BIB-VERSION:: AST-PP-v1.0
ID:: epreps.stsci//prep1217
ENTRY:: March 9, 1998
TITLE::  The Problem of Hipparcos Distances to Open Clusters. II. Constraints from Nearby Field Stars 
SUBTITLE:: 
AUTHOR:: Soderblom, David R. (1)
AUTHOR:: King, Jeremy R. (1)
AUTHOR:: Hanson, Robert B. (2)
AUTHOR:: Jones, Burton  F. (2)
AUTHOR:: Fischer, Debra (3)
AUTHOR:: Stauffer, John R. (4)
AUTHOR:: Pinsonneault, Marc H.  (5)
AFFIL:: (1) Space Telescope Science Institute    3700 San Martin Drive    Baltimore, MD 21218    USA
AFFIL:: (2) University of California Observatories/Lick Observatory Board of Studies in Astronomy and Astrophysics University of California, Santa Cruz CA 95064
AFFIL:: (3) Dept. of Physics and Astronomy San Francisco State University, San Francisco CA 94132
AFFIL:: (4) Harvard-Smithsonian Center for Astrophysics 60 Garden Street, Cambridge MA 02138
AFFIL:: (5) Astronomy Department, Ohio State University 174 West 18th Avenue, Columbus OH 43210
DATE:: February 1998
JOURNAL:: To appear in:  The Astrophysical Journal
SUBMITTED:: 24 December 1997
ACCEPTED:: 27 January 1998 
OTHER_ACCESS:: 
COPYRIGHT:: Copyright 1998 The Association of Universities for Research in Astronomy, Inc.  All Rights Reserved.
LANGUAGE:: English
ABSTRACT::

 This paper examines the discrepancy between distances to nearby open 
clusters as determined by parallaxes from Hipparcos compared to 
traditional main sequence fitting.  The biggest difference is seen for 
the Pleiades, and our hypothesis is that if the Hipparcos distance to 
the Pleiades is correct, then similar subluminous ZAMS stars should 
exist elsewhere, including the immediate solar neighborhood.  We 
examine a color-magnitude diagram of very young and nearby solar-type 
stars and show that none of them lie below the traditional ZAMS, 
despite the fact that the Hipparcos Pleiades parallax would place its 
members 0.3 magnitude below that ZAMS.  We 
also present analyses and observations of solar-type stars that do lie 
below the ZAMS and show that they are subluminous because of low 
metallicity and that they have the kinematics of old stars.



END:: epreps.stsci//prep1217