[Mesa-users] Modeling DC spectral type WDs

[Montgomery, Michael H]

Hi Momin,

“DC” is a spectral classification meaning no lines, just “continuum”. Using AI I got this reasonable description:


  *   Atmospheric Composition: Most DC white dwarfs are believed to have helium-dominated atmospheres. However, as they cool, even hydrogen-rich white dwarfs can become DC types.
  *   Temperature Range: DC types typically appear at lower effective temperatures (
[wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==.gif]
Teff
𝑇eff
):
     *   Helium atmospheres transition from DB to DC below approximately 11,000 K.
     *   Hydrogen atmospheres transition from DA to DC below roughly 5,000 K.
  *   The "Line-Free" Mechanism: The lack of spectral features occurs because the star's atmosphere is too cool to provide the energy needed to excite atomic transitions<https://science.nasa.gov/asset/hubble/signature-of-a-white-dwarf/> in helium or hydrogen, making the lines invisible to optical telescopes

So, if you wait for the evolutionary model to get cool enough, it will eventually look like a DC, even though when it was hotter it was a normal DA or DB.

Does this help?

Cheers,

Mike
_____________________________________

Michael Houston Montgomery
Research Scientist
Director of WCAPP
Research Educator, FRI Program
Department of Astronomy
University of Texas
mikemon at astro.as.utexas.edu
www.as.utexas.edu/~mikemon/
_____________________________________

On Feb 25, 2026, at 10:30 AM, Khan, Momin via Mesa-users <mesa-users at lists.mesastar.org> wrote:

Hello all,

I am wanting to model a DC spectral type white dwarf in MESA and am troubled on how to start. I have successfully made H rich white dwarfs in MESA using existing test suites and now want to make something slightly different. These stars are void of any spectral features, so is it enough to remove surface abundances of H, He, etc. with some remove envelope function? Or just by cooling my H rich WD down enough will I have "made" a DC WD? Any suggestions would be greatly appreciated, thanks!


Momin Khan
Graduate Teaching Assistant
Department of Physics and Astronomy
Baylor Science Building E.362R.1
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