Results for "Timothy R. Bedding"

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Predicting radial-velocity jitter induced by stellar oscillations based on Kepler dataJun 30 2018Radial-velocity (RV) jitter due to intrinsic stellar variability introduces challenges when characterizing exoplanet systems, particularly when studying small (sub-Neptune-sized) planets orbiting solar-type stars. In this Letter we predicted for dwarfs ... More
Surface gravities for 15,000 Kepler stars measured from stellar granulation and validated with Gaia DR2 parallaxesJul 10 2018Jul 12 2018We have developed a method to estimate surface gravity (log g) from light curves by measuring the granulation background, similar to the "flicker" method by Bastien et al. (2016) but working in the Fourier power spectrum. We calibrated the method using ... More
Asteroseismic analysis of solar-mass subgiants KIC 6442183 and KIC 11137075 observed by KeplerJun 03 2015Jun 05 2015Asteroseismology provides a powerful way to constrain stellar parameters. Solar-like oscillations have been observed on subgiant stars with the \emph{Kepler\/} mission. The continuous and high-precision time series enables us to carry out a detailed asteroseismic ... More
Asteroseismology of main-sequence F stars with \textit{Kepler}: overcoming short mode lifetimesFeb 14 2019Asteroseismology is a powerful way of determining stellar parameters and properties of stars like the Sun. However, main-sequence F-type stars exhibit short mode lifetimes relative to their oscillation frequency, resulting in overlapping radial and quadrupole ... More
The period-luminosity relation for delta Scuti stars using Gaia DR2 parallaxesApr 17 2019Apr 29 2019We have examined the period-luminosity (P-L) relation for delta Scuti stars using Gaia DR2 parallaxes. We included 228 stars from the catalogue of Rodriguez et al. (2000), as well as 1124 stars observed in the four-year Kepler mission. For each star we ... More
{\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability stripFeb 28 2019We study the fraction of stars in and around the {\delta} Scuti instability strip that are pulsating, using {\em Gaia} DR2 parallaxes to derive precise luminosities. We classify a sample of over 15,000 {\em Kepler} A and F stars into {\delta} Sct and ... More
Period spacings of $γ$ Doradus pulsators in the \textit{Kepler} field: Rossby and gravity modes in 82 starsApr 28 2019Rossby modes are the oscillations in a rotating fluid, whose restoring force is the Coriolis force. They provide an additional diagnostic to understand the rotation of stars, which complicates asteroseismic modelling. We report 82 $\gamma$\,Doradus stars ... More
Photometry Using Kepler "Superstamps" of Open Clusters NGC 6791 & NGC 6819Sep 24 2013The Kepler space telescope has proven to be a gold mine for the study of variable stars. Unfortunately, Kepler only returns a handful of pixels surrounding each star on the target list, which omits a large number of stars in the Kepler field. For the ... More
Asteroseismic modelling of the subgiant μ Herculis using SONG data: lifting the degeneracy between age and model input parametersOct 30 2018We model the oscillations of the SONG target $\mu$ Herculis to estimate the parameters of the star. The $\ell$ = 1 mixed modes of $\mu$ Her provide strong constraints on stellar properties. The mass and age given by our asteroseismic modelling are 1.10$^{+0.11}_{-0.06}$ ... More
Echelle diagrams and period spacings of g modes in gamma Doradus stars from four years of Kepler observationsNov 07 2014We use photometry from the Kepler Mission to study oscillations in gamma Doradus stars. Some stars show remarkably clear sequences of g modes and we use period echelle diagrams to measure period spacings and identify rotationally split multiplets with ... More
Asteroseismology of 16000 Kepler Red Giants: Global Oscillation Parameters, Masses, and RadiiFeb 13 2018Apr 03 2018The Kepler mission has provided exquisite data to perform an ensemble asteroseismic analysis on evolved stars. In this work we systematically characterize solar-like oscillations and granulation for 16,094 oscillating red giants, using end-of-mission ... More
Binary star detectability in $Kepler$ data from phase modulation of different types of oscillationsMay 11 2016Detecting binary stars in photometric time series is traditionally done by measuring eclipses. This requires the orbital plane to be aligned with the observer. A new method without that requirement uses stellar oscillations to measure delays in the light ... More
A unifying explanation of complex frequency spectra of gamma Dor, SPB and Be stars: combination frequencies and highly non-sinusoidal light curvesApr 16 2015There are many Slowly Pulsating B (SPB) stars and gamma Dor stars in the Kepler Mission data set. The light curves of these pulsating stars have been classified phenomenologically into stars with symmetric light curves and with asymmetric light curves. ... More
Stellar population synthesis based modelling of the Milky Way using asteroseismology of dwarfs and subgiants from KeplerJan 10 2017Early attempts to apply asteroseismology to study the Galaxy have already shown unexpected discrepancies for the mass distribution of stars between the Galactic models and the data; a result that is still unexplained. Here, we revisit the analysis of ... More
Stellar population synthesis based modelling of the Milky Way using asteroseismology of 13000 Kepler red giantsMar 17 2016With current space-based missions it is now possible to obtain age-sensitive asteroseismic information for tens of thousands of red giants. This provides a promising opportunity to study the Galactic structure and evolution. We use asteroseismic data ... More
Testing Newtonian Gravity with AAOmega: Mass-to-Light Profiles of Four Globular ClustersAug 05 2009Testing Newtonian gravity in the weak-acceleration regime is vital to our understanding of the nature of the gravitational interaction. It has recently been claimed that the velocity dispersion profiles of several globular clusters flatten out at large ... More
Testing Newtonian Gravity with AAOmega: Mass-To-Light Profiles and Metallicity Calibrations From 47 Tuc and M55Oct 05 2009Globular clusters are an important test bed for Newtonian gravity in the weak-acceleration regime, which is vital to our understanding of the nature of the gravitational interaction. Recent claims have been made that the velocity dispersion profiles of ... More
Modelling Kepler Red Giants in Eclipsing Binaries:Calibrating the Mixing Length Parameter with AsteroseismologyDec 05 2017Stellar models rely on a number of free parameters. High-quality observations of eclipsing binary stars observed by Kepler offer a great opportunity to calibrate model parameters for evolved stars. Our study focuses on six Kepler red giants with the goal ... More
Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992Dec 17 2014We have found a rotationally split series of core g-mode triplets and surface p-mode multiplets in a main sequence F star, KIC 9244992. Comparison with models shows that the star has a mass of about 1.45 M$_\odot$, and is at an advanced stage of main ... More
Asteroseismology of KIC 7107778: a binary comprising almost identical subgiantsJan 27 2018We analyze an asteroseismic binary system: KIC 7107778, a non-eclipsing, unresolved target, with solar-like oscillations in both components. We used \emph{Kepler} short cadence time series spanning nearly two years to obtain the power spectrum. Oscillation ... More
AAOmega Observations of 47 Tucanae: Evidence for a Past Merger?Feb 03 2010The globular cluster 47 Tucanae is well studied but it has many characteristics that are unexplained, including a significant rise in the velocity dispersion profile at large radii, indicating the exciting possibility of two distinct kinematic populations. ... More
Oscillation frequencies and mode lifetimes in alpha Centauri AJun 21 2004We analyse our recently-published velocity measurements of alpha Cen A (Butler et al. 2004). After adjusting the weights on a night-by-night basis in order to optimize the window function to minimize sidelobes, we extract 42 oscillation frequencies with ... More
Ultra-high-precision velocity measurements of oscillations in alpha Cen ANov 17 2003We have made differential radial velocity measurements of the star alpha Cen A using two spectrographs, UVES and UCLES, both with iodine absorption cells for wavelength referencing. Stellar oscillations are clearly visible in the time series. After removing ... More
AAOmega spectroscopy of 29 351 stars in fields centered on ten Galactic globular clustersApr 13 2011May 02 2011Galactic globular clusters have been pivotal in our understanding of many astrophysical phenomena. Here we publish the extracted stellar parameters from a recent large spectroscopic survey of ten globular clusters. A brief review of the project is also ... More
Evidence for solar-like oscillations in beta HydriDec 20 2000We have made a clear detection of excess power, providing strong evidence for solar-like oscillations in the G2 subgiant beta Hyi. We observed this star over five nights with the UCLES echelle spectrograph on the 3.9-m Anglo-Australian Telescope, using ... More
Halo globular clusters observed with AAOmega: dark matter content, metallicity and tidal heatingApr 27 2010Globular clusters have proven to be essential to our understanding of many important astrophysical phenomena. Here we analyse spectroscopic observations of ten Halo globular clusters to determine their dark matter content, their tidal heating by the Galactic ... More
Solar-like oscillations in alpha Centauri BAug 29 2005We have made velocity observations of the star alpha Cen B from two sites, allowing us to identify 37 oscillation modes with l=0-3. Fitting to these modes gives the large and small frequency separations as a function of frequency. The mode lifetime, as ... More
Solar-like oscillations and activity in Procyon: A comparison of the 2007 MOST and ground-based radial velocity campaignsFeb 14 2011Mar 09 2011We compare the simultaneous 2007 space-based MOST photometry and ground-based radial velocity observations of the F5 star Procyon. We identify slow variations in the MOST data that are similar to those reported in the radial velocity (RV) time series, ... More
Dynamical masses, absolute radii and 3D orbits of the triply eclipsing star HD 181068 from Kepler photometryOct 03 2012HD 181068 is the brighter of the two known triply eclipsing hierarchical triple stars in the Kepler field. It has been continuously observed for more than 2 years with the Kepler space telescope. Of the nine quarters of the data, three have been obtained ... More
Solving the mode identification problem in asteroseismology of F stars observed with KeplerMay 02 2012Asteroseismology of F-type stars has been hindered by an ambiguity in identification of their oscillation modes. The regular mode pattern that makes this task trivial in cooler stars is masked by increased linewidths. The absolute mode frequencies, encapsulated ... More
Evidence for compact binary systems around Kepler red giantsMay 01 2017We present an analysis of 168 oscillating red giants from NASA's $Kepler$ mission that exhibit anomalous peaks in their Fourier amplitude spectra. These peaks result from ellipsoidal variations which are indicative of binary star systems, at frequencies ... More
Hipparcos Luminosities and AsteroseismologyOct 31 2000Asteroseismology involves using the resonant frequencies of a star to infer details about its internal structure and evolutionary state. Oscillation frequencies are most useful when accompanied by accurate measurements of the more traditional stellar ... More
Optical and infrared interferometryNov 29 2000Interferometric techniques are at the forefront of modern astronomical instrumentation. A new generation of instruments are either operating or nearing completion, including arrays of small telescopes as well as the ``big guns'' (VLTI and Keck). A number ... More
Solar-like Oscillations: An Observational PerspectiveJul 08 2011Solar-like oscillations are excited stochastically by convection. They occur in stars with an outer convection zone, which includes the Sun and other stars on the lower main sequence, as well as cool subgiants and red giants. This chapter reviews the ... More
Introduction to InterferometrySep 12 1996This tutorial gives a general introduction to optical and infrared interferometry, specifically addressing two questions: `Can I use VLTI to observe my favourite object?' and `What will it tell me?' The observables measured by an interferometer are fringe ... More
The Orbit of the Binary Star Delta ScorpiiMay 22 1993Although delta Scorpii is a bright and well-studied star, the details of its multiplicity have remained unclear. Here we present the first diffraction-limited image of this 0.12 arcsec binary star, made using optical interferometry, and resolve the confusion ... More
Solar-like oscillations in semiregular variablesSep 18 2002Sep 25 2002Power spectra of the light curves of semiregular variables, based on visual magnitude estimates spanning many decades, show clear evidence for stochastic excitation. This supports the suggestion by Christensen-Dalsgaard et al. (2001) that oscillations ... More
Prospects for observing pulsating red giants with the MONS Star TrackersMar 17 2000K and M giants show variability on timescales from years down to days and possibly even hours. I discuss the contribution that can be made with high-precision photometry that will be obtained by the MONS Star Trackers. These include observations of flare-like ... More
Replicated Echelle Diagrams in Asteroseismology: A Tool for Studying Mixed Modes and Avoided CrossingsSep 27 2011In oscillating stars, mixed modes have p-mode character in the envelope and g-mode character in the core. They are observed in subgiants and red giants, in which the large density gradient outside the core effectively divides the star into two coupled ... More
New methods for masked-aperture and speckle interferometryJan 18 1999Diffraction-limited images can be obtained with a large optical telescope using interferometry. One such method for objects of sufficient brightness is non-redundant masking (NRM), in which observations are made through a pupil mask that contains an array ... More
Testing asteroseismology with Gaia DR2: Hierarchical models of the Red ClumpApr 16 2019Apr 18 2019Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have ... More
Testing asteroseismology with Gaia DR2: Hierarchical models of the Red ClumpApr 16 2019Asteroseismology provides fundamental stellar parameters independent of distance, but subject to systematics under calibration. Gaia DR2 has provided parallaxes for a billion stars, which are offset by a parallax zero-point. Red Clump (RC) stars have ... More
Modeling Kepler Observations of Solar-like Oscillations in the Red-giant Star HD 186355Sep 05 2011Nov 28 2011We have analysed oscillations of the red giant star HD 186355 observed by the NASA Kepler satellite. The data consist of the first five quarters of science operations of Kepler, which cover about 13 months. The high-precision time-series data allow us ... More
Tidally Induced Oscillations and Orbital Decay in Compact Triple-Star SystemsNov 29 2012Jan 28 2013We investigate the nature of tidal effects in compact triple-star systems. The hierarchical structure of a triple system produces tidal forcing at high frequencies unobtainable in binary systems, allowing for the tidal excitation of high frequency p-modes ... More
Stellar populations in NGC 5128 with the VLT: evidence for recent star formationSep 24 2001We resolve stars of the nearest giant elliptical galaxy NGC 5128 using VLT with FORS1 and ISAAC. We construct deep U, V and Ks color-magnitude and color-color diagrams in two different halo fields (in the halo and in the north-eastern diffuse shell). ... More
Amplitudes of solar-like oscillations: a new scaling relationApr 08 2011Solar-like oscillations are excited by near-surface convection and are being observed in growing numbers of stars using ground and space-based telescopes. We have previously suggested an empirical scaling relation to predict their amplitudes (Kjeldsen ... More
The MONS Star TrackersMar 17 2000The MONS satellite will have two Star Trackers to sense the spacecraft attitude, and we plan to use them as scientific instruments to perform high-precision photometry of thousands of stars. We briefly describe the current plans for the Star Trackers ... More
Long Period Variables in NGC 5128: II. Near-IR propertiesSep 12 2003Long Period Variable stars are ubiquitous among the bright red giant branch stars in NGC 5128. Mostly they are found to be brighter than the tip of the first ascent giant branch with magnitudes ranging from about K=19 to K=21.5. They have periods between ... More
Scaled oscillation frequencies and echelle diagrams as a tool for comparative asteroseismologyJan 27 2010We describe a method for comparing the frequency spectra of oscillating stars. We focus on solar-like oscillations, in which mode frequencies generally follow a regular pattern. On the basis that oscillation frequencies of similar stars scale homologously, ... More
Asteroseismology from solar-like oscillationsFeb 19 2007There has been tremendous progress in observing oscillations in solar-type stars. In a few short years we have moved from ambiguous detections to firm measurements. We briefly review the recent results, most of which have come from high-precision Doppler ... More
Observations of solar-like oscillationsSep 28 2006There has been tremendous progress in observing oscillations in solar-type stars. In a few short years we have moved from ambiguous detections to firm measurements. We review the recent results, most of which have come from high-precision Doppler measurements. ... More
Validation of the Exoplanet Kepler-21b using PAVO/CHARA Long-Baseline InterferometryFeb 23 2012Mar 09 2012We present long-baseline interferometry of the Kepler exoplanet host star HD179070 (Kepler-21) using the PAVO beam combiner at the CHARA Array. The visibility data are consistent with a single star and exclude stellar companions at separations ~1-1000 ... More
Asteroseismology of the Hyades red giant and planet host epsilon TauriJan 18 2019Feb 22 2019Asteroseismic analysis of solar-like stars allows us to determine physical parameters such as stellar mass, with a higher precision compared to most other methods. Even in a well-studied cluster such as the Hyades, the masses of the red giant stars are ... More
Solar-like Oscillations (Invited Review)May 22 2003Aug 22 2003The five-minute oscillations in the Sun have provided a wealth of information about the solar interior. After many attempts, positive detections of similar oscillations in solar-type stars have now been made. This review discusses the properties of solar-like ... More
Solar-like oscillations: the search goes onSep 29 1997Despite numerous attempts and many hours of telescope time, there has so far been no confirmed detection of solar-like oscillations in any star except the Sun. We review recent efforts, with particular emphasis on the technique of monitoring equivalent ... More
Observing solar-like oscillationsApr 04 1997We review techniques for measuring stellar oscillations in solar-type stars. Despite great efforts, no unambiguous detections have been made. A new method, based on monitoring the equivalent widths of strong lines, shows promise but is yet to be confirmed. ... More
Observations of solar-like oscillationsMay 10 2007There has been tremendous progress in observing oscillations in solar-type stars. In a few short years we have moved from ambiguous detections to firm measurements. We briefly review the recent results, most of which have come from high-precision Doppler ... More
Current status of AsteroseismologyNov 19 2000Oscillation frequencies are the most accurate properties one can measure for a star, potentially allowing detailed tests of stellar models and evolution theories. We briefly review asteroseismology for two classes of stars. In delta Scuti variables, the ... More
Observing solar-like oscillationsFeb 04 2008The past few years have seen great progress in observing oscillations in solar-type stars, lying on or just above the main sequence. We review the most recent results, most of which were obtained using high-precision velocity measurements. We also briefly ... More
Observing solar-like oscillations: recent resultsOct 14 2005We review recent progress in observations of ground-based oscillations. Excellent observations now exist for a few stars (alpha Cen A and B, mu Ara), while there is some controversy over others (Procyon, eta Boo). We have reached the stage where single-site ... More
Mode switching in the nearby Mira-like variable R DoradusAug 28 1998We discuss visual observations spanning nearly 70 years of the nearby semiregular variable R Doradus. Using wavelet analysis, we show that the star switches back and forth between two pulsation modes having periods of 332 days and about 175 days, the ... More
Colour ratios of pulsation amplitudes in red giantsJun 04 2003We have analysed the three-colour photometry of 34 pulsating red giants that was published by Percy, Wilson and Henry (2001). As is common with semiregulars, many of these stars have long secondary periods (LSPs) of several years, in addition to the usual ... More
Variability in red supergiant stars: pulsations, long secondary periods and convection noiseAug 21 2006We study the brightness variations of galactic red supergiant stars using long-term visual light curves collected by the American Association of Variable Star Observers (AAVSO) over the last century. The full sample contains 48 red semiregular or irregular ... More
Photometry of Very Bright Stars with Kepler and K2 Smear DataSep 30 2015High-precision time series photometry with the Kepler satellite has been crucial to our understanding both of exoplanets, and via asteroseismology, of stellar physics. After the failure of two reaction wheels, the Kepler satellite has been repurposed ... More
Testing the Asteroseismic Mass Scale Using Metal-Poor Stars Characterized with APOGEE and KeplerMar 07 2014Fundamental stellar properties, such as mass, radius, and age, can be inferred using asteroseismology. Cool stars with convective envelopes have turbulent motions that can stochastically drive and damp pulsations. The properties of the oscillation frequency ... More
Kepler-432: a red giant interacting with one of its two long period giant planetsNov 17 2014Apr 20 2015We report the discovery of Kepler-432b, a giant planet ($M_b = 5.41^{+0.32}_{-0.18} M_{\rm Jup}, R_b = 1.145^{+0.036}_{-0.039} R_{\rm Jup}$) transiting an evolved star $(M_\star = 1.32^{+0.10}_{-0.07} M_\odot, R_\star = 4.06^{+0.12}_{-0.08} R_\odot)$ ... More
Fast core rotation in red-giant stars revealed by gravity-dominated mixed modesDec 13 2011When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant, in which convection occupies a large fraction of the star. Conservation of angular ... More
Kepler-93b: A Terrestrial World Measured to within 120 km, and a Test Case for a New Spitzer Observing ModeMay 14 2014We present the characterization of the Kepler-93 exoplanetary system, based on three years of photometry gathered by the Kepler spacecraft. The duration and cadence of the Kepler observations, in tandem with the brightness of the star, enable unusually ... More
Solar-like oscillations in the G2 subgiant beta Hydri from dual-site observationsMar 29 2007May 15 2007We have observed oscillations in the nearby G2 subgiant star beta Hyi using high-precision velocity observations obtained over more than a week with the HARPS and UCLES spectrographs. The oscillation frequencies show a regular comb structure, as expected ... More
The GALAH Survey and Gaia DR2: (Non)existence of five sparse high-latitude open clustersJul 02 2018Sparse open clusters can be found at high galactic latitudes where loosely populated clusters are more easily detected against the lower stellar background. Because most star formation takes place in the thin disk, the observed population of clusters ... More
Angular Diameters of Compact Planetary NebulaeSep 14 1993We have obtained H$\alpha$ CCD images of 21 compact planetary nebulae in the galactic bulge. All objects are resolved and, after deconvolving the seeing disk, we find diameters of 1--2$''$ with typical uncertainties of 20\%. The values are generally in ... More
Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection RunDec 02 2013Feb 03 2014We present revised properties for 196,468 stars observed by the NASA Kepler Mission and used in the analysis of Quarter 1-16 (Q1-Q16) data to detect and characterize transiting exoplanets. The catalog is based on a compilation of literature values for ... More
The γ Dor stars as revealed by Kepler : A key to reveal deep-layer rotation in A and F starsSep 12 2017The {\gamma} Dor pulsating stars present high-order gravity modes, which make them important targets in the intermediate-and low-mass main-sequence region of the Hertzsprung-Russell diagram. Whilst we have only access to rotation in the envelope of the ... More
Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant starsMar 30 2011Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our ... More
Accretion disk models and their X-ray reflection signatures. I. Local spectraMay 31 2000X-ray illumination of accretion disks is an invaluable diagnostic of the structure of these disks because of the associated iron K$\alpha$ emission. Here we point out that the resulting reflected spectra depend very sensitively on the geometry of the ... More
The GALAH survey: The data reduction pipelineAug 15 2016We present the data reduction procedures being used by the GALAH survey, carried out with the HERMES fibre-fed, multi-object spectrograph on the 3.9~m Anglo-Australian Telescope. GALAH is a unique survey, targeting 1 million stars brighter than magnitude ... More
Bisectors of the cross-correlation function applied to stellar spectra. Discriminating stellar activity, oscillations and planetsApr 11 2006Aims: We investigate whether bisectors derived from cross-correlation functions (CCF) of single-exposure spectra can be used to provide information on stellar atmospheres, and whether they can be used to discriminate between radial velocity changes caused ... More
Multi-wavelength Diameters of Nearby Miras and SemiregularsFeb 13 2004We have used optical interferometry to obtain multi-wavelength visibility curves for eight red giants over the wavelength range 650--1000 nm. The observations consist of wavelength-dispersed fringes recorded with MAPPIT (Masked APerture-Plane Interference ... More
Astro2020 Science White Paper: Stellar Physics and Galactic Archeology using Asteroseismology in the 2020'sMar 19 2019Asteroseismology is the only observational tool in astronomy that can probe the interiors of stars, and is a benchmark method for deriving fundamental properties of stars and exoplanets. Over the coming decade, space-based and ground-based observations ... More
Radial velocities of five globular clusters obtained with AAOmegaMay 24 2007Using the recently commissioned multi-object spectrograph AAOmega on the 3.9m AAT we have obtained medium-resolution near-infrared spectra for 10,500 stars in and around five southern globular clusters. The targets were 47 Tuc, M12, M30, M55 and NGC 288. ... More
A wide-field kinematic survey for tidal tails around five globular clustersMar 11 2007Using the AAOmega instrument of the Anglo-Australian Telescope, we have obtained medium-resolution near-infrared spectra of 10,500 stars in two-degree fields centered on the galactic globular clusters 47 Tuc, NGC 288, M12, M30 and M55. Radial velocities ... More
The relation between $Δν$ and $ν_{max}$ for solar-like oscillationsSep 28 2009Establishing relations between global stellar parameters and asteroseismic quantities can help improve our understanding of stellar astrophysics and facilitate the interpretation of observations. We present an observed relation between the large frequency ... More
Ellipsoidal Variability and Long Secondary Periods in MACHO Red Giant StarsAug 29 2006We present a period-luminosity-amplitude analysis of 5899 red giant and binary stars in the Large Magellanic Cloud, using publicly available observations of the MACHO project. For each star, we determined new periods, which were double-checked in order ... More
Defining the instability strip of pulsating post-AGB binary stars from ASAS and NSVS photometryDec 08 2006We analyse public domain time-series photometric observations of 30 known and candidate binary post-AGB stars for measuring pulsation and orbital periods. We derive periodicities for 17 stars for the first time in the literature. Besides identifying five ... More
Wavelength dependence of angular diameters of M giants: an observational perspectiveNov 05 1999We discuss the wavelength dependence of angular diameters of M giants from an observational perspective. Observers cannot directly measure an optical-depth radius for a star, despite this being a common theoretical definition. Instead, they can use an ... More
Multi-wavelength visibility measurements of the red giant R DoradusMay 09 2000We present visibility measurements of the nearby Mira-like star R Doradus taken over a wide range of wavelengths (650--990 nm). The observations were made using MAPPIT (Masked APerture-Plane Interference Telescope), an interferometer operating at the ... More
Multi-wavelength observations of the red giant R Doradus with the MAPPIT interferometerNov 29 2000We present visibility measurements of the nearby Mira-like star R Doradus taken over a wide range of wavelengths (650-990 nm). The observations were made using MAPPIT (Masked APerture-Plane Interference Telescope), an interferometer operating at the 3.9-m ... More
Asteroseismic diagrams from a survey of solar-like oscillations with KeplerOct 06 2011Photometric observations made by the NASA Kepler Mission have led to a dramatic increase in the number of main-sequence and subgiant stars with detected solar-like oscillations. We present an ensemble asteroseismic analysis of 76 solar-type stars. Using ... More
Calibrating Convective properties of Solar-like Stars in the Kepler Field of ViewJul 11 2012Stellar models generally use simple parametrizations to treat convection. The most widely used parametrization is the so-called "Mixing Length Theory" where the convective eddy sizes are described using a single number, \alpha, the mixing-length parameter. ... More
Measurements of Stellar Properties through Asteroseismology: A Tool for Planet Transit StudiesJul 03 2008Oscillations occur in stars of most masses and essentially all stages of evolution. Asteroseismology is the study of the frequencies and other properties of stellar oscillations, from which we can extract fundamental parameters such as density, mass, ... More
Hipparcos parallaxes for eta Boo and kappa_2 Boo: two successes for asteroseismologySep 01 1997The release of the Hipparcos catalogue provides an opportunity to check results from asteroseismology. Here we show that Hipparcos parallaxes for two stars are in good agreement with oscillation results. For eta Boo, a probable detection of solar-like ... More
Surface correction of main sequence solar-like oscillators with the $Kepler$ LEGACY sampleJun 26 2018Poor modelling of the surface regions of solar-like stars causes a systematic discrepancy between the observed and model pulsation frequencies. We aim to characterise this frequency discrepancy for main sequence solar-like oscillators for a wide range ... More
Bayesian Inference from Observations of Solar-Like OscillationsAug 26 2006Stellar oscillations can provide a wealth of information about a star, which can be extracted from observed time series of the star's brightness or radial velocity. In this paper we address the question of how to extract as much information as possible ... More
A planet in an 840-d orbit around a Kepler main-sequence A star found from phase modulation of its pulsationsAug 09 2016Aug 11 2016We have detected a 12 M$_{\rm Jup}$ planet orbiting in or near the habitable zone of a main-sequence A star via the pulsational phase shifts induced by orbital motion. The planet has an orbital period of $840\pm20$ d and an eccentricity of 0.15. All known ... More
Finding binaries from phase modulation of pulsating stars with Kepler. IV. Detection limits and radial velocity verificationJul 26 2016Aug 01 2016We explore the detection limits of the phase modulation (PM) method of finding binary systems among multi-periodic pulsating stars. The method is an attractive way of finding non-transiting planets in the habitable zones of intermediate mass stars, whose ... More
A search for solar-like oscillations in alpha Cen AOct 31 1997Dec 03 1997We have been using a new method to search for solar-like oscillations that involves measuring temperature changes via their effect on the equivalent widths of the Balmer hydrogen lines. We observed alpha Cen A over six nights in 1995 with the 3.9-metre ... More
Correcting stellar oscillation frequencies for near-surface effectsJul 11 2008In helioseismology, there is a well-known offset between observed and computed oscillation frequencies. This offset is known to arise from improper modeling of the near-surface layers of the Sun, and a similar effect must occur for models of other stars. ... More
Hipparcos calibration of the tip of the Red Giant BranchAug 20 2009We have detected the tip of the Red Giant Branch (TRGB) in the solar neighborhood using near infrared photometry from the 2MASS and DIRBE catalogs, and revised Hipparcos parallaxes. We confirm that the revised Hipparcos parallaxes are superior to the ... More
A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass starsDec 31 2015Jan 06 2016Magnetic fields play a role in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective ... More
Solar-like oscillations in eta BooNov 03 1994We have observed evidence for $p$-mode oscillations in the G0 IV star etaBoo (V = 2.68). This represents the first clear evidence of solar-like oscillations in a star other than the Sun. We used a new technique which measures fluctuations in the temperature ... More