts, which tend metal-rich. This implies small, including Earth-size, planets may have readily formed at earlier epochs in the Universe's history when metals were scarce. We report Kepler spacecraft observations Kepler-444, a metal-poor Sun-like star from old population Galactic thick disk and host compact system five transiting with sizes between...
The evolved solar-type stars 16 Cyg A and B have long been studied as solar analogs, yielding a glimpse into the future of our own Sun. orbital period binary system is too to provide meaningful dynamical constraints on stellar properties, but asteroseismology can help because are among brightest in Kepler field. We present an analysis three months nearly uninterrupted photometry from Keplerspace telescope. extract total 46 41 oscillation frequencies for two components, respectively,...
Results on the obliquity of exoplanet host stars—the angle between stellar spin axis and planetary orbital axis—provide important diagnostic information for theories describing formation. Here we present first application asteroseismology to problem determination in systems with transiting planets Sun-like stars. We consider two observed by NASA Kepler mission which have multiple small (super-Earth sized) planets: previously reported Kepler-50 a new system, Kepler-65, whose validate this...
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...
(Abridged) We present the first APOKASC catalog of spectroscopic and asteroseismic data for 415 dwarfs subgiants. Asteroseismic have been obtained by Kepler in short cadence. The parameters are based on spectra taken as part APOGEE correspond to DR13 SDSS. analyze our using two Teff scales, values from those derived SDSS griz photometry. use differences results arising these choices a test systematic Teff, find that they can lead significant stellar properties. Determinations surface gravity...
Solar-like oscillations have been observed by Kepler and CoRoT in several solar-type stars, thereby providing a way to probe the stars using asteroseismology. We provide mode frequencies of various required perform comparison with those obtained from stellar modelling. used time series nine months data for each star. The 61 were categorised three groups: simple, F-like mixed-mode. simple group includes which identification degree is obvious. ambiguous. mixed-mode evolved modes do not follow...
The advent of space-based missions like $Kepler$ has revolutionized the study solar-type stars, particularly through measurement and modeling their resonant modes oscillation. Here we analyze a sample 66 main-sequence stars showing solar-like oscillations as part seismic LEGACY project. We use short-cadence data, which each star at least 12 months, to create frequency power spectra optimized for asteroseismology. For identify its oscillation extract parameters such frequency, amplitude, line...
Abstract We present a comparison of parallaxes and radii from asteroseismology Gaia DR1 (TGAS) for 2200 Kepler stars spanning the main sequence to red-giant branch. show that previously identified offsets between TGAS distances derived eclipsing binaries have likely been overestimated <?CDATA $\lesssim 5\mbox{--}10$?> mas (≈90%–98% sample). The observed differences in our sample can furthermore be partially compensated by adopting hotter ${T}_{\mathrm{eff}}$?> scale (such as infrared flux...
With the loss of a second reaction wheel, resulting in inability to point continuously and stably at same field view, NASA Kepler satellite recently entered new mode observation known as K2 mission. The data from this redesigned mission present specific challenge; targets systematically drift position on an ∼6 hr timescale, inducing significant instrumental signal photometric time series—this greatly impacts ability detect planetary signals perform asteroseismic analysis. Here we detail our...
The solar analogs 16 Cyg A and B are excellent asteroseismic targets in the \Kepler field of view together with a red dwarf Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation current data but instead use technique asteroseimology to determine rotational properties both B. We find periods be $23.8^{+1.5}_{-1.8} \rm \, days$ $23.2^{+11.5}_{-3.2} days$, angles inclination $56^{+6}_{-5} ^{\circ}$ $36^{+17}_{-7} ^{\circ}$, for...
The unparalleled photometric data obtained by NASA's Kepler space telescope led to an improved understanding of red giant stars and binary stars. Seismology allows us constrain the properties giants. In addition eclipsing binaries, eccentric non-eclipsing exhibiting ellipsoidal modulations, have been detected with Kepler. We aim study systems containing a star derive parameters primary component. apply asteroseismic techniques determine masses radii component each system. For selected...
Kepler has revolutionized our understanding of both exoplanets and their host stars. Asteroseismology is a valuable tool in the characterization stars an excellent observing facility to perform asteroseismology. Here we select sample 35 solar-type which transiting (or planet candidates) with detected solar-like oscillations. Using available short cadence data up Quarter 16 create power spectra optimized for asteroseismology We identify modes oscillation estimate mode frequencies by ‘peak...
Aims. The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations derive ages from chemical abundances. Methods. We derived sets using Padova Yonsei–Yale isochrones H IPPARCOS Gaia parallaxes for a sample more than 1000 FGK dwarf stars which he have high-resolution ( R ~ 115 000) high-quality spectra the HARPS-GTO program. analyzed temporal evolution abundance ratios find best clocks....
NASA's re-purposed Kepler mission—dubbed K2—has brought new scientific opportunities that were not anticipated for the original mission. One science goal makes optimal use of K2's capabilities, in particular its 360° ecliptic field view, is galactic archaeology—the study evolution Galaxy from fossil stellar record. The thrust this research to exploit high-precision, time-resolved photometry K2 order detect oscillations red giant stars. This asteroseismic information can provide estimates...