diff --git a/Exec/science/circular_det/_prob_params b/Exec/science/circular_det/_prob_params
index e781e95b79..44e0db3a3a 100644
--- a/Exec/science/circular_det/_prob_params
+++ b/Exec/science/circular_det/_prob_params
@@ -10,13 +10,16 @@ nfrac                real          0.0_rt         y
 
 ofrac                real          0.0_rt         y
 
+# dimensionless width of transition between hot and cold
 w_T                  real          5.e-4_rt       y
 
-center_T             real          0.3_rt         y
+# dimensionless semi-major axis
+a_T                  real          0.3_rt         y
 
-smallx               real          1.e-12_rt      y
+# eccentricity
+ecc_T                real          0.0            y
 
-idir                 integer       1              y
+smallx               real          1.e-12_rt      y
 
 ihe4                 integer       -1
 
diff --git a/Exec/science/circular_det/inputs b/Exec/science/circular_det/inputs
index cfb75abb68..e86483d1d9 100644
--- a/Exec/science/circular_det/inputs
+++ b/Exec/science/circular_det/inputs
@@ -40,7 +40,7 @@ castro.use_flattening = 1
 castro.riemann_solver = 1
 
 # TIME STEP CONTROL
-castro.cfl            = 0.5     # cfl number for hyperbolic system
+castro.cfl            = 0.4     # cfl number for hyperbolic system
 castro.init_shrink    = 0.1     # scale back initial timestep
 castro.change_max     = 1.05    # scale back initial timestep
 
@@ -82,8 +82,9 @@ problem.smallx = 1.e-10
 
 problem.idir = 1
 
-problem.w_T = 1.e-3
-problem.center_T = 0.1
+problem.w_T = 1.e-2
+problem.a_T = 0.15
+problem.ecc_T = 0.7
 
 # refinement
 
diff --git a/Exec/science/circular_det/problem_initialize_state_data.H b/Exec/science/circular_det/problem_initialize_state_data.H
index 9c820e2845..579e3346c8 100644
--- a/Exec/science/circular_det/problem_initialize_state_data.H
+++ b/Exec/science/circular_det/problem_initialize_state_data.H
@@ -15,18 +15,22 @@ void problem_initialize_state_data (int i, int j, int k,
     const Real* problo = geomdata.ProbLo();
     const Real* probhi = geomdata.ProbHi();
 
-    Real width = problem::w_T * (probhi[0] - problo[0]);
-    Real c_T = problem::center_T * (probhi[0] - problo[0]);
+    // semi-major axis
+    Real a = problem::a_T * (probhi[0] - problo[0]);
+
+    // semi-minor axis
+    Real b = a * std::sqrt(1.0 - problem::ecc_T * problem::ecc_T);
 
     // compute distance from the center
     Real xx = problo[0] + dx[0] * (static_cast<Real>(i) + 0.5_rt) - problem::center[0];
     Real yy = problo[1] + dx[1] * (static_cast<Real>(j) + 0.5_rt) - problem::center[1];
 
-    Real r = std::sqrt(xx * xx + yy * yy);
+    Real r = std::sqrt((xx / a) * (xx / a) +
+                       (yy / b) * (yy / b));
 
     state(i,j,k,URHO) = problem::dens;
 
-    Real sigma = 1.0_rt / (1.0_rt + std::exp(-(c_T - r)/ width));
+    Real sigma = 1.0_rt / (1.0_rt + std::exp(-(1.0_rt - r)/ problem::w_T));
 
     state(i,j,k,UTEMP) = problem::T_l + (problem::T_r - problem::T_l) * (1.0_rt - sigma);