Dust in the Outer Layers of Stars M. Dikpati [Thesis]

By: Contributor(s): Material type: TextTextDescription: iii, 165pOnline resources: Dissertation note: Doctor of Philosophy Karnataka university,Dharwad 1990 Summary: We have studied the effects of expansion of dusty matter in spherically symmetric atmospheres I on equivalent widths of the spectral lines form in such media. We have treated a two level atom in non-LTE. Initially the hydrogen Lyman Alpha line has been studied for the purpose of calculating the effects of number density of the neutral atoms on equivalent widths. The temperature variation has been derived from the assumption that the Planck function varies as l/r2 in an atmospheres with pure hydrogen gas. Using this temperature structure and Boltzmann equation I we calculated the number of neutral atoms which formed the hydrogen Lyman Alpha Line. The dust has been introduced assuming that there is no reemission from the dust and that dust scatters isotropic ally. This is because the emission of dust will be in the infrared and will not contribute to the emission to the hydrogen Lyman commoving frame method line transfer equation. Alpha Line. We have employed the for obtaining the solution of the The velocities of expansion are measured in terms of mean thermal units and the amounts of gas and dust are measured in terms of the respective optical depths. We have considered two atmospheres: onewithout emission and two- with emission in the medium due to thermalization of photons. In a static medium we obtain symmetric profiles and when the velocity of expansion is introduced we generally obtain P-Cygni type profiles i.e. the absorption being shifted towards the violet side or emission peak remains at the center gravity of the line. If we introduce dust the emission reduce considerably whiIe dust scatters more photons into the absorpiton core. When there is no dust the absorption core is very wide extending approximately to three Doppler units of either side of the center of the lines.
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Doctor of Philosophy Karnataka university,Dharwad 1990

We have studied the effects of expansion of dusty
matter in spherically symmetric atmospheres I on equivalent
widths of the spectral lines form in such media. We have
treated a two level atom in non-LTE. Initially the hydrogen
Lyman Alpha line has been studied for the purpose of calculating
the effects of number density of the neutral atoms on
equivalent widths. The temperature variation has been derived
from the assumption that the Planck function varies
as l/r2 in an atmospheres with pure hydrogen gas. Using
this temperature structure and Boltzmann equation I we calculated
the number of neutral atoms which formed the hydrogen
Lyman Alpha Line.
The dust has been introduced assuming that there
is no reemission from the dust and that dust scatters isotropic ally.
This is because the emission of dust will be
in the infrared and will not contribute to the emission
to the hydrogen Lyman
commoving frame method
line transfer equation.
Alpha Line. We have employed the
for obtaining the solution of the
The velocities of expansion are
measured in terms of mean thermal units and the amounts
of gas and dust are measured in terms of the respective
optical depths. We have considered two atmospheres: onewithout
emission and two- with emission in the medium due
to thermalization of photons.
In a static medium we obtain symmetric profiles and
when the velocity of expansion is introduced we generally
obtain P-Cygni type profiles i.e. the absorption being shifted
towards the violet side or emission peak remains at the
center gravity of the line. If we introduce dust the emission
reduce considerably whiIe dust scatters more photons
into the absorpiton core. When there is no dust the absorption
core is very wide extending approximately to three
Doppler units of either side of the center of the lines.

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