Travis Metcalfe

1. Monitoring Stellar Magnetic Activity Cycles with SONG Travis Metcalfe

2. Solar and stellar activity cycles • Magnetic regions on the Sun are bright in Mg II (UV) and Ca II (optical) • Measure ratio of total emission in line cores to flux in the wings • Use disk-integrated time series measurements to track magnetic cycles http://spacescience.spaceref.com/

3. Salabert et al. (2004) Cycle-induced frequency shifts • Solar p-mode shifts first detected in 1990, depend on frequency and degree • Even the lowest degree solar p-modes are shifted by the solar cycle • Unique constraints on the mechanism could come from solar-type stars Libbrecht & Woodard (1990)

4. Mount Wilson survey • Started by O. Wilson in mid-1960’s with 100-inch telescope on 91 stars • Continued through 1980’s and 1990’s with 60-inch on hundreds of stars • Stopped in early 2000’s after more than 30 years of observations Baliunas et al. (1995)

5. Lowell survey • 1.1-m telescope close to Flagstaff Arizona, allocate 7 nights/month bright time • Solar observations 3-6x per week, 50 target stars sampled a few nights/mo. • Solar/stellar/comparison all fed to spectrograph through a single fiber Hall & Lockwood (1995)

6. Solar-Stellar spectrograph • Built at NCAR, delivered to Lowell in 1988, regular observations since 1995 • Dedicated to long-term observations of the Sun and Sun-like stars • Example: observations of the “solar twin” 18 Sco show ~7 yr activity cycle Hall, Lockwood & Henry (2007)

7. SMARTS survey • Small telescopes at CTIO now run by a consortium; NCAR is a minor partner • Monitor bright southern asteroseismic targets for stellar activity variations • Example: observations of the exoplanet host star HD 17051 = HR 810 Metcalfe et al. (2009, arXiv:0909.5464)

8. SONG at MLSO