since 2001 August 29
This page created by Adam Burgasser
http://www.gps.caltech.edu/~pa/adam/classification/index.html
| We present near-infrared spectra for a sample of T dwarfs, including eleven new discoveries made using the Two Micron All Sky Survey. These objects are distinguished from warmer (L-type) brown dwarfs by the presence of methane absorption bands in the 1--2.5 um spectral region. A first attempt at a near-infrared classification scheme for T dwarfs is made, based on the strengths of CH4 and H2O bands and the shapes of the 1.25, 1.6, and 2.1 um flux peaks. Subtypes T1 V through T8 V are defined, and spectral indices useful for classification are presented. The subclasses appear to follow a decreasing Teff scale, based on the evolution of CH4 and H2O bands and the properties of L and T dwarfs with known distances. However, we speculate that this scale is not linear with spectral type for cool dwarfs, due to the settling of dust layers below the photosphere and subsequent rapid evolution of spectral morphology around Teff ~ 1300--1500 K. Similarities in near-infrared colors and continuity of spectral features suggest that the gap between the latest L dwarfs and earliest T dwarfs has been nearly bridged. This argument is strengthened by the possible role of CH4 as a minor absorber shaping the K-band spectra of the latest L dwarfs. Finally, we discuss one peculiar T dwarf, 2MASS 0937+2931, which has very blue near-infrared colors (J-Ks = -0.89+/-0.24) due to suppression of the 2.1 um peak. The feature is likely caused by enhanced collision-induced H2 absorption in a high pressure or low metallicity photosphere. |
The following table lists coordinates, spectral types, and 2MASS JHKs mags for new T dwarfs identified in the paper. For a list of all the known T dwarfs, please see the table on the T dwarf page. Photometric errors are listed in parentheses. Finder charts for these objects are given at the bottom of the page.
| Object | J2000 Coord | Subtype | 2MASS J | 2MASS H | 2MASS Ks |
|---|---|---|---|---|---|
| 2MASS 0243-2453 | 02 43 13.7 -24 53 29 |
T6 V | 15.40(0.05) | 15.15(0.10) | 15.21(0.17) |
| 2MASS 0415-0935 | 04 15 19.5 -09 35 06 |
T8 V | 15.71(0.06) | 15.57(0.12) | 15.45(0.20) |
| 2MASS 0727+1710 | 07 27 18.2 +17 10 01 |
T7 V | 15.55(0.07) | 15.82(0.18) | 15.56(0.21) |
| 2MASS 0755+2212 | 07 55 48.0 +22 12 18 |
T5 V: | 15.72(0.07) | 15.66(0.14) | 15.77(0.21) |
| 2MASS 0937+2931 | 09 37 34.7 +29 31 42 |
T6 Vp | 14.65(0.04) | 14.68(0.07) | 15.54(0.24) |
| 2MASS 1534-2952 | 15 34 49.8 -29 52 27 |
T5.5 V | 14.90(0.04) | 14.89(0.09) | 14.86(0.11) |
| 2MASS 1546-3325 | 15 46 27.1 -33 25 11 |
T5.5 V | 15.60(0.05) | 15.44(0.09) | 15.42(0.17) |
| 2MASS 1553+1532 | 15 53 02.2 +15 32 36 |
T7 V | 15.81(0.08) | 15.92(0.17) | 15.51(0.19) |
| 2MASS 2254+3123 | 22 54 18.8 +31 23 49 |
T5 V | 15.28(0.05) | 15.04(0.09) | 14.83(0.14) |
| 2MASS 2339+1352 | 23 39 10.1 +13 52 30 |
T5.5 V | 15.88(0.08) | 16.04(0.17) | 15.70(0.28) |
| 2MASS 2356-1553 | 23 56 54.7 -15 53 10 |
T6 V | 15.80(0.06) | 15.64(0.10) | 15.83(0.19) |
This table lists the available spectra for confirmed T dwarfs from the classification paper. Also check out the spectra on the T dwarf page. I also encourage interested parties to also visit Sandy Legget's vast repository of spectral and photometric data at ftp://ftp.jach.hawaii.edu/pub/ukirt/skl/. You can also download all of the NIRC and OSIRIS data in one shot if you are so inclined. You may need to massage the headers for these files in order to read them in to your favorite software. Please remember to cite the paper if you are going to use these data, it's the only way some of us keep our jobs :)
| Object (finder chart) |
Type | NIRC 1-2.5um R~60-120 |
OSIRIS 1.2-2.35um R~1200 |
|---|---|---|---|
| 2MASS 0243-2453 | T6 V | [000124] | [991221] |
| 2MASS 0415-0935 | T8 V | [991118] [000124] |
. |
| 2MASS 0559-1404 | T5 V | [000123] [000124 |
[991220] |
| 2MASS 0727+1710 | T7 V | [000123] | [991220] |
| 2MASS 0937+2931 | T6 Vp | [000123] [000124] |
[991221] |
| 2MASS 1047+2124 | T6.5 V | [000123] [000124] |
. |
| 2MASS 1217-0311 | T7.5 V | [000123] | . |
| 2MASS 1225-2739 | T6 V (T6 V) |
. | [000718] |
| 2MASS 1237+6526 | T6.5 Ve | [000124] | . |
| SDSS 1254-0122 | T2 V | . | [000716] |
| SDSS 1346-0031 | T6 V | [000123] | . |
| Gliese 570D | T8 V | [000124] | [000716] |
| 2MASS 1534-2952 | T5.5 V | . | [000718] |
| 2MASS 1546-3325 | T5.5 V | . | [000719] |
| 2MASS 1553+1532 | T7 V | [000722] | [000717] [000718] |
| SDSS 1624+0029 | T6 V | . | [000715] |
| 2MASS 2254+3123 | T5 V | [000722] | [000716] |
| 2MASS 2339+1352 | T5.5 V | [000722] | [000716] |
| 2MASS 2356-1553 | T6 V | [991118] | [000717] |
|
Subtypes are from
Burgasser et al. 2002, ApJ, 564, 421. 6-digit identifiers are UT observation dates YYMMDD. |
[All NIRC spectra] [All OSIRIS spectra] | ||