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Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum

  • Collier Cameron, A ORCID Centre for Exoplanet Science, University of St Andrews, College Gate, St Andrews KY16 9AJ, UK
  • Mortier, A ORCID Astrophysics Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
  • Phillips, D Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Dumusque, X Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Haywood, R D Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Langellier, N Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
  • Watson, C A Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN, UK
  • Cegla, H M Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Costes, J Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN, UK
  • Charbonneau, D Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Coffinet, A Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Latham, D W Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Lopez-Morales, M Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Malavolta, L ORCID Dipartimento di Fisica e Astronomia ‘Galileo Galilei’, Universita’ di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova, Italy
  • Maldonado, J ORCID INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-0134 Palermo, Italy
  • Micela, G INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-0134 Palermo, Italy
  • Milbourne, T Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
  • Molinari, E INAF-Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius, Italy
  • Saar, S H Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Thompson, S Astrophysics Group, Cavendish Laboratory, J.J. Thomson Avenue, Cambridge CB3 0HE, UK
  • Buchschacher, N Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Cecconi, M INAF-Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja, Tenerife, Spain
  • Cosentino, R INAF-Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja, Tenerife, Spain
  • Ghedina, A INAF-Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja, Tenerife, Spain
  • Glenday, A Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Gonzalez, M INAF-Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja, Tenerife, Spain
  • Li, C-H Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Lodi, M INAF-Fundación Galileo Galilei, Rambla José Ana Fernandez Pérez 7, E-38712 Breña Baja, Tenerife, Spain
  • Lovis, C Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Pepe, F Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Poretti, E INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
  • Rice, K ORCID Centre for Exoplanet Science, University of Edinburgh, James Clerk Maxwell Building, Peter Guthrie Tait Road, Edinburgh EH9 3FD, UK
  • Sasselov, D Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Sozzetti, A INAF-Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese, Italy
  • Szentgyorgyi, A Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
  • Udry, S Observatoire Astronomique de l’Université de Génève, 51 Chemin des Maillettes, 1290 Sauverny, Suisse
  • Walsworth, R Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA
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  • 2019-5-4
Published in:
  • Monthly Notices of the Royal Astronomical Society. - Oxford University Press (OUP). - 2019, vol. 487, no. 1, p. 1082-1100
Space and Planetary Science
Astronomy and Astrophysics
English Abstract
The time-variable velocity fields of solar-type stars limit the precision of radial-velocity determinations of their planets’ masses, obstructing detection of Earth twins. Since 2015 July, we have been monitoring disc-integrated sunlight in daytime using a purpose-built solar telescope and fibre feed to the HARPS-N stellar radial-velocity spectrometer. We present and analyse the solar radial-velocity measurements and cross-correlation function (CCF) parameters obtained in the first 3 yr of observation, interpreting them in the context of spatially resolved solar observations. We describe a Bayesian mixture-model approach to automated data-quality monitoring. We provide dynamical and daily differential-extinction corrections to place the radial velocities in the heliocentric reference frame, and the CCF shape parameters in the sidereal frame. We achieve a photon-noise-limited radial-velocity precision better than 0.43 m s−1 per 5-min observation. The day-to-day precision is limited by zero-point calibration uncertainty with an RMS scatter of about 0.4 m s−1. We find significant signals from granulation and solar activity. Within a day, granulation noise dominates, with an amplitude of about 0.4 m s−1 and an autocorrelation half-life of 15 min. On longer time-scales, activity dominates. Sunspot groups broaden the CCF as they cross the solar disc. Facular regions temporarily reduce the intrinsic asymmetry of the CCF. The radial-velocity increase that accompanies an active-region passage has a typical amplitude of 5 m s−1 and is correlated with the line asymmetry, but leads it by 3 d. Spectral line-shape variability thus shows promise as a proxy for recovering the true radial velocity.
Language
  • English
Open access status
bronze
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https://folia.unifr.ch/global/documents/42587
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