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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",
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"name": "English"
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"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>",
"creator": [
{
"affiliation": "Department of Astronomy of the University of Geneva",
"@type": "Person",
"name": "X. Dumusque"
}
],
"url": "https://zenodo.org/record/5596351",
"datePublished": "2021-10-25",
"keywords": [
"exoplanets; solar radial velocity; stellar activity"
],
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"identifier": "https://doi.org/10.5281/zenodo.5596351",
"@id": "https://doi.org/10.5281/zenodo.5596351",
"@type": "PresentationDigitalDocument",
"name": "Extremely precise HARPS-N solar RV to overcome the challenge of stellar signal"
}
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