Matteo Cantiello edited We_quantify_the_mass_dependence__.tex  over 8 years ago

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We quantify the mass-dependence in Fig. 3 by  showing the relative number of dipole-suppressed stars (those below the dashed  line in Fig. 2) in narrow mass intervals.   We see no suppression in stars below 1.1\msun.   This coincides with the mass below  which stars do not form convective cores during their hydrogen-core burning phase \citep{Kippenhahn_1990}.  The onset of magnetic suppression above this threshold suggests the existence of  convectively driven magnetic dynamos in the cores of at least some hydrogen-core burning (main-sequence)  stars, as shown in 3D hydrodynamical modeling of these stars \citep{Brun_2005}. Red giants do not contain convective cores, therefore we conclude the strong fields in suppressed oscillators are the remnants of the fields produced by core dynamos during the main sequence.  %This agrees well with theoretical predictions based on 3D hydrodynamical modeling of the cores of main-sequence stars \citep{Brun_2005}.  %[THE SENTENCE BEFORE AND AFTER DONT REALLY WORK TOGTHER BUT I FEEL WE NEED TO SAY SOMEHOW WHAT IS SAID IN THE FOLLOWING SENTENCE]  %The resulting strong magnetic fields must have survived long after the dynamo terminated at the end of hydrogen-core burning in order to be detected during the red giant phase. Therefore, dynamo-generated fields are frequently able to settle into long-lived stable configurations \citep{Braithwaite_2004,Braithwaite_2006,Duez_2010}, a result that was not certain from the 3D hydrodynamical simulations.  % The gradual increase in suppression may result from the increasing size of  % the convective core in more massive stars, which generates stronger  % magnetic fields that survive after hydrogen burning ceases in the core.   % [Jim/Matteo elaborate?]  Figure We quantify the mass dependence in Fig.  3 shows that by showing  the incidence of magnetic suppression increases with mass.  Red giants above 1.6\msol\ show a remarkable suppression rate relative number  of 50-60\%.  These evolved from main-sequence A-type stars, among which only up to $\approx 10$\% are observed to have strong fields at their surfaces  \citep{2008CoSka..38..443P}.   %We conclude that main sequence magnetic A dipole-suppressed  stars can only account for a small fraction of (those below  the dashed line in Fig. 2) in narrow  mass intervals. We see no suppression in  red giants below 1.1\msol, which   coincides  withsuppressed modes.  We conclude that these magnetic A stars represent only  the tip of mass below which they did not have convective cores  during  the iceberg, and core-hydrogen-burning phase \citep{Kippenhahn_1990}. The onset  of magnetic suppression above this threshold suggests  that a much larger fraction at least some  of A those  stars have strong had convectively driven  magnetic fields hidden dynamos  in their cores.   %The rapid fractional increase reaching 50-60\% for stars above 1.6\msol, coincides  %with the mass beyond which about 10\% of hydrogen-core burning A-stars are  %known to show strong magnetic fields on cores during  the surface [Power2008].   %[The large fraction core-hydrogen-burning (main-sequence) phase. This is supported by 3D  hydrodynamical modeling  of suppressed these  stars above 1.6\msol\ coinsides with  %the masses of A stars, of which up to 10\% are known \citep{Brun_2005}. Red giants no  longer contain convective cores, leading us  to have strong  %surface fields[REFS].]   %This further supports that the suppression arises from a magnetic field.  %Even more interesting, it shows conclude  that the previously known strong  magneticA   %stars detected through their surface  fields in suppressed oscillators  areonly  the tip remnants  of the%iceberg and a much larger fraction of A stars host strong magnetic  fields %hidden in their core.   %, than anticipated purely from their observable surface fields. produced by core dynamos during the main sequence.