Cool Stars 14 - Submitted Abstract # 137
This version created on 05 October 2006

Chromospheric Activity in Cool Stars from the California & Carnegie
Planet Search


Jason T. Wright, University of California, Berkeley
Emily Rauscher, Columbia University
Geoff W. Marcy, University of California, Berkeley

We present three major results from measurements of Ca II H & K
emission lines for cool stars from the California & Carnegie Planet
Search (CCPS).  These measurements were taken from the same Keck/HIRES
data used for precision radial velocity work.  We show haw radial
velocity precision is a function of stellar activity.  Young stars
show significantly higher levels of radial velocity "jitter" both
because rotation broadens their lines and because flows and
inhomogeneities on the stellar surface produce line-profile variations
which mimic radial velocity variations.  The SPOCS catalog measured
precise abundances, effective temperatures, and gravities for the CCPS
sample.  Combining this with Hipparcos data and our activity
measurements, we show that the usual age-activity relation is
uncalibrated for metallicity and gravity effects in stars older than ~
2 Gyr.  Finally, we have analyzed the detailed shapes of the H & K
line cores for 147 late type (K7-M5) stars and found an increase in
FWHM, equivalent width, and line luminosities of more than a factor of
3 over a small range of stellar masses.  We also find significant and
time-variable line asymmetries, suggesting velocities of chromospheric
material of order 100  m/s.

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