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Discovery of Two Nearby, Peculiar L Dwarfs from the 2MASS Proper Motion Survey: Young or Metal-Rich? | | Dagny L. Looper
; J. Davy Kirkpatrick
; Roc M. Cutri
; Travis Barman
; Adam J. Burgasser
; Michael C. Cushing
; Thomas Roellig
; Mark R. McGovern
; Ian S. McLean
; Emily Rice
; Brandon J. Swift
; Steven D. Schurr
; | | Date: |
5 Jun 2008 | | Abstract: | We present the discovery of two nearby L dwarfs from our 2MASS proper motion
search, which uses multi-epoch 2MASS observations covering ~4700 square degrees
of sky. 2MASS J18212815+1414010 and 2MASS J21481628+4003593 were overlooked by
earlier surveys due to their faint optical magnitudes and their proximity to
the Galactic Plane (10 degrees < |b| < 15 degrees). Assuming that both dwarfs
are single, we derive spectrophotometric distances of ~10 pc, thus increasing
the number of known L dwarfs within 10 pc to 10. In the near-infrared, 2MASS
J21481628+4003593 shows a triangular-shaped H-band spectrum, strong CO
absorption, and a markedly red J-Ks color (2.38+/-0.06) for its L6 optical
spectral type. 2MASS J18212815+1414010 also shows a triangular-shaped H-band
spectrum and a slightly red J-Ks color (1.78+/-0.05) for its L4.5 optical
spectral type. Both objects show strong silicate absorption at 9-11 microns.
Cumulatively, these features imply an unusually dusty photosphere for both of
these objects. We examine several scenarios to explain the underlying cause for
their enhanced dust content and find that a metal-rich atmosphere or a
low-surface gravity are consistent with these results. 2MASS J18212815+1414010
may be young (and therefore have a low-surface gravity) based on its low
tangential velocity of 10 km/s. On the other hand, 2MASS J21481628+4003593 has
a high tangential velocity of 62 km/s and is therefore likely old. Hence, high
metallicity and low-surface gravity may lead to similar effects. | | Source: | arXiv, 0806.1059 | | Services: | Forum | Review | PDF | Favorites | |
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