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A systematic approach to determining the properties of an iodine absorption cell for high-precision radial velocity measurements

  • Absorption cells filled with diatomic iodine are frequently employed as wavelength reference for high-precision stellar radial velocity determination due to their long-term stability and low cost. Despite their wide-spread usage in the community, there is little documentation on how to determine the ideal operating temperature of an individual cell. We have developed a new approach to measuring the effective molecular temperature inside a gas absorption cell and searching for effects detrimental to a high-precision wavelength reference, utilizing the Boltzmann distribution of relative line depths within absorption bands of single vibrational transitions. With a high-resolution Fourier transform spectrometer, we took a series of 632 spectra at temperatures between 23 and 66◦C. These spectra provide a sufficient basis to test the algorithm and demonstrate the stability and repeatability of the temperature determination via molecular lines on a single iodine absorption cell. The achievable radial velocity precision σ RV is found to be independent of the cell temperature and a detailed analysis shows a wavelength dependence, which originates in the resolving power of the spectrometer in use and the signal- to-noise ratio. Two effects were found to cause apparent absolute shifts in radial velocity, a temperature-induced shift of the order of ∼1 m s−1 K−1 and a more significant effect resulting in abrupt jumps of ≥50 m s−1 is determined to be caused by the temperature crossing the dew point of the molecular iodine

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Metadaten
Author:Phillip Huke, Volker Perdelwitz
DOI:https://doi.org/10.1093/mnras/sty1523
Parent Title (English):Monthly Notice of the Royal Astronomy Society
Document Type:Article
Language:English
Date of first Publication:2018/06/11
Release Date:2025/01/21
Tag:iodine; molecular; radial velocities.; spectrographs
Volume:Vol. 479
Issue:1
First Page:768
Last Page:775
Institutes:Fachbereich Technik
Research Focus Areas:nachhaltige Technologien und Prozesse