Organized by Laboratory for High Energy Astrophysics NASA Goddard Space Flight Center Scientific Organizing Committee Manuel Bautista (NASA/GSFC), co-chair Timothy Kallman (NASA/GSFC), co-chair Peter Beiersdorfer (LLNL) Nancy Brickhouse (CfA) Duane Liedahl (LLNL) Richard Mushotzky (NASA/GSFC) Anil Pradhan (Ohio State Univ.) Nicholas White (NASA/GSFC) Local Organizing Committee Manuel Bautista (NASA/GSFC) Timothy Kallman (NASA/GSFC)

Atomic Data Needs
for X-ray Astronomy:
Proceedings

Editors:
M. A. Bautista,
T. R. Kallman,
A. K. Pradhan

This publication contains written versions of most of the invited talks presented at the workshop on "Atomic Data Needs for X-ray Astronomy", which was held at NASA's Goddard Space Flight Center on December 16-17, 1999.

The idea of hosting such a workshop emerged from an imminent need to update and complete current atomic datasets in anticipation of a new era of high quality X-ray spectra starting with the launching of Chandra and XMM-Newton observatories. At first, our vision of the workshop was of a short and limited attendance event, given the specialization of the topic. But it was soon realized, from the response to the first workshop announcement, that the topic was of much interest to researchers working in X-ray spectra (physicists and astronomers). As a result, the workshop grew to approximately 120 participants from several countries.

The kind of atomic data that interests us are those parameters needed for analysis and modeling of spectra shortward of ~ 100 Å and relevant to ionic species of astronomical interest. The physical mechanisms of interest in the formation of spectra include photoionization, collisional ionization, recombination (radiative and dielectronic), collisional excitation (by electrons and protons), and radiative deexcitation. Unique to X-ray spectroscopy are the ionization and excitation processes from inner-closed shells, in addition to the challenges in interpreting the medium resolution (/ ~ 0.05 - 0.1) data obtained by current X-ray astronomy experiments. Line wavelengths are of interest too, particularly owing to the high resolution spectra from the new experiments.

The workshop was divided into five major areas: Observational Spectroscopy, Theoretical Calculations of Atomic Data, Laboratory Measurements of Atomic Paramenters, Spectra Modeling, and Atomic Databases.

One comforting finding from the workshop is that the enthusiasm felt by X-ray astronomers about the new observational missions seems to be shared by theoretical and experimental physicists. Talks were presented about several exciting new projects and experimental and theoretical techniques devoted to X-ray spectroscopy. Simultaneously, several new tools for spectral analysis and modeling have recently been developed, together with improved atomic databases.

These proceeding are expected to be of interests to producers and users of atomic data. Moreover, the contributions presented here have been written in a way that can be used by a general audience of scientists and graduate students in X-ray astronomy, modelling, and in computational and experimental atomic physics.

Contents

I. Observational Spectroscopy

Spectroscopy and X-Ray Astronomy
Stephen S. Holt   1

Initial Results from the Chandra High Energy Transmission Grating Spectrometer
C.R. Canizares, D.S. Davis, D. Dewey, K.A. Flanagan, J. Houck, D.P. Huenemoerder, H.L. Marshall, M.L. Schattenburg, N.S. Schulz, M. Wise   5

First Results of the Chandra-LETGS
P. Predehl, B. Aschenbach H. Bräuninger, W. Burkert, V. Burwitz, G. Hartner, J. Trümper   11

Chandra and the Emission Line Project
N. S. Brickhouse and J. J. Drake   19