Journal
ASTROPHYSICAL JOURNAL
Volume 833, Issue 1, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.3847/1538-4357/833/1/95
Keywords
open clusters and associations: individual (TW Hya); stars: distances; stars: kinematics and dynamics; stars: pre-main sequence
Categories
Funding
- National Science Foundation [1313043]
- NASA Astrobiology Institute [NNA09-DA81A]
- National Aeronautics and Space Administration
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1313043] Funding Source: National Science Foundation
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The TW Hya Association (TWA) is a nearby stellar association with an age of similar to 5-10 Myr. This is an important age for studying the late stages of star and planet formation. We measure the parallaxes of 14 candidate members of TWA. That brings to 38 the total number of individual stars with fully measured kinematics, i.e., proper motion, radial velocity, and parallax, to describe their motions through the Galaxy. We analyze these kinematics to search for convergence to a smaller volume in the past, but we find that the association is never much more compact than it is at present. We show that it is difficult to measure traceback ages for associations such as TWA that have expected velocity dispersions of 1-2 km s(-1) with typical measurement uncertainties. We also use our stellar distances and pre-main-sequence evolutionary tracks to find the average age of the association of 7.9 +/- 1.0 Myr. Additionally, our parallax measurement of TWA 32 indicates that it should be considered a bona fide member of TWA. Two new candidate members have high membership probabilities, and we assign them TWA numbers: TWA 45 for 2MASS J11592786-4510192 and TWA 46 for 2MASS J12354615-4115531.
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