J/MNRAS/474/2094 Inferring probabilistic stellar rotation periods (Angus+, 2018)
Inferring probabilistic stellar rotation periods using Gaussian processes.
Angus R., Morton T., Aigrain S., Foreman-Mackey D., Rajpaul V.
<Mon. Not. R. Astron. Soc., 474, 2094-2108 (2018)>
=2018MNRAS.474.2094A 2018MNRAS.474.2094A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets
Keywords: methods: data analysis - methods: statistical -
techniques: photometric - stars: rotation - stars: solar-type -
starspots
Abstract:
Variability in the light curves of spotted, rotating stars is often
non-sinusoidal and quasi-periodic - spots move on the stellar
surface and have finite lifetimes, causing stellar flux variations to
slowly shift in phase. A strictly periodic sinusoid therefore cannot
accurately model a rotationally modulated stellar light curve.
Physical models of stellar surfaces have many drawbacks preventing
effective inference, such as highly degenerate or high-dimensional
parameter spaces. In this work, we test an appropriate effective
model: a Gaussian Process with a quasi-periodic covariance kernel
function. This highly flexible model allows sampling of the posterior
probability density function of the periodic parameter, marginalizing
over the other kernel hyperparameters using a Markov Chain Monte Carlo
approach. To test the effectiveness of this method, we infer rotation
periods from 333 simulated stellar light curves, demonstrating that
the Gaussian process method produces periods that are more accurate
than both a sine-fitting periodogram and an autocorrelation function
method. We also demonstrate that it works well on real data, by
inferring rotation periods for 275 Kepler stars with previously
measured periods. We provide a table of rotation periods for these and
many more, altogether 1102 Kepler objects of interest, and their
posterior probability density function samples. Because this method
delivers posterior probability density functions, it will enable
hierarchical studies involving stellar rotation, particularly those
involving population modelling, such as inferring stellar ages,
obliquities in exoplanet systems, or characterizing star-planet
interactions. The code used to implement this method is available
online (https://github.com/RuthAngus/GProtation/).
Description:
We have attempted to recover the rotation periods of 333 simulated
Kepler-like light curves for solid-body rotators (Aigrain et al.,
2015MNRAS.450.3211A 2015MNRAS.450.3211A) using three different methods: a GP method, an
ACF method and an LS periodogram method. We demonstrate that the GP
method produces the most accurate rotation periods of the three
techniques.
The posterior samples of the model parameters for the Kepler objects
of interest are available online:
https://zenodo.org/record/292340#.WKWpiBIrJE4
Samples of the rotation period posterior PDFs are available online:
https://doi.org/10.5281/zenodo.804440
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 128 1073 Rotation periods and Kepler input catalogue (KIC)
properties for 1102 Kepler objects of interest
--------------------------------------------------------------------------------
See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- KOI KOI number
6- 10 F5.2 [-] [Fe/H] ? KIC metallicity
13- 17 F5.3 [-] e_[Fe/H] ? Lower uncertainty on the KIC metallicity
19- 23 F5.3 [-] E_[Fe/H] ? Upper uncertainty on the KIC metallicity
26- 30 F5.3 [cm/s2] logg ? KIC surface gravity
33- 37 F5.3 [cm/s2] e_logg ? Lower uncertainty on the KIC surface gravity
39- 43 F5.3 [cm/s2] E_logg ? Upper uncertainty on the KIC surface gravity
45- 63 F19.16 d Per Stellar rotation period
65- 86 F22.19 d e_Per Lower uncertainty on the stellar
rotation period
88-108 F21.18 d E_Per Upper uncertainty on the stellar
rotation period
110-115 F6.1 K Teff ? KIC effective temperature
118-122 F5.1 K e_Teff ? Lower uncertainty on the KIC
effective temperature
124-128 F5.1 K E_Teff ? Upper uncertainty on the KIC
effective temperature
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Oct-2019