A method to deconvolve stellar profiles

The non-rotating line utilizing Gaussian sum approximation

¹ Escuela de Ingeniería Eléctrica, Facultad de Ingeniería, Pontificia Universidad Católica de Valparaíso, Valparaiso, Chile
e-mail: pedro.escarate@pucv.cl
² Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
e-mail: michel.cure@uv.cl
³ Centro de Óptica e Información Cuántica, Vicerrectoría de Investigación, Universidad Mayor, Santiago, Chile
⁴ Electronics Engineering Department, Universidad Técnica Federico Santa María, Valparaíso, Chile
⁵ Department of Geography, University of Bayreuth, Universitätsstraße 30, 95447 Bayreuth, Germany
⁶ Departamento de Espectroscopía, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (UNLP), Paseo del Bosque s/n, B1900FWA, Argentina
⁷ Instituto de Astrofísica La Plata, CCT La Plata, CONICET-UNLP, Paseo del Bosque s/n, 1900 La Plata, Argentina
⁸ Departamento de Física, Universidade Federal de Sao Paulo, Rua Prof. Artur Riedel, 275, 09972-270 Diadema, SP, Brazil
⁹ Departmento de Informática, Universidad Técnica Federico Santa María, Valparaíso, Chile
¹⁰ Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
¹¹ Instituto de Astrofísica de Canarias, Avenida Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain

Received: 3 April 2023
Accepted: 9 June 2023

Abstract

Context. Currently, one of the standard procedures used to determine stellar and wind parameters of massive stars involves to comparing the observed spectral lines with a grid of synthetic lines. These synthetic lines are calculated using non-local thermodynamic equilibrium radiative transfer codes. In this standard procedure, after estimating the stellar-projected rotational speed (v sin i), all synthetic models need to be convolved using this value in order to perform the comparison with the observed line and estimate the stellar parameters.

Aims. In this work, we propose a methodology to deconvolve the observed line profile to one from a non-rotating star. Thus, to perform a comparison, we will not need to convolve all the synthetic profiles, saving significant time and resources.

Methods. The proposed deconvolution method is based on transforming this inverse problem into an optimization of a direct problem. We propose using a Gaussian sum approximation (GSA) to obtain the line profile without the broadening effect due to stellar rotation. After selecting the most adequate model to derive the fundamental GSA parameters, we convolved it with the known v sin i in order to obtain the profile considering the v sin i. Finally, we compared this approximated line profile directly with the observed spectrum.

Results. The performance of the proposed method is analyzed using synthetic and observed lines. The results show that the proposed deconvolution method yields accurate non-rotating profiles.

Conclusions. The proposed approach utilizing GSA is an accurate method to deconvolve spectral lines.