Effects of high velocities on photoionization lines |
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| Authors: | A Peraiah G Raghunath |
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| Institution: | (1) Indian Institute of Astrophysics, 560034 Bangalore |
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| Abstract: | We have treated formation of spectral lines in a commoving frame where photoionization is predominant over collisional processes.
We have assumed that the radiation field for causing photoionization is a function of Planck function. We have also considered
the situation in which the continuum contributes to the radiation in the line. In all the models the quantityB/A (ratio of outer to inner radii) is kept equal to 10 and the total optical depth is taken to be 103. The velocity is assumed to be varying according to the lawdV/dτ ∼ < 1/τ whereτ is the optical depth (τ > 0) in the given shell. The velocities at the innermost radius (r =A) are set equal to 0 and at the outermost radius (r =B), the maximum velocities are taken to be 0, 1, 3 and 10 Doppler units. The calculated line profiles are those seen by an observer
at infinity.P Cygni-type profiles are observed in the case of a medium with no continuum absorption. For a medium with continuum absorption
double peaked asymmetric profiles are noticed when the velocities are small; the two emission peaks merge into a single asymmetric
peak for larger velocities. |
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| Keywords: | photoionization lines— comoving frame— radiative transfer equation |
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