( Mostly) Atomic and (Some ) Molecular Data for Analytic Stellar Spectroscopy. Charles R. Cowley: U. Michigan Saul J. Adelman: The Citadel Donald J. Bord: UM Dearborn. Lots of help from many others!!. Outline of Talk. Ionization Energies for neutrals and first four ions.
(Mostly) Atomic and (Some ) Molecular Data for AnalyticStellar Spectroscopy
Charles R. Cowley: U. Michigan
Saul J. Adelman: The Citadel
Donald J. Bord: UM Dearborn
Lots of help from many others!!
Outline of Talk
2. Atomic Data Bases
3. Partition functions
4. Opacity: photoionization cross sections; TopBase
Part 1: Ionization Energies
Visit our website:
Or, a number of others for more general info:
Part 2: Atomic Data
For Atomic Data, conveniently arranged for
spectral synthesis, two primary sources:
There may be other instances in the history of
science where so many have owed so much to
so few, but I don’t know of them.
Both of these sites are under continuous
Generally speaking: Either of these sources will
provide the basis for an encouraging synthesis
of atomic features in most stars.
Details are another matter. Even within small wavelength intervals,
of 5 to 10 A, there are generally a few features for which one cannot
find an appropriate atomic line, even by modifying the oscillator
strength by an order of magnitude or more.
This is typical in a region with molecular features, when using VALD,
which has not (as of May 2002) yet included molecules.
But it is also common in other regions, and very probably due to
incompleteness of atomic data: Either the lines are not in the
data bases, or the oscillator strengths are egregiously in error.
Here is a rather shocking plot comparing VALD
and Kurucz-site log(gf)’s for Fe I
Standard deviation: 0.86
Standard error: 0.05
The big differences are all for “second-generation
lines,” lines not in the Multiplet Tables. So they are
not lines typically studied.
However, they are all from classifies levels, and
would appear in any spectrum synthesis.
Generally speaking, one might prefer VALD for
elements heavier than the iron peak.
Changes in the Kurucz data beyond what is on
the CDRoms (and therefore in VALD) are mostly
for the important spectra of Fe I and Fe II.
This was the situation when I browsed the
Kurucz site at the end of March 2002, and it
it subject to change.
We have choices other than just RLK
Check the NIST site, and hunt around among the
links. An E-book is nearing completion, which
will contain much useful information on the first
two spectra of elements from H to Es. There will
be wavelengths for some 11,000 lines, but gf’s
for only about 2500 lines.
A NIST project that is just beginning will have much more extensive data, including gf’s and hfs.
Of course, any improvements by NIST should be
incorporated in VALD and Kurucz data bases!
The Main Problem is PERSON Power
Snooping on the internet can bring up a wealth
of relevant information.
Here are just a few examples of places from which
one can get useful data:
Be advised that sometimes, one must get a
reference, and then pull up the journal electronically.
Here is an incomplete example of what one can find.
Part 3: Partition functions
Focus on two aspects of partition functions:
1. Completeness of low levels.
2. Treatment of levels above those known
Various algorithms are in use to give the
partition function u(T). Undoubtedly some
are better than others. All must be based
on data that is sufficiently complete.
Partition functions are important, algorithms
Added levels from
Cowan code, or
REE III (1994)
Ho II, W, Os
Mostly the changes are
small—a few per cent,
except in cases where
ranks were D, E, or
For Ho II, nearly 50%:
Following a little-known study by Van’t Veer-Menneret
(CR, 253, 380, 1961), we assert that the contribution
to the partition function from levels above those
typically known, ARE NOT IMPORTANT for the cal-
culation of line strengths.
It is easy to see this in a simple case. We consider
the situation where the dominant ion is the first—
virtually all atoms are first ionized. But, we are
to compute a line arising from the first (neutral)
We assert that in general, the partition function
for the atom or ion (i) is unimportant for the
line strength if the element is predominantly
(i+1)-th fold ionized.
It is easy to see from the previous slide that this
must be approximately the case, but the assertion
covers a lot of parameter space, and should be
checked for special cases.
Part 4: Photoionization cross sections
“Opacity of opacity, saith the Preacher, opacity
of opacity; all is opacity.”
From a recently translated Agnostic gospel.
Red level interacts
First ionization limit
are in Kurucz
Solid line: TopBase
(H and K)
It is straightforward to smooth these TopBase
cross sections without changing the net absorption.
This has been done by a number of people, and
systematically by Prieto (2002).
The next step, already being carried out, is to
parameterize the smoothed fits for use in opacity
routines, such as si1op, al1op, fe1op, etc. used
in the Atlas codes. These routines give what I
call the “K-factor”:
Ca I 4s4d 1D
Epilog: Molecular Spectra, et al.
Best overall site: cfaku5.harvard.edu. New TiO, H2O
RadEn Database: www.chem.msu.su/eng/raden/
Atomic and Molecular Data and software: ccp7.dur.ac.uk
DREAM (REE): www.umh.ac.be/~astro/dream.shtml
Thank you Thank you Thank you