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

    • Non-grey dimming events of KIC 8462852 from GTC spectrophotometry
      We report ground-based spectrophotometry of KIC 8462852 obtained during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour signature and are deeper in visual blue than in red wavelengths. The wavelength dependency of the flux loss can be described with an absorption Ångström coefficient of 2.19 ± 0.45
      Deeg, H. J. et al.

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      2
      2018
      Citations
      15
    • The First Post-Kepler Brightness Dips of KIC 8462852
      We present a photometric detection of the first brightness dips of the unique variable star KIC 8462852 since the end of the Kepler space mission in 2013 May. Our regular photometric surveillance started in 2015 October, and a sequence of dipping began in 2017 May continuing on through the end of 2017, when the star was no longer visible from Earth
      Boyajian, T. S. et al.

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      1
      2018
      Citations
      43
    • The Influence of Metallicity on Stellar Differential Rotation and Magnetic Activity
      Observations of Sun-like stars over the past half-century have improved our understanding of how magnetic dynamos, like that responsible for the 11 yr solar cycle, change with rotation, mass, and age. Here we show for the first time how metallicity can affect a stellar dynamo. Using the most complete set of observations of a stellar cycle ever
      Karoff, C. et al.

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      1
      2018
      Citations
      69
    • Photospheric activity of the Sun with VIRGO and GOLF. Comparison with standard activity proxies
      We study the variability of solar activity using new photospheric proxies originally developed for the analysis of stellar magnetism with the CoRoT and Kepler photometric observations. These proxies were obtained by tracking the temporal modulations in the observations associated with the spots and magnetic features as the Sun rotates. We analyzed
      Salabert, D. et al.

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      12
      2017
      Citations
      32
    • Asteroseismic masses of retired planet-hosting A-stars using SONG
      To better understand how planets form, it is important to study planet occurrence rates as a function of stellar mass. However, estimating masses of field stars is often difficult. Over the past decade, a controversy has arisen about the inferred occurrence rate of gas-giant planets around evolved intermediate-mass stars - the so-called `retired A
      Stello, D. et al.

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      12
      2017
      Citations
      28
    • Search for rings and satellites around the exoplanet CoRoT-9b using Spitzer photometry
      Using Spitzer photometry at 4.5 microns, we search for rings and satellites around the long period transiting planet CoRoT-9b. We observed two transits in 2010 and 2011. From their non-detection, we derive upper limits on the plausible physical characteristics of these objects in the planet environment. We show that a satellite larger than about 2
      Lecavelier des Etangs, A. et al.

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      7
      2017
      Citations
      16
    • Asymptotic g modes: Evidence for a rapid rotation of the solar core
      Context. Over the past 40 years, helioseismology has been enormously successful in the study of the solar interior. A shortcoming has been the lack of a convincing detection of the solar g modes, which are oscillations driven by gravity and are hidden in the deepest part of the solar body - its hydrogen-burning core. The detection of g modes is
      Fossat, E. et al.

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      8
      2017
      Citations
      73
    • Atmospheric Extinction Coefficients in the Ic Band for Several Major International Observatories: Results from the BiSON Telescopes, 1984-2016
      Over 30 years of solar data have been acquired by the Birmingham Solar Oscillations Network (BiSON), an international network of telescopes used to study oscillations of the Sun. Five of the six BiSON telescopes are located at major observatories. The observational sites are, in order of increasing longitude: Mount Wilson (Hale) Observatory (MWO)
      Hale, S. J. et al.

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      9
      2017
      Citations
      3
    • On the signatures of flare-induced global waves in the Sun: GOLF and VIRGO observations
      Recently, several efforts have been made to identify the seismic signatures of flares and magnetic activity in the Sun and Sun-like stars. In this work, we have analysed the disc-integrated velocity and intensity observations of the Sun obtained from the Global Oscillations at Low Frequencies (GOLF) and Variability of solar IRradiance and Gravity
      Jiménez, A. et al.

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      11
      2017
      Citations
      1
    • A deeper view of the CoRoT-9 planetary system. A small non-zero eccentricity for CoRoT-9b likely generated by planet-planet scattering
      CoRoT-9b is one of the rare long-period (P = 95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already published
      Santerne, A. et al.

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      7
      2017
      Citations
      11
    • Limits to the presence of transiting circumbinary planets in CoRoT Data
      Aims: During its flight phase, from 2007-2012, the CoRoT mission delivered light curves for over 2000 eclipsing binaries. Data from the Kepler mission have proven the existence of several transiting circumbinary planets. While light curves from CoRoT typically have lower precision and shorter coverage, the number of CoRoT targets is similar to that
      Almenara, J. M. et al.

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      6
      2017
      Citations
      16
    • Evidence of chaotic modes in the analysis of four δ Scuti stars
      Context. Since CoRoT observations unveiled the very low amplitude modes that form a flat plateau in the power spectrum structure of δ Scuti stars, the nature of this phenomenon, including the possibility of spurious signals due to the light curve analysis, has been a matter of long-standing scientific debate. Aims: We contribute to this debate by
      Barceló-Forteza, S. et al.

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      5
      2017
      Citations
      16
    • Kepler observations of the asteroseismic binary HD 176465
      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
      White, T. R. et al.

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      5
      2017
      Citations
      31
    • Kepler sheds new and unprecedented light on the variability of a blue supergiant: Gravity waves in the O9.5Iab star HD 188209
      Stellar evolution models are most uncertain for evolved massive stars. Asteroseismology based on high-precision uninterrupted space photometry has become a new way to test the outcome of stellar evolution theory and was recently applied to a multitude of stars, but not yet to massive evolved supergiants.Our aim is to detect, analyse and interpret
      Aerts, C. et al.

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      6
      2017
      Citations
      39
    • Internal rotation of 13 low-mass low-luminosity red giants in the Kepler field
      Context. The Kepler space telescope has provided time series of red giants of such unprecedented quality that a detailed asteroseismic analysis becomes possible. For a limited set of about a dozen red giants, the observed oscillation frequencies obtained by peak-bagging together with the most recent pulsation codes allowed us to reliably determine
      Triana, S. A. et al.

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      6
      2017
      Citations
      42
    • CoRoT 223992193: Investigating the variability in a low-mass, pre-main sequence eclipsing binary with evidence of a circumbinary disk
      CoRoT 223992193 is the only known low-mass, pre-main sequence eclipsing binary that shows evidence of a circumbinary disk. The system displays complex photometric and spectroscopic variability over a range of timescales and wavelengths. Using two optical CoRoT runs from 2008 and 2011/2012 (spanning 23 and 39 days), along with infrared Spitzer 3.6
      Gillen, E. et al.

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      2
      2017
      Citations
      11
    • First Results from the Hertzsprung SONG Telescope: Asteroseismology of the G5 Subgiant Star μ Herculis
      We report the first asteroseismic results obtained with the Hertzsprung Stellar Observations Network Group Telescope from an extensive high-precision radial-velocity observing campaign of the subgiant μ Herculis. The data set was collected during 215 nights in 2014 and 2015. We detected a total of 49 oscillation modes with l values from zero to
      Grundahl, F. et al.

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      2
      2017
      Citations
      74
    • TEE, an estimator for the precision of eclipse and transit minimum times
      Context. Transit or eclipse timing variations have proven to be a valuable tool in exoplanet research. However, no simple way to estimate the potential precision of such timing measures has been presented yet, nor are guidelines available regarding the relation between timing errors and sampling rate. Aims: A timing error estimator (TEE) equation
      Deeg, H. J. et al.

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      3
      2017
      Citations
      10
    • Asteroseismology of Solar-Type Stars with K2: Detection of Oscillations in C1 Data
      We present the first detections by the NASA K2 mission of oscillations in solar-type stars, using short-cadence data collected during K2 Campaign 1 (C1). We understand the asteroseismic detection thresholds for C1-like levels of photometric performance, and we can detect oscillations in subgiants having dominant oscillation frequencies around 1000
      Lund, M. N. et al.

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      11
      2015
      Citations
      33
    • Transiting exoplanets from the CoRoT space mission⋆. XXVIII. CoRoT-33b, an object in the brown dwarf desert with 2:3 commensurability with its host star
      We report the detection of a rare transiting brown dwarf with a mass of 59 MJup and radius of 1.1 RJup around the metal-rich, [Fe/H] = +0.44, G9V star CoRoT-33. The orbit is eccentric (e = 0.07) with a period of 5.82 d. The companion, CoRoT-33b, is thus a new member in the so-called brown dwarf desert. The orbital period is within 3% to a 3:2
      Csizmadia, Sz. et al.

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      12
      2015
      Citations
      57

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