Discovery of an old photoevaporating disk in sigma Orionis

TL;DR

This paper reports the first detection of a late-stage photoevaporating circumstellar disk around a low-mass star in sigma Orionis, characterized by a weak wind and low accretion, influenced by nearby ionizing radiation.

Contribution

It presents the first observational evidence of a disk in the final phase of photoevaporation, expanding understanding of disk dissipation processes in star-forming regions.

Findings

Detected a photoevaporating disk with a tenuous wind.

Observed strong forbidden emission lines indicating ionization.

Identified the influence of a nearby O star on disk evolution.

Abstract

The photoevaporation of circumstellar disks is a powerful process in the disk dissipation at the origin of the Orion proplyds. This Letter reports the first detection of a photoevaporating disk in the final but long-lasting phase of its evolution. The disk is associated to a low-mass T Tauri member of the sigma Orionis Cluster. It is characterized by a very low (if any) accretion rate and by a tenuous (Mloss ~ 10^{-9} Msun/yr) photoevaporation wind, which is unambiguously detected in the optical spectrum of the object. The wind emits strong forbidden lines of [SII] and [NII] because the low-mass star is close to a powerful source of ionizing photons, the O9.5 star sigma Ori.