Matteo Cantiello edited Mode Visibility.tex  almost 9 years ago

Commit id: 9cd957f4828e64f5925e190b0091348eedd32ed6

deletions | additions      

       

where $\Delta \nu \simeq (2 t_{\rm cross})^{-1}$ \cite{Chaplin_2013} is the large frequency separation between overtone modes, and $\tau$ is the damping time of a radial mode with similar frequency. The value of $T^2$ can be calculated from a stellar model, whereas {\bf $\tau \approx 5 \! - \! 10 \, {\rm days}$} {\bf \cite{Dupret_2009,Corsaro_2012,Grosjean_2014,Corsaro_2015} } for stars ascending the RGB.  Most observed modes are near the frequency $\nu_{\rm max}$, which is determined by the evolutionary state of the star. On the RGB, more evolved stars generally have smaller $\nu_{\rm max}$.   Figure \ref{fig:moneyplot} compares our estimate for suppressed dipole mode visibility (equation \ref{eqn:vis}) with {\it Kepler} observations \cite{Mosser_2011,Garcia_2014}. The stars {\bf objects  classified by \cite{Mosser_2011} as suppressed pulsators depressed dipole modes (DDM)} stars  lie very close to our estimate. The striking agreement holds over a large baseline in $\nu_{\rm max}$ extending from the very early red giants KIC 8561221 \cite{Garcia_2014} and KIC 9073950 at high $\nu_{\rm max}$ to near the luminosity bump at low $\nu_{\rm max}$. We conclude that the cores of stars with suppressed dipole modes efficiently trap waves tunneling through the evanescent region. This is further supported by the normal $\ell=0$ mode visibility in suppressed pulsators (because radial modes do not propagate within the inner core) and the lack (or perhaps smaller degree) of suppression observed in $\ell=2$ modes by \cite{Mosser_2011}, because quadrupole modes have a smaller transmission coefficient $T$.