Spectroscopic rotational velocities of brown dwarfs
Abbreviated Journal Title
stars : individual (DENIS-P J0255.0-4700, GL 570D, LP 944-20, [Pleiades]; PPl 1, SDSS J053951.99-005902.0, SDSS J134646.45-003150.4, SDSS; J162414.37+002915.6, SDSSp J125453.90-012247.4, 2MASS J00361617+1821104, ; 2MASS J03341218-4953322, 2MASS J04151954-0935066, 2MASS; J05591914-1404488, 2MASS J12171110-0311131, 2MASS J15031961+2525196, ; 2MASS J15530228+1532369AB, 2MASS J16322911+1904407, 2MASS; J17281150+3948593AB, 2MASS J22244381-0158521, vB 10); stars : low-mass; brown dwarfs; stars : rotation; LOW-MASS STARS; EXTRASOLAR GIANT PLANETS; HIGH-RESOLUTION SPECTRA; H-ALPHA EMISSION; X-RAY-EMISSION; L FIELD DWARFS; ALL-SKY SURVEY; PHOTOMETRIC VARIABILITY; T-DWARF; CHROMOSPHERIC ACTIVITY; Astronomy & Astrophysics
We have obtained projected rotation velocities (nu(rot) sin i) of a sample of 19 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 young brown dwarfs, two likely field stars, and 15 likely brown dwarfs (30-72 M-Jup) in the solar neighborhood. Our results indicate that the T-type dwarfs are fast rotators in marked contrast to M-type stars. We have derived nu(rot) sin i velocities between <= 15 and 40 km s(-1) for them and have found no clear evidence for T dwarfs rotating strongly faster than L dwarfs. However, there is a hint for an increasing lower envelope on moving from mid-M to L spectral types in the nu(rot) sin i-spectral-type diagram that was previously reported in the literature; our nu(rot) sin i results extend it to even cooler types. Assuming that field brown dwarfs have a size of 0.08-0.1 R-circle dot, we can place an upper limit of 12.5 hr on the equatorial rotation period of T-type brown dwarfs. In addition, we have compared our nu(rot) sin i measurements to spectroscopic rotational velocities of very young brown dwarfs of similar mass available in the literature. The comparison, although model dependent, suggests that brown dwarfs lose some angular momentum during their contraction; however, their spin-down time seems to be significantly longer than that of solar-type to early M stars.
"Spectroscopic rotational velocities of brown dwarfs" (2006). Faculty Bibliography 2000s. 7869.