Calculations of Periodicity From Hα Profiles of Proxima Centauri

The Hα region of example spectra of Proxima Centauri taken from harps on 27 May 2004 02:10:14 UTC (black) and 15 March 2006 09:16:35 (brown).

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-year period as well as photometric observations of Proxima Centauri from asas and hst.

We measure the H{\alpha} equivalent width and H{\alpha} 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 H{\alpha} 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 H{\alpha}, 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.

John M. Collins, Hugh R.A. Jones, John R. Barnes
(Submitted on 28 Aug 2016)

Comments: 7 pages, 5 figures, revised version in response to A&A referee comments
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1608.07834 [astro-ph.SR] (or arXiv:1608.07834v1 [astro-ph.SR] for this version)
Submission history
From: John Collins
[v1] Sun, 28 Aug 2016 17:34:36 GMT (549kb,D)
http://arxiv.org/abs/1608.07834

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