Nielsen, Martin Bo

[["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.issue","2"],["dc.bibliographiccitation.journal","Monthly Notices of the Royal Astronomical Society"],["dc.bibliographiccitation.volume","446"],["dc.contributor.author","Karoff, Christoffer"],["dc.contributor.author","Metcalfe, T. S."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","Frandsen, S."],["dc.contributor.author","Grundahl, F."],["dc.contributor.author","Kjeldsen, Hans"],["dc.contributor.author","Christensen-Dalsgaard, Joergen"],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Frimann, S."],["dc.contributor.author","Thygesen, A. O."],["dc.contributor.author","Arentoft, T."],["dc.contributor.author","Amby, T. M."],["dc.contributor.author","Sousa, S. G."],["dc.contributor.author","Buzasi, D. L."],["dc.date.accessioned","2018-11-07T10:02:16Z"],["dc.date.available","2018-11-07T10:02:16Z"],["dc.date.issued","2015"],["dc.format.extent","1139"],["dc.identifier.doi","10.1093/mnras/stu2114"],["dc.identifier.isi","000350272200002"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/38192"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","1365-2966"],["dc.relation.issn","0035-8711"],["dc.title","Sounding stellar cycles with Kepler - II. Ground-based observations (vol 433, pg 3227, 2013)"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","A34"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","572"],["dc.contributor.author","Garcia, R. A."],["dc.contributor.author","Ceillier, T."],["dc.contributor.author","Salabert, D."],["dc.contributor.author","Mathur, S."],["dc.contributor.author","van Saders, J. L."],["dc.contributor.author","Pinsonneault, M."],["dc.contributor.author","Ballot, J."],["dc.contributor.author","Beck, P. G."],["dc.contributor.author","Bloemen, S."],["dc.contributor.author","Campante, Tiago L."],["dc.contributor.author","Davies, G. R."],["dc.contributor.author","do Nascimento, J.-D., Jr."],["dc.contributor.author","Mathis, S."],["dc.contributor.author","Metcalfe, T. S."],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Suarez, J. C."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","Jimenez, Alfredo"],["dc.contributor.author","Karoff, Christoffer"],["dc.date.accessioned","2018-11-07T09:31:55Z"],["dc.date.available","2018-11-07T09:31:55Z"],["dc.date.issued","2014"],["dc.description.abstract","Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the main-sequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature."],["dc.identifier.doi","10.1051/0004-6361/201423888"],["dc.identifier.isi","000346101700050"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11407"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/31636"],["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//SPACEINN"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/269194/EU//ASK"],["dc.relation","info:eu-repo/grantAgreement/EC/FP7/227224/EU//PROSPERITY"],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.relation.orgunit","Fakultät für Physik"],["dc.title","Rotation and magnetism of Kepler pulsating solar-like stars Towards asteroseismically calibrated age-rotation relations"],["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","A54"],["dc.bibliographiccitation.journal","Astronomy and Astrophysics"],["dc.bibliographiccitation.volume","570"],["dc.contributor.author","Lund, Mikkel N."],["dc.contributor.author","Lundkvist, Mia S."],["dc.contributor.author","Aguirre, Victor Silva"],["dc.contributor.author","Houdek, Gunter"],["dc.contributor.author","Casagrande, Luca"],["dc.contributor.author","van Eylen, Vincent"],["dc.contributor.author","Campante, Tiago L."],["dc.contributor.author","Karoff, Christoffer"],["dc.contributor.author","Kjeldsen, Hans"],["dc.contributor.author","Albrecht, Simon"],["dc.contributor.author","Chaplin, William J."],["dc.contributor.author","Nielsen, Martin Bo"],["dc.contributor.author","Degroote, Pieter"],["dc.contributor.author","Davies, Guy R."],["dc.contributor.author","Handberg, Rasmus"],["dc.date.accessioned","2018-11-07T09:34:03Z"],["dc.date.available","2018-11-07T09:34:03Z"],["dc.date.issued","2014"],["dc.description.abstract","Context. The measurement of obliquities - the angle between the orbital and stellar rotation -in star-planet systems is of great importance for understanding planet system formation and evolution. The bright and well-studied HAT-P-7 (Kepler-2) system is intriguing because several Rossiter-McLaughlin (RM) measurements found a high projected obliquity in this system, but it was not possible so far to determine whether the orbit is polar and/or retrograde. Aims. The goal of this study is to measure the stellar inclination and hereby the full 3D obliquity of the HAT-P-7 system instead of only the 2D projection as measured by the RM effect. In addition, we provide an updated set of stellar parameters for the star. Methods. We used the full set of available observations from Kepler spanning Q0-Q17 to produce the power spectrum of HAT-P-7. We extracted oscillation-mode frequencies via an Markov chain Monte Carlo peak-bagging routine and used the results from this to estimate the stellar inclination angle. Combining this with the projected obliquity from RM and the inclination of the orbital plane allowed us to determine the stellar obliquity. Furthermore, we used asteroseismology to model the star from the extracted frequencies using two different approaches to the modelling, for which either the stellar evolution codes MESA or GARSTEC were adopted. Results. Our updated asteroseismic modelling shows, i.a., the following stellar parameters for HAT-P-7: M- = 1.51(-0.05)(+0.04) M-circle dot, R- =2.00(-0.02)(+0.01) R-circle dot, and age = 2.07(-0.23)(+0.28) Gyr. The modelling offers a high precision on the stellar parameters, the uncertainty on age, for instance, is of the order similar to 11%. For the stellar inclination we estimate i( ) < 36.5 degrees, which translates into an obliquity of 83 degrees < psi < 111 degrees. The planet HAT-P-7b is likely retrograde in its orbit, and the orbit is close to being polar. The new parameters for the star give an updated planetary density of rho(p) = 0.65 +/- 0.03 g cm(-3), which is lower than previous estimates."],["dc.identifier.doi","10.1051/0004-6361/201424326"],["dc.identifier.isi","000344158500103"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/11397"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/32098"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Edp Sciences S A"],["dc.relation.issn","1432-0746"],["dc.relation.issn","0004-6361"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Asteroseismic inference on the spin-orbit misalignment and stellar parameters of HAT-P-7"],["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","3227"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Monthly Notices of the Royal Astronomical Society"],["dc.bibliographiccitation.lastpage","3238"],["dc.bibliographiccitation.volume","433"],["dc.contributor.author","Karoff, Christoffer"],["dc.contributor.author","Metcalfe, T. S."],["dc.contributor.author","Chaplin, W. J."],["dc.contributor.author","Frandsen, S."],["dc.contributor.author","Grundahl, F."],["dc.contributor.author","Kjeldsen, Hans"],["dc.contributor.author","Christensen-Dalsgaard, Joergen"],["dc.contributor.author","Nielsen, M. B."],["dc.contributor.author","Frimann, S."],["dc.contributor.author","Thygesen, A. O."],["dc.contributor.author","Arentoft, T."],["dc.contributor.author","Amby, T. M."],["dc.contributor.author","Sousa, S. G."],["dc.contributor.author","Buzasi, D. L."],["dc.date.accessioned","2018-11-07T09:21:58Z"],["dc.date.available","2018-11-07T09:21:58Z"],["dc.date.issued","2013"],["dc.description.abstract","We have monitored 20 Sun-like stars in the Kepler field-of-view for excess flux with the Fibre-fed Echelle Spectrograph on the Nordic Optical Telescope since the launch of Kepler spacecraft in 2009. These 20 stars were selected based on their asteroseismic properties to sample the parameter space (effective temperature, surface gravity, activity level, etc.) around the Sun. Though the ultimate goal is to improve stellar dynamo models, we focus the present paper on the combination of space-based and ground-based observations that can be used to test the age-rotation-activity relations. In this paper we describe the considerations behind the selection of these 20 Sun-like stars and present an initial asteroseismic analysis, which includes stellar age estimates. We also describe the observations from the Nordic Optical Telescope and present mean values of measured excess fluxes. These measurements are combined with estimates of the rotation periods obtained from a simple analysis of the modulation in photometric observations from Kepler caused by starspots, and asteroseismic determinations of stellar ages, to test relations between age, rotation and activity."],["dc.identifier.doi","10.1093/mnras/stt964"],["dc.identifier.isi","000322405900035"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/29230"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Oxford Univ Press"],["dc.relation.issn","0035-8711"],["dc.title","Sounding stellar cycles with Kepler - II. Ground-based observations"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]