Spectroscopic and Photometric Analyses of the Trapezium Stars θ1 Ori A and θ1 Ori D

Abstract

In this paper, we report on the spectroscopic and photometric observations of the two Trapezium stars, ${\theta }^1$ Ori A and ${\theta }^1$ Ori D. The spectra of these stars were extracted from the ESO and ESPaDOnS archives. Both stars exhibit nebular emission features, particularly within the core of the Balmer profiles and He I lines at $\lambda 5875$ and $\lambda 6680$. Additionally, the spectral energy distributions of these targets were constructed, revealing an infrared excess in both. These emission structures and infrared excesses are attributed to the H II region caused by ${\theta }^1$ Ori C. Furthermore, detailed spectroscopic analysis performed to ${\theta }^1$ Ori A and ${\theta }^1$ Ori D revealed similar abundance patterns, with slight differences in carbon, magnesium, and aluminum. The effective temperatures derived from the spectroscopic analysis were used to determine their positions on the Hertzsprung-Russell (H-R) diagram. Additionally, the evolutionary tracks and isochrones constructed on the H-R diagram allowed for the estimation of their evolutionary masses and ages. Finally, TESS observations of the target stars were obtained to investigate their light variations.