NICMOS Narrow-band Infrared Photometry of TW Hya Association Stars

Abstract

We have obtained 1.64, 1.90 and 2.15 micron narrow-band images of five T Tauri stars in the TW Hya Association (TWA) using the Near-Infrared Camera and Multiobject Spectrometer aboard the Hubble Space Telescope. Most of the T Tauri stars in our study show evidence of absorption by H2O vapor in their atmospheres; in addition, the low-mass brown dwarf candidate, TWA 5B, is brighter at 1.9 microns than predicted by cool star models that include the effects of H2O vapor but neglect dust. We conclude that the effect of atmospheric dust on the opacity is important at 1.9 microns for TWA 5B, the coolest object in our sample. The available evidence suggests that the TWA is 5-15 MY old. Comparison of the colors of TWA 5B with theoretical magnitudes as a function of age and mass then confirms previous claims that TWA 5B is substellar with a mass in the range 0.02-0.03 solar masses. The accurate single-epoch astrometry of the relative positions and separation of TWA 5A and TWA 5B reported here should permit the direct measurement of the orbital motion of TWA 5B within only a few years.

21 pages, 6 figures, to appear in the Astrophysical Journal

References in corpus (3)

• Discovery of seven T Tauri stars and a brown dwarf candidate in the nearby TW Hydrae Association
• The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Taurus
• A Candidate Substellar Companion to CoD -33 7795 (TWA 5)

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• An Optical Spectroscopic Study of T Tauri Stars. I. Photospheric Properties
• The TW Hya Disk at 870 microns: Comparison of CO and Dust Radial Structures
• Nearby debris disk systems with high fractional luminosity reconsidered
• Constraining the X-ray and Cosmic Ray Ionization Chemistry of the TW Hya Protoplanetary Disk: Evidence for a Sub-interstellar Cosmic Ray Rate
• On the age of the TW Hydrae Association and 2M1207334-393254
• Silicon and Nickel Enrichment in Planet-Host Stars: Observations and Implications for the Core-Accretion Theory of Planet Formation
• The state of protoplanetary material 10 Myr after stellar formation: circumstellar disks in the TW Hydrae association
• Near-Infrared Spectroscopy of TW Hya: A Revised Spectral Type and Comparison with Magnetospheric Accretion Models
• 8--13 um spectroscopy of YSOs: Evolution of the silicate feature
• Mapping the Shores of the Brown Dwarf Desert III: Young Moving Groups
• Truncated Disks in TW Hya Association Multiple Star Systems
• Dust Processing in Disks around T Tauri Stars
• Keck Adaptive Optics Imaging of Nearby Young Stars: Detection of Close Multiple Systems
• The Enigmatic Young Low-Mass Variable TWA 30
• The TW Hya Rosetta Stone Project III: Resolving the Gaseous Thermal Profile of the Disk
• The Coronal X-ray Spectrum of the Multiple Weak-Lined T Tauri Star System HD 98800
• Coronal X-ray emission from an intermediate-age brown dwarf
• Gas and dust in the TW Hydrae Association as seen by the Herschel Space Observatory
• Magnetic Properties of Young Stars in the TW Hydrae Association
• ROSAT X-ray Spectral Properties of Nearby Young Associations: TW Hydrae, Tucana-Horologium, and the beta Pic Moving Group
• No Transition Disk? Infrared Excess, PAH, H2, and X-rays from the Weak-Lined T Tauri Star DoAr 21
• A coplanar circumbinary protoplanetary disk in the TWA 3 triple M dwarf system
• Silicate Emission in the TW Hydrae Association
• The TWA 3 Young Triple System: Orbits, Disks, Evolution
• Orbits and masses in the young triple system TWA 5
• Physical parameters of late M-type members of Chamaleon I and TW Hydrae Association: Dust settling, age dispersion and activity
• Orbital motion of the young brown dwarf companion TWA 5 B
• Infrared Photometry of Starless Dense Cores