  The presence of blue-cored dwarf early-type galaxies (dE(bc)s) in
high-density environments supports the scenario of the transformation of
infalling late-type galaxies into quiescent dwarf early-type galaxies by
environmental effects. While low-density environments lacking environmental
processes could not be relevant to the formation of dE(bc)s, we discovered a
large sample of rare dE(bc)s in isolated environments at z < 0.01 using the
NASA-Sloan Atlas catalog. Thirty-two isolated dE(bc)s were identified by visual
inspection of the Sloan Digital Sky Survey images and g - r color profiles. We
found that (1) isolated dE(bc)s exhibit similar structural parameters to
dE(bc)s in the Virgo cluster; (2) based on the ultraviolet-r color-magnitude
relation, color gradients, and optical emission lines of dE(bc)s, isolated
dE(bc)s show more vigorous, centrally concentrated SF compared to their
counterparts in the Virgo cluster; (3) at a given stellar mass, isolated
dE(bc)s tend to have a larger fraction of gas mass than their Virgo
counterparts. We discuss a scenario of episodic SF sustained by gas accretion,
suggested by Sanchez Almeida et al., in which the star-bursting blue compact
dwarf galaxy (BCD)-quiescent BCD (QBCD) cycle can be repeated during the Hubble
time. We suggest that, in this cadence, isolated dE(bc)s might be QBCDs at pre-
or post-BCD stages. Our results imply that dE(bc)s comprise a mixture of
objects with two types of origins, nature or nurture, depending on their
environment.
