* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
MHD Days 2014 Dec 3 2014, Potsdam New results on the ageactivity relation from Kepler Stellar dynamo from asteroseismology Alfio Bonanno INAF Catania Astrophysical observatory [email protected] Bonanno, A. Corsaro, E., Karoff, C. A&A 571, 35, 2014 Solar-like Oscillations n Acoustic waves in outer convective envelope (p modes) ⌫n,l,m Tiny brightness variations Observed in > 15000 low mass stars from MS to Red Giants Beck & Kallinger S&W 2013 2 Alfio Bonanno MHD Days 2014 Solar-like Oscillations • • Chaplin et al. Science 2011 Evidence is a N-dimensional integral if considered over the free parameters ⌫max = f (g, Te↵ ) Power Spectral ! Density = PSD Amax = f (L, Te↵ ) ! ! Convert evidence into a one dimensional integral (X = A2max fraction of prior volume - i.e. prior mass) 3 Alfio Bonanno MHD Days 2014 Solar-like Oscillations p ⌫ / 1/ ⇢¯ • • • • Chaplin et al. Science 2011 ⌫ l=1 dc ⌫/ dr l=0 l=0 Age, Amax l=1 l=2 l=2 l=3 ⌫max , Introduction The sample The new method First results l=3 ⌫ 4 Alfio Bonanno MHD Days 2014 Main goal of asteroseismology 5 Asteroseismic age-activity relation Sample of 19 MS stars observed at NOT, see Karoff et al. 2013 SM W / ⌫ 0.25 6 Asteroseismic age-activity relation SM W / r1.09 BUT THE DATA is MUCH MORE DISPERSED! 7 Effect of magnetic field on amplitude of oscillation Numerical simulations (Jacoutot8 et al., 2008) Alfio Bonanno MHD Days 2014 Total oscillation power (in quiet Sun units) Numerical simulations (Jacoutot et al., 2008) 1.0 0.8 0.6 0.4 0.2 0.0 0 200 400 600 800 1000 Initial magnetic field, Bz0, (G) 1200 9 Alfio Bonanno MHD Days 2014 Activity vs oscillation amplitude SM W p / 1/ Amax Amax / 1/B 2 10 CONCLUSIONS • The activity decreases more efficiently with the evolutionary status of the star rather then with the age • The scattering of the LC is not a very good activity indicator compared to the S-index • The amplitude of the oscillations are suppressed with the total magnetic energy released in the atmosphere • Further data needed to extend these scaling relations to other stars, but direct numerical simulations can now be tested along the HR diagram “Where is your Ekman number?” Thank you Guenther !