Time variability of accretion, outflows and star–disk interaction in Young Stellar Objects

• Applicant: Professorin Dr. Beate Stelzer
• Subject Area: Astrophysics and Astronomy
• Term: from 2018 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413113723

Throughout the first few million years following their birth, young stars are surrounded by a disk from which they accrete matter along magnetic field lines. Jets and outflows are observed from such Young Stellar Objects (YSOs), and are thought to remove excess angular momentum. The evolution of the star-disk environment is regulated by magnetospheric interactions between the star and the inner disk. The star-disk interaction is a dynamic process due to both intrinsic changes of the mass accretion rate and viewing effects produced by the geometric configuration of the star-disk-magnetosphere-observer system combined with rotation. The dynamics and time evolution of disk accretion is also intimately linked to the timescales of planet formation and migration. While the inner disk regions of YSOs where the accretion and outflow processes are operating can not be studied yet with direct imaging observations, both spectroscopy and photometric time-series studies carry the potential for disentangling the complex YSO phenomenology and establishing the relevant time-scales (rotational modulation, accretion-regime changes, secular evolution). To this effect, the proposed project will examine YSO variability with two detailed case studies and a pilot project on a statistical sample. The targets have been identified in an extensive spectroscopic survey of YSOs at the Very Large Telescope (VLT) of the European Southern Observatory in which the PI of this funding request has played a major role. The basis of the proposed study are observations obtained by the PI in Guest Observer time at the VLT and at the Rapid Eye Mount (REM), a small robotic telescope on La Silla. The use of broad-band spectroscopy and multi-band photometry on time-scales of hours to years makes these observations of exceptional value for examining as yet unexplained aspects of the dynamic YSO environment. The prime targets for the two detailed case studies, Par-Lup3-4 and TWA30AB, represent benchmark systems in critical parameter space (low stellar mass, late disk-evolution stage, high inclination favorable for detecting geometric variability effects).

• DFG Programme: Research Grants