Chemical Links between a Young M-type T Tauri Star and its Substellar Companion: Spectral Analysis and C/O Measurement of DH Tau A

TL;DR

This study measures the chemical abundances of a young star and its substellar companion, revealing similar C/O ratios that suggest a common formation mechanism via gravitational collapse.

Contribution

It provides the first detailed spectral analysis of DH Tau A and its companion, confirming chemical homogeneity and supporting a specific formation scenario.

Findings

Both star and companion have near-solar C/O ratios.

Chemical homogeneity suggests formation by gravitational collapse.

Supports direct formation scenario over core accretion.

Abstract

The chemical abundance measurements of host stars and their substellar companions provide a powerful tool to trace the formation mechanism of the planetary systems. We present a detailed high-resolution spectroscopic analysis of a young M-type star, DH Tau A, which is located in the Taurus molecular cloud belonging to the Taurus-Auriga star-forming region. This star is host to a low-mass companion, DH Tau b, and both star and the companion are still in their accreting phase. We apply our technique (Hejazi et al. 2024) to measure the abundances of carbon and oxygen using carbon- and oxygen-bearing molecules, such as CO and OH, respectively. We determine a near-solar carbon-to-oxygen abundance ratio of C/O=0.555$\pm$0.063 for the host star DH Tau A. We compare this stellar abundance ratio with that of the companion from our previous study (C/O=0.54$^{+0.06}_{-0.05}$, Xuan et al. 2024), which also has a near-solar value. This confirms the chemical homogeneity in the DH Tau system, which suggests a formation scenario for the companion consistent with a direct and relatively fast gravitational collapse, rather than a slow core accretion process.