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Calculations of periodicity from Hα profiles of Proxima Centauri

Collins, John M.; Jones, Hugh R. A. and Barnes, John R. (2017). Calculations of periodicity from Hα profiles of Proxima Centauri. Astronomy & Astrophysics, 602, article no. A48.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1051/0004-6361/201628827
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Abstract

We investigate retrieval of the stellar rotation signal for Proxima Centauri. We make use of high-resolution spectra taken with UVES and HARPS of Proxima Centauri over a 13-yr period as well as photometric observations of Proxima Centauri from ASAS and HST. We measure the Hα equivalent width and Hα index, skewness and kurtosis and introduce a method that investigates the symmetry of the line, the peak ratio, which appears to return better results than the other measurements. Our investigations return a most significant period of 82.6 ± 0.1 days, confirming earlier photometric results and ruling out a more recent result of 116.6 days which we conclude to be an alias induced by the specific HARPS observation times. We conclude that whilst spectroscopic Hα measurements can be used for period recovery, in the case of Proxima Centauri the available photometric measurements are more reliable. We make 2D models of Proxima Centauri to generate simulated Hα, finding that reasonable distributions of plage and chromospheric features are able to reproduce the equivalent width variations in observed data and recover the rotation period, including after the addition of simulated noise and flares. However the 2D models used fail to generate the observed variety of line shapes measured by the peak ratio. We conclude that only 3D models which incorporate vertical motions in the chromosphere can achieve this.

Item Type: Journal Item
Copyright Holders: 2017 ESO
ISSN: 1432-0746
Project Funding Details:
Funded Project NameProject IDFunding Body
Consolidated grantST/P000584/1STFC (Science & Technology Facilities Council)
Consolidated grantST/L000776/1STFC
Keywords: methods: miscellaneous; line: profiles; stars: late-type; techniques: spectroscopic
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 54961
Depositing User: John Barnes
Date Deposited: 03 May 2018 09:37
Last Modified: 23 May 2019 22:47
URI: http://oro.open.ac.uk/id/eprint/54961
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