Note:
This page describes an access to the old version of topbase;
use preferably the TIPTOP dabase of the
OPACITY project and Iron Project.
1 The Opacity Project
The name
Opacity Project (OP) refers to an international collaboration
that was formed in 1984 to calculate the extensive atomic data
required to estimate
stellar envelope opacities and to compute Rosseland-mean opacities
and other related quantities.
It has involved research groups from France,
Germany, the United Kingdom, the United States and Venezuela. The approach
adopted by the OP to calculate opacities is based on a new formalism of the
equation of state (see
MHD)
and on the computation of accurate atomic properties such
as energy levels, f-values and photoionization cross sections.
References:
- Hummer, D.G. and Mihalas, D., 1988.
Astrophys. J. 331, 794 (1988ApJ...331..794H)
(MHD)
- Seaton, M.J., 1987. J. Phys. B 20, 6363 (1987JPhB...20.6363S)
- Seaton, M.J., Zeippen, C.J., Tully, J.A., Pradhan, A.K., Mendoza, C.,
Hibbert, A. and Berrington, K.A., 1992. Rev. Mexicana Astron. Astrofis.
23, 19 (1992RMxAA..23...19S)
- Cunto, W. and Mendoza, C., 1992. Rev. Mexicana Astron. Astrofis.
23, 107 (1992RMxAA..23..107C)
- The Opacity Project Team, 1995, The Opacity Project, Vol. 1,
Institute Of Physics Publishing, Bristol, ISBN 0-7503-0288-7
- Seaton, M.J., Yu Yan, Mihalas, D., Pradhan, A.K., 1994,
MNRAS 266, 805 (SYMP) (1994MNRAS.266..805S)
2 What is TOPbase ?
TOPbase is a read-only database system specially designed for general use of
the OP atomic data. It contains energy levels, f-values and photoionization
cross sections for astrophysically abundant elements. The software tool
is an attempt to provide a suitable and uniform framework capable of offering:
- The possibility of intensive use of the OP atomic data
- Access to a complete and accurate dataset
- Transparency for a wide range of computational platforms
- Time and space efficiency
- Low cost.
The present TOPbase version (0.6) has been specifically developed for
interactive use of the data, and allows the ftp of selected data files.
It contains data for ions with the following atomic and electron numbers:
- NZ=1-14; NZ=16; NZ=18; NZ=20; NZ=26
- NE=1-24 (where for any ion NE .LE. NZ)
It can load in main memory at any time up to 250K records (e-levels or
f-values) and up to 500K photoionization-cross-section points.
References:
- Cunto, W., Mendoza, C., Ochsenbein, F., Zeippen, C.J., 1993,
A&A 275, L5 (1993A&A...275L...5C)
Documentation:
A TOPbase user manual is now available
on the web;
the tex version of
the user manual is provided through ftp.
Access to the TOPbase program:
- European site at CDS, Strasbourg:
Connect via ssh2 to
topbase@cdsarc.u-strasbg.fr
(give as password: Seaton+ )
enter as username: topbase
as password: Seaton+
and the TOPbase programs starts immediately. The user is provided with a
temporary directory from which files can be ftp'ed at the end of the session.
Graphic plots are available on X11 station, if you specify your
DISPLAY
internet address. A
DISPLAY variable is normally your Xstation Internet
number followed by :0, for instance
130.12.12.17:0
User support:
Questions and problems concerning the present implementation of Topbase
can be mailed to:
3 Data for OP opacities
The monochromatic opacities
σν(k) for each element
k
have been calculated assuming local thermodynamical equilibrium (LTE)
and have been archived as functions of frequency
ν on a mesh
of values of
(T, Ne) where
T is temperature and
Ne is electron density.
Calculations have been made for 17 elements:
H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe and Ni.
The amount of data is large, some 650 Mb as binary files.
- Tables of Rosseland- and Planck-mean opacities
in standard OP format for S92 metal abundances (defined in SYMP)
and 213 fixed values of mass fractions
X (hydrogen) and Z (metals). Together with a code opfit
which allows interpolation to any required values of
temperature T and mass-density ρ
(see OPF).
Click here for Opacity Computations.
- Tables of opacities and information about their
derivatives with respect to abundances. A code ixz allows
for interpolations in X and Z. It can be used to obtain
tables in standard format for any chosen values of X and Z
(see IXZ)
- Data for the calculation of radiative forces
(to be added shortly)
Assuming large optical depths, the radiative force per atom is
G = (1/c) σR γF
where σR is the Rosseland mean cross section,
γ is a dimensionless contant, and
F is the radiative flux.
Let χ(l) be the factor by which the abundance
of element l is enhanced or depleted.
Files are created for each initial mixture A(k)
and each chemical element l, giving for each
(T, Ne) mesh-point the values of
σR,
dσR/dχ, and
dγ(l)/dχ,
on each mesh-point for χ.
An interpolation code ACCFIT.FOR then enables one to calculate
σR and γ(l) for any required combination of
em T, ρ and χ (see ACC).
Opacity files and programs may be copied via
Anonymous FTP
at node cdsarc.u-strasbg.fr.
References:
- (OPF)
Seaton, M.J., 1993, MNRAS 265, 25P (1993MNRAS.265...25P)
- (IXZ) Seaton, M.J., 1996, MNRAS 279, 95
(1996MNRAS.279...95S)
- (ACC) Seaton, M.J., 1997, MNRAS 289, 700
(1997MNRAS.289..700S)
