THE ROLE OF ACCRETION AND EJECTION VARIABILITY IN THE EVOLUTION OF YOUNG STARS AND THEIR DISKS

19 - 22 MAY 2025

GARCHING NEAR MUNICH, GERMANY

 

Rationale

Variability in young stellar objects (YSOs) has long been observed, both photometrically and spectroscopically, across a range of amplitudes and timescales (hours, days, and years). This variability happens at the time of formation of stars and planets, two closely linked events. Variability in the dynamical processes within the system, such as accretion onto the star and ejection of material from the disk, must therefore be characterised to reveal the conditions for planet formation. Understanding time-variable accretion directly addresses the question of how young stars gain mass. However, how this variability affects further disk properties, such as disk chemistry and temperature gradients, which would significantly impact the composition of planetary atmospheres, is an ongoing challenge. Furthermore, with the ratio of accretion to ejection still not fully understood, it remains an open question how exactly protoplanetary disks lose their mass and disperse. Since the mass budget within disks directly influences how and where planets can form, it is critical to understand the time-dependent nature of these environments.

With new results from recent and ongoing observational studies, such as the HST DDT ULLYSES and contemporaneous ESO/VLT PENELLOPE Large programs, which obtained multi-wavelength and multi-epoch spectroscopy of ~100 YSOs, the first three years of JWST observations of YSOs, as well as ongoing efforts from TESS, providing lightcurves for thousands of YSOs, it is a perfect time to bring together experts in this field to address the open questions on YSO variability.

New AO-assisted instruments such as VLT/ERIS or VLT/MUSE-NFM are now enabling unprecedented resolution in comparing YSO outflows to archival HST observations. Interferometric variability studies have started with VLTI/GRAVITY and interferometric monitoring will soon become feasible with GRAVITY+. New survey instruments such as the Vera Rubin Observatory (LSST) and ESO/SoXS will also be operational in 2025.  Recent ALMA surveys of protoplanetary disks are systematically quantifying the outer disk composition and morphology of disks in nearby star-forming regions with Large Programs such as AGE-PRO, exoALMA, and DECO. As theoretical work on this subject improves with the requirement of simulating more complex scenarios, the exchange of the most recent research on these topics is crucial to advancing our knowledge.

Specifically, this workshop aims to address the following topics:

Accretion variability, long (>decades) and short (<days) across a range of amplitudes and wavelength ranges from high cadence multifilter photometry and mid-high-resolution spectroscopy.

Outflow variability, including disk winds and jets, observationally and theoretical studies on launching mechanisms, composition, and kinematics.

Accretion-outflow connection, mass flow ratios, observational challenges

Connection to outer disk scales, chemical composition of the disks and of the forming planets, disk substructure formation and evolution, and planet migration.

 

Programme outline

Monday 19th May – Thursday 22nd May

Begin Monday after lunch

Finish Thursday before lunch

Includes welcome reception and workshop dinner

The workshop will be held at the ESO headquarters in Garching near Munich from Monday afternoon until Thursday, at lunch time.

E-mail: RAVEYSO@eso.org

Partly funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) in the framework of the YTTHACA Project 469334657

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