Lines as Continuous Opacity. Collaborators: D. J. Bord (Umich, Dearborn) Glenn Wahlgren, (Lund) Thanks to many others for advice. Main questions:. 1. Computational practicalities: ODF, OS, “individualized abundances. 2. Unclassified lines and their relation to photoionization “resonances.”.
Collaborators: D. J. Bord (Umich, Dearborn)
Glenn Wahlgren, (Lund)
Thanks to many others for advice.
1. Computational practicalities: ODF, OS, “individualized abundances.
2. Unclassified lines and their relation to photoionization “resonances.”
3. Relation to standard continuous opacity sources.
Relative importance of weak and strong lines.
4. Harmonic vs. straight means.
All questions depend on parameter space--
a. What is the wavelength interval?
b. What are the abundances?
c. What are the physical conditions (T, P, xt)?
d. How will integration through an atmosphere affect
answers to the above questions?
Current procedure is an in vitro approach, the physical
conditions are fixed. Some modification for production
is surely in order (cf. Piskunov&Kupka ApJ, 547 (2001)
Calculations based primarily on Kurucz CDRoms 20, 21,
22. Therefore Ca-Ni. Some REE III to be noted later.
Pull off all lines of first through third spectra within
20A intervals at selected wavelengths. Reformat
data; use very nearly input to standard Michigan
Line lists are typically 20-40,000 lines.
partition functions, so that for each line, the relevant number
density (cm-3) can be calculated.
Arrange filter so that in addition to using all lines, one may
a. classified lines (levels found in laboratory).
b. unclassified lines
c. lines with upper levels below first ionization limit
(take only lines subject to autoionization)
difference in this and synthesis code is there is only one
set of physical conditions—no integration through atmosphere.
Arbitrary abundances are possible.
Get ODF’s. We use 1024 points at 0.02A spacings. Divide
into 8 bins of 128 points.
ODF’s are much like histograms, except that one first does
an intensity sort before binning.
The straight mean of the opacity for the 1024 points is by
definition the same as the straight mean of the opacity in
the 8 bins.
mean is the more physical quantity, since the radiation
will escape through the transparent windows.
The harmonic mean for the 1024 points is not the same
as the harmonic mean of the 8 bins.
The harmonic mean of the bins is typically some five
per cent larger than the harmonic mean of the 1024
Photoionization Resonances (TopBase).
Transitions to levels subject to autoionization will in
principle have counterparts in photoionization cross sections.
In practice, this is only approximately true because of
incompleteness in both sets of calculations.
At the moment, Kurucz has more realistic sets of
states than TopBase, but no specific treatment of
interaction with continuum states.
If one calculates ODF’s including lines subject to autoionization and later includes TopBase continuous opacities, some transitions
are going to be counted twice! This may be only a difficulty in principle, as the opacity from the transitions in question is typically a small fraction of the total.
Line Opacity: All CDRom 20, 21, 22
Contributions from individual metals all below here
T = 6000K, Log(Pg) = 5.0, Solar Abundances 3800A
All 27627 lines
702 Classified Lines
Straight mean 1.94 E-06 1.92 E-06
Harmonic mean 1.94 E-08 1.07 E-08
Virtually all of the line opacity comes from the strong lines,
but the weaker lines are significant for the transparency
(Rosseland or harmonic mean).
Standard opacity sources:
Fe I (Atlas7)
This time Z = 10 – 28 10 x Solar
Using all 27627 lines
Straight mean of lines: 3.45E-5
Harmonic mean: 3.65E-7
Harmonic of 8 bins 3.84E-7
Total Continuous: 2.71E-7
Now, using 10 x Solar, but only unclassified lines (26925)
Straight mean of lines: 9.17E-7
Harmonic mean: 1.57E-7
Harmonic of 8 bins 1.62E-7
contribution relative to the standard continuous opacity
Among the unclassified lines, some will be strong, and
recognized as lines in the stellar spectrum, but will not
These lines will not be a part of the quasi-continuum, the
weak-line haze that cannot be distinguished from continuous
Some fraction of the unclassified lines should be added
to the continuous absorption.
to add to the continuous opacity when doing spectral
In solar work, we have augmented standard opacity
sources until the calculated specific intensity matches
In the UV, say 3600A, that can mean multiplying the
known continuous opacity by 1.6 or so!
If we don’t match the observed intensity, we aren’t
doing a calculation for the real sun!!
the effect of line opacity on a cool Ap or CP star.
In particular, we are interested in knowing what the
effects of lines from the third spectra of the REE might
We have calculated lines of Nd III and Sm III, and included
a few additional lines from the DREAM site.
What we found is that even with the REE overabundant
by a factor of 1000, the lines from the third spectra do
not seriously compete with standard opacity sources or
lines from the iron group.
10 x Z=22-28
1000 x Z> 57
10 x Z=22-28
Standard continuous opacity: 1.78E-07
Mostly b-f of neutral hydrogen
T = 8000 Log(Pg) = 4.0
Iron Group x 0.1, Lanthanides x 1000
Straight mean: 1.06 E-08
Harmonic mean: 1.80 E-10
Harmonic bins: 1.90 E-10
Standard Cont: 1.78 E-07
Conclusions: It does not seem likely that line opacity
from the third spectra of the REE competes significantly
with standard continuous opacity sources for most
For our 1024-point regions, we have not had much success
with opacity sampling. Perhaps it is just our limited
Random sampling 256 points can give a result in error by
a factor of two. Table gives ratio of sample to average of
all 1024 points. Since sample is random, 1024 points do
not give exact result.
Sample/No points Mrich Solar84