Safari, Hossein/0000-0003-2326-3201; Moya, Andres/0000-0003-1665-5389; Szabo, Robert/0000-0002-3258-1909; Serenelli, Aldo/0000-0001-6359-2769; Mazumdar, Anwesh/0000-0003-2409-2942; Handberg, Rasmus/0000-0001-8725-4502; Lysgaard Rorsted, Jakob/0000-0001-9234-430X; Lund, Mikkel Norup/0000-0001-9214-5642; Christensen-Dalsgaard, Jorgen/0000-0001-5137-0966; YILDIZ, Mutlu/0000-0002-7772-7641; Stokholm, Amalie/0000-0002-5496-365X; Verma, Kuldeep/0000-0003-0970-6440; Bazot, Michael/0000-0003-0166-1540; Lundkvist, Mia Sloth/0000-0002-8661-2571 ; WOS: 000508167700003 ; Over the course of its history, the Milky Way has ingested multiple smaller satellite galaxies1. Although these accreted stellar populations can be forensically identified as kinematically distinct structures within the Galaxy, it is difficult in general to date precisely the age at which any one merger occurred. Recent results have revealed a population of stars that were accreted via the collision of a dwarf galaxy, called Gaia-Enceladus1, leading to substantial pollution of the chemical and dynamical properties of the Milky Way. Here we identify the very bright, naked-eye star. Indi as an indicator of the age of the early in situ population of the Galaxy. We combine asteroseismic, spectroscopic, astrometric and kinematic observations to show that this metal-poor, alpha-element-rich star was an indigenous member of the halo, and we measure its age to be 11.0 +/- 0.7 (stat) +/- 0.8 (sys) billion years. the star bears hallmarks consistent with having been kinematically heated by the Gaia-Enceladus collision. Its age implies that the earliest the merger could have begun was 11.6 and 13.2 billion years ago, at 68% and 95% confidence, respectively. Computations based on hierarchical cosmological models slightly reduce the above limits. ; NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center; UK Science and Technology Facilities Council (STFC)Science & Technology Facilities Council (STFC); UK Space Agency; Danish National Research FoundationDanmarks Grundforskningsfond [DNRF106]; National Science FoundationNational Science Foundation (NSF) [NSF PHY-1748958, AST-1903828, AST-1717000]; ERCEuropean Research Council (ERC) [772293]; Center for Cosmology and AstroParticle Physics at the Ohio State UniversityOhio State University; NYU Abu Dhabi Center for Space Science [G1502]; Spanish GovernmentSpanish Government [ESP2017-82674-R]; Generalitat de CatalunyaGeneralitat de Catalunya [2017-SGR-1131]; BelspoBelgian Federal Science Policy Office; European Social Fund via the Lithuanian Science Council [09.3.3-LMT-K-71201-0103]; NSFNational Science Foundation (NSF) [AST-1514676]; NASANational Aeronautics & Space Administration (NASA) [NNX16AB76G, 80NSSC19K0374, NAS5-26555]; Independent Research Fund Denmark [7027-00096B]; National Aeronautics and Space Administration through the TESS Guest Investigator Program [80NSSC18K1585, 80NSSC19K0379]; Max Planck Institute for Solar System Research; European UnionEuropean Union (EU) [749962, 792848, 664931]; FCT/MCTES through national funds (PIDDAC) [UID/FIS/04434/2019]; European Research Council under the European CommunityEuropean Research Council (ERC) [338251]; MINECO FPI-SO [SEV-2015-0548-17-2, BES2017-082610]; German space agency (Deutsches Zentrum fur Luft-und Raumfahrt) under PLATO data grant [50OO1501]; UK Science and Technology Facilities Council (STFC)Science & Technology Facilities Council (STFC) [ST/L000733/1]; Carlsberg FoundationCarlsberg Foundation [CF17-076]; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK:118F352]; Spanish ministry through the Ramon y Cajal fellowship [RYC-2015-17697]; Premiale 2015 MITiC; NKFIH [K-115709]; Lendulet program of the Hungarian Academy of Science [20187/2019]; NASA through the NASA Hubble Fellowship - Space Telescope Science Institute [51424]; FEDER through COMPETE2020 [POCI-01-0145-FEDER-030389]; Government of India, Department of Atomic EnergyDepartment of Atomic Energy (DAE) [12-RD-TFR-6.04-0600] ; This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. W.J.C. acknowledges support from the UK Science and Technology Facilities Council (STFC) and UK Space Agency. Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation (grant agreement number DNRF106). This research was partially conducted during the Exostar19 programme at the Kavli Institute for Theoretical Physics at UC Santa Barbara, which was supported in part by the National Science Foundation under grant number NSF PHY-1748958. A.M., J.T.M., F.V. and J.M. acknowledge support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, grant agreement number 772293). F.V. acknowledges the support of a Fellowship from the Center for Cosmology and AstroParticle Physics at the Ohio State University. W.H.B. and M.B.N. acknowledge support from the UK Space Agency. K.J.B. is supported by the National Science Foundation under award AST-1903828. M.B.N. acknowledges partial support from the NYU Abu Dhabi Center for Space Science under grant number G1502. A.M.S. is partially supported by the Spanish Government (ESP2017-82674-R) and Generalitat de Catalunya (2017-SGR-1131). T.M. acknowledges financial support from Belspo for contract PRODEX PLATO. H.K. acknowledges support from the European Social Fund via the Lithuanian Science Council grant number 09.3.3-LMT-K-71201-0103. S.B. acknowledges support from NSF grant AST-1514676 and NASA grant 80NSSC19K0374. V.S.A. acknowledges support from the Independent Research Fund Denmark (research grant 7027-00096B). D.H. acknowledges support by the National Aeronautics and Space Administration (80NSSC18K1585, 80NSSC19K0379) awarded through the TESS Guest Investigator Program and by the National Science Foundation (AST-1717000). T.S.M. acknowledges support from a visiting fellowship at the Max Planck Institute for Solar System Research. Computational resources were provided through XSEDE allocation TG-AST090107. D.L.B. acknowledges support from NASA under grant NNX16AB76G. T.L.C. acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement number 792848 (PULSATION). This work was supported by FCT/MCTES through national funds (PIDDAC) by means of grant UID/FIS/04434/2019. K.J.B., S.H., J.S.K. and N.T. are supported by the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement number 338251 (StellarAges). E.C. is funded by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement number 664931. L.G.-C. acknowledges support from the MINECO FPI-SO doctoral research project SEV-2015-0548-17-2 and predoctoral contract BES2017-082610. P.G. is supported by the German space agency (Deutsches Zentrum fur Luft-und Raumfahrt) under PLATO data grant 50OO1501. R.K. acknowledges support from the UK Science and Technology Facilities Council (STFC), under consolidated grant ST/L000733/1. M.S.L. is supported by the Carlsberg Foundation (grant agreement number CF17-076). Z.C.O., S.O. and M.Y. acknowledge support from the Scientific and Technological Research Council of Turkey (TUBITAK:118F352). S.M.; acknowledges support from the Spanish ministry through the Ramon y Cajal fellowship number RYC-2015-17697. T.S.R. acknowledges financial support from Premiale 2015 MITiC (PI B. Garilli). R.Sz. acknowledges the support from NKFIH grant project No. K-115709, and the Lendulet program of the Hungarian Academy of Science (project number 20187/2019). J.T. acknowledges support was provided by NASA through the NASA Hubble Fellowship grant number 51424 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. This work was supported by FEDER through COMPETE2020 (POCI-01-0145-FEDER-030389. A.M.B. acknowledges funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 749962 (project THOT). A.M. and P.R. acknowledge the support of the Government of India, Department of Atomic Energy, under Project No. 12-R&D-TFR-6.04-0600. K.J.B. is an NSF Astronomy and Astrophysics Postdoctoral Fellow and DIRAC Fellow.
[Contact] The large quantity of high-quality asteroseismic data that have been obtained from space-based photometric missions and the accuracy of the resulting frequencies motivate a careful consideration of the accuracy of computed oscillation frequencies of stellar models, when applied as diagnostics of the model properties. ; [Aims] Based on models of red-giant stars that have been independently calculated using different stellar evolution codes, we investigate the extent to which the differences in the model calculation affect the model oscillation frequencies and other asteroseismic diagnostics. ; [Methods] For each of the models, which cover four different masses and different evolution stages on the red-giant branch, we computed full sets of low-degree oscillation frequencies using a single pulsation code and, from these frequencies, typical asteroseismic diagnostics. In addition, we carried out preliminary analyses to relate differences in the oscillation properties to the corresponding model differences. ; [Results] In general, the differences in asteroseismic properties between the different models greatly exceed the observational precision of these properties. This is particularly true for the nonradial modes whose mixed acoustic and gravity-wave character makes them sensitive to the structure of the deep stellar interior and, hence, to details of their evolution. In some cases, identifying these differences led to improvements in the final models presented here and in Paper I; here we illustrate particular examples of this. ; [Conclusions] Further improvements in stellar modelling are required in order fully to utilise the observational accuracy to probe intrinsic limitations in the modelling and improve our understanding of stellar internal physics. However, our analysis of the frequency differences and their relation to stellar internal properties provides a striking illustration of the potential, in particular, of the mixed modes of red-giant stars for the diagnostics of stellar interiors. ; Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (Grant agreement No. DNRF106). The research was supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (Grant agreement No. 267864). This research was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958. VSA acknowledges support from VILLUM FONDEN (research grant 10118) and the Independent Research Fund Denmark (Research grant 7027-00096B). DS is the recipient of an Australian Research Council Future Fellowship (project number FT1400147). SC acknowledges support from Premiale INAF MITiC, from INAF "Progetto mainstream" (PI: S. Cassisi), and grant AYA2013-42781P from the Ministry of Economy and Competitiveness of Spain. AMS is partially supported by grants ESP2017-82674-R (Spanish Government) and 2017-SGR-1131 (General-itat de Catalunya). TC acknowledges support from the European Research Council AdG No 320478-TOFU and the STFC Consolidated Grant ST/R000395/1. SH received funding for this research from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no 338251 (StellarAges). AM acknowledges the support of the Government of India, Department of Atomic Energy, under Project No. 12-R&D-TFR-6.04-0600. DB is supported in the form of work contract FCT/MCTES through national funds and by FEDER through COMPETE2020 in connection to these grants: UID/FIS/04434/2019; PTDC/FIS-AST/30389/2017 & POCI-01-0145-FEDER-030389.
WOS: 000469975500005 ; We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 mu Hz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R-* = 2.943 +/- 0.064 R-circle dot), mass (M-* = 1.212 +/- 0.074 M-circle dot), and age (4.9 +/- 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (R-p = 9.17 +/- 0.33 R-circle plus) with an orbital period of similar to 14.3 days, irradiance of F = 343 +/- 24 F-circle plus, and moderate mass (M-p = 60.5 +/- 5.7 M-circle plus) and density (rho(p) = 0.431 +/- 0.062 g cm(-3)). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R-circle plus) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to similar to 15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology. ; National Aeronautics and Space Administration through the TESS Guest Investigator Program [80NSSC18K1585]; National Science FoundationNational Science Foundation (NSF) [AST-1717000]; Science and Technology Facilities CouncilScience & Technology Facilities Council (STFC); UK Space Agency; European Social Fund via the Lithuanian Science Council [09.3.3-LMT-K-712-01-0103]; Danish National Research FoundationDanmarks Grundforskningsfond [DNRF106]; FONDECYT projectComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [1171208]; CONICYT projectComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) [BASAL AFB-170002]; Ministry for the Economy, Development, and Tourism's Programa Iniciativa Cientifica Milenio [IC 120009]; FONDECYTComision Nacional de Investigacion Cientifica y Tecnologica (CONICYT)CONICYT FONDECYT [3180246]; Millennium Institute of Astrophysics (MAS); MINECOSpanish Ministry of Economy & Competitiveness [ESP2017-82674-R]; AGAURAgencia de Gestio D'Ajuts Universitaris de Recerca Agaur (AGUAR) [SGR2017-1131]; PLATO grant from the CNES; European Research Council under the European Community's Seventh Framework Programme (FP72007-2013) ERC grant [338251]; European Research Council through the SPIRE grant [647383]; FCT (Portugal); FEDER through COMPETE2020 [UID/FIS/04434/2013, POCI-01-0145-FEDER-007672, PTDC/FIS-AST/30389/2017, POCI-01-0145-FEDER-030389]; European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grantEuropean Union (EU) [792848]; European UnionEuropean Union (EU) [664931]; Independent Research Fund Denmark [7027-00096B]; Australian Research CouncilAustralian Research Council; NASANational Aeronautics & Space Administration (NASA) [NNX16AI09G, AS5-26555]; NSFNational Science Foundation (NSF) [AST-1514676]; Australian Research CouncilAustralian Research Council [DP150100250]; ERCEuropean Research Council (ERC) [772293]; Ramon y Cajal fellowshipMinistry of Education and Science, Spain [RYC-2015-17697]; Carlsberg FoundationCarlsberg Foundation [CF17-0760]; HBCSE-NIUS programme; NASA through Hubble Fellowship grants - Space Telescope Science Institute [HST-HF2-51399.001, HST-HF2-51424.001]; Premiale 2015 MITiC; NKFIH [K-115709]; Lendulet Program of the Hungarian Academy of Sciences [LP2018-7/2018]; NASA's Science Mission directorate ; The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawai'ian community. We are most fortunate to have the opportunity to conduct observations from this mountain. We thank Andrei Tokovinin for helpful information on the Speckle observations obtained with SOAR. D.H. acknowledges support by the National Aeronautics and Space Administration through the TESS Guest Investigator Program (80NSSC18K1585) and by the National Science Foundation (AST-1717000). A.C. acknowledges support by the National Science Foundation under the Graduate Research Fellowship Program. W.J.C., W.H.B., A.M., O.J.H., and G.R.D. acknowledge support from the Science and Technology Facilities Council and UK Space Agency. H.K. and F.G. acknowledge support from the European Social Fund via the Lithuanian Science Council grant No. 09.3.3-LMT-K-712-01-0103. Funding for the Stellar Astrophysics Centre is provided by The Danish National Research Foundation (grant DNRF106). A.J. acknowledges support from FONDECYT project 1171208, CONICYT project BASAL AFB-170002, and by the Ministry for the Economy, Development, and Tourism's Programa Iniciativa Cientifica Milenio through grant IC 120009, awarded to the Millennium Institute of Astrophysics (MAS). R.B. acknowledges support from FONDECYT Post-doctoral Fellowship Project 3180246, and from the Millennium Institute of Astrophysics (MAS). A.M.S. is supported by grants ESP2017-82674-R (MINECO) and SGR2017-1131 (AGAUR). R.A.G. and L.B. acknowledge the support of the PLATO grant from the CNES. The research leading to the presented results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP72007-2013) ERC grant agreement No. 338251 (StellarAges). S.M. acknowledges support from the European Research Council through the SPIRE grant 647383. This work was also supported by FCT (Portugal) through national funds and by FEDER through COMPETE2020 by these grants: UID/FIS/04434/2013 and POCI-01-0145-FEDER-007672, PTDC/FIS-AST/30389/2017, and POCI-01-0145-FEDER-030389. T.L.C. acknowledges support from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 792848 (PULSATION). E.C. is funded by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 664931. V.S.A. acknowledges support from the Independent Research Fund Denmark (Research grant 7027-00096B). D.S. acknowledges support from the Australian Research Council. S.B. acknowledges NASA grant NNX16AI09G and NSF grant AST-1514676. T.R.W. acknowledges support from the Australian Research Council through grant DP150100250. A.M. acknowledges support from the ERC Consolidator Grant funding scheme (project ASTEROCHRONOMETRY, G.A. n. 772293). S.M. acknowledges support from the Ramon y Cajal fellowship number RYC-2015-17697. M.S.L. is supported by the Carlsberg Foundation (grant agreement No. CF17-0760). A.M. and P.R. acknowledge support from the HBCSE-NIUS programme. J.K.T. and J.T. acknowledge that support for this work was provided by NASA through Hubble Fellowship grants HST-HF2-51399.001 and HST-HF2-51424.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract AS5-26555. T.S.R. acknowledges financial support from Premiale 2015 MITiC (PI B. Garilli).; This project has been supported by the NKFIH K-115709 grant and the Lendulet Program of the Hungarian Academy of Sciences, project No. LP2018-7/2018.; Based on observations made with the Hertzsprung SONG telescope operated on the Spanish Observatorio del Teide on the island of Tenerife by the Aarhus and Copenhagen Universities and by the Instituto de Astrofisica de Canarias. Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST).