[Mesa-users] The color and V band mag of the current Sun and solar-type stars

[Aaron Dotter]

Hi,

Does the MESA colors module, independently of the evolutionary track, give
a sufficiently accurate solar color?  (Keeping in mind that to measure the
color of the sun is notoriously difficult because it is so bright.)

It sounds like, for you, the answer to question 2 is No.  You cannot "fix"
this issue with additional physics in the evolutionary track.  The issue
lies within the colors data file used by the MESA colors module.

To make further progress, you would need to access an independent module
for calculating synthetic magnitudes (or calculate them yourself).  There
are a handful of these available.

How important is it that you are able to match B-V to better than 0.03?
There are a variety of small details that matter at this level . . .

Cheers,
Aaron


On Sat, Oct 5, 2019 at 4:50 PM M Sun <sunmeng1118 at gmail.com> wrote:

> Hello Aaron,
>
> Thank you very much for your suggestion! I've tested with working in
> simplex_solar_calibration directory and could produce a model close to the
> current Sun. When I checked back the (B - V) mag, it still bluer than
> observation about 0.03 mag. Here I attach the HR diagram, the color
> magnitude diagram and R vs Age plot when running solar calibration
> simulations. The initial conditions and the controls are attached as well.
>
> The stars I am working on have a different metallicity, the (B - V) mag
> disagreement between simulation and observation is bigger than this
> (although L and Teff are in a good agreement, there is a 0.06 mag of (B -V)
> between model and data). I am wondering if I forget some important physics
> when computing the colors. Or does anyone have this issue before and how do
> we fix it, especially near ZAMS and MS phase? Thanks!
>
> cheers,
> Meng
>
> On Fri, Oct 4, 2019 at 3:05 PM Aaron Dotter <aaron.dotter at gmail.com>
> wrote:
>
>> Before checking the magnitudes, I recommend you try to reproduce the
>> solar Teff, L, and R.  See, for example, the simplex_solar_calibration in
>> the test suite.
>>
>> Independently, check whether or not the mesa/colors module is able to
>> reproduce the solar colors for the solar metallicity, Teff and log(g).
>> This can be done irrespective of the solar evolutionary track; you can
>> simply call the colors module with the solar parameters as input.
>>
>> On Fri, Oct 4, 2019 at 3:54 PM M Sun via Mesa-users <
>> mesa-users at lists.mesastar.org> wrote:
>>
>>> Hello MESA users,
>>>
>>> Recently I am trying to produce some evolutionary tracks for solar-type
>>> stars in an open cluster. The luminosity, effective temperature agree with
>>> the observation very well. However, when I check the color magnitude
>>> diagram, those solar-type stars seem much bluer than observation near the
>>> main sequence phase.
>>>
>>> Then I tried to make a track for the current Sun with different initial
>>> metallicities and mixing length factors (still in the proper range I
>>> think), it is bluer than I expected as well. Here I attached my plot. The V
>>> mag and B mag I used for the current Sun (shown in the red star in the
>>> plot) are --
>>> solar_abs_V = 4.83
>>> solar_abs_B = 5.48
>>> The open circles indicate the age at 1, 2 ... 6 Gyrs from the
>>> bottom right to top left. I terminate the simulations after 6 Gyrs.
>>>
>>> I am using MESA 12115 in the test_suite working directory
>>> "1M_pre_ms_to_wd". Here I attached my inlists and please let me know if you
>>> need more information. The atmosphere table I used is 'photosphere'. Many
>>> thanks!!
>>>
>>> cheers,
>>> Meng
>>> --------------
>>> Meng Sun
>>> University of Wisconsin Madison
>>> https://sunmeng1118.wixsite.com/mysite
>>> _______________________________________________
>>> mesa-users at lists.mesastar.org
>>> https://lists.mesastar.org/mailman/listinfo/mesa-users
>>>
>>>
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