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Extremely precise HARPS-N solar RV to overcome the challenge of stellar signal

X. Dumusque

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  "inLanguage": {
    "alternateName": "eng", 
    "@type": "Language", 
    "name": "English"
  "description": "<p>Detecting and measuring the masses of&nbsp;Earth-like&nbsp;planets in the presence of stellar signals is the main challenge when using the radial-velocity (RV) technique. Even in the&nbsp;<em>PLATO</em>&nbsp;era where&nbsp;the satellite will provide the period of Earth-like&nbsp;planetary&nbsp;candidates,&nbsp;measuring precisely their mass, which is critical to&nbsp;1) confirm those candidates, 2)&nbsp;constrain further planetary composition and thus planetary formation&nbsp;and 3)&nbsp;constrain further&nbsp;planetary atmospheres,&nbsp;will be extremely&nbsp;challenging.</p>\n\n<p>&nbsp;</p>\n\n<p>Critical to a better understanding of RV variations induced by stellar signals and finding correction techniques is RV data with a sampling&nbsp;and SNR&nbsp;sufficient to probe&nbsp;stellar signals&nbsp;ranging from minutes to years. To address this challenge,&nbsp;we can use the unprecedented data from the&nbsp;solar telescope that feed sunlight into HARPS-N, which allows us to obtain Sun-as-a-star RVs at a sub-m/s precision.</p>\n\n<p>&nbsp;</p>\n\n<p>In this talk, I will discuss how to reduce properly the HARPS-N solar data to reach a precision of about 50 cm/s on the short and long-term. This implies optimizing the wavelength solution recipe, carefully selecting the most stable thorium lines, but also compensating for the ageing of thorium-argon lamps inducing a drift of thorium lines with time. I will show how those optimizations improve the quality of the data, and therefore will advise any team working in extremely precise RV to perform similar upgrades.</p>\n\n<p>&nbsp;</p>\n\n<p>The obtained solar data, published last October, have already been used in several studies that demonstrate that analyzing the HARPS-N solar&nbsp;spectral (or cross-correlation functions) time-series using machine learning algorithms can mitigate stellar signals down to a level where Earth-like planets in the habitable zone could be detected (30 cm/s in semi-amplitude, signal three times larger than Earth).</p>", 
  "license": "", 
  "creator": [
      "affiliation": "Department of Astronomy of the University of Geneva", 
      "@type": "Person", 
      "name": "X. Dumusque"
  "url": "", 
  "datePublished": "2021-10-25", 
  "keywords": [
    "exoplanets; solar radial velocity; stellar activity"
  "@context": "", 
  "identifier": "", 
  "@id": "", 
  "@type": "PresentationDigitalDocument", 
  "name": "Extremely precise HARPS-N solar RV to overcome the challenge of stellar signal"
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