add a utility to find xrb ignition condition following "settle"

networks/general_null/xrb_ignition.net

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+# this is the null description for the X-ray burst ignition condition
+#
+
+# name short-name aion zion
+ hydrogen-1   H1    1.0  1.0
+ helium-4     He4   4.0  2.0
+ oxygen-14    O14  14.0  8.0
+ oxygen-15    O15  15.0  8.0

util/xrb_ignition/GNUmakefile

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+PRECISION  = DOUBLE
+PROFILE    = FALSE
+
+DEBUG      = FALSE
+
+DIM        = 3
+
+COMP       = gnu
+
+USE_MPI    = FALSE
+USE_OMP    = FALSE
+
+USE_REACT = TRUE
+
+EBASE = main
+
+# define the location of the Microphysics top directory
+MICROPHYSICS_HOME  := ../..
+
+# This sets the EOS directory
+EOS_DIR     := helmholtz
+
+# This sets the network directory
+NETWORK_DIR := general_null
+NETWORK_INPUTS := xrb_ignition.net
+
+USE_CONDUCTIVITY := TRUE
+CONDUCTIVITY_DIR := stellar
+
+USE_SCREENING := TRUE
+SCREEN_METHOD := screen5
+
+USE_SIMPLIFIED_SDC = TRUE
+
+EXTERN_SEARCH += .
+
+Bpack   := ./Make.package
+Blocs   := .
+
+include $(MICROPHYSICS_HOME)/unit_test/Make.unit_test

util/xrb_ignition/Make.package

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+CEXE_sources += main.cpp
+CEXE_headers += ignition_condition.H

util/xrb_ignition/README.md

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+# `xrb_ignition`
+
+`xrb_ignition` finds the ignition condition of the X-ray burst
+based on https://github.com/andrewcumming/settle
+See DOI: 10.1086/317191 for details.
+
+Usage:
+./main.ex <X> <Z> <Fb> <mdot> <COMPRESS>
+
+X: Hydrogen massfraction
+Z: CNO massfraction
+Fb: Base Flux in MeV/nucleon/mdot
+mdot: Local accretion rate in Eddington unit
+COMPRESS: To include compressional heating or not.

util/xrb_ignition/_parameters

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+@namespace: unit_test
+
+run_prefix    string     ""
+
+X             real    0.71
+Z             real    0.01
+mdot          real    0.1
+Fb            real    150.0
+COMPRESS      int     0