Disk Braking in young Stars: Probing Rotation in Chamaeleon i and Taurus-Auriga
Abstract
We present a comprehensive study of rotation, disk, and accretion signatures for 144 T Tauri stars in the young (~2 Myr old) Chamaeleon I and Taurus-Auriga star-forming regions based on multi-epoch high-resolution optical spectra from the Magellan Clay 6.5 m telescope supplemented by mid-infrared photometry from the Spitzer Space Telescope. In contrast to previous studies in the Orion Nebula Cluster and NGC 2264, we do not see a clear signature of disk braking in Tau-Aur and Cha I. We find that both accretors and non-accretors have similar distributions of vsin i. This result could be due to different initial conditions, insufficient time for disk braking, or a significant age spread within the regions. The rotational velocities in both regions show a clear mass dependence, with F-K stars rotating on average about twice as fast as M stars, consistent with results reported for other clusters of similar age. Similarly, we find the upper envelope of the observed values of specific angular momentum j varies as M 0.5 for our sample which spans a mass range of ~0.16-3 M sun. This power law complements previous studies in Orion which estimated j vprop M 0.25 for lsim2 Myr stars in the same mass regime, and a sharp decline in j with decreasing mass for older stars (~10 Myr) with M < 2 M sun. Furthermore, the overall specific angular momentum of this ~10 Myr population is five times lower than that of non-accretors in our sample, and implies a stellar braking mechanism other than disk braking could be at work. For a subsample of 67 objects with mid-infrared photometry, we examine the connection between accretion signatures and dusty disks: in the vast majority of cases (63/67), the two properties correlate well, which suggests that the timescale of gas accretion is similar to the lifetime of inner disks.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2009
- DOI:
- 10.1088/0004-637X/695/2/1648
- arXiv:
- arXiv:0902.0001
- Bibcode:
- 2009ApJ...695.1648N
- Keywords:
-
- accretion;
- accretion disks;
- circumstellar matter;
- stars: evolution;
- stars: formation;
- stars: pre-main sequence;
- stars: rotation;
- stars: statistics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted to ApJ. 10 pages, 7 figures, 2 tables. Formatted with emulateapj