1998A&A...338..694V -
Astronomy and Astrophysics, volume 338, 694-712 (1998/10-2)
Detection of spatial variations in the (D/H) ratio in the local interstellar medium.
VIDAL-MADJAR A., LEMOINE M., FERLET R., HEBRARD G., KOESTER D., AUDOUZE J., CASSE M., VANGIONI-FLAM E. and WEBB J.
Abstract (from CDS):
We present high resolution (Δλ≃3.7km/s) HST-GHRS observations of the DA white dwarf G191-B2B, and derive the interstellar D/H ratio on the line of sight. We have observed and analysed simultaneously the interstellar lines of HI, DI, NI, OI, SiII and SiIII. We detect three absorbing clouds, and derive a total HI column density N(HI)=2.4±0.1x10
18cm
–2, confirming our Cycle 1 estimate, but in disagreement with other previous measurements. We derive an average D/H ratio over the three absorbing clouds N(Di)
total/N(HI)
total=1.12±0.08x10
–5, in disagreement with the previously reported value of the local D/H as reported by Linsky et al. (
1995ApJ...451..335L) toward Capella. We re-analyze the GHRS data of the Capella line of sight, and confirm their estimate, as we find (D/H)
Capella=1.56±0.1x10
–5 in the Local Interstellar Cloud in which the solar system is embedded. This shows that the D/H ratio varies by at least ∼30% within the local interstellar medium. Furthermore, the Local Interstellar Cloud is also detected toward G191-B2B, and we show that the D/H ratio in this component, toward G191-B2B, can be made compatible with that derived toward Capella. However, this comes at the expense of a much smaller value for the D/H ratio as averaged over the other two components, of order 0.9x10
–5, and in such a way that the D/H ratio as averaged over all three components remains at the above value, i.e. (D/H)
Total=1.12x10
–5. We thus conclude that, either the D/H ratio varies from cloud to cloud, and/or the D/H ratio varies within the Local Interstellar Cloud, in which the Sun is embedded, although our observations neither prove nor disprove this latter possibility.
Abstract Copyright:
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Journal keyword(s):
stars: individual: G191-B2B - ISM: abundances - ISM: atoms and ions - cosmology: observations - ultraviolet: ISM
Simbad objects:
6
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