[Mesa-users] Formicola 2004 reaction rate

Francis Timmes fxt44 at mac.com
Mon Oct 16 01:03:17 EDT 2017


given an s-factor as a function of energy E in the center of mass frame, 
as in fig 6 of formicola et al 2004, the formula on slide 24 of hendrik's notes 
gives the integral to be calculated numerically for each desired temperature 
to obtain the maxwellian averaged cross section of a charged particle reaction. 
multiply by the avogadro constant to get the reaction listed in common reaction rate compilations. 

plot the ratio of your calculated rate over the rate given in common compilations 
to check that (a) your calculated rate is reasonable and (b) deviations from the 
common compilation rate occur where and of the magnitude one expects.

fxt






> On Oct 15, 2017, at 4:19 PM, Meisel, Zach <meisel at ohio.edu> wrote:
> 
> Greetings Earl,
>  
> One of the best online references I can think of for this would be Hendrik Schatz’s nuclear astrophysics lecture notes. For the s-factor, this lecture should be useful: https://people.nscl.msu.edu/~schatz/PHY983_13/Lectures/rates_direct.pdf
>  
> -Zach
>  
> ----
> Zach Meisel
> Asst. Prof. of Physics & Astronomy
> Ohio University
> Email: meisel at ohio.edu
> Web: http://inpp.ohiou.edu/~meisel
>  
> From: Earl Bellinger
> Sent: Sunday, October 15, 2017 9:32 AM
> To: Francis Timmes
> Cc: mesa-users
> Subject: Re: [Mesa-users] Formicola 2004 reaction rate
>  
> Thanks Josiah and Francis for your useful replies. I've run through
> the inlists and now can get all that to work.
> 
> I am still running into some difficulties however putting this into
> practice in the context of the Formicola result. The update to this
> rate comes in the form of the astrophysical s-factor. In other
> evolution codes (e.g. YREC) it is possible to alter s-factors
> individually. In an earlier mesa-users thread [1] however, Rob Farmer
> explains that the s-factors cannot be altered directly in MESA;
> instead, new reaction rates must be computed with the new s-factor. Is
> that still the case? If so, does anyone have any advice as to how I
> can calculate the rates manually with this different s-factor, so that
> I may then insert them using the procedures described above?
> 
> Thanks again for any assistance.
> 
> [1] https://lists.mesastar.org/pipermail/mesa-users/2016-September/007051.html
> 
> Best regards,
> Earl Bellinger
> 
> ---
> earlbellinger.github.io
> Earl Bellinger, Ph.D. Candidate
> SAGE Group, Max Planck Institute for Solar System Research
> Department of Astronomy, Yale University
> 
> 
> On Fri, Sep 29, 2017 at 7:56 AM, Francis Timmes <fxt44 at mac.com> wrote:
> >
> > hi earl,
> >
> > 1) unzip the attached rate_tables.zip file.
> >
> > 2) place the "rate_tables" folder in your mesa work directory.
> >
> > 3) inspect the contents of "rate_tables" :
> >
> >    "rate_list.txt" holds the (rate name, rate file) pair for strong and e&m rates.
> >    in this example, it is set to use (r_c12_ag_o16, new_c12_ag_adopted.txt) pair,
> >    so the c12(a,g) will be replaced by whatever is in "new_c12_ag_adopted.txt".
> >
> >    "weak_rate_list.txt" holds the (rate name, rate file) pair for weak reactions.
> >    in this example, it is empty.
> >
> >    "new_c12_ag_adopted.txt" holds the (T8,rate) pairs to be interpolated and tabularized.
> >    in this example, its a rendition of the new deboer et al 2017 c12(a,g) rate.
> >
> > 4) in the &star_job part of your inlist activate the custom rate with
> >
> > ! set any specific reaction rates
> >        rate_tables_dir  = './rate_tables'
> >
> >
> > hopefully (a) i haven't forgotten anything and (b) you can morph this into whatever rate(s) one wants.
> >
> > fxt
> >
> >
> >
> >
> >
> > > On Sep 28, 2017, at 11:06 AM, Josiah Schwab via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> > >
> > > Hi Earl,
> > >
> > > Sorry for the extremely brief reply.  (Maybe more later.)
> > >
> > >> As far as I understand it, the default nuclear reaction rates in MESA
> > >> are the NACRE rates from Angulo et al. 1999 [1].
> > >>
> > >> In 2004, Formicola et al. [2] provided an update to the 14 N(p, γ) 15
> > >> O reaction.
> > >>
> > >> Is this rate in MESA at present, perhaps with a hook to toggle it?
> > >
> > > No.  But MESA has JINA reaclib v2.2, where the default is
> > >
> > >  https://groups.nscl.msu.edu/jina/reaclib/db/n14(p,g)o15/im05/
> > >
> > > from G. Imbriani et al. (2005).
> > >
> > > I would guess those are quite similar since Imbriani was 2nd author of
> > > Formicola, but I don't know.
> > >
> > >> Some grepping around indicates that the answer is 'probably not,' and
> > >> so short of that, has anyone implemented it already for their own use
> > >> and would be kind enough to share it?
> > >>
> > >> If not, I can implement it myself. I have a rough idea how to do it,
> > >> although having never waded here before, suggestions for how to do it
> > >> would also be appreciated :-)
> > >
> > > Take a look at the test_case custom rates for an example.
> > >
> > > Josiah
> >
> >
> >




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