Travis Metcalfe

Monitoring Stellar Magnetic Activity Cycles with SONG

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/

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)

Salabert et al. (2004)

Mount Wilson survey

Baliunas et al. (1995)

• 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

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)

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)

SMARTS survey

Metcalfe et al. (2009, arXiv:0909.5464)

• 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

SONG at MLSO