While following up L dwarf candidates selected photometrically from the Two Micron All Sky Survey , we uncovered an unusual object designated 2MASS J01415823 - 4633574 .
Its optical spectrum exhibits very strong bands of vanadium oxide but abnormally weak absorptions by titanium oxide , potassium , and sodium .
Morphologically such spectroscopic characteristics fall intermediate between old , field early-L dwarfs ( log ( g ) { \approx } 5 ) and very late M giants ( log ( g ) { \approx } 0 ) , leading us to favor low gravity as the explanation for the unique spectral signatures of this L dwarf .
Such a low gravity can be explained only if this L dwarf is much lower in mass than a typical old field L dwarf of similar temperature and is still contracting to its final radius .
These conditions imply a very young age .
Further evidence of youth is found in the near-infrared spectrum , including a triangular-shaped H-band continuum reminiscent of young brown dwarf candidates discovered in the Orion Nebula Cluster .
Using the above information along with comparisons to brown dwarf atmospheric and interior models , our current best estimate is that this L dwarf has an age of 1-50 Myr and a mass of 6-25 M _ { Jupiter } .
Although the lack of a lithium detection ( pseudo equivalent width < 1 Å ) might appear to contradict other evidence of youth , we suggest that lithium becomes weaker at lower gravity like all other alkali lines and thus needs to be carefully considered before being used as a diagnostic of age or mass for objects in this regime .
The location of 2MASS 0141 - 4633 on the sky coupled with a distance estimate of \sim 35 pc and the above age estimate suggests that this object may be a brown dwarf member of either the 30-Myr-old Tucana/Horologium Association or the \sim 12-Myr-old \beta Pic Moving Group .
Distance as determined through trigonometric parallax ( underway ) and a measure of the total space motion are needed to test this hypothesis .