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A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. II. L/T Transition Atmospheres and Young Discoveries

Best, W.M.J.; Liu, M.C.; Magnier, E.A.; Deacon, N.R.; Aller, K.M.; Redstone, J.; Burgett, W.S.; Chambers, K.C.; Draper, P.; Flewelling, H.; Hodapp, K.W.; Kaiser, N.; Metcalfe, N.; Tonry, J.L.; Wainscoat, R.J.; Waters, C.

A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. II. L/T Transition Atmospheres and Young Discoveries Thumbnail


W.M.J. Best

M.C. Liu

E.A. Magnier

N.R. Deacon

K.M. Aller

J. Redstone

W.S. Burgett

K.C. Chambers

P. Draper

H. Flewelling

K.W. Hodapp

N. Kaiser

J.L. Tonry

R.J. Wainscoat

C. Waters


The evolution of brown dwarfs from L to T spectral types is one of the least understood aspects of the ultracool population, partly for lack of a large, well-defined, and well-characterized sample in the L/T transition. To improve the existing census, we have searched ≈28,000 deg2 using the Pan-STARRS1 and Wide-field Infrared Survey Explorer surveys for L/T transition dwarfs within 25 pc. We present 130 ultracool dwarf discoveries with estimated distances ≈9–130 pc, including 21 that were independently discovered by other authors and 3 that were previously identified as photometric candidates. Seventy-nine of our objects have near-IR spectral types of L6–T4.5, the most L/T transition dwarfs from any search to date, and we have increased the census of L9–T1.5 objects within 25 pc by over 50%. The color distribution of our discoveries provides further evidence for the "L/T gap," a deficit of objects with (J − K)MKO ≈ 0.0–0.5 mag in the L/T transition, and thus reinforces the idea that the transition from cloudy to clear photospheres occurs rapidly. Among our discoveries are 31 candidate binaries based on their low-resolution spectral features. Two of these candidates are common proper motion companions to nearby main sequence stars; if confirmed as binaries, these would be rare benchmark systems with the potential to stringently test ultracool evolutionary models. Our search also serendipitously identified 23 late-M and L dwarfs with spectroscopic signs of low gravity implying youth, including 10 with vl-g or int-g gravity classifications and another 13 with indications of low gravity whose spectral types or modest spectral signal-to-noise ratio do not allow us to assign formal classifications. Finally, we identify 10 candidate members of nearby young moving groups (YMG) with spectral types L7–T4.5, including three showing spectroscopic signs of low gravity. If confirmed, any of these would be among the coolest known YMG members and would help to determine the effective temperature at which young brown dwarfs cross the L/T transition.


Best, W., Liu, M., Magnier, E., Deacon, N., Aller, K., Redstone, J., …Waters, C. (2015). A Search for L/T Transition Dwarfs with Pan-STARRS1 and WISE. II. L/T Transition Atmospheres and Young Discoveries. Astrophysical Journal, 814(2), Article 118.

Journal Article Type Article
Acceptance Date Aug 16, 2015
Online Publication Date Nov 24, 2015
Publication Date Dec 1, 2015
Deposit Date Apr 5, 2016
Publicly Available Date Apr 8, 2016
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 814
Issue 2
Article Number 118


Published Journal Article (4.3 Mb)

Copyright Statement
© 2015. The American Astronomical Society. All rights reserved.

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