The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs
| dc.creator | Mohanty, Subhanjoy | |
| dc.creator | Jayawardhana, Ray | |
| dc.creator | Basri, Gibor | |
| dc.date | 2005-02-08 | |
| dc.date.accessioned | 2026-07-07T10:27:24Z | |
| dc.date.available | 2026-07-07T10:27:24Z | |
| dc.description | Using the largest high-resolution spectroscopic sample to date of young, very low mass stars (VLMS) and brown dwarfs (BDs), we investigate disk accretion in objects ranging from just above the hydrogen-burning limit all the way to nearly planetary masses. Our 82 targets span spectral types from M5 to M9.5, or masses from 0.15 Msun down to ~15 Jupiters. They are confirmed members of the rho Oph, Taurus, Cha I, IC 348, R CrA, Upper Sco and TW Hydrae regions, with ages <1 to ~10 Myr. The sample contains 41 BDs (spectral types >= M6.5). We find that: (1) classical T Tauri-like disk-accretion persists in the BD domain down to nearly the deuterium-burning limit; (2) in addition to H-alpha, permitted emission lines of CaII, OI and HeI are also good accretion indicators, as in CTTs; (3) the CaII 8662A flux is an excellent quantitative measure of the accretion rate (Mdot) in VLMS and BDs(as in CTTs); (4) Mdot diminishes as M^2 -- our measurements support previous findings of this correlation, and extend it to the entire range of sub-stellar masses; (5) the accretor fraction among VLMS and BDs decreases substantially with age, as in higher-mass stars; (6) at any given age, the VLMS and BD accretor fraction is comparable to that in higher-mass stars; and (7) a number of sources with IR disk excesses do not evince measurable accretion, with the incidence of such a mismatch increasing with age: this implies that disks in the low mass regime can persist beyond the main accretion phase, and parallels the transition from the classical to post-T Tauri stage in more massive stars. These strong similarities at young ages, between higher-mass stars and low-mass bodies close to and below the hydrogen-burning limit, are consistent with a common formation mechanism in the two mass regimes. (abridged) | |
| dc.description | 64 pages, 7 figures. ApJ accepted | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0502155 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0502155 | |
| dc.identifier | Astrophys.J.626:498-522,2005 | |
| dc.identifier | doi:10.1086/429794 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/177140 | |
| dc.subject | Astrophysics | |
| dc.title | The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs | |
| dc.type | text |