Calculations of periodicity from Hα profiles of Proxima Centauri

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-year 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 $\pm$ 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.

7 pages, 5 figures, revised version in response to A&A referee comments

References in corpus (15)

• A terrestrial planet candidate in a temperate orbit around Proxima Centauri
• Radial velocity planets de-aliased. A new, short period for Super-Earth 55 Cnc e
• Stellar Activity Masquerading as Planets in the Habitable Zone of the M dwarf Gliese 581
• Introduction to astroML: Machine Learning for Astrophysics
• Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs
• Periodograms for Multiband Astronomical Time Series
• The habitability of Proxima Centauri b. I. Irradiation, rotation and volatile inventory from formation to the present
• Rotation periods of late-type dwarf stars from time-series high-resolution spectroscopy of chromospheric indicators
• The Solar Neighborhood XXXV: Distances to 1404 M Dwarf Systems Within 25 pc in the Southern Sky
• The IAG solar flux atlas: Accurate wavelengths and absolute convective blueshift in standard solar spectra
• MOST Observations of our Nearest Neighbor: Flares on Proxima Centauri
• Disentangling Planets and Stellar Activity for Gliese 667C
• Ca II H and K Chromospheric Emission Lines in Late K and M Dwarfs
• A possible activity cycle in Proxima Centauri
• Periodic Halpha variations in GL 581: Further evidence for an activity origin to GL 581d

Cited by in corpus (7)

• A temperate rocky super-Earth transiting a nearby cool star
• Magnetic Inflation and Stellar Mass II: On the Radii of Single, Rapidly Rotating, Fully Convective M Dwarf Stars
• Tuning the Exo-Space Weather Radio for Stellar Coronal Mass Ejections
• Was Proxima captured by alpha Centauri A and B?
• Temporal changes of the flare activity of Proxima Cen
• A Multi-Year Search For Transits Of Proxima Centauri. I: Light Curves Corresponding To Published Ephemerides
• The Effect of Atmospheric Chemistry on the Optical Geometric Albedos of Hot Jupiters