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Space Velocities of Land T-type Dwarfs
| Content Provider | Semantic Scholar |
|---|---|
| Author | Osorio, Maŕıa Rosa Zapatero Mart́ın, E. L. Béjar, Vı́ctor J. S. Bouy, H. Deshpande, Rohit R. |
| Abstract | We have obtained radial velocities of a sample of 18 ultracool dwarfs with spectral types in the interval M6.5–T8 using high-resolution, near-infrared spectra obtained with NIRSPEC and the Keck II telescope. Among our targets there are two likely field stars of type late M, one M6.5 Pleiades brown dwarf, and fifteen L and T likely brown dwarfs of the solar neighborhood with estimated masses in the range 30–75 M Jup. Two dwarfs, vB 10 (M8V) and Gl 570 D (T7.5V/T8V), are known wide companions to low-mass stars. We have confirmed that the radial velocity of Gl 570 D is coincident with that of the K-type primary star Gl 570 A, thus providing additional support for their true companionship. The presence of planetary-mass companions around 2MASS J05591914−1404488 (T4.5V) has been analyzed using five NIRSPEC radial velocity measurements obtained over a period of 4.37 yr. Using our radial velocity data and the radial velocities of an additional set of eight L-type dwarfs compiled from the literature in combination with their proper motions and trigonometric parallaxes, we have computed U V W space motions for the complete expanded sample, which comprises a total of 21 L and T dwarfs within 20 pc of the Sun. This ultracool dwarf population shows U V W velocities that nicely overlap the typical kinematics of solar to M-type stars within the same spatial volume. However, the mean Galactic (v tot = 44.2 km s −1) and tangential (v t = 36.5 km s −1) velocities of the L and T dwarfs appear to be smaller than those of G to M stars. A significant fraction (∼40%) of the L and T dwarfs lies near the Hyades moving group (0.4–2 Gyr), which contrasts with the 10–12% found 1 for earlier-type stellar neighbors. Additionally, the distributions of all three U V W components (σ UV W = 30.2, 16.5, 15.8 km s −1) and the distributions of the total Galactic (σ vtot = 19.1 km s −1) and tangential (σ vt = 17.6 km s −1) velocities derived for the L and T dwarf sample are narrower than those measured for nearby G, K, and M-type stars, but similar to the dispersions obtained for F stars. This suggests that, in the solar neighborhood, the Land T-type ultracool dwarfs in our sample (including brown dwarfs) is kinematically younger than solar-type to early M stars with likely ages in the interval … |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://arxiv.org/pdf/0706.0784v1.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | 2MASS ABRA gene Command & Conquer:Yuri's Revenge Compiler DWARF GUCY2C protein, human Image resolution Motion Planetary scanner PlayStation All-Stars Battle Royale Pleiades (supercomputer) Radial (radio) Stars, Celestial Stellar (payment network) Velocity (software development) |
| Content Type | Text |
| Resource Type | Article |
