We examine phantom dark energy models produced by a field with a negative kinetic term and a potential that satisfies the slow roll conditions : [ ( 1 / V ) ( dV / d \phi ) ] ^ { 2 } \ll 1 and ( 1 / V ) ( d ^ { 2 } V / d \phi ^ { 2 } ) \ll 1 .
Such models provide a natural mechanism to produce an equation of state parameter , w , slightly less than -1 at present .
Using techniques previously applied to quintessence , we show that in this limit , all such phantom models converge to a single expression for w ( a ) , which is a function only of the present-day values of \Omega _ { \phi } and w .
This expression is identical to the corresponding behavior of w ( a ) for quintessence models in the same limit .
At redshifts z \lesssim 1 , this limiting behavior is well fit by the linear parametrization , w = w _ { 0 } + w _ { a } ( 1 - a ) , with w _ { a } \approx - 1.5 ( 1 + w _ { 0 } ) .