2006/06/27 by Brian M. Patten, B. M. Patten, John R. Stauffer +16 · 13 citations
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Metallicity #Parallax #Photometry (optics) #Physics #Spitzer Space Telescope #Stars #Stellar classification #Stellar, planetary, and galactic studies #Telescope #astro-ph
paper · pdf · doi:10.1086/507264
published as Astrophys.J.651:502-516,2006 · 32 pages, 18 figures, accepted for publication to ApJ: revised to adjust acknowledgments, add a few more references, and the correct typographical errors in text and tables 1 and 3 (note as binaries sds0926+5847 and 2ma1553+1532)
arxiv created 2006/06/27 · openalex publication_date 2006/10/27 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present the results of a program to acquire photometry for 86 late M, L, and T dwarfs using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope . We examine the behavior of these cool dwarfs in various color-color and color-magnitude diagrams composed of near-IR and IRAC data. The T dwarfs exhibit the most distinctive positions in these diagrams. In M 5.8 versus [5.8]-[8.0], the IRAC data for T dwarfs are not monotonic in either magnitude or color, giving the clearest indication yet that the T dwarfs are not a one-parameter family in T eff . Because metallicity does not vary enough in the solar neighborhood to act as the second parameter, the most likely candidate then is gravity , which in turn translates to mass . Among objects with similar spectral type, the range of mass suggested by our sample is about a factor of 5 (~70 M J to ~15 M J ), with the less massive objects making up the younger members of the sample. We also find the IRAC 4.5 μm fluxes to be lower than expected, from which we infer a stronger CO fundamental band at ~4.67 μm. This suggests that equilibrium CH 4 /CO chemistry underestimates the abundance of CO in T dwarf atmospheres, confirming earlier results based on M -band observations from the ground. In combining IRAC photometry with near-IR JHK photometry and parallax data, we find the combination of K s , IRAC 3.6 μm, and 4.5 μm bands to provide the best color-color discrimination for a wide range of M, L, and T dwarfs. Also noteworthy is the M versus K s -[4.5] relation, which shows a smooth progression over spectral type, and splits the M, L, and T types cleanly.