Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs
| dc.creator | Burgasser, Adam J. | |
| dc.creator | Cruz, Kelle L. | |
| dc.creator | Kirkpatrick, J. Davy | |
| dc.date | 2006-10-03 | |
| dc.date.accessioned | 2026-07-07T10:23:45Z | |
| dc.date.available | 2026-07-07T10:23:45Z | |
| dc.description | We present Gemini GMOS and Magellan LDSS-3 optical spectroscopy for seven ultracool subdwarf candidates color-selected from the Two Micron All Sky Survey. Five are identified as late-type subdwarfs, including the previously reported sdM9.5 SSSPM 1013-1356 and L subdwarf 2MASS 1626+3925, and a new sdM8.5 2MASS 0142+0523. 2MASS 1640+1231 exhibits spectral features intermediate between a late-type M dwarf and subdwarf, similar to the previously identified high proper motion star SSSPM 1444-2019, and we classify both sources as mild subdwarfs, d/sdM9. 2MASS 1227-0447 is a new ultracool extreme subdwarf, spectral type esdM7.5. Spectral model fits yield metallicities that are consistent with these metallicity classifications. Effective temperatures track with numerical subtype within a metallicity class, although they are not equivalent across metallicity classes. As a first attempt to delineate subtypes in the L subdwarf regime we classify 2MASS 1626+3925 and the previously identified 2MASS 0532+8246 as sdL4 and sdL7, respectively, to reflect their similarity to equivalently classified, solar metallicity L-type field dwarfs over the 7300-9000 A region. We also detail preliminary criteria for distinguishing L subdwarf optical spectra as a roadmap for defining this new spectral class. The strong TiO bands and Ca I and Ti I lines in the spectrum of 2MASS 1626+3925 provide further evidence that condensate formation may be inhibited in metal-deficient L subdwarfs. We conclude with a compendium of currently known, optically classified ultracool subdwarfs. | |
| dc.description | 27 pages, 14 figures, 6 tables; accepted for publication to ApJ. Figures 2a-2e are included in PDF format in the source files | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0610096 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0610096 | |
| dc.identifier | Astrophys.J.657:494-510,2007 | |
| dc.identifier | doi:10.1086/510148 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/175947 | |
| dc.subject | Astrophysics | |
| dc.title | Optical Spectroscopy of 2MASS Color-Selected Ultracool Subdwarfs | |
| dc.type | text |