R. S. Levenhagen

A Fourier Transform Method for Vsin i Estimations under Nonlinear Limb-darkening Laws

Star rotation offers us a large horizon for the study of many important physical issues pertaining to stellar evolution. Currently, four methods are widely used to infer rotation velocities, namely those related to line width calibrations, on the fitting of synthetic spectra, interferometry, and on Fourier transforms (FTs) of line profiles. Almost all of the estimations of stellar projected rotation velocities using the Fourier method in the literature have been addressed with the use of linear limb-darkening (LD) approximations during the evaluation of rotation profiles and their cosine FTs, which in certain cases, lead to discrepant velocity estimates. In this work, we introduce new mathematical expressions of rotation profiles and their Fourier cosine transforms assuming three nonlinear LD laws—quadratic, square-root, and logarithmic—and study their applications with and without gravity-darkening (GD) and geometrical flattening (GF) effects. Through an analysis of He I models in the visible range accounting for both limb and GD, we find out that, for classical models without rotationally driven effects, all the Vsin i values are too close to each other. On the other hand, taking into account GD and GF, the Vsin i obtained with the linear law result in Vsin i values that are systematically smaller than those obtained with the other laws. As a rule of thumb, we apply these expressions to the FT method to evaluate the projected rotation velocity of the emission B-type star Achernar (α Eri).

The Remarkable Be+sdOB Binary HD 55606. I. Orbital and Stellar Parameters*

Prompted by peculiar spectroscopic variability observed in SDSS/APOGEE

A Grid of Synthetic Spectra for Hot da White Dwarfs and Its Application in Stellar Population Synthesis

H

ANÁLISE TÉCNICA E FINANCEIRA DE USINA HÍBRIDA EÓLICA FOTOVOLTAICA

-band spectra, we monitored the Be star HD 55606 using optical spectroscopy and found that it is an exotic double-lined spectroscopic binary (SB2) consisting of a Be star and a hot, compact companion that is probably an OB subdwarf (sdOB) star. Motion of the sdOB star is traced by its impact on the strong He~I lines, observed as radial velocity (

The periodicity of the ? Carinae events

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Chemical abundance analysis of the Be star HD 171054

) variable, double-peaked emission profiles with narrow central absorption cores. Weak He II 4686 A absorption associated with the companion star is detected in most spectra. Use of the emission peaks of low-ionization emission lines to trace the Be star

Application of computed tomography images in the evaluation of magnetic nanoparticles biodistribution

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Physical parameters and chemical abundances of δ Ceti

and the He I lines to trace the companion star

Kinematics and chemical abundances of the B star HD 28248

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ANÁLISE TÉCNICA E FINANCEIRA DE USINA HÍBRIDA EÓLICA FOTOVOLTAICA TECHNICAL ANALYSIS AND FINANCIAL PLANT HYBRID WIND-PHOTOVOLTAIC

yields a circular orbital solution with a 93.8-day period and masses of