Why Do T Tauri Disks Accrete?
| dc.creator | Hartmann, Lee | |
| dc.creator | D'Alessio, Paola | |
| dc.creator | Calvet, Nuria | |
| dc.creator | Muzerolle, James | |
| dc.date | 2006-05-11 | |
| dc.date.accessioned | 2026-07-07T10:38:59Z | |
| dc.date.available | 2026-07-07T10:38:59Z | |
| dc.description | Observations of T Tauri stars and young brown dwarfs suggest that the accretion rates of their disks scale strongly with the central stellar mass, approximately $\mdot \propto M_*^2$. No dependence of accretion rate on stellar mass is predicted by the simplest version of the layered disk model of Gammie (1996), in which non-thermal ionization of upper disk layers allows accretion to occur via the magnetorotational instability. We show that a minor modification of Gammie's model to include heating by irradiation from the central star yields a modest dependence of $\mdot$ upon the mass of the central star. A purely viscous disk model could provide a strong dependence of accretion rate on stellar mass if the initial disk radius (before much viscous evolution has occurred) has a strong dependence on stellar mass. However, it is far from clear that at least the most massive pre-main sequence disks can be totally magnetically activated by X-rays or cosmic rays. We suggest that a combination of effects are responsible for the observed dependence, with the lowest-mass stars having the lowest mass disks, which can be thoroughly magnetically active, while the higher-mass stars have higher mass disks which have layered accretion and relatively inactive or ``dead'' central zones at some radii. In such dead zones, we suggest that gravitational instabilities may play a role in allowing accretion to proceed. In this connection, we emphasize the uncertainty in disk masses derived from dust emission, and argue that T Tauri disk masses have been systematically underestimated by conventional analyses. Further study of accretion rates, especially in the lowest-mass stars, would help to clarify the mechanisms of accretion in T Tauri stars. | |
| dc.description | 18 pages, 1 figure, ApJ, in press | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0605294 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0605294 | |
| dc.identifier | Astrophys.J.648:484-490,2006 | |
| dc.identifier | doi:10.1086/505788 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/180877 | |
| dc.subject | Astrophysics | |
| dc.title | Why Do T Tauri Disks Accrete? | |
| dc.type | text |