add a readme for subchandra (#2776)

also fix a typo and formatting in the flame_wave readme

Exec/science/flame_wave/README.md

@@ -1,28 +1,34 @@
 # flame_wave
 
-This is the XRB flame setup.  I has been used for several
-papers, including:
+This is the XRB flame setup.  It has been used for several papers,
+including:
 
-* Eiden et al. 2020 (https://ui.adsabs.harvard.edu/abs/2020ApJ...894....6E)
+* Eiden et al. 2020
+  (https://ui.adsabs.harvard.edu/abs/2020ApJ...894....6E)
 
   This modeled pure He flames and used "boosted" flames, which were
   artificially sped up.
 
-* Harpole et al. 2021 (https://ui.adsabs.harvard.edu/abs/2021ApJ...912...36H/abstract)
+* Harpole et al. 2021
+  (https://ui.adsabs.harvard.edu/abs/2021ApJ...912...36H/abstract)
 
-  This also modeled pure He flames, but without any boosting.  A variety of
-  rotation rates were explored.  The inputs files for this are in `inputs_He/`
+  This also modeled pure He flames, but without any boosting.  A
+  variety of rotation rates were explored.  The inputs files for this
+  are in `inputs_He/`
 
-* Zingale et al. 2023 (https://ui.adsabs.harvard.edu/abs/2023ApJ...952..160Z/abstract)
+* Zingale et al. 2023
+  (https://ui.adsabs.harvard.edu/abs/2023ApJ...952..160Z/abstract)
 
   This explored both 2D and 3D pure He flames.  Another change was in
   the lower boundary condition -- a reflecting boundary was used an
   `castro.use_pslope` was enabled.  The inputs files for this are in
   `inputs_He/` and also available on Zenodo:
   https://zenodo.org/record/7692201
 
-* Chen et al. 2023 (https://ui.adsabs.harvard.edu/abs/2023ApJ...955..128C/abstract)
+* Chen et al. 2023
+  (https://ui.adsabs.harvard.edu/abs/2023ApJ...955..128C/abstract)
 
-  This looked at 2D pure He flames and explored different reaction networks.
-  The inputs files are available on Zenodo: https://zenodo.org/record/8117761
+  This looked at 2D pure He flames and explored different reaction
+  networks.  The inputs files are available on Zenodo:
+  https://zenodo.org/record/8117761
 

Exec/science/subchandra/README.md

@@ -0,0 +1,24 @@
+# subchandra
+
+This is the double detonation Type Ia supernova setup.  It takes a 1-d
+initial model representing a sub-Chandra WD and a surface He layer and
+initializes a small perturbation at the pole in the He layer.
+
+Initial models for this setup can be created via
+https://github.com/AMReX-Astro/initial_models in the sub_chandra/ directory.
+
+This setup has been used in the following papers:
+
+* Zingale et al. 2022
+  (https://ui.adsabs.harvard.edu/abs/2022ApJ...936....6Z/abstract)
+
+  This paper introduced the simplified-SDC time-integration method and
+  used the double detonation setup as a test problem.
+
+* Zingale et al. 2024
+  (https://ui.adsabs.harvard.edu/abs/2023arXiv230901802Z/abstract)
+
+  This paper showed that the simplified-SDC method can model double
+  detonations without cutting the timestep or limiting the reaction
+  rates.  It also explored disabling burning in shocks for this
+  problem.