A critical evaluation of the principal component analysis detection of polarized signatures using real stellar data

Paletou, F.

doi:10.1051/0004-6361/201219399

Cited by 12 publications

(9 citation statements)

References 13 publications

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“…One popular and very successful extraction technique which follows this line of arguments is the so called least-squares deconvolution (LSD, Donati et al 1997;Kochukhov et al 2010). Another method is the principal component analysis (PCA, Carroll et al 2007;Martínez González et al 2008;Carroll et al 2009;Paletou 2012) or the simple but very effective coherent addition of line profiles in the velocity or logarithmic wavelength domain (Semel et al 2009;Ramírez et al 2010).…”

Section: Methodsmentioning

confidence: 99%

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Carroll

Strassmeier

Rice

et al. 2012

A&A

114

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Aims. In a follow-up investigation we present Zeeman-Doppler maps of the weak-lined T Tauri star (WTTS) V410 Tau. As a rapid rotating star and a typical WTTS the stellar surface of V410 Tau is accessible to surface imaging techniques and allows us to detect and reconstruct the major magnetic surface features on this pre-main sequence star. Methods. The polarized signals we are measuring are on the order of 10 −4 to 10 −3 and are hidden well below the noise level of a single observation. A new line profile reconstruction technique based on a singular value decomposition (SVD) allows us to extract the weak polarized line profiles (Stokes V) as well as the intensity profiles (Stokes I). One of the key features of the line profile reconstruction is that the SVD line profiles are amenable to radiative transfer modeling within our Zeeman-Doppler Imaging code iMap. The code also utilizes a new iterative regularization scheme which is independent of any additional surface constraints. To provide more stability a vital part of our inversion strategy is to invert both Stokes I and Stokes V profiles to simultaneously reconstruct the temperature and magnetic field surface distribution of V410 Tau. A new image-shear analysis is also implemented to allow the search for image and line profile distortions induced by a differential rotation of the star. Results. The magnetic field structure we obtain for V410 Tau shows a good spatial correlation with the surface temperature and is dominated by a strong field within the cool polar spot. The Zeeman-Doppler maps exhibit a large-scale organization of both polarities around the polar cap in the form of a twisted bipolar structure. The magnetic field reaches a value of almost 2 kG within the polar region but smaller fields are also present down to lower latitudes. The pronounced non-axisymmetric field structure and the nondetection of a differential rotation for V410 Tau supports the idea of an underlying α 2 -type dynamo, which is predicted for WTTS.

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Section: Methodsmentioning

confidence: 99%

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Carroll

Strassmeier

Rice

et al. 2012

A&A

114

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“…This allows a very fast processing of the data. Another advantage is the denoising of the original data (see e.g., Bailer-Jones et al 1998or Paletou 2012in another con-A&A 573, A67 (2015 text though). The PCA also differs from the projection method Matisse, which uses specific projection vectors that are attached to each stellar parameter that is to be inverted (Recio-Blanco et al 2006).…”

Section: Introductionmentioning

confidence: 99%

“…As compared to alternative methods such as χ 2 fitting to a library of (synthetic) spectra, as done by Munari et al (2005) for the analysis of the RAVE survey, for instance, the main advantages of PCA are in the reduction of dimensionality -a critical issue when dealing with high-resolution spectra also covering a very large bandwith -which allows a very fast processing of the data, and in the "denoising" of the original data (see e.g., Bailer-Jones et al 1998or Paletou 2012 in another context though). It also differs from another projection method such as Matisse which uses specific projection vectors attached, say, to each stellar parameter to be inverted (Recio-Blanco et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Inversion of stellar fundamental parameters from ESPaDOnS and Narval high-resolution spectra

Paletou

Böhm

Watson

et al. 2014

A&A

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The general context of this study is the inversion of stellar fundamental parameters from high-resolution Echelle spectra. We aim at developing a fast and reliable tool for the post-processing of spectra produced by ESPaDOnS and Narval spectropolarimeters. Our inversion tool relies on principal component analysis. It allows reducing dimensionality and defining a specific metric for the search of nearest neighbours between an observed spectrum and a set of observed spectra taken from the Elodie stellar library. Effective temperature, surface gravity, total metallicity, and projected rotational velocity are derived. Various tests presented in this study that were based solely on information coming from a spectral band centred on the Mg  b-triplet and had spectra from FGK stars are very promising.

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“…Since PCA can represent the database in a scalar and vectoral manner, one can easily observe the direction change of the spectral lines in vectoral representation of the spectral database [24]. Paletou et al, 2012 showed that PCA is an efficient tool to extract Stokes parameters of the polarized stellar data [25]. Fig.…”

Section: B Pca Analysis Of L Shell Mo Synthetic Databasementioning

confidence: 99%

Investigation of electron beam effects on L-shell Mo plasma produced by a compact LC generator using pattern recognition

Yilmaz

Danışman

Özdemir

et al. 2019

Matter and Radiation at Extremes

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In this paper, the effects of electron beam on the X pinch produced spectra of L-shell Mo plasma have been investigated by principal component analysis (PCA), and this analysis is compared with that of line ratio diagnostics. Spectral database for PCA extraction was arranged using the non-LTE collisional radiative L-shell Mo model. PC vector spectra of L shell Mo including F, Ne, Na and Mg-like transitions were studied to investigate the polarization types of these transitions. PC1 vector spectra of F, Ne, Na and Mg-like transitions resulted in linear polarization of Stokes Q profiles. Besides, PC2 vector spectra showed linear polarization of Stokes U profiles of 2p 5 3s of Ne like transitions which were recognized as responsive to the magnetic field (Trabert et al., 2017). 3D representation of PCA coefficients demonstrated that addition of electron beam to the non-LTE model generates the quantized collective clusters which are translations of each other and follow Vshaped cascade trajectories except for the case f = 0.0. The extracted principal coefficients were used as a database for the Artifical Neural Network (ANN) to estimate the plasma electron temperature, density and beam fractions of time integrated spatially resolved L-shell Mo X-pinch plasma spectrum. PCA based ANN provides advantage in reducing the network topology with a more efficient Backpropagation supervised learning algorithm. The modeled plasma electron temperature is about T e~6 60 eV and density n e =1x10 20 cm -3 in the presence of the fraction of the beams with f~0.1 and centered energy of 5 keV.

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A critical evaluation of the principal component analysis detection of polarized signatures using real stellar data

Cited by 12 publications

References 13 publications

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

The magnetic field topology of the weak-lined T Tauri star V410 Tauri

Inversion of stellar fundamental parameters from ESPaDOnS and Narval high-resolution spectra

Investigation of electron beam effects on L-shell Mo plasma produced by a compact LC generator using pattern recognition

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