HDE 245059: A Weak-Lined T Tauri Binary Revealed by Chandra and Keck

TL;DR

This study uses Chandra and Keck observations to analyze the binary nature, stellar properties, and X-ray emission characteristics of the young weak-lined T Tauri star HDE 245059, revealing insights into its coronal activity and evolutionary status.

Contribution

First detailed high-resolution X-ray and near-infrared analysis of HDE 245059 as a binary, providing new mass, age, and coronal property estimates for a WTTS in Lambda Orionis.

Findings

Binary separation of 0.87" with component masses 3 and 2.5 solar masses.

X-ray emission dominated by plasma at 8-15 MK with additional components at 4 MK and 50 MK.

No evidence of high densities in the X-ray triplet lines.

Abstract

We present the Chandra High Energy Transmission Grating Spectrometer (HETGS) and Keck observations of HDE 245059, a young weak-lined T Tauri star (WTTS), member of the pre-main sequence group in the Lambda Orionis Cluster. Our high spatial resolution, near-infrared observations with Keck reveal that HDE 245059 a binary separated by 0.87". Based on this new information we have obtained an estimate of the masses of the binary components; 3M_{sun} and 2.5M_{sun} for the north and south components, respectively. We have estimated the age of the system to be ~2-3 Myr. We detect both components of the binary in the zeroth order Chandra image and in the grating spectra. Our fits to the spectrum of the binary have shown that the emission is dominated by a plasma between 8 and 15 MK, a soft component at 4 MK and a hard component at 50 MK are also detected. The value of the hydrogen column density was low, 8 x 10^{19} cm^{-2}, likely due to the clearing of the inner region of the Lambda Orionis cloud. The abundance pattern shows an inverse First Ionization Potential (FIP) effect for all elements from O to Fe, the only exception being Ca. A 3-T model was fitted to the individual zeroth order spectra using the abundances derived for the binary. We have also obtained several lines fluxes from the grating spectra. The fits to the triplets show no evidence of high densities. We conclude that the X-ray properties of the weak-lined T Tau binary HDE 245059 are similar to those generally observed in other weak-lined T Tau stars. Although its accretion history may have been affected by the clearing of the interstellar material around Lambda Ori, its coronal properties appears not to have been strongly modified.