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Re: [mesa-users] instability strip definition (no MESA content)
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From: Bill P. <pa...@ki...> - 2017-06-01 17:18:57
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Hi Earl, this is just to say how much I appreciate your input to mesa-users. keep it up! cheers, bill On Jun 1, 2017, at 10:11 AM, Earl Bellinger wrote: > errata: I found a little mistake in my previous email - I meant to say > that RR Lyrae are core-and-shell burning, not double-shell burning. > > Best regards, > Earl Bellinger > > --- > www.earlbellinger.com > Department of Astronomy, Yale University > Stellar Ages & Galactic Evolution Group, Max Planck Institute > > > On Thu, Jun 1, 2017 at 12:03 PM, Earl Bellinger <bel...@mp...> wrote: >> Dear Aaron, >> >> I am probably not going to say anything you don't already know, but >> here are my two cents on the matter... >> >> From a theoretical point of view, the instability strip is found by >> determining when stars become unstable to fundamental (or >> low-overtone) radial oscillations. More specifically, this occurs when >> the imaginary component of radial mode eigenfrequencies change sign. >> >> This happens at several stages during evolution: on the main sequence >> (delta Scuti and other types of stars), during a "blue straggle" (SX >> Phoenicis variables), during the Hertzsprung gap in the sub-giant >> phase (first-crossing Cepheids), during blue loops after ignition of >> core helium burning in the star's ascent up the giant branch >> (Cepheids), on the horizontal branch with double-shell burning (RR >> Lyraes), etc... >> >> On the red edge, the location of the sign change depends on the >> details of pulsation-convection interaction which, as far as I know, >> is neglected in pulsation codes such as GYRE and ADIPLS, and as such >> is typically regarded as being unreliable. The location of the blue >> edge is more reliable but depends for example on one's choice of the >> mixing length parameter. So a theoretical definition of the >> instability strip in terms of Teff, log g, or L will depend on >> potentially arbitrary assumptions. That being said, one can find >> empirical instability strips from real stars in the literature. >> >> I hope what I have said is correct. If there are any errors, I hope >> someone will please correct me. >> >> Best regards, >> Earl Bellinger >> >> --- >> www.earlbellinger.com >> Department of Astronomy, Yale University >> Stellar Ages & Galactic Evolution Group, Max Planck Institute >> >> >> On Thu, Jun 1, 2017 at 11:13 AM, Aaron Dotter <aar...@gm...> wrote: >>> Hi all, >>> >>> (Sorry for the non-MESA request. Too much expertise on this mailing list to >>> resist asking here!) >>> >>> Does anyone have a favorite definition of the realm of the instability strip >>> in the H-R diagram? There are lots of cartoons out there, most of which are >>> vague and/or conflicting. I'm not aware of a solid theoretical or empirical >>> definition of the bounds of the IS in terms of Teff, surface gravity, and/or >>> luminosity. >>> >>> Thanks, >>> Aaron >>> >>> ------------------------------------------------------------------------------ >>> Check out the vibrant tech community on one of the world's most >>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot >>> _______________________________________________ >>> mesa-users mailing list >>> mes...@li... >>> https://lists.sourceforge.net/lists/listinfo/mesa-users >>> > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > mesa-users mailing list > mes...@li... > https://lists.sourceforge.net/lists/listinfo/mesa-users |
