The Curious Case of Glass I: High Ionization and Variability of Different Types

TL;DR

This study reports the first detection of high ionization emission lines in the young star Glass Ib, revealing extreme ultraviolet radiation and variability that suggest dynamic processes like accretion or flaring influence its environment.

Contribution

It provides the first observation of [SIV] and a high [NeIII]/[NeII] ratio in a young star, indicating the presence of hard radiation and exploring the variability and ionization mechanisms of Glass Ib.

Findings

Detection of high ionization lines [NeIII] and [SIV] in Glass Ib.

Glass Ib exhibits significant variability across multiple wavelengths.

The high ionization may be driven by variable accretion or X-ray flares.

Abstract

Our Spitzer IRS observation of the infrared companion Glass Ib revealed fine structure emission with high ionization ([NeIII]/[NeII]=2.1 and [SIV]/[SIII]=0.6) that indicates the gas is likely illuminated by hard radiation. While models suggest extreme ultraviolet radiation could be present in T Tauri stars (Hollenbach & Gorti 2009 and references therein), this is the first detection of [SIV] and such a high [NeIII]/[NeII] ratio in a young star. We also find that Glass Ib displays the molecules HCN, CO2, and H2O in emission. Here we investigate the Glass I binary system and consider possible mechanisms that may have caused the high ionization, whether from an outflow or disk irradiation. We also model the spectral energy distributions of Glass Ia and Ib to test if the system is a young member of the Chameleon I star-forming region, and consider other possible classifications for the system. We find Glass Ib is highly variable, showing changes in continuum strength and emission features at optical, near-infrared, and mid-infrared wavelengths. The optical light curve indicates that a central stellar component in Glass Ib became entirely visible for 2.5 years beginning in mid-2002, and that possibly displayed periodic variability with repeated, short-period dimming during that time. As the fine structure emission was not detected in observations before or after our Spitzer IRS observation, we explore whether the variable nature of Glass Ib is related to the gas being highly ionized, possibly due to variable accretion or an X-ray flare.