A method to deconvolve stellar profiles The Non-Rotating Line utilizing Gaussian Sum Approximation

Abstract

Context. Nowadays, one of the standard procedures to determine stellar and wind parameters of massive stars is to compare theobserved spectral lines with a grid of synthetic lines. These synthetic lines are calculated using NLTE radiative transfer codes.Aims. In this standard procedure, after estimating the stellar projected rotational speed (v sin i), all synthetic models need to beconvolved using this value to perform the comparison with the observed line and estimate the stellar parameters.Methods. In this work, we propose a methodology to deconvolve the observed line profile to one from a non-rotating star. Thus,to perform the comparison, we do not need to convolve all the synthetic profiles, sparing them significant time resources. Thisis a challenging inverse problem and our proposed deconvolution method is based on transforming this inverse problem into anoptimization of a direct problem. We propose to use a Gaussian Sum Approximation (GSA) to obtain the line profile without thebroadening effect due to stellar rotation. After selecting the most adequate model to derive the fundamental GSA’a parameters, weconvolve it with the known v sin i to obtain the profile considering the v sin i. Finally, we compare this approximated line profiledirectly with the observed spectrum.Results. The performance of the proposed method is analyzed using synthetic and observed lines. The results show that the proposeddeconvolution method yields accurate non-rotating profiles.Conclusions. The proposed approach with Gaussian Sum Approximation is an accurate method to deconvolve spectral lines.