M. Peña
Instituto de Astronomía, UNAM, Apdo. Postal 70-264, 04510 México D. F., México (miriam@astroscu.unam.mx).
Received, 2005 January 17
Accepted, 2005 May 16
]]> RESUMEN
Se analizan datos espectroscópicos de alta y baja resolución de las nebulosas planetarias con estrella central [WC] tardía, HuDo 1 y HuBi 1. Ambos objetos pertenecen al disco galáctico y tienen velocidades radiales heliocéntricas de —12 km s-1 (HuDo 1) y 57 km s-1 (HuBi 1). El enrojecimiento logarítmico, c(H/β), es de 2.04 para HuDo 1 y 1.22 para HuBi 1. Se deriva la composición química del plasma, obteniéndose log(O/H)+12 = 8.43 y 8.57, y N/O = 0.2 y 0.1 para HuDo 1 y HuBi 1 respectivamente. HuBi 1 es la única NP excitada por una estrella [WC10] muy tardía que muestra líneas intensas de He I. A partir de las líneas estelares, se deriva un tipo espectral [WC 10] para ambas estrellas, aunque la estrella de HuBi 1 debe ser ligeramente más caliente para proporcionar suficientes fotones ionizantes de He0. Al comparar los parámetros estelares de estos objetos con los de objetos similares, se encuentra que las estrellas de HuDo 1 y HuBi 1 deben ser intrínsecamente más débiles. En particular HuBi 1 parece ser una nebulosa ionizada por una estrella de baja masa que evoluciona lentamente.
ABSTRACT
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-1 (HuDo 1) and 57 km s-1 (HuBi 1). C(H/β) 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 He I recombination lines. From the stellar lines we derive a [WC 10] type for both stars, although HuBi 1 central star should be slightly hotter to provide a large amount of He0 ionizing photons. Nebular and stellar parameters of HuDo 1 and HuBi 1 are compared with those of other [WC 10] objects, and we conclude 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.
Key Words: Planetary Nebulae: Individual (HuDo 1, HuBi 1) — Stars: Post-AGB — Stars: Wolf-Rayet.
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ACKNOWLEDGMENTS
]]> Professional and technical support from the members of the staff at Observatorio Astronómico Nacional, M. Richer, F. Montalvo, and G. García, is gratefully acknowledged. This work received partial financial support from CONACYT-México and DGAPA-UNAM (grant IN114601).
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1 Based on data collected at the Observatorio Astronómico Nacional, San Pedro Mártir, Ensenada, B. C., México.
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