Limb darkening parameters

PHOEBE keyword	Type	Short description
XBOL1	adjustable	Bolometric LD coefficient $x_1$
YBOL1	adjustable	Bolometric LD coefficient $y_1$
XBOL2	adjustable	Bolometric LD coefficient $x_2$
YBOL2	adjustable	Bolometric LD coefficient $y_2$
X1ALC	adjustable	Passband LD coefficient $x_1^{LC}$
Y1ALC	adjustable	Passband LD coefficient $y_1^{LC}$
X2ALC	adjustable	Passband LD coefficient $x_2^{LC}$
Y2ALC	adjustable	Passband LD coefficient $x_2^{LC}$