Bibcode
Vladilo, G.; Centurion, M.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 240, no. 2, Dec. 1990, p. 476-480.
Fecha de publicación:
12
1990
Número de citas
2
Número de citas referidas
2
Descripción
We present a new determination of the interstellar
12CH+/13CH+ ratio in the
solar neighbourhood, based on high spectral resolution CCD observations
of the CH+ molecule in the direction of the star HD 26676 (d
≃ 150 pc). The measured absorption at λ4233 Å is one
of the most intense 12CH+ lines detected so far
(Wλ =23.5 mÅ), and is produced in the reflection
nebula surrounding HD 26676. The corresponding
13CH+ absorption (Wλ =
0.37±0.l7 mÅ), observed for the first time in a star
fainter than mυ = 6m, is detected at 3.6
level. After taking into account the saturation effects, we derive an
abundance ratio of
12CH+/13CH+ = 77±36,
where the error bar includes a conservative estimate of the uncertainty
in the continuum level. Our result is only marginally consistent with
the low values (12CH+/13CH+
≃ 41) derived by Hawkins & Jura (1987) for two reflection
nebulae (20 Tau, 23 Tau) in the same Galactic region as HD 26676, and
therefore it does not support a decrease by a factor of 2 of the
12C/13C ratio since formation of the Sun. A modest
decrease of this ratio in the solar vicinity, in agreement with the most
recent models of Galactic chemical evolution, and similar to the one
observed by Stahl et al. (1989) towards ζ Oph, is more consistent
with our result.