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We have analyzed 866 RXTE observations of the 2006-2007 outburst of theaccreting neutron star XTE J1701-462, during which the source evolves fromsuper-Eddington luminosities to quiescence. The X-ray color evolution firstresembles the Cyg X-2 subgroup of Z sources, with frequent excursions on thehorizontal and normal branches (HB/NB). The source then decays and evolves tothe Sco X-1 subgroup, with increasing focus on the flaring branch (FB) and thelower vertex of the "Z". Finally, the FB subsides, and the source transformsinto an atoll source, with the lower vertex evolving to the atoll soft state.Spectral analyses suggest that the atoll stage is characterized by a constantinner disk radius, while the Z stages exhibit a luminosity-dependent expansionof the inner disk, which we interpret as effects related to the local Eddingtonlimit. Contrary to the view that the mass accretion rate ($\dot{m}$) changesalong the Z, we find that changes in $\dot{m}$ are instead responsible for thesecular evolution of the Z and the subclasses. Motion along the Z branchesappears to be caused by three different mechanisms that may operate at roughlyconstant $\dot{m}$. For the Sco X-1-like Z stage, we find that the FB is aninstability track that proceeds off the lower vertex when the inner disk radiusshrinks from the value set by the X-ray luminosity toward the value measuredfor the atoll soft state. Excursions up the NB occur when the apparent size ofthe boundary layer increases while the disk exhibits little change. The HB isassociated with Comptonization of the disk emission. The Z branches for the CygX-2-like stage are more complicated, and their origin is unclear. Finally, ourspectral results lead us to hypothesize that the lower and upper Z verticescorrespond to a standard thin disk and a slim disk, respectively.

Spectral States of XTE J1701-462: Link between Z and Atoll Sources