\authors{Hillenbrand, Mamajek, Stauffer, Soderblom, TBD et als}

\section{Introduction}

Age indicators for stars fall into four main categories. First, position
on the Hertzsprung-Russell diagram may be related to age through 
theoretical models.  For stars in the pre-main sequence or post-main sequence 
phases of stellar evolution a unique (though inaccurate due to systematics
in the still imperfect input physics)
age may be determined.  For stars on the main sequence a lower limit 
to the age is derived for those stars with turn-off ages older than the age
of the universe while for younger main sequence stars both lower and upper 
limits are found.  
Second, stellar rotation and its proxies coronal activity,
chromospheric activity, and lithium abundance can provide meaningful 
constraints on stellar ages, particularly for young pre-main and main sequence
stars.  Third and fourth are stellar kinematics and metallicity which can
be statistially but not quantitatively related to stellar age.

In this paper we consider a sample of field and cluster stars with 
astrophysical data sufficient for placement on the HR diagram and 
measurement of activity/lithium indices.  
We only briefly consider kinematics and metallicity as age indicators.
Our approach is to calibrate the various age indicators using
well-studied nearby young open clusters having well-determined ages, and to 
then apply these calibrations to our field star sample. Although there are
extant calibrations in the literature, the revision of open cluster ages upward
over the past decade necessitates a revisitation of these calibrations.
Finally, we weight the ages and/or constraints derived from the various
indicators and estimate a most probable age or age range for each star.

\section{Sample}

\section{Estimators of Stellar Age}

\subsection{Membership in an Open Cluster or Kinematic Group}

\subsection{Hertzsprung-Russell Diagram}

\subsection{Rotation}
\subsubsection{V$\times$sin$i$}
\subsubsection{Period}

\subsection{X-ray Luminosity}

\subsection{UV Excess}

\subsection{CaII H\&K Emission}

\subsection{Halpha Emission}

\subsection{Lithium 6707$\AA$ Absorption}

\subsection{Kinematics}

\subsection{Metallicity}

\section{Correlation of Age Estimators}

\section{Cluster Calibration of Age Estimators}

IC 2602 (55 Myr)
Alpha Per (90 Myr; )
Pleiades (125 Myr; Stauffer et al 1998)
M34 (250 Myr; )
Hyades (625 Myr; Perryman et al 1998)
Praesepe (900 Myr; Hambly et al 1995)

present fits and standard deviations

\section{Results}
\subsection{Ages and Age Errors from Individual Methods}
\subsection{Comparison of Ages from Different Methods}
\subsection{Adopted Ages}