Accretion and OH Photodissociation at a Nearby T Tauri System in the beta Pictoris Moving Group

TL;DR

This study reports on an old binary T Tauri star system in the beta Pictoris group showing accretion and OH photodissociation signatures, revealing ongoing disk processes in mature stars.

Contribution

First detection of OH photodissociation and accretion signatures in the oldest known dwarf T Tauri stars within a nearby moving group.

Findings

Both stars exhibit oxygen forbidden line emission.

The dustier star has hot dust at 900 K and high infrared luminosity.

These stars are among the oldest showing such phenomena.

Abstract

We present spectra of an M-type, binary star system (LDS 5606) that belongs to the nearby ~20 Myr old beta Pictoris moving group. Both stars are very dusty; the dustier member displays optical emission lines from eight elements indicative of ongoing mass accretion. The spectra of both stars contain oxygen forbidden line emission at 6302 and 5579 A, consistent with a recent model of far ultraviolet photodissociation of OH molecules in a circumstellar disk. These are the oldest dwarf stars presently known to display such a phenomenon. The spectral energy distribution of the dustier star indicates substantial quantities of dust as hot as 900 K, and its fractional infrared luminosity (L_IR)/L_bol) is almost as large as that of the main sequence record holder, V488 Per. The LDS 5606 binary joins a remarkable group of very dusty, old, T Tauri stars that belong to widely separated multiple systems.