Ball, Warrick Heinz

[["dc.bibliographiccitation.artnumber","A25"],["dc.bibliographiccitation.journal","Astronomy & Astrophysics"],["dc.bibliographiccitation.volume","582"],["dc.contributor.author","Appourchaux, Thierry"],["dc.contributor.author","Antia, H. M."],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Creevey, O. L."],["dc.contributor.author","Lebreton, Y."],["dc.contributor.author","Verma, K."],["dc.contributor.author","Vorontsov, S."],["dc.contributor.author","Campante, T. L."],["dc.contributor.author","Davies, G. R."],["dc.contributor.author","Gaulme, P."],["dc.contributor.author","Régulo, C."],["dc.contributor.author","Horch, E."],["dc.contributor.author","Howell, S. B."],["dc.contributor.author","Everett, M."],["dc.contributor.author","Ciardi, D."],["dc.contributor.author","Fossati, L."],["dc.contributor.author","Miglio, A."],["dc.contributor.author","Montalbán, J."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","García, R. A."],["dc.contributor.author","Gizon, Laurent"],["dc.date.accessioned","2017-09-07T11:48:37Z"],["dc.date.available","2017-09-07T11:48:37Z"],["dc.date.issued","2015"],["dc.description.abstract","Context. Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe stars using asteroseismology.Aims. The derivation of stellar parameters has usually been done with single stars. The aim of the paper is to derive the stellar parameters of a double-star system (HIP 93511), for which an interferometric orbit has been observed along with asteroseismic measurements.Methods. We used a time series of nearly two years of data for the double star to detect the two oscillation-mode envelopes that appear in the power spectrum. Using a new scaling relation based on luminosity, we derived the radius and mass of each star. We derived the age of each star using two proxies: one based upon the large frequency separation and a new one based upon the small frequency separation. Using stellar modelling, the mode frequencies allowed us to derive the radius, the mass, and the age of each component. In addition, speckle interferometry performed since 2006 has enabled us to recover the orbit of the system and the total mass of the system.Results. From the determination of the orbit, the total mass of the system is 2.34-0.33+0.45 M⊙. The total seismic mass using scaling relations is 2.47 ± 0.07 M⊙. The seismic age derived using the new proxy based upon the small frequency separation is 3.5 ± 0.3 Gyr. Based on stellar modelling, the mean common age of the system is 2.7–3.9 Gyr. The mean total seismic mass of the system is 2.34–2.53 M⊙  consistent with what we determined independently with the orbit. The stellar models provide the mean radius, mass, and age of the stars as RA = 1.82−1.87R⊙, MA = 1.25−1.39 M⊙, AgeA = 2.6–3.5 Gyr; RB = 1.22−1.25 R⊙, MB = 1.08−1.14 M⊙, AgeB = 3.35–4.21 Gyr. The models provide two sets of values for Star A: [1.25–1.27] M⊙ and [1.34–1.39] M⊙. We detect a convective core in Star A, while Star B does not have any. For the metallicity of the binary system of Z ≈ 0.02, we set the limit between stars having a convective core in the range [1.14–1.25] M⊙."],["dc.identifier.doi","10.1051/0004-6361/201526610"],["dc.identifier.gro","3146954"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/12450"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/4724"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","public"],["dc.notes.submitter","chake"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","A seismic and gravitationally bound double star observed by Kepler"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","no"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A82"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","601"],["dc.contributor.author","White, Timothy R."],["dc.contributor.author","Benomar, O."],["dc.contributor.author","Aguirre, Victor Silva"],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Bedding, Timothy R."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","Christensen-Dalsgaard, Joergen"],["dc.contributor.author","Garcia, R. A."],["dc.contributor.author","Gizon, Laurent"],["dc.contributor.author","Stello, Dennis"],["dc.contributor.author","Aigrain, S."],["dc.contributor.author","Antia, H. M."],["dc.contributor.author","Appourchaux, T."],["dc.contributor.author","Bazot, M."],["dc.contributor.author","Campante, Tiago L."],["dc.contributor.author","Creevey, O. L."],["dc.contributor.author","Davies, G. R."],["dc.contributor.author","Elsworth, Yvonne P."],["dc.contributor.author","Gaulme, P."],["dc.contributor.author","Handberg, Rasmus"],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Houdek, Gunter"],["dc.contributor.author","Howe, R."],["dc.contributor.author","Huber, D."],["dc.contributor.author","Karoff, Christoffer"],["dc.contributor.author","Marques, J. P."],["dc.contributor.author","Mathur, S."],["dc.contributor.author","McQuillan, A."],["dc.contributor.author","Metcalfe, T. S."],["dc.contributor.author","Mosser, B."],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Regulo, C."],["dc.contributor.author","Salabert, D."],["dc.contributor.author","Stahn, Thorsten"],["dc.date.accessioned","2018-11-07T10:24:05Z"],["dc.date.available","2018-11-07T10:24:05Z"],["dc.date.issued","2017"],["dc.description.abstract","Binary star systems are important for understanding stellar structure and evolution, and are especially useful when oscillations can be detected and analysed with asteroseismology. However, only four systems are known in which solar-like oscillations are detected in both components. Here, we analyse the fifth such system, HD 176465, which was observed by Kepler. We carefully analysed the system's power spectrum to measure individual mode frequencies, adapting our methods where necessary to accommodate the fact that both stars oscillate in a similar frequency range. We also modelled the two stars independently by fitting stellar models to the frequencies and complementary parameters. We are able to cleanly separate the oscillation modes in both systems. The stellar models produce compatible ages and initial compositions for the stars, as is expected from their common and contemporaneous origin. Combining the individual ages, the system is about 3.0 +/- 0.5 Gyr old. The two components of HD 176465 are young physically-similar oscillating solar analogues, the first such system to be found, and provide important constraints for stellar evolution and asteroseismology."],["dc.identifier.doi","10.1051/0004-6361/201628706"],["dc.identifier.isi","000402313500082"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15004"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/42591"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Edp Sciences S A"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/338251/EU//STELLARAGES"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Kepler observations of the asteroseismic binary HD 176465"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A14"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","592"],["dc.contributor.author","Reese, Daniel R."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","Davies, G. R."],["dc.contributor.author","Miglio, Andrea"],["dc.contributor.author","Antia, H. M."],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Basu, S."],["dc.contributor.author","Buldgen, G."],["dc.contributor.author","Christensen-Dalsgaard, Joergen"],["dc.contributor.author","Coelho, Hugo R."],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Houdek, Gunter"],["dc.contributor.author","Lebreton, Yveline"],["dc.contributor.author","Mazumdar, Anupam"],["dc.contributor.author","Metcalfe, T. S."],["dc.contributor.author","Aguirre, Victor Silva"],["dc.contributor.author","Stello, Dennis"],["dc.contributor.author","Verma, Kuldeep"],["dc.date.accessioned","2018-11-07T10:10:38Z"],["dc.date.available","2018-11-07T10:10:38Z"],["dc.date.issued","2016"],["dc.description.abstract","Context. Detailed oscillation spectra comprising individual frequencies for numerous solar-type stars and red giants are either currently available, e.g. courtesy of the CoRoT, Kepler, and K2 missions, or will become available with the upcoming NASA TESS and ESA PLATO 2.0 missions. The data can lead to a precise characterisation of these stars thereby improving our understanding of stellar evolution, exoplanetary systems, and the history of our galaxy. Aims. Our goal is to test and compare different methods for obtaining stellar properties from oscillation frequencies and spectroscopic constraints. Specifically, we would like to evaluate the accuracy of the results and reliability of the associated error bars, and to see where there is room for improvement. Methods. In the context of the SpaceInn network, we carried out a hare-and-hounds exercise in which one group, the hares, simulated observations of oscillation spectra for a set of ten artificial solar-type stars, and a number of hounds applied various methods for characterising these stars based on the data produced by the hares. Most of the hounds fell into two main groups. The first group used forward modelling (i.e. applied various search/optimisation algorithms in a stellar parameter space) whereas the second group relied on acoustic glitch signatures. Results. Results based on the forward modelling approach were accurate to 1:5% (radius), 3.9% (mass), 23% (age), 1.5% (surface gravity), and 1.8% (mean density), as based on the root mean square difference. Individual hounds reached different degrees of accuracy, some of which were substantially better than the above average values. For the two 1 M-circle dot stellar targets, the accuracy on the age is better than 10% thereby satisfying the requirements for the PLATO 2.0 mission. High stellar masses and atomic diffusion (which in our models does not include the effects of radiative accelerations) proved to be sources of difficulty. The average accuracies for the acoustic radii of the base of the convection zone, the He II ionisation, and the Gamma(1) peak located between the two He ionisation zones were 17%, 2.4%, and 1.9%, respectively. The results from the forward modelling were on average more accurate than those from the glitch fitting analysis as the latter seemed to be affected by aliasing problems for some of the targets. Conclusions. Our study indicates that forward modelling is the most accurate way of interpreting the pulsation spectra of solar-type stars. However, given its model-dependent nature, this method needs to be complemented by model-independent results from, e.g. glitch analysis. Furthermore, our results indicate that global rather than local optimisation algorithms should be used in order to obtain robust error bars."],["dc.identifier.doi","10.1051/0004-6361/201527987"],["dc.identifier.isi","000384722600072"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/14281"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39895"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/312844/EU/Exploitation of Space Data for Innovative Helio- and Asteroseismology/SPACEINN"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/267864/EU/ASTERoseismic Investigations with SONG and Kepler/ASTERISK"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/338251/EU/Accurate ages of stars/StellarAges"],["dc.relation.issn","1432-0746"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","SpaceInn hare-and-hounds exercise: Estimation of stellar properties using space-based asteroseismic data"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]