AAS 201st Meeting, January, 2003
Session 12. Activity in Cool Stars
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

## [12.11] The Chromospheric Activity-Age Relation for M Dwarf Stars in Wide Binary Systems

N.M. Silvestri (Florida Institute of Technology)

We present new chromospheric activity-age relations for M dwarf stars in wide binary systems with white dwarf companions. This study is unique in that we use the cooling age of the white dwarf to determine the age of the M dwarf star in the binary system. Assuming that the members of the gravitationally bound system are coeval, the age of the white dwarf is therefore the age of the M dwarf companion.

The colors and magnitudes at which chromospheric activity becomes pervasive (at the H\alpha limit") in M stars have been shown to correlate linearly with log(age) in young (\leq 4 Gyr) cluster M dwarfs. We find that M dwarfs in wide binaries older than 4 Gyr depart from this linear relation and are found to have activity at colors and magnitudes both bluer and brighter than predicted by M dwarf cluster relations. Also, activity is present in nearly all cluster M dwarfs above the H\alpha limit", whereas not all binary M dwarfs are found to be active above this limit.

These relations differ considerably from the rotationally driven dynamo relation for F, G, and K stars that suggests a different magnetic heating mechanism for M dwarf stars. The new relations extend to ages beyond the oldest ages provided by cluster M dwarf activity-age estimates. However, more work is necessary to decrease the uncertainties in these new relations and extend them to later (\geq M5.5) spectral types.

This work was supported by the NASA Graduate Researchers Program Grant NGT 200415; A Grant-in-Aid of Research from the National Academy of Sciences administered by Sigma Xi, The Scientific Research Society; NASA Grant Y701296; and NSF Grant AST 0206115.

The author(s) of this abstract have provided an email address for comments about the abstract: nicole@astro.fit.edu

Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.