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The Low Excitation Planetary Nebulae HuDo 1 and HuBi 1 and their [WC10] Central Stars

Low- and high-resolution spectra of the planetary nebulae HuDo 1 and HuBi 1, around [WC-late] stars, are analyzed. The objects belong to the galactic disk, with heliocentric radial velocities of -12 km/s (HuDo 1) and 57 km/s (HuBi 1). C(Hbeta) reddening values are of 2.04 for HuDo 1 and 1.22 for HuBi 1. Plasma line ratios are used to estimate physical conditions and abundances. We find log (O/H)+12 = 8.43 and 8.57, and N/O = 0.2 and 0.1 for HuDo 1 and HuBi 1 respectively. HuBi 1 is the only PN excited by a very late [WC] star showing intense nebular HeI recombination lines. From the stellar lines we derive a [WC 10] type for both stars, although HuBi 1 central star should be slightly hotter for providing a large amount of He^0 ionizing photons. Nebular and stellar parameters of HuDo 1 and HuBi 1 are compared with those of other [WC 10] objects, concluding that the stars of HuDo 1 and HuBi 1 should be intrinsically fainter. In particular HuBi 1 seems a low-density evolved nebula around a low-mass slowly-evolving star.