Transcript Monitoring Stellar Magnetic Activity Cycles with SONG

Monitoring Stellar Magnetic
Activity Cycles with SONG
Travis Metcalfe
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
Salabert et al. (2004)
• 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)
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)
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
• 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)
SONG at MLSO