Transcript (ppt)

RR Lyraes
Bi-Qing For
Chris Sneden (UT)
George Preston (Carnegie Observatory)
What are RR Lyrae stars?
APOD 23 Feb 2001
What happens when stars cross
the instability strip?
They pulsate like a jello!
Scientific Computing in the School of Physics at the University of Sydney
RR Lyraes
Max radius
Typical time scale = 0.57 day
Different types of RR Lyraes
What drives stellar pulsations?
• Kappa-mechanism (RR Lyrs)
– “steam engine”
Contract
Absorb heat
Restore the
balance
inside the
star
Expand
Release heat / cool off
Why RR Lyraes are interesting?
• Most of RR Lyraes have
– stable pulsation
– stable pulsational period
– high luminosity
• Easy to be identified at large distances
• Standard candles for distance scale
• Tracers for Studying Galactic structure
Distance scale to Globular Clusters
M3
https://www.cfa.harvard.edu/~jhartman/M3_movies.html
Tracers for studying Galactic structure
Duffau et al. (2006)
Special: Blazhko effect
Sergey Blazhko
created by D. Welch based on MACHO project data, Alcock et al. 2000
What am I studying?
• Chemical compositions throughout the
pulsational cycle.
• Line profile variation
• Where do we get the spectra?
George Preston
LCO
Du Pont
100 inch
What do we learn?
Line profile variation
Chemical Compositions
Current Missions
CoRoT - COnvection, ROtation & Transits planétaires
Kepler Space Telescope
 Many new RR Lyrs have been
discovered
 New properties have been found
in the lightcurves of RR Lyrs