Using machine learning algorithms to measure stellar magnetic fields⋆
Instituto de Astronomía – Universidad Nacional Autónoma de México, Apdo. Postal 877, 22860 Ensenada, BC, Mexico
2 Laboratorio de Cómputo Inteligente – Instituto Politécnico Nacional, Av. Juan de Dios Bátiz s/n, 07738 CDMX, Mexico
3 CUCEA, Universidad de Guadalajara, Periférico Norte 799, Los Belenes, 45100 Zapopan Jalisco, Mexico
Accepted: 26 July 2018
Context. Regression methods based on machine learning algorithms (MLA) have become an important tool for data analysis in many different disciplines.
Aims. In this work, we use MLA in an astrophysical context; our goal is to measure the mean longitudinal magnetic field in stars (Heff) from polarized spectra of high resolution, through the inversion of the so-called multi-line profiles.
Methods. Using synthetic data, we tested the performance of our technique considering different noise levels: In an ideal scenario of noise-free multi-line profiles, the inversion results are excellent; however, the accuracy of the inversions diminish considerably when noise is taken into account. We therefore propose a data pre-process in order to reduce the noise impact, which consists of a denoising profile process combined with an iterative inversion methodology.
Results. Applying this data pre-process, we find a considerable improvement of the inversions results, allowing to estimate the errors associated to the measurements of stellar magnetic fields at different noise levels.
Conclusions. We have successfully applied our data analysis technique to two different stars, attaining for the first time the measurement of Heff from multi-line profiles beyond the condition of line autosimilarity assumed by other techniques.
Key words: magnetic fields / line: profiles / polarization / radiative transfer / methods: data analysis
The training data sets used here are available at www.astrosen.unam.mx/~julio/ML_mzs and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A22
© ESO 2018