Ball, Warrick Heinz

[["dc.bibliographiccitation.artnumber","31"],["dc.bibliographiccitation.firstpage","31"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.volume","830"],["dc.contributor.author","Bellinger, Earl P."],["dc.contributor.author","Angelou, George C."],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Basu, Sarbani"],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Guggenberger, Elisabeth"],["dc.date.accessioned","2020-12-10T18:47:32Z"],["dc.date.available","2020-12-10T18:47:32Z"],["dc.date.issued","2016"],["dc.description.abstract","Owing to the remarkable photometric precision of space observatories like Kepler, stellar and planetary systems beyond our own are now being characterized en masse for the first time. These characterizations are pivotal for endeavors such as searching for Earth-like planets and solar twins, understanding the mechanisms that govern stellar evolution, and tracing the dynamics of our Galaxy. The volume of data that is becoming available, however, brings with it the need to process this information accurately and rapidly. While existing methods can constrain fundamental stellar parameters such as ages, masses, and radii from these observations, they require substantial computational effort to do so. We develop a method based on machine learning for rapidly estimating fundamental parameters of main-sequence solar-like stars from classical and asteroseismic observations. We first demonstrate this method on a hare-and-hound exercise and then apply it to the Sun, 16 Cyg A and B, and 34 planet-hosting candidates that have been observed by the Kepler spacecraft. We find that our estimates and their associated uncertainties are comparable to the results of other methods, but with the additional benefit of being able to explore many more stellar parameters while using much less computation time. We furthermore use this method to present evidence for an empirical diffusion-mass relation. Our method is open source and freely available for the community to use."],["dc.identifier.doi","10.3847/0004-637X/830/1/31"],["dc.identifier.eissn","1538-4357"],["dc.identifier.isi","000400461900001"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/78796"],["dc.notes.intern","DOI Import GROB-354"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Iop Publishing Ltd"],["dc.relation.issn","1538-4357"],["dc.relation.issn","0004-637X"],["dc.title","Fundamental Parameters of Main-Sequence Stars in an Instant with Machine Learning"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","05003"],["dc.bibliographiccitation.journal","EPJ Web of Conferences"],["dc.bibliographiccitation.volume","160"],["dc.contributor.author","Bellinger, Earl P."],["dc.contributor.author","Angelou, George C."],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Basu, Sarbani"],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Guggenberger, Elisabet"],["dc.contributor.editor","Monteiro, M.J.P.F.G."],["dc.contributor.editor","Cunha, M.S."],["dc.contributor.editor","Ferreira, J.M.T.S."],["dc.date.accessioned","2020-12-10T18:11:58Z"],["dc.date.available","2020-12-10T18:11:58Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.1051/epjconf/201716005003"],["dc.identifier.eissn","2100-014X"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/74199"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Stellar Parameters in an Instant with Machine Learning"],["dc.title.alternative","Application to\n Kepler\n LEGACY Targets"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["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"]]

[["dc.bibliographiccitation.artnumber","A105"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","564"],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Ball, Warrick H."],["dc.date.accessioned","2018-11-07T09:41:47Z"],["dc.date.available","2018-11-07T09:41:47Z"],["dc.date.issued","2014"],["dc.description.abstract","Context. Recently, the CoRoT target HD 175272 (F5V), which shows a weak signal of solar-like oscillations, was modelled by a differential asteroseismic analysis (Ozel et al. 2013, A&A, 558, A79) relative to a seismically similar star, HD 181420 (F2V), for which there is a clear signature of solar-like oscillations. The results provided by Ozel et al. indicate the possibility of HD 175272 having subsolar mass, while being of the order of 1000 K hotter than the Sun. This seems unphysical - standard stellar evolution theory generally does not predict solar-metallicity stars of subsolar mass to be hotter than about 6000 K - and calls for a reanalysis of this star. Aims. We aim to compare the performance of differential asteroseismic analysis with that of grid-based modelling. Methods. We use two sets of stellar model grids and two grid-fitting methods to model HD 175272 and HD 181420 using their effective temperatures, metallicities, large frequency separations (Delta v), and frequencies of maximum oscillation power (v(max)) as observational constraints. Results. We find that we are able to model both stars with parameters that are both mutually compatible and comparable with other modelling efforts. Hence, with modest spectroscopic and asteroseismic inputs, we obtain reasonable estimates of stellar parameters. In the case of HD 175272, the uncertainties of the stellar parameters from our grid-based modelling are smaller, and hence more physical, than those reported in the differential analysis. For both stars, the models have significantly lower values of v(max) than the reported observed values. Furthermore, when using the asymptotic large frequency separation as opposed to the scaling relation to compute Delta v, we find that our modelling results are significantly more self-consistent when v(max) is ignored. Conclusions. Grid-based modelling is a useful tool even in cases of weak solar-like oscillations. It provides more precise and more realistic results than obtained with differential seismology. The difference in the observed and modelled values of v(max) indicates that the four observational constraints are not fully consistent with the stellar models used here, with v(max) most likely to be the inconsistent constraint for these two stars."],["dc.identifier.doi","10.1051/0004-6361/201323121"],["dc.identifier.fs","609711"],["dc.identifier.isi","000334671000105"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/10918"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/33808"],["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/FP7/338251/EU//STELLARAGES"],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Grid-based seismic modelling at high and low signal-to-noise ratios HD 181420 and HD 175272"],["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.firstpage","23"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","The Astrophysical Journal Supplement Series"],["dc.bibliographiccitation.volume","233"],["dc.contributor.author","Serenelli, Aldo"],["dc.contributor.author","Johnson, Jennifer"],["dc.contributor.author","Huber, Daniel"],["dc.contributor.author","Pinsonneault, Marc"],["dc.contributor.author","Ball, Warrick H."],["dc.contributor.author","Tayar, Jamie"],["dc.contributor.author","Aguirre, Victor Silva"],["dc.contributor.author","Basu, Sarbani"],["dc.contributor.author","Troup, Nicholas"],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Kallinger, Thomas"],["dc.contributor.author","Stello, Dennis"],["dc.contributor.author","Davies, Guy R."],["dc.contributor.author","Lund, Mikkel N."],["dc.contributor.author","Mathur, Savita"],["dc.contributor.author","Mosser, Benoit"],["dc.contributor.author","Stassun, Keivan G."],["dc.contributor.author","Chaplin, William J."],["dc.contributor.author","Elsworth, Yvonne"],["dc.contributor.author","García, Rafael A."],["dc.contributor.author","Handberg, Rasmus"],["dc.contributor.author","Holtzman, Jon"],["dc.contributor.author","Hearty, Fred"],["dc.contributor.author","García-Hernández, D. A."],["dc.contributor.author","Gaulme, Patrick"],["dc.contributor.author","Zamora, Olga"],["dc.date.accessioned","2020-12-10T18:47:36Z"],["dc.date.available","2020-12-10T18:47:36Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.3847/1538-4365/aa97df"],["dc.identifier.eissn","1538-4365"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/78821"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","The First APOKASC Catalog of Kepler Dwarf and Subgiant Stars"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","80"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","The Astrophysical Journal"],["dc.bibliographiccitation.volume","851"],["dc.contributor.author","Bellinger, Earl P."],["dc.contributor.author","Basu, Sarbani"],["dc.contributor.author","Hekker, Saskia"],["dc.contributor.author","Ball, Warrick H."],["dc.date.accessioned","2020-12-10T18:47:34Z"],["dc.date.available","2020-12-10T18:47:34Z"],["dc.date.issued","2017"],["dc.identifier.doi","10.3847/1538-4357/aa9848"],["dc.identifier.eissn","1538-4357"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/78806"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Model-independent Measurement of Internal Stellar Structure in 16 Cygni A and B"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]