342 research outputs found
Adenine Abundance in a Collapsing Molecular Cloud
A vital ingredient of DNA molecule named adenine may be produced by
successive addition of HCN during molecular cloud collapse and star formation.
We compute its abundance in a collapsing cloud as a function of the reaction
rate and show that in much of the circumstances the resulting amount may be
sufficient to contaminate planets, comets and meteorites. We introduce a
-parameter which may be used to study the abundance where radiative
association takes place.Comment: Six pages and one figure. Accepted for Publication in Indian Journal
of Physics (April 1, 2000 issue
Global Solutions of Viscous Transonic Flows in Kerr Geometry I: Weak Viscosity Limit
We present fully general relativistic equations governing viscous transonic
flows in vertical equilibrium in Kerr geometry. We find the complete set of
global solutions (both for Optically thick and optically thin flows) in the
weak viscosity limit. We show that for a large region of parameter space,
centrifugal pressure supported standing shocks can form in accretion and winds
very close to the black hole horizon, both for co-rotating and contra-rotating
flows. We compute the nature of the shear tensor for complete transonic
solutions and discuss the consequences of its reversal properties.Comment: Latex 10 pages, special macro psfig.tex are include
Spectral Softening due to Winds in Accretion Disks
Accretion flows may produce profuse winds when they have positive specific
energy. Winds deplete matter from the inner region of the disk and makes the
inner region thinner, optically. Since there are fewer electrons in this
region, it becomes easier to Comptonize this part by the soft photons which are
intercepted from the Keplerian disk farther out. We present a self-consistent
picture of winds from an accretion disk and show how the spectra of the disk is
softened due to the outflowing wind.Comment: 6 Latex pages and three figures. Correction in figure description.
Published in Indian Journal of Physics, V. 72B, p. 565-569, 199
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