The Variability of Sunlike Stars on Decadal Timescales
Abstract
Thirty-four stars similar to the Sun have been monitored in chromospheric Ca II HK emission since 1966 from Mount Wilson Observatory and in Strömgren b and y photometry between 1984-2000 from Lowell Observatory and since 1993 from Fairborn Observatory. We have just completed an updated analysis of these time series in which we have successfully merged the Lowell and Fairborn data. We find that the precision per observation of these two photometric datasets is almost identical although the Fairborn observations are considerably more plentiful. Overall our results confirm what we published previously (Radick et al. 1998 ApJ Suppl 118 239): the Sun's variability pattern is not uncommon among sunlike stars. The Sun's current behavior however may be unusually regular - many of the stars in our sample vary more erratically than the Sun. We also encounter stars whose chromospheric and photometric ouputs appear to be uncoupled - one varying but not the other. Finally we continue to find examples of stars with time-averaged chromospheric emission levels comparable to that of the present-day Sun but photometric amplitudes several times larger. Such ""ill-behaved"" stars may be telling us about activity patterns that deviate from the ""standard"" solar model.
- Publication:
-
Stars as Suns : Activity, Evolution and Planets
- Pub Date:
- January 2004
- Bibcode:
- 2004IAUS..219..264R