Towards a comprehensive view of accretion, inner disks, and extinction in classical T Tauri stars: an ODYSSEUS study of the Orion OB1b association

TL;DR

This study models accretion and inner disk properties of nine classical T Tauri stars in Orion OB1b, revealing relatively high accretion rates at 5 Myr and characterizing inner disk wall temperatures and locations.

Contribution

It provides detailed magnetospheric accretion and inner disk wall fits for T Tauri stars using multi-wavelength spectra, expanding understanding of disk evolution at intermediate ages.

Findings

Accretion rates range from 0.5 to 17.2 x 10^{-8} M_sun/yr.

Inner disk walls are at 0.05-0.10 AU with temperatures of 1200-1800 K.

Accretion rate measurements are sensitive to extinction law assumptions.

Abstract

The coevolution of T Tauri stars and their surrounding protoplanetary disks dictates the timescales of planet formation. In this paper, we present magnetospheric accretion and inner disk wall model fits to NUV-NIR spectra of nine classical T Tauri stars in Orion OB1b as part of the Outflows and Disks around Young Stars: Synergies for the Exploration of ULLYSES Spectra (ODYSSEUS) Survey. Using NUV-optical spectra from the Hubble UV Legacy Library of Young Stars as Essential Standards (ULLYSES) Director's Discretionary Program and optical-NIR spectra from the PENELLOPE VLT Large Programme, we find that the accretion rates of these targets are relatively high for the region's intermediate age of 5.0 Myr; rates range from $0.5-17.2 \times 10^{-8}$ M$_{\odot}$/yr, with a median value of $1.2\times 10^{-8}$ M$_{\odot}$/yr. The NIR excesses can be fit with 1200-1800 K inner disk walls located at 0.05-0.10 AU from the host stars. We discuss the significance of the choice in extinction law, as the measured accretion rate depends strongly on the adopted extinction value. This analysis will be extended to the complete sample of T Tauri stars being observed through ULLYSES to characterize accretion and inner disks in star-forming regions of different ages and stellar populations.