Post on 18-Mar-2016
description
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