X-ray Emission and Corona of the Young Intermediate Mass Binary $\theta^1$ Ori E

TL;DR

This study presents high-resolution X-ray spectra of the young binary Theta 1 Ori E, revealing coronal activity similar to magnetically confined plasma in G-type stars, with unique abundance patterns and low variability.

Contribution

First detailed X-ray spectral analysis of a young, intermediate-mass G-type binary, showing coronal characteristics and elemental abundances, suggesting a convective dynamo mechanism.

Findings

System exhibits active corona with broad temperature distribution.

Coronal elemental abundances are sub-Solar, with Ne highest.

Low variability compared to other active stars.

Abstract

Theta 1 Ori E is a young, moderate mass binary system, a rarely observed case of spectral-type G-giants of about 3 Solar masses, which are still collapsing towards the main sequence. We have obtained high resolution X-ray spectra with Chandra and find that the system is very active and similar to coronal sources, having emission typical of magnetically confined plasma: a broad temperature distribution with a hot component and significant high energy continuum; narrow emission lines from H- and He-like ions, as well as a range of Fe ions, and relative luminosity, L_x/L_bol = 0.001. Density, while poorly constrained, is consistent with the low density limits as determined from Mg XI and Ne IX emission lines. Coronal elemental abundances are sub-Solar, with Ne being the highest at about 0.4 times Solar. We find a possible trend in Trapezium hot plasmas towards low relative abundances of Fe, O, and Ne, which is hard to explain in terms of the dust depletion scenarios of low-mass young stars. Variability was unusually low relative to other coronally active stars. The emission is similar to post main-sequence G-stars. Coronal structures could be compact or comparable to the dimensions of the stellar radii. We conclude that the X-rays in theta 1 Ori E are generated by a convective dynamo.