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Deuterated Molecules in Star-Forming Regions

Kulczak-Jastrzębska M.

Acta Astronomica

2018

Vol. 68, No. 2

125--140

Imaging of the spatial distribution of deuterated molecules in several nearby low-mass star forming regions, as traced by the DCO+ (3-2) emission, suggests that the deuterated material is often displaced with respect to the highest column density regions, as traced by submillimeter dust continuum emission and sometimes appears to be associated with the high-velocity CO (2-1) emission, tracing outflow activity. High deuteration levels in isolated prestellar cores can be explained by gas-phase or grain-surface chemistry in dense, cold regions, where abundant gas-phase species are frozen onto dust grains - a process that is now relatively well understood. We argue that an alternative mechanism may operate in dense gas in the vicinity of embedded young stellar objects, where slow C-type shocks associated with molecular outflows may produce conditions favorable for deuterium fractionation either by increasing the gas volume density in the post-shock gas and thus, shortening the depletion and gas-phase reaction time-scales, or by evaporating grain mantle ices.

Orientation of the Orbital Planes of Visual Binary Systems

Głębocki R.

Acta Astronomica

2000

Vol. 50, No. 2

211--220

The space distribution of orbital poles for 252 visual binaries is analyzed to check a possible tendency towards parallelism. It is confirmed that orbital planes do not show any trend to be parallel to the Galactic plane. No strong evidence is found for a preferential orientation of the orbital planes for subgroups of binaries with similar periods and eccentricities. Asymmetry in the distribution of orbital poles is seen only for a subgroup of 19 binaries lying closer than 10 pc. Small differences in the distribution of orbital poles are also detected for subgroups with different location on HR diagram.