Detailed spectroscopic analysis of the Trapezium cluster stars inside the Orion nebula

TL;DR

This study provides a detailed spectroscopic analysis of stars in the Trapezium cluster, deriving stellar parameters, wind characteristics, and oxygen abundances, with implications for nebular composition and dust depletion.

Contribution

It introduces a comprehensive spectroscopic methodology combining Fourier analysis and synthetic profile fitting to derive stellar and nebular parameters.

Findings

Rotational velocities agree with linewidth measurements.

Oxygen abundances are consistent with nebular gas-phase results.

Lower dust depletion factor of oxygen than previously estimated.

Abstract

We present the results of a spectroscopic analysis of the Trapezium cluster stars inside the Orion Nebula. The rotational velocities have been obtained using Fourier analysis method, finding agreement with values derived from the usual method, based on linewidth measurements. The rotational velocity derived for theta 1 Ori C through this method is consistent with the variability of some of its spectral features that have a period of 15.42 days. By means of the fit of H, HeI and HeII observed profiles with FASTWIND synthetic profiles, stellar parameters and wind characteristics have been derived. This methodology let us estimate the errors associated with these parameters. It is found that macroturbulence effects have to be included for a good fit to the HeI-II lines in the spectrum of theta 1 Ori C. By means of a very accurate study, oxygen abundances have been derived for the three B0.5V stars theta 1 Ori A, D and theta 2 Ori B. Final abundances are consistent with the nebular gas-phase results presented in Esteban et al. (2004) and are lower than those given by Cunha and Lambert (1994). Our results suggest a lower dust depletion factor of oxygen than previous estimations for the Orion nebula.