ALMA and VLA Observations of EX Lupi in its Quiescent State

TL;DR

This study uses ALMA and VLA observations to analyze the circumstellar disk of EX Lupi after its 2008 outburst, revealing grain growth, disk structure, and emission mechanisms, providing insights into outburst impacts on disk evolution.

Contribution

First detailed modeling of EX Lupi's disk in quiescence post-outburst using multi-frequency data, revealing grain growth and inward migration of the ice line.

Findings

Disk radius of 45 au and mass of 0.01 M$_{ ext{sun}}$

Evidence of grain growth to at least 3 mm

Detection of non-thermal emission components

Abstract

Extreme outbursts in young stars may be a common stage of pre-main-sequence stellar evolution. These outbursts, caused by enhanced accretion and accompanied by increased luminosity, can also strongly impact the evolution of the circumstellar environment. We present ALMA and VLA observations of EX Lupi, a prototypical outburst system, at 100 GHz, 45 GHz, and 15 GHz. We use these data, along with archival ALMA 232 GHz data, to fit radiative transfer models to EX Lupi's circumstellar disk in its quiescent state following the extreme outburst in 2008. The best fit models show a compact disk with a characteristic dust radius of 45 au and a total mass of 0.01 M$_{\odot}$. Our modeling suggests grain growth to sizes of at least 3 mm in the disk, possibly spurred by the recent outburst, and an ice line that has migrated inward to $0.2-0.3$ au post-outburst. At 15 GHz, we detected significant emission over the expected thermal disk emission which we attribute primarily to stellar (gyro)synchrotron and free-free disk emission. Altogether, these results highlight what may be a common impact of outbursts on the circumstellar dust.