Herschel PACS observations of 4-10 Myr old Classical T Tauri stars in Orion OB1

TL;DR

This study uses Herschel PACS observations to analyze 8 classical T Tauri stars in Orion OB1, revealing their (pre)transitional disk structures, dust composition, and implications for planet formation at ages of 4-10 million years.

Contribution

First detailed Herschel PACS analysis of 4-10 Myr old T Tauri stars in Orion OB1, showing disk structures and dust properties relevant to planet formation.

Findings

Disks are (pre)transitional with small optically thin dust inside cavities.

Crystalline silicates found inside some disk gaps, amorphous in others.

Disk masses are lower than needed for giant planet formation.

Abstract

We present \emph{Herschel} PACS observations of 8 Classical T Tauri Stars in the $\sim 7-10$ Myr old OB1a and the $\sim 4-5$ Myr old OB1b Orion sub-asscociations. Detailed modeling of the broadband spectral energy distributions, particularly the strong silicate emission at 10 $\mu$m, shows that these objects are (pre)transitional disks with some amount of small optically thin dust inside their cavities, ranging from $\sim 4$ AU to $\sim 90$ AU in size. We analyzed \emph{Spitzer} IRS spectra for two objects in the sample: CVSO-107 and CVSO-109. The IRS spectrum of CVSO-107 indicates the presence of crystalline material inside its gap while the silicate feature of CVSO-109 is characterized by a pristine profile produced by amorphous silicates; the mechanisms creating the optically thin dust seem to depend on disk local conditions. Using millimeter photometry we estimated dust disk masses for CVSO-107 and CVSO-109 lower than the minimum mass of solids needed to form the planets in our Solar System, which suggests that giant planet formation should be over in these disks. We speculate that the presence and maintenance of optically thick material in the inner regions of these pre-transitional disks might point to low-mass planet formation.