From accurate atomic data to elaborate stellar modeling

218 Pages·2016·4.65 MB·English

From accurate atomic data to elaborate
stellar modeling: Structure and collisional
data, opacities, radiative accelerations.
DISSERTATION
Presented in Partial Fulflllment of the Requirements for
the Degree Doctor of Philosophy in the
Graduate School of The Ohio State University
By
Franck Delahaye
*****
The Ohio State University
2005
Dissertation Committee: Approved by
Prof. Anil K. Pradhan, Adviser
Prof. Marc H. Pinsonneault
Adviser
Astronomy Graduate Program
Prof. Donald M. Terndrup
Dr. Claude J. Zeippen
ABSTRACT
The Atomic physics fleld has served astronomy for a long time and it has also
been stimulated by it. Despite the maturity of the fleld, the new requirements for
accuracy and completeness from astronomers demand more challenging calculations.
Current problems require the relaxation of approximations and a detailed study of
difierent efiects like relativistic efiects, radiation damping and target expansions. We
carry out elaborate relativistic atomic calculations using the Breit-Pauli R-matrix
method to generate radiative and collisional data for atoms and ions of astrophysical
interest.
Electron impact excitation of He-like ions (N, O, Ne, Mg, Al, Si, S and Ca)
have been calculated including relativistic efiects, the levels up to the complex n = 4
and radiation damping. A detailed study of their efiects is presented here and the
comparison with previous works shows difierences of up to 30% in the efiective
collision strength for the z-line. This line with 3 other transitions between the
complexes n = 1 and n = 2 constitute an important tool for plasma diagnostics and
such difierences will have strong consequences in the analysis of X-Ray spectra of
astronomical objects.
ii
We present the relativistic calculation of Kfi resonances for oxygen ions that
are responsible for X-Ray absorption features observed in the spectrum of the
Seyfert 1 galaxy MCG-6-30-15 and other AGNs. The resonance oscillator strengths
have been computed from the photoionization cross sections and appear to be
strong. Comparison with the recent experimental and theoretical study of Kfi
photoionization of O II shows good agreement. These data should allow a more
complete analysis of X-Ray spectra from AGNs and reflne the general picture of such
complex objects.
We report the flrst large relativistic calculation of the photoionization cross
section of Fe II. The detailed flne structure in the present work agrees well with the
experimental results from Kjeldsen et al. (2002) and represents an improvement
over the previous non-relativistic results based on the LS coupling approximation.
As a complement to the X-Ray analysis of AGNs, these data should be useful to
the theoretical template of Fe II emissions crucial in the analysis of the UV/O/IR
counterpart of the spectrum.
The new OP opacities are presented, outlining the importance of the inner-shell
transitions for opacities at high temperature - high density regimes. Despite the
overall good agreement with another source of data (OPAL), the difierences are
noticeable. This new set of data is used to determine constraints on the solar
composition and to shed some light on the ’Solar Convection Problem’. While the
discrepancies between the two sources are minor for the Rosseland mean opacities,
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they afiect more severely the radiative accelerations. The comparison between the
accelerations computed with OPAL data and those obtained with OP data outlines
how sensitive they are to details in monochromatic opacities. The consequences for
stellar models are discussed.
iv
To Jeanne-Claire, Hubert, Sol(cid:181)ene and Mael.
v
ACKNOWLEDGMENTS
I am greatly indebted and grateful to Claude J. Zeippen who introduced me to
the work of a researcher long ago. He allowed me to discover a new, exciting and
stimulating world. He never stopped supporting me at all levels. He encouraged me
in the right direction even when I had lost all hope. I thank him for his competence,
his patience and his humor.
I would like to thank my adviser, Anil K. Pradhan, who warmly welcomed me
in his group at OSU. I thank him for his guidance and fruitful discussions, for his
precious help and constant support during these di–cult - but rewarding - years of a
PhD student.
I would like to thank Marc H. Pinsonneault who introduced and hooked me to
this exciting topic of stellar theory. His rigorous and knowledgeable approach taught
me a lot and serves me immensely. I am greatful for his endless patience and help.
I thank Mike J. Seaton for his advice and constructive discussions on opacity
and radiative accelerations. He gave me generously of his time and knowledge.
I would like to thank Werner Eissner for his help on running and debugging the
codes, and conversations on theoretical questions. I am grateful to Georges Alecian,
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Keith A. Berrington, Emile Bi¶emont, Claudio Mendoza and Peter J. Storey for their
helpful comments and suggestions.
I thank my collaborators Anil K. Pradhan, Sultana N. Nahar, Guo-Xin Chen
and Justin Oelgoetz for allowing me to present our joint work in the present thesis.
It has been very important for me to be part of the international Iron Project
team. I am grateful to all the project members for excellent collaboration.
I would like to thank all the people in the Department of Astronomy at OSU
who always diligently solved all the problems I have encountered in sometimes very
tricky situations. They always did their best and even more. I will not endeavour to
give here a list of names for fear of forgetting someone among all those who helped
me and make this department a stimulating and peaceful place. Their care allowed
me to pursue my PhD endeavor in the best conditions.
I would like to thank the CNRS and the Observatoire de Paris for the flnancial
and logistic support provided during my stays in Meudon, France. In particular, I
am grateful to Fabienne Casoli, former Deputy Director of the INSU, for her help.
While in France, I have been an associate member of two laboratories at the
Observatoire de Paris: flrst the DAEC and more recently the LUTh, with the much
appreciated support of their respective heads, Georges Alecian and Jean-Michel
Alimi.
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I thank my parents heartily for insisting on my going to the university, always
leaving open for me as many options as possible.
Both Jeanne Claire and I want to thank our families and friends for their warm
support during this extraordinary journey.
Spending six years in the United States led us to meet many interesting people
and I want to thank all of them for helping us to make this adventure so wonderful.
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VITA
November 26, 1968 ............. Born { Versailles, France
1992 ........................... B.S. Physics, Universit¶e Paris 7, France
1995 ........................... M.S. in Geophysics, I.P.G.P. - Universit¶e Paris 7, France
1999 { 2005 .................... Graduate Teaching and Research Associate,
The Ohio State University
PUBLICATIONS
Research Publications
1. F. Delahaye, M. H. Pinsonneault, "Comparison of radiative accelerations
obtained with atomic data from OP and OPAL", ApJ 625, pp 563-574 (2005).
2. N. R. Badnell, M. A. Bautista, K. Butler, F. Delahaye, C. Mendoza, P.
Palmeri, C. J. Zeippen and M. J. Seaton, "Up-dated opacities from the Opacitiy
Project", MNRAS 360, pp 458-464 (2005).
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3. F. Delahaye, Sultana N. Nahar, Anil K. Pradhan and Hong Lin Zhang,
"Resolution and accuracy of the resonances in R-matrix cross section", J. Phys. B:
At. Mol. Opt. Phys., Volume 37, Issue 12, pp. 2585-2592 (2004).
4. A.K. Pradhan, G.X. Chen, F. Delahaye, S. Nahar, J. Oelgoetz, "X-ray
absorption via K-alpha resonance complexes in oxygen ions", Monthly Notices of
Roy. Astro. Soc. 341, 1268 (2003).
5. F. Delahaye and A.K. Pradhan, "Electron impact excitation of Helium-
like oxygen up to n=4 levels including radiation damping", J.Phys. B: At. Mol.
Opt. Phys., Volume 35, pp. 3377-3390 (2002).
6. S.N. Nahar, F. Delahaye, A.K. Pradhan, C.J. Zeippen, "Atomic data
from the Iron Project XLIII. Transition probabilities for FeV", Astron. Astrophys.
Suppl. Ser., 144, 141-155 (2000).
7. E. Bi¶emont, F. Delahaye, C.J. Zeippen, "Transition rates for the doublet-
quadruplet intersystem lines in C II and N III", J. Phys. B: At. Mol. Opt. Phys.,
Volume 27, Issue 24, pp. 5841-5849 (1994).
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