Investigating 2M1155-7919B: a Nearby, Young, Low-Mass Star Actively Accreting from a Nearly Edge-on, Dusty Disk

TL;DR

This study characterizes 2M1155-7919B, a young, nearby low-mass star actively accreting from a nearly edge-on dusty disk, providing insights into early star and planet formation processes around low-mass stars.

Contribution

It identifies and analyzes a rare nearby young low-mass star with an edge-on accreting disk, using multi-wavelength data and radiative transfer modeling.

Findings

2M1155-7919B is a young, late-M star with an active accreting disk.

The mid-infrared excess is from the disk around 2M1155-7919B, not its companion.

The system is a promising target for studying star and planet formation.

Abstract

We investigate the nature of an unusually faint member of the $\epsilon$ Cha Association ($D\sim100$ pc, age $\sim5$ Myr), the nearest region of star formation of age $<$8 Myr. This object, 2MASS J11550336-7919147 (2M1155$-$79B), is a wide ($\sim$580 AU) separation, comoving companion to low-mass (M3) $\epsilon$ Cha Association member 2MASS J11550485-7919108 (2M1155$-$79A). We present near-infrared spectra of both components, along with analysis of photometry from Gaia EDR3, 2MASS, VHS, and WISE. The near-IR spectrum of 2M1155$-$79B displays strong He I 1.083 emission, a sign of active accretion and/or accretion-driven winds from a circumstellar disk. Analysis of WISE archival data reveals that the mid-infrared excess previously associated with 2M1155$-$79A instead originates from the disk surrounding 2M1155$-$79B. Based on these results, as well as radiative transfer modeling of its optical/IR spectral energy distribution, we conclude that 2M1155$-$79B is most likely a young, late-M, star that is partially obscured by, and actively accreting from, a nearly edge-on circumstellar disk. This would place 2M1155$-$79B among the rare group of nearby ($D\lesssim100$ pc), young (age $<$10 Myr) mid-M stars that are orbited by and accreting from highly inclined protoplanetary disks. Like these systems, the 2M1155$-$79B system is a particularly promising subject for studies of star and planet formation around low-mass stars.