Unlocking the dynamics of Young Stellar Objects: Time-Domain Interferometry with six 4-m class telescopes

TL;DR

The paper advocates a time-domain interferometry facility built from six or more 4 m telescopes to image the inner astronomical unit of Young Stellar Objects in 4D, capturing rapid variability due to magnetospheric accretion, disk dynamics, and planet formation. By leveraging rapid alerts from next-generation time-domain surveys and broad V-to-N band coverage, the approach delivers instantaneous uv-coverage and 6D tomography that connects optical/IR variability to spatial changes. It outlines concrete science cases, including accretion/ejection geometry, dipper phenomena, CPD detection, and FUor/EXor eruptions, and demonstrates how snapshot imaging can overcome the time-blurring barrier. The facility would act as a dynamical counterpart to JWST, ALMA, and the ELT, enabling a complete tomography of the planet-forming region and anchoring time-domain astronomy within ESO’s broader multi-wavelength ecosystem.

Abstract

The dynamics of the inner regions of young stellar objects (YSOs) is driven by a variety of physical phenomena, from magnetospheres and accretion to the dust sublimation rim and inner disk flows. These inner environments evolve on timescales of hours to days, exactly when bursts, dips, and rapid structural changes carry the most valuable information about star and planet formations, but remain hardly reachable with current facilities. A better reactive infrastructure with six or more telescopes, combined with alerts from large time-domain surveys (e.g., at the era of LSST/Rubin type facilities), and equipped with instruments spanning from the V-band to the thermal infrared (N), would provide the instantaneous uv-coverage and spectral diagnostics needed to unambiguously interpret and image these events as they happen. Such a world's first time-domain interferometric observatory would enable qualitatively new science: directly linking optical and infrared variability to spatially resolved changes in magnetospheric accretion, inner-disk geometry, and dust and gas dynamics in the innermost astronomical unit. Crucially, connecting these processes to outer-scale unresolved information from JWST, ALMA, and the ELT would yield a complete tomography of the planet-forming region.

Figures (2)

• Figure 1: YSOs exhibit diverse, rapid, multi-scale variability modes that challenge the temporal resolution of existing arrays Fischer2023. Unveiling their origin requires capturing the inner geometry simultaneously with the observed variability.
• Figure 2: Accessible parameter space ($G_{RP}$ vs $K$) for YSOs. The upgrade to 4-m class (violet) bridges the gap between current ATs (gray) and UTs (dark gray), unlocking hundreds of targets for time-domain interferometry.