Helio and Astero-Seismology and Exoplanets Search

    General
    Description

    The principal objectives of this project are: 1) to study the structure and dynamics of the solar interior, 2) to extend this study to other stars, 3) to search for extrasolar planets using photometric methods (primarily by transits of their host stars) and their characterization (using radial velocity information) and 4) the study of the planetary atmospheres.

    To reach our first objective, we use Global Helioseismology (analysis of the solar oscillation eigenmodes) and Local Helioseismology (that uses travel waves). Solar seismology allows to accurately infer information about the internal structure and dynamics of the Sun,. This project covers the various necessary aspects to attain the aforementioned objectives: instrumental, observational, reduction, analysis and interpretation of data and, finally, theoretical developments of inversion techniques and development of structure and evolution models.

    On the other hand, the Astroseismology aims to obtain a similar knowledge of other stars. Thanks to the huge number of stars observed by CoRoT, Kepler and TESS space missions it is possible to extract seismic global parameters of hundreds of stars; both solar type and red giants. Furthermore, the recent deployment and beginning of observations with the high precision spectrographs of the SONG (Stellar Observations Network Group) ground-based telescopes will substantially improve the characterization of the eigenmodes spectrum in bright stars.

    The strategy of using planetary transits to discover new planets around other stars consists of the photometric detection of the dimming of the light of the star when one of its planets passes, or ‘transits’ in front of it. Currently this method is the preferred one for the study of small planets, not only due to its sensitivity, but also because this method allows a more detailed investigation of the planets found (e.g. Planetary atmospheres). This technique is similar to the one that is used for helio- and asteroseismology and so some of its methods are a logical extension from that. However, it is also important to develop new algorithms and observing methods for the unequivocal detection and analysis of planets and to be able to distinguish them from false alarms.

    The current horizon for studies of exoplanets with space missions involves new missions, beginning with the launch of CHEOPS, followed by TESS, JWST and in 2026, PLATO. Thus, there is presently a window of opportunity for ground-based facilities, and we are pursuing observations using mainly TNG, NOT y GTC.

    Principal investigator

    Milestones

    1. Members of the team (P. G. Beck, H. Deeg, S. Mathur, F. H. Perez, C. Regulo) were involved in the discovery and characterization of a warm Saturn transiting a slightly evolved solar-like star (HD 89345) observed with the NASA K2 mission and confirmed with RV measurements. The seismic analysis of the star led to precise estimates of the stellar parameters.
    2. P.G.Beck lead two papers on binary systems hosting red-giant binaries, using asteroseismic techniques and data from the Kepler space telescope. Beck et al (2018a,b) allow a better understanding of the stellar structure of the stellar components, and the tidal interaction in binary systems. The internal mixing was investigated through measurements lithium.
    3. S. Mathur participated in the analysis of the first planet discovered with the NASA TESS mission, orbiting the star Pi Men. The seismic analysis led to a very marginal detection but gave a hint of the asteroseismic potential with the TESS data (Gandolfi et al. 2018).
    4. Project "Solar-SONG". For the first time, stellar instrumentation (SONG spectrograph) has been used to obtain precise measurements of the radial velocity of the Sun with high temporal cadence (4 sec.) and long duration (57 consecutive days) to allow the detailed study of the spectrum of oscillations ( p-modes) and obtain their global parameters
    5. The researchers Hans J. Deeg and Juan Antonio Belmonte coordinated the edition of the "Handbook of Exoplanets", four volumes with 160 articles by more than 300 specialists in exoplanetology. Three years of intensive work have resulted in a complete documentation on the state of the art of the studies of the planets beyond the Solar System.

    Related publications

    • A giant impact as the likely origin of different twins in the Kepler-107 exoplanet system
      Measures of exoplanet bulk densities indicate that small exoplanets with radius less than 3 Earth radii (R ⊕) range from low-density sub-Neptunes containing volatile elements 1 to higher-density rocky planets with Earth-like 2 or iron-rich 3 (Mercury-like) compositions. Such astonishing diversity in observed small exoplanet compositions may be the
      Bonomo, Aldo S. et al.

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      2
      2019
      Citations
      75
    • The K2 Galactic Caps Project - going beyond the Kepler field and ageing the Galactic disc
      Analyses of data from spectroscopic and astrometric surveys have led to conflicting results concerning the vertical characteristics of the Milky Way. Ages are often used to provide clarity, but typical uncertainties of >40 per cent from photometry restrict the validity of the inferences made. Using the Kepler APOKASC sample for context, we explore
      Rendle, B. M. et al.

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      12
      2019
      Citations
      33
    • Multicolour photometry for exoplanet candidate validation
      Context. The TESS and PLATO missions are expected to find vast numbers of new transiting planet candidates. However, only a fraction of these candidates will be legitimate planets, and the candidate validation will require a significant amount of follow-up resources. Radial velocity (RV) follow-up study can be carried out only for the most
      Parviainen, H. et al.

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      10
      2019
      Citations
      56
    • Revisiting the impact of stellar magnetic activity on the detection of solar-like oscillations by Kepler
      Over 2,000 stars were observed for one month with a high enough cadence in order to look for acoustic modes during the survey phase of the Kepler mission. Solar-like oscillations have been detected in about 540 stars. The question of why no oscillations were detected in the remaining stars is still open. Previous works explained the non-detection
      Mathur, Savita et al.

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      7
      2019
      Citations
      41
    • Masses and ages for metal-poor stars. A pilot programme combining asteroseismology and high-resolution spectroscopic follow-up of RAVE halo stars
      Context. Very metal-poor halo stars are the best candidates for being among the oldest objects in our Galaxy. Samples of halo stars with age determination and detailed chemical composition measurements provide key information for constraining the nature of the first stellar generations and the nucleosynthesis in the metal-poor regime. Aims: Age
      Valentini, M. et al.

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      7
      2019
      Citations
      41
    • Greening of the brown-dwarf desert. EPIC 212036875b: a 51 MJ object in a 5-day orbit around an F7 V star
      Context. Although more than 2000 brown dwarfs have been detected to date, mainly from direct imaging, their characterisation is difficult due to their faintness and model-dependent results. In the case of transiting brown dwarfs, however, it is possible to make direct high-precision observations. Aims: Our aim is to investigate the nature and
      Persson, Carina M. et al.

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      8
      2019
      Citations
      23
    • Acoustic oscillations and dynamo action in the G8 sub-giant EK Eridani
      We present further evidence of acoustic oscillations in the slowly rotating overactive G8 sub-giant EK Eri. This star was observed with the 1m Hertzsprung SONG telescope at the Observatorio del Teide for two different runs of 8 and 13 nights, respectively, that were separated by about a year. We determined a significant excess of power around νmax
      Bonanno, A. et al.

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      8
      2019
      Citations
      4
    • Influence of magnetic activity on the determination of stellar parameters through asteroseismology
      Magnetic activity changes the gravito-acoustic modes of solar-like stars and in particular their frequencies. There is an angular-degree dependence that is believed to be caused by the non-spherical nature of the magnetic activity in the stellar convective envelope. These changes in the mode frequencies could modify the small separation of low
      Pérez Hernández, Fernando et al.

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      5
      2019
      Citations
      12
    • A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS
      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 μHz and
      Huber, Daniel et al.

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      6
      2019
      Citations
      86
    • First detection of oscillations in the Halo giant HD 122563: Validation of seismic scaling relations and new parameters
      Aims: The nearby metal-poor giant HD 122563 is an important astrophysical laboratory in which to test stellar atmospheric and interior physics. It is also a benchmark star for which to calibrate methods to apply to large scale surveys. Recently it has been remeasured using various methodologies given the new high precision instruments at our
      Creevey, O. et al.

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      5
      2019
      Citations
      14
    • The Transiting Multi-planet System HD15337: Two Nearly Equal-mass Planets Straddling the Radius Gap
      We report the discovery of a super-Earth and a sub-Neptune transiting the star HD 15337 (TOI-402, TIC 120896927), a bright (V = 9) K1 dwarf observed by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 3 and 4. We combine the TESS photometry with archival High Accuracy Radial velocity Planet Searcher spectra to confirm the planetary
      Gandolfi, Davide et al.

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      5
      2019
      Citations
      33
    • FliPerClass: In search of solar-like pulsators among TESS targets
      The NASA Transiting Exoplanet Survey Satellite (TESS) is about to provide full-frame images of almost the entire sky. The amount of stellar data to be analysed represents hundreds of millions stars, which is several orders of magnitude more than the number of stars observed by the Convection, Rotation and planetary Transits satellite (CoRoT), and
      Bugnet, L. et al.

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      4
      2019
      Citations
      7
    • HD 219666 b: a hot-Neptune from TESS Sector 1
      We report on the confirmation and mass determination of a transiting planet orbiting the old and inactive G7 dwarf star HD 219666 (M⋆ = 0.92 ± 0.03 M⊙, R⋆ = 1.03 ± 0.03 R⊙, τ⋆ = 10 ± 2 Gyr). With a mass of Mb = 16.6 ± 1.3 M⊕, a radius of Rb = 4.71 ± 0.17 R⊕, and an orbital period of Porb ≃ 6 days, HD 219666 b is a new member of a rare class of
      Esposito, M. et al.

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      3
      2019
      Citations
      31
    • A search for red giant solar-like oscillations in all Kepler data
      The recently published Kepler mission Data Release 25 (DR25) reported on ˜197 000 targets observed during the mission. Despite this, no wide search for red giants showing solar-like oscillations have been made across all stars observed in Kepler's long-cadence mode. In this work, we perform this task using custom apertures on the Kepler pixel files
      Hon, M. et al.

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      6
      2019
      Citations
      28
    • Detection and characterization of an ultra-dense sub-Neptunian planet orbiting the Sun-like star K2-292
      We present the discovery and characterization of a new transiting planet from Campaign 17 of the Kepler extended mission K2. The planet K2-292 b is a warm sub-Neptune on a 17 day orbit around a bright (V = 9.9 mag) solar-like G3 V star with a mass and radius of M⋆ = 1.00 ± 0.03 M⊙ and R⋆ = 1.09 ± 0.03 R⊙, respectively. We modeled simultaneously the
      Luque, R. et al.

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      3
      2019
      Citations
      16
    • Oscillations in the Sun with SONG: Setting the scale for asteroseismic investigations
      Context. We present the first high-cadence multiwavelength radial-velocity observations of the Sun-as-a-star, carried out during 57 consecutive days using the stellar échelle spectrograph at the Hertzsprung SONG Telescope operating at the Teide Observatory. Aims: Our aim was to produce a high-quality data set and reference values for the global
      Fredslund A. M. et al.

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      3
      2019
      Citations
      0
    • Conducting the SONG: The Robotic Nature and Efficiency of a Fully Automated Telescope
      We present a description of “the Conductor,” an automated software package that handles all observations at the first Stellar Observations Network Group (SONG) node telescope at the Teide Observatory on the island of Tenerife. The idea was to provide a complete description on the automated procedures for target selection and execution of
      Fredslund Andersen, M. et al.

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      4
      2019
      Citations
      0
    • Asteroseismology of the Hyades red giant and planet host ɛ Tauri⋆
      Context. Asteroseismic 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 not well known, and previous mass estimates are based on model calculations (isochrones)
      Arentoft, T. et al.

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      2
      2019
      Citations
      22
    • The Second APOKASC Catalog: The Empirical Approach
      We present a catalog of stellar properties for a large sample of 6676 evolved stars with Apache Point Observatory Galactic Evolution Experiment spectroscopic parameters and Kepler asteroseismic data analyzed using five independent techniques. Our data include evolutionary state, surface gravity, mean density, mass, radius, age, and the
      Pinsonneault, M. H. et al.

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      12
      2018
      Citations
      235
    • Tools for Transit and Radial Velocity Modeling and Analysis
      An overview over analysis or modelling tools related to the radial velocity and transit methods for exoplanet detection and characterization is given, with over 40 software tools presented. Tools that cover related subjects, such as physical exoplanet modelling, stellar activity, limb darkening, or stellar parameter estimates, are included as well
      Deeg, Hans J.

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      2018
      Citations
      0

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