We study the phase structure and equation of state for two-flavor quark
matter at low temperature under compact star constraints within a nonlocal
chiral quark model. We find that the occurence of a two-flavor color
superconducting (2SC) phase is sensitive to variations of both the formfactor
of the interaction and the ratio \eta between the coupling constants in the
diquark and the scalar meson channels. Our study suggests that for standard
values of the coupling ratio 0.5<\eta<0.75 either the 2SC phase does not occur
(Gaussian formfactor) or it exists only in a mixed phase with normal quark
matter (NQ-2SC) with a volume fraction less than 20 - 40 %, occuring at high
baryon chemical potentials \mu_B >1200 MeV and most likely not relevant for
compact stars. We also present the relevant region of the phase diagram for
compact star applications and obtain that no gapless 2SC occurs at low
temperatures.Comment: 19 pages, 9 figures, Subsec.2.5: "Phase diagram" adde