DR, Photoionization and Opacities

Nigel R. Badnell

University of Strathclyde
Department of Physics,
Glasgow, G4 0NG, U.K.

We review methodologies for describing dielectronic recombination (DR). We look briefly at the state-of-play of theory vs experiment. We then discuss how to deliver DR data in a form suitable for modelling and we review the status of the partial and total DR database being assembled for the modelling of dynamic finite-density plasmas. We comment on the role of fields and how modelling l-changing collisions approximately models the dynamic part of the plasma microfield.

We also consider the inverse process of photoionization and discuss how the same approach to DR is being used for inner-shell photoionization and the determination of opacities in stellar interiors. In particular, we pay attention to the role of opacity in resolving the discrepancy between the helioseismology observations and stellar evolution models for the position of the base of the solar convective zone.


X-ray Spectroscopy of Chemically Peculiar B Stars, or
Their Unseen Companions

Ehud Behar

Department of Physics
Haifa, 32000 Israel

Late type B stars are not supposed to emit X-rays. Their apparent detection by X-ray telescopes gives rise to the companion hypothesis. We will present spectroscopic methods for testing this hypothesis and dwell on the importance of the atomic data used, the methods for obtaining it, and on its accuracy.

We will apply these methods to high-resolution Chandra and XMM-Newton observations of the chemically peculiar late-type B star mu Lep and show that, indeed, in this case the X-rays can be traced back to a previously unresolved companion (mu Lep B), whose X-ray spectrum resembles that of a coronal source.

We will present evidence that supports mu Lep B being a pre-main-sequence star, most likely of the non-accreting magnetically-active type.

 Laboratory Studies of the Fe K Shell Emission

Peter Beiersdorfer

Lawrence Livermore National Laboratory
7000 East Ave, L-260
Livermore, CA 94550

The importance of the Fe K shell emission for astrophysics has been evident for many years. Data have typically been obtained with rather low-resolution solid-state detectors such as those used on ASCA or presently on Chandra. Next year's launch of ASTRO-E2 is expected to provide Fe K shell spectra with high-resolution (E/DE 1000). This will enable real spectroscopy of the Fe K lines and their use as diagnostics of such source parameters as temperature, ionization equilibrium, and electron density. In order to analyze Fe K shell data spectral models must be both complete and accurate. The Fe K shell spectrum has been studied in much detail on tokamaks and the Livermore electron beam ion traps. Laboratory data now include accurate line lists and identifications, even of several forbidden lines, electron-ion collision cross sections, innershell ionization phenomena and cross sections, dielectronic recombination resonance strengths, spectra produced by charge exchange recombination, electron beam polarization effects, resonance excitation, and radiative cascade contributions. These measurements have provided an assessment of the completeness and accuracy of the atomic data, and we will present results of such measurements.

This work was performed under the auspices of the U.S. DOE by UC-LLNL under contract W-7405-Eng-48 and support by NASA's Astronomy and Physics Research and Analysis Program under contract S-06553-G.

 Fe XVII Emission from Hot, Collisional Plasmas

Peter Beiersdorfer

Lawrence Livermore National Laboratory
7000 East Ave, L-260
Livermore, CA 94550

Poster Abstract

The ratios of the 3s-2p and 3d-2p lines in FeXVII observed from the Sun and astrophysical sources have not been reproduced by spectral modelling codes such as APEC. The reason for the discrepancy has been the object of much speculation. Here we present a comparison of available laboratory data. Using the SAO microcalorimeter and the NIST electron beam ion trap excellent agreement between measurement and calculations was obtained. But a discrepancy of almost a factor of two was found with astrophysical data suggesting that unknown processes need to be invoked. By contrast, tokamak data and measurements using the Livermore electron beam ion traps disagree with model calculations but nicely reproduce astrophysical data. The results suggest that the collisional processes in tokamak plasma and the Livermore electron beam ion traps are a good description of FeXVII excitation found in hot, collisional astrophysical plasmas. We conclude that non-collisional processes need not be invoked.



Surface Atomic Spectral Lines from Weakly Magnetized Rotating Neutron Stars

Sudip Bhattacharyya, M. Coleman Miller, *Frederick K. Lamb

Department of Astronomy,
University of Maryland at College Park,
College Park, MD 20742


The report by Cottam et al. (2002) of iron lines in the thermonuclear burst spectrum of EXO 0748-676 motivates detailed studies of the information about neutron star structure and emission geometry that can be obtained from spectral line profiles in future observations. We calculate the structures of surface atomic spectral lines from rotating neutron stars, considering the full effects of general relativity (including light-bending and frame-dragging). We find that, even for spin frequencies up to 600 Hz, the stellar mass to radius ratio can be inferred from surface line profiles to better than 5%, which is the precision required for strong constraints on the equation of state of neutron stars. Our results also indicate that a signature of frame-dragging may be detected with future instruments in surface line profiles.


Probing the Interaction Between Comets and the Solar Wind

Dennis Bodewits, R. Hoekstra, and A.G.G.M. Tielens *

KVI Atomic Physics
Zernikelaan 25
9747 AA Groningen
The Netherlands

*Kapteyn Astronomical Institute/SRON

Comets are bright emitters in X-ray and Far-Ultraviolet (XUV). The main driver of this emission is charge exchange between solar wind ions and neutrals in the cometary coma. We study these reactions in the laboratory and use our results to model cometary XUV emission.

Recent observations show that cometary XUV emission depends on properties of both the comet (mass loss, composition, distance to the sun) and the solar wind (speed, composition). The understanding of their interaction requires a deep insight in the atomic processes that constitute it. Unfortunately, there are still many gaps in our knowledge about some of the crucial charge exchange reactions in cometary atmospheres. Two examples are collisions involving Hydrogen-like highly charged ions and collisions between solar wind ions and atomic oxygen.

An interdisciplinary effort is therefore called for to turn the next generation cometary XUV observations into valuable, remote diagnostics for studying solar system plasmas.


Progress and Plans for the Astrophysical Plasma Emission Code (APEC)

Nancy Brickhouse, Ronnie Hoogerwerf, Randall Smith

Center for Astrophysics
60 Garden Street, MS 15
Cambridge, MA 02138

Poster Abstract

APEC models for collisional ionization equilibrium are now available in Sherpa and XSPEC. These basic models have been benchmarked against astrophysical coronal spectra and show reasonable agreement; however, several atomic data issues need to be addressed. We plan to conduct an atomic data needs assessment and set priorities over the next year.

New tools are under development to broaden the applicability of APEC models. We will discuss the status of this development.

This project is supported by NASA contract NAS8-39073 to the Smithsonian Astrophysical Observatory for the Chandra X-ray Center.

 Laboratory Studies of X-ray Emission from Fe L-shell Transitions and Their Diagnostic Utility

Gregory V. Brown

High Energy Density Physics and Astrophysics Division
Lawrence Livermore National Laboratory
Livermore, CA 94550

Non-terrestrial objects are home to complex, dynamic, intriguing environments. High-resolution x-ray spectra from these sources measured by satellites such as the Chandra x-ray Observatory, XMM-Newton, the Solar Maximum Mission, and the soon-to-be-launched Astro-E2 provide a means for understanding the physics governing these sources. Especially rich is the x-ray emission from L-shell transitions in highly-charged iron ions. This emission is the source of a variety of diagnostics whose utility lies in the accuracy of the atomic data employed to model the x-ray spectra either globally or using ratios of key emission lines. The atomic data used to describe these diagnostics are generally provided by large theoretical calculations and benchmarked by laboratory data. I will discuss the laboratory measurements of Fe L-shell x-ray emission, past, present, and future, how these data are being implemented in spectral modeling packages, and how models are being built using data obtained exclusively in the laboratory. Work at LLNL was completed under the auspices of the US D.o.E. by the University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48 and supported by NASAs Astronomy and Physics Research and Analysis Program under work order S-06553-G.

 X-ray Diagnostics with Full Radiative Transfer (ALI Method)

Loïc Chevallier, Anne-Marie Dumont, Olivier Godet, Suzy Collin

Observatoire de Paris - section de Meudon
5 place Jules Janssen

With the advent of the present and future spatial X-ray missions, it becomes crucial to model correctly the line spectrum of X-ray emitting media. We have built a photoionization code, TITAN, solving the transfer of a thousand lines and of the continuum with the "Accelerated Lambda Iteration" method (ALI), which is most reliable for line transfer. We give some details about this method and a justification of its use as a complement to usual approximations (e.g., escape probability or two-stream approximation) made at present in other codes. Using our TITAN code, new diagnostics based on He-like ion lines of the n=2 complex are presented, in the case of photoionised media, for conditions appropriate for the Warm Absorber in Seyfert 1 galaxies or the X-ray emitting region in Seyfert 2 galaxies. We show in particular the influence of the transfer method used on the G and R ratios of He-like ions.


Chandra-LETGS Observation Of Mrk279: Modeling the AGN Internal Structure Through High Resolution Spe

Elisa Costantini, J.S. Kaastra, K.C., Steenbrugge, N. Arav, J.R. Gabel

SRON, Space Research Organization Netherlands
Sorbonnelaan, 2
3584CA Utrecht
The Netherlands

Poster Abstract

Thanks to the capabilities of the X-ray grating spectrometers, the soft X-ray spectrum of Seyfert galaxies can be studied in great detail. However, many characteristics of the ionized medium in the vicinity of the black hole such as the geometry of the outflow, its origin, the ionization structure, and the distance are still not understood. We present a $\sim$350 ks observation of the Sey 1 Mrk279, performed by Chandra-LETGS. The primary emission is absorbed by ionized gas outflowing at $\sim$270 km/s. The opening angle of the outflow is very narrow, (Omega<1.3 sr), disfavoring a spherical geometry of the absorbing gas. The best fit to the continuum shows positive residuals around the main features of oxygen and nitrogen (OVIII, OVII, NVII). These may be modeled as relativistic broadened lines. Alternatively, we quantitatively discuss the hypothesis that these residuals are the features of the broad emission line region.


The XRS Microcalorimieter

Jean Cottam & the XRS Instrument Team

Laboratory for High Energy
Code 662
Greenbelt, MD 20771

The XRS microcalorimeter will be launched in early 2005 as part of the Astro-E2 mission. It will cover the energy band from 0.3 to 10 keV with a nearly constant energy resolution of 6.0 eV and a peak effective area of 200 cm2 at 1.5 keV. The XRS will provide unprecedented throughput and resolving power, particularly at high energies. Detailed spectral features in the Fe K region will be resolved for the first time, providing access to spectroscopic diagnostics for a wide range of astrophysical objects. In this presentation we will describe the XRS instrument, details of its spectral performance, and how it compares to the current high-resolution instruments on the Chandra and XMM-Newton Observatories.


Importance of Dielectronic Recombination for Laboratory Astrophysical Plasmas

Arati Dasgupta and J. M. Laming

Naval Research Laboratory
Code 6720
4555 Overlook Avenue, SW
Washington, DC 20375

Poster Abstract

Accurate determination of Dielectronic Recombination (DR) rate coefficients is crucial for reliable X-ray diagnostics of astrophysical as well as laboratory Z-pinch plasmas. In the temperature region of maximum abundances, these DR rates have significant effects in ionization balance calculations and line identification for radiation from these X-ray sources. Reliable recombination rates are especially important in modeling time-dependent ionization balance, as for instance in the radiative instability of recombining plasmas in various astrophysical sources. Calculations of level-specific DR rates involving many doubly excited states can amount to significant time and effort. Simple empirical formulas are not adequate, though detailed perturbative methods often predict more accurate DR rates than more complex close-coupling calculations. We present scaling coefficients using Distorted-Wave approximations for K- and L-shell recombination. These coefficients can then be used to obtain DR rates for any temperature of interest for any ions of elements in the third and fourth rows of the periodic table. The scaling accuracy was verified by comparing the scaling relation predictions to detailed data obtained for a few selected ions. The DR rate coefficients that are calculated from the scaled DR data are generally most accurate for intermediate to high-temperature collisional plasmas.



Comparison of Fe XVIII and Fe XIX Line Emissions with Spectral Models

Priya Desai, N. S. Brickhouse, J.J Drake, A.K Dupree, R. Hoogerwerf

Harvard Smithsonian Center For Astrophysics
60 Garden Street, MS 64
Cambridge, MA 02138

R.K Smith


Poster Abstract

We discuss here the observations of FeXVIII and FeXIX emission lines and compare the X-ray, EUV and FUV lines with the spectral codes widely used today (e.g. FAC and APEC). We assess the relative accuracy of these spectral models and try to identify the critical missing atomic data.

Capella with its narrow enhancement in its emission measure distribution at 6MK provides a unique opportunity to test the Fe XVIII and Fe XIX model emissivities which peak around 6MK. We use the summed spectra from Chandra HETG/ACIS-S and LETG/HRC-S, as well as contemporaneous EUVE and FUSE observations, to measure line ratios for comparison with predictions.

This work is supported in part by the Chandra X-ray Observatory Center (NAS8-39073).



"Usin' what we got": Calculating X-ray Spectra for Non-Equilibrium Plasmas

Daniel Dewey and John C. Houck

M.I.T. Center for Space Research

It is desirable to calculate the X-ray emission spectrum from a (region of a) plasma that is not in ionization equilibrium, e.g., with application to supernova remnants, SNRs. Such a plasma will generally have ionization fractions that are not directly related to the local electron temperature and, in the case of SNR ejecta, may contain little or no H and He. This poster describes the use of the currently available database, APED/C, and software, ISIS, to generate spectra for a non-equilibrium plasma that is specified by explicit densities and ionization fractions for the ions and an explicit, independent electron temperature, Te. Example spectra are shown and discussed. This approach does have some deficiencies currently, specifically: Cr lines are not in APED/C, not all relevant inner-shell lines are included, and continua spectra are not available on an ion-by-ion basis. On a note of progress, the generalization of the ion fraction specificiation in ISIS is described and simplifies NEI plasma specification and evaluation.

 Fe XV Lines in Solar and Stellar Soft X-ray Spectra

Jeremy J. Drake, F.P. Keenan, S.M. Chung, N.S. Brickhouse

60 Garden Street
Cambridge, MA 02138

Poster Abstract

Fe~XV lines in the soft X-ray range (50-75~\AA) have been investigated in solar and stellar spectra, in order to confront empirical line intensity measurements with theoretical predictions based on new R-matrix calculations of electron impact excitation rates. Line intensities for a variety of multiplets are presented, based on measurements of co-added archival Chandra LETG+HRC-S observations of Capella and on a solar flare spectrum obtained by a rocket-borne spectrograph (Acton et al.\ 1985, ApJ, 291, 865). A comparison of the observed line ratios with theoretical predictions shows good agreement for many lines, but significant discrepancies for some. Hidden blends are thought to be largely responsible for the inconsistencies, although other issues affecting the predictions and measurements will be discussed, together with an assessment of the diagnostic utility of soft X-ray Fe~XV lines. Several new identifications of Fe~XV lines are proposed, based on the analysis of the solar flare spectrum.

 Lessons from Non-X-ray Photoionized Spectroscopy

Gary J. Ferland

Physics Department
U of Kentucky
Lexington, KY 40506

The two greatest lessons I have learned from analysis of optical, UV, and IR spectra of Active Galactic Nuclei (AGN) are to beware of the atomic physics selection effects introduced by inhomogeneities, and to consider the consequences of a particular model derived from one spectral region for allothers, including the X-ray.

The "Locally Optimally-emitting Clouds" (LOC) model of AGN was developed in response to variability observations showing that the emitting gas was spatially extended. Atomic physics selection effects, together with gas with a broad range of density and distance from the source of ionizing radiation, reproduce the observed spectrum, including profiles, intensities, and variability, without resorting to finely tuned free parameters.

A second example is the long-standing attempts at understanding the very hot dust, T ~ 1,000K, which is known to exist in AGN. Most work considered the dust by itself, neglecting the gas which must also be present. Detailed predictions of the properties of both the dust and gas show that the gas associated with the dust is hot, with a temperature of roughly a million degrees, and so likely to be visible in the X-rays.


Application of Laboratory Experiments and Atomic Physics Modeling to Astrophysical Observations

Kevin B. Fournier, M. Finkenthal, M.J. May, M. Mattioli, W.H. Goldstein, S.B. Hansen

Lawrence Livermore National Laboratory
PO Box 808, L-473
7000 East Avenue,
Livermore, CA 94550

We present examples of observations of x-ray and XUV emission spectra from magnetically confined laboratory plasmas. We emphasize the strengths of these thermal-plasmas: the control over plasma and sample conditions and accurate measurements of the main plasma parameters (electron temperature, density), the high brightness of emitted spectra, and their similarities to astrophysical plasmas, and their challenges, such as blending problems between emission from intrinsic and injected 'impurities' (the main plasma is composed of hydrogen or deuterium atoms). Specific emphasis is given to study of line ratios and ionization balance for L- and M-shell Fe ions. Interpretation of the spectra relies on complex collisional-radiative modeling and high quality atomic data. A specific application of observations and calculations of M-shell Fe ionization balance to recent CHIPS results is presented.

This work performed under the auspices of the US DoE by UC LLNL under contract No. W-7405-Eng-48.


Resolution of the Overprediction of the 3C/3D Line-Intensity Ratio in Mid-Z Neonlike Ions

Kevin B. Fournier, Stephanie B. Hansen

Lawrence Livermore National Laboratory
PO Box 808, L-473
7000 East Avenue
Livermore, CA 94550

Poster Abstract

The Ne-like resonance 1S - 1P (3C) to intercombination 1S - 3D (3D) line ratio, R(3C/3D), has been studied through high-accuracy measurements and calculations of atomic structure and collision cross sections; even state-of-the-art atomic-physics codes generally predict values of R(3C/3D) that are larger than observed in experiments. In this paper, predictions of R(3C/3D) across the Ne-like isosequence are brought into agreement with coronal-density measurements in two steps: first by including a semi-empirical correction in the collisional data due to configuration-interaction (CI) effects, and next by including the effects of cascades on the level populations. The CI correction is inspired by the observation that nearly all data-production codes fail to predict R(3C/3D) correctly and is justified theoretically by an analysis of CI contributions to level energies. The dependence of R(3C/3D) on electron density and its agreement with moderate-density measurements are shown.

 A Variable Emission Line in the Symbiotic Neutron-Star Binary 4U1700+24/HD 154791

Duncan Galloway

Center for Space Research
77 Massachusetts Avenue
Cambridge, MA 02139

During a rare outburst in 2002, XMM-Newton/RGS spectra of the symbiotic neutron-star binary 4U 1700+24 revealed a single broad emission line around 19 angstrom, tentatively identified as redshifted O VIII. I will describe additional XMM-Newton observations which showed that the equivalent width increased as the continuum flux decreased during the fade into quiescence. The line centroid varied between 19.02-19.20 angstrom, which for O VIII indicates redshift velocities of 800-3000 km/s. The line centroid and width varied on timescales as short as 40 min, which cannot be attributed to orbital motions since the estimated orbital period is at least 400 d. The centroid energy was proportional to the power-law spectral index of the continuum emission. The redshift may arise from bulk motion in the accretion stream which is along the line-of-sight in this face-on system. Alternatively, the line may be Ne IX emission, in which case the redshift is ~0.4 and the line likely arises from the neutron star surface.

 Production and Decay of Atomic Inner-Shell Vacancy States

Thomas Gorczyca
Department of Physics
Western Michigan University
1903 West Michigan Avenue
Kalamazoo, MI 49008-5252

Our recent investigations on the accuracy of the existing1s-vacancy fluorescence and Auger data base, which is crucial for the interpretation of spectra from X-ray photoionized plasmas and for supernova remnants under conditions of non-equilibrium ionization, will be reviewed. In particular, effects such as non-hydrogenic scaling, correct initial state averaging, configuration interaction (CI), and spin-orbit mixing, which were not included in the earlier calculations but sometimes affect profoundly our computed fluorescence yields, will be discussed. Furthermore, the production of1s-vacancy states through photoabsorption will be reviewed, with emphasis on orbital relaxation and spectator Auger broadening of the resonance edge. How our recent oxygen photoabsorption data contribute to elemental abundance studies of the inter-stellar medium will also be discussed.

Recent Theoretical Developments on Atomic Data for Fe L-shell Ions

 Ming F. Gu

Stanford University
382 Via Pueblo
Varian 334
Stanford, CA 94305

Emission lines from L-shell ions of iron dominates the soft X-ray spectral band for hot collisionally-ionized plasmas with tempeparatures near $10^6$ K. These lines also contribute significantly in the spectra of photoionized plasmas. To accurately model such spectra, a large set of atomic data is needed, including wavelengths, radiative transition rates, collisional excitation, radiative and dielectronic recombination rates, and collisional
ionization. We review the recent theoretical efforts in producing such atomic parameters and assess their accuracy by comparing with the experimental measurements wherever available. We also compare the close-coupling and distorted-wave theoretical approaches in treating the collisional excitation and recombination of Fe L-shell ions.

 K-alpha Emission Spectra from Non-Equilibrium Ionizing Plasmas

Verne L. Jacobs, V. Decaux, P. Beiersdorfer

Naval Research Laboratory, Code 6390
4555 Overlook Avenue, S. W.
Washington, D. C. 20375

K-alpha X-ray emission spectra from highly charged Fe ions have been theoretically predicted using a detailed and systematic spectral model. Account has been taken of the fundamental atomic radiative-emission processes associated with inner-shell electron collisional excitation and ionization, as well as dielectronic recombination. Particular emphasis has been directed at extreme non-equilibrium or transient-ionization conditions, which can occur in astrophysical and tokamak plasmas. Good agreement has been found in comparisons with spectral observations on the EBIT-II electron beam ion trap at the Lawrence Livermore National Laboratory. We have identified spectral features that can serve as diagnostics of the electron density, the line-formation mechanism, and the charge-state distribution.

This work has been supported by NASA, ONR, and DOE.


Non-Equilibrium X-Ray Spectral Model: Applications in Star Cluster Winds

Li Ji, Q. Daniel Wang, John, Kwan

University of Massachusetts at Amherst
Department of Astronomy
Amherst, MA 01002

Poster Abstract

We have constructed a non-equilibrium ionization spectral model for star cluster wind in a dynamical and thermal self-consistent way, based on the most updated atomic data. The model has been implemented into XSPEC. The interested physical quantities(mass-loss rate, terminal velocity and average metallicity) could be obtained directly by fitting the data. In a meanwhile, model also could produce surface brightness profile, which can be used to confine physical quantities when combined with predicted spectra. A preliminary test of model on NGC3603 is given. Some interesting line diagnostics are presented and compared with those in equilibrium case.

 Accretion Disk Atmospheres

Mario Jimenez-Garate

77 Massachusetts Avenue
NE80-6009, Center for Space Research
Cambridge, MA 02139

The window on high-resolution X-ray spectroscopy opened by Chandra and XMM-Newton is revealing the nature of the atmospheres and coronae of accretion disks. Observations of X-ray binaries show that dense photoionized plasmas blanket the disk. We compare accretion disk model atmospheres with observed X-ray spectra in order to derive ionization and density structure, opacity, spatial distribution, elemental composition, energetics, thermal stability,
and kinematics.

We calculated the spectrum for a disk atmosphere surrounding a supermassive Kerr black hole. I show the observable line emission signature in the soft X-rays from the flow near the horizon. This spectrum is subject to line transfer effects. Via a Monte Carlo, we find that the line ratios will be modified after repeated photoionizations and recombinations inside the atmosphere. Lines such O VIII (654 eV) and C VI (367 eV) are enhanced, while others such as Ne X (1022 eV) and O VIII RRC (871 eV) are suppressed. We predict an anti-correlation between the Fe K fluorescence and the recombination line intensities, traceable to the atmospheric structure. Our results suggest that the O VIII and N VII lines identified with XMM-Newton in MCG-6-30-15 (Branduardi-Raymont et al., 2001) are overly bright, but may be physically tenable.


Rolf Mewe: A Career Devoted to X-Ray Spectroscopy

Jelle Kaastra

Sorbonnelaan 2
Utrecht, 3584 CA The Netherlands

In this contribution I will present an overview of the life and work of Rolf Mewe (1935-2004) as an X-ray spectroscopist. He was one of the pioneers in the field of X-ray spectroscopy. His work illustrates nicely how this field developed from the early days up to the present high-resolution era. His plasma emission codes, developed by him and collaborators over several decades, is one of the most widely used. His thorough knowledge of the field, as well as his ability and enthousiasm to cooperate with many colleagues, made his carrer a succes. He will be missed by all of us for his work and personality.

 Charge-Exchange Mechanism of X-ray Emission

V. Kharchenko

Harvard-Smithsonian Center for Astrophysics
60 Garden Street
Cambridge, MA 02138

The charge-exchange mechanism of X-ray emissions induced by the Solar Wind (SW) ions form the cometary and planetary atmospheres and from the interstellar gas is discussed. The X-ray photon spectra of individual highly charged SW ions (Oq+, Cq+, Nq+, Neq+, and other ions) are described in detail. Spectra of cascading X-ray and EUV emissions of heavy SW ions are calculated for various ion velocities and compared with the results of laboratory measurements. Relative intensities of different spectral lines of the charge-exchange X-ray/EUV emission are used for the remote diagnostic of the compositions and velocities of the SW plasma. The synthetic X-ray spectra, computed for the slow and fast solar winds, are applied for the analysis of the observed cometary and planetary X-rays and for predictions of X-ray spectra from the interstellar gas. The contribution of the charge-transfer emission into the X-ray diffuse background is discussed.

 Accurate wavelengths for X-ray spectroscopy and the NIST
Hydrogen and Hydrogen-Like ion databases

S. A. Kotochigova1;2, K. P. Kirby3, N. S. Brickhouse4

1National Institute of Standards and Technology, 100 Bureau Drive, stop 8423, Gaithersburg, Maryland 20899 USA
2Department of Physics, Temple University, Philadelphia, PA 19122 USA
3Institute for Theoretical Atomic and Molecular Physics, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 USA
4Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 USA

We describe our ab initio relativistic approach that is developed to provide accurate wavelengths for X-ray spectroscopy. This approach is based on computational techniques that are well suited to treat relativistic and correlation effects in highly charged ions. We use the large-scale configuration-interaction (CI) Dirac-Fock method to solve the Dirac-Coulomb-Breit equation and calculate energies, transition frequencies and probabilities, using non-orthogonal bases. To generate CI basis sets we solve Dirac-Fock equations for occupied orbitals and the Dirac-Fock-Sturm equations for virtual or non-occupied orbitals numerically. Since the Dirac-Fock-Sturm operator has a complete and discrete set of eigenfunctions, the basis set includes the continuous part of the spectrum.

The performance of our computational technique is tested by comparing our calculations of the p - s and p - d transitions in Fe XVIII and Fe XIX to known experimental results. An estimate of the Lamb shift for these transitions shows that it may start to play a role at this level of 10-3Å accuracy and therefore it has to be included for more precise calculations.

Finally, I will present my work on NIST databases. In particular, I will show two interactive databases designed to calculate total energies and transition frequencies of hydrogen and deuterium as well as hydrogen-like ions. The values are highly accurate and based on current knowledge of the relevant theory, which includes relativistic, quantum electrodynamic, recoil, and nuclear size effects. The hydrogen-like ion database is possibly of interest for X-ray spectroscopy, whereas the hydrogen and deuterium data base lays the theoretical groundwork for precise determination of ground and excited energies.

 X-ray Diagnostics of Physical Conditions in Warm Absorbers

*Yair E. Krongold, N.S. Brickhouse, D.A. Liedahl, F. Nicastro

Instituto de Astronomía
Universidad Nacional Autónoma de México
Apartado Postal 70 - 264
Ciudad Universitaria
México, D.F., CP 04510

We will discuss diagnostic techniques for photoionized plasmas, focusing on warm absorbers in Active Galactic Nuclei. Despite the great progress boosted by X-ray grating spectrometers in our understanding of the ionized medium in the nuclear environment of active galaxies, little is known about the location, geometry, and origin of these winds. We will review the few cases where these properties can be constrained, and discuss how plasma diagnostic techniques can improve our knowledge in this field, when applied to data obtained with the present and future X-ray instruments.

 Open Issues Concerning Ionization

J. Martin Laming

Naval Research Laboratory
Code 7674L
Washington DC 20375

I will survey the state of atomic data relevant to calculations of ionization balance, and highlight applications of plasma diagnostics where uncertainties in ionization balance may play an important role. Such effects, and strategies for dealing with them are by now well known in the case of plasmas in collisional ionization equilibrium, such as stellar coronae. However time-dependent plasmas, either ionizing or recombining, where the departure from ionization equilibrium is itself an important diagnostic, or static plasma where radiative instability plays a role, place new demands on the accuracy of the atomic data. I will illustrate such issues with examples from x-ray observations of supernova remnants and modeling work on winds from accreting black holes.

 Recent Advances on the CHIANTI Database in the X-Ray Range

Enrico Landi

Artep, Inc
Naval Research Laboratory
Code 7660
4555 Overlook Ave. S.W.
Washington, DC 20375

CHIANTI is a database of atomic data and transition rates necessary for the analysis of optically thin astrophysical plasmas. CHIANTI data have been benchmarked with observations in the EUV, UV and X-ray range. I will describe the recent improvements in the CHIANTI database and atomic models that will lead to the next version of the database. The main changes consist of

1 - Inclusion of ionization and recombination in ion fraction population
2 - New data for high-energy configurations in Fe XVII-XXIII
3 - Re-assessment of wavelengths and energy levels in the X-ray range
4 - New/improved data for the EUV and UV spectral ranges

The new version of CHIANTI has been benchmarked with SMM/FCS spectra of a solar flare, and I will present the results of this comparison.

 Can We Determine the Grain Composition of the Interstellar Medium with Astro E2 ?

Julia C. Lee, Bruce Ravel (NRL)

Harvard Center for Astrophysics
60 Garden Street, MS70
Cambridge, MA 02138

I will discuss the ability of the Astro E2 XRS to directly probe the grain composition of the ISM. Using experimental data taken at the National Synchrotron Light Source at Brookhaven National Laboratory, I will discuss our current prospects for (1) distinguishing gas from dust phase absorption, and (2) determining the chemical composition of interstellar grains, through the details of X-ray absorption fine structure.


The K Spectrum of Iron L-Shell Ions in Photoionized Plasmas

Dr. Duane Liedahl

Lawrence Livermore National Lab
P. O. Box 808, L-473
Livermore, CA 94550

Advancements in detector capabilities, exemplified by the XRS on Astro-E 2, promise to uncover the spectral complexity in the iron K spectrum in several classes of celestial X-ray source, complexity that has been observed only in solar and laboratory plasmas thus far. I have calculated detailed atomic models that include the effects of inner-shell photoionization, autoionization, collisional excitation at relatively high particle number densities, and photoexcitation in plasmas with high X-ray and/or UV energy densities. The primary applications of these models are accretion disk atmospheres and winds in X-ray binaries.


PINTofALE: Sensitivity of Emission Measure Analysis to Input Atomic Data

LiWei Lin, Vinay L. Kashyap, Jeremy J. Drake

Smithsonian Astrophysical Observatory
60 Garden St. , MS 67
Cambridge, MA 02138

Poster Abstract

The Package for Interactive Analysis of Line Emission (PINTofALE) is a software suite of modularized IDL routines geared towards, but not limited to, the analysis of coronal plasma line emission. It fuses the otherwise disparate and numerous atomic databases and data analysis packages necessary for UV-X-ray spectral analysis into one transparent, flexible, and freely available software package. We describe here tools to undertake spectral line identification and the implementation of Monte Carlo methods in \poa for determining plasma emission measure distributions, and highlight in particular the effects of using different atomic databases on the results. We illustrate the case with a new analysis of a solar active region observed with both SoHO CDS spectra and TRACE narrow band images.


Benchmark Exercises for Stellar X-ray Spectroscopy Testing (BEXST)

Antonio Maggio

INAF - Osservatorio Astronomico di Palermo
piazza del Parlamento 1
I-90134 Palermo, Italy

Jeremy Drake

Cambridge, MA, USA

Fabio Favata

Noordwijk, NL

Manuel Guedel

Villigen, Switzerland

Poster Abstract

In recent years, different teams active in the field of stellar coronal physics have used different approaches for the reduction and analysis of spectra taken with Chandra and XMM-Newton. Various methods have been employed, which differ in many respects (numerical algorithms, selection of emission lines, atomic physics databases, free model parameters). At present, there is no study available about whether all the different approaches produce compatible results, or whether some (or all) of them lead to biases in the resulting physical parameters. This situation is made more complex by the growing indications that some of the usual assumptions in the above analyses (uniform densities or pressure equilibrium, steady heating, uniform chemical composition) are in fact invalid. We are going to organize a "hares and hound exercise" open to the whole community, aimed to address the above issues. This poster presents the rationale for this exercise, its organization, and its possible contents.


 Benchmark Exercises for Stellar X-ray Spectroscopy Testing (BEXST)

Antonio Maggio

INAF - Osservatorio Astronomico di Palermo
piazza del Parlamento 1
I-90134 Palermo, Italy

Jeremy Drake

Cambridge, MA, USA

Fabio Favata

Noordwijk, NL

Manuel Guedel

Villigen, Switzerland

Poster Abstract

In recent years, different teams active in the field of stellar coronal physics have used different approaches for the reduction and analysis of spectra taken with Chandra and XMM-Newton. Various methods have been employed, which differ in many respects (numerical algorithms, selection of emission lines, atomic physics databases, free model parameters). At present, there is no study available about whether all the different approaches produce compatible results, or whether some (or all) of them lead to biases in the resulting physical parameters. This situation is made more complex by the growing indications that some of the usual assumptions in the above analyses (uniform densities or pressure equilibrium, steady heating, uniform chemical composition) are in fact invalid. We are going to organize a "hares and hound exercise" open to the whole community, aimed to address the above issues. This poster presents the rationale for this exercise, its organization, and its possible contents.

The value of density measurements in stellar coronae 

Jan-Uwe Ness

Oxford University
Theoretical Physics,
1 Keble Road,
Oxford, OX1 3NP, UK

The grating instruments on board Chandra and XMM-Newton allow measurement of
electron densities. The diagnostics are based on ratios of emission lines, where either one or both lines depend on collissions between upper levels. The Chandra LETGS can measure density sensitive lines which were used in EUVE analyses that returned incidental cases of high densities. I will show my results comparing EUVE and Chandra measurements. The He-like triplets are for the first time available to stellar X-ray spectroscopy, but were in the recent literature mostly reported to deliver only low-density limits. I report on density measurements in a large sample, and show that the density information actually available is extremely useful to reveal systematic trends of coronal filling factors.


Photoionization Modeling: the K Lines and Edges of Iron

Dr. Patrick Palmeri, T.R. Kallman, C. Mendoza, M.A. Bautista, J. Krolik

Astrophysique et Spectroscopie - UMH
20 Place du Parc
B-7000 Mons, Belgium

We calculate the efficiency of iron K line emission and iron K absorption in photoionized models using a new set of atomic data. These data are more comprehensive than those previously applied to the modeling of iron K lines and edges from photoionized gases, and allow us to systematically examine the behavior of the properties of line emission and absorption as a function of the ionization parameter, density and column density of model constant density clouds.

 Modeling CHANDRA Low Energy Transmission Grating Spectrometer Observations of Classical Novae

Alexander Petz, Peter H. Hauschildt, Jan--Uwe Ness, and Sumner Starrfield

Hamburger Sternwarte
Gojenbergsweg 112
21029 Hamburg, Germany

Poster Abstract

We use the {\tt PHOENIX} code package to model the X--ray spectrum of Nova V4743 Sagittarii observed with the LETGS onboard the Chandra satellite on March 2003. To analyze nova atmospheres and related systems with an underlying nuclear burning envelope at X--ray wavelengths, it was necessary to update the code with new microphysics. We demonstrate that the X--ray emission is dominated by thermal bremsstrahlung and that the hard X--rays are dominated by Fe and N absorption. Preliminary models are calculated assuming solar abundances. It is shown that the models can be used to determine
in the nova ejecta by increasing the absorption in the shell and considering more elements in the NLTE calculations.


Dielectronic Satellites Near the 1s2-1snp (n>2) Lines of He-like Ions in Solar Flare X-ray Spec

Kenneth J. Phillips, J. Sylwester, B. Sylwester, J. Dubau

NRC/Goddard Space Flight Center
Code 682
Greenbelt, MD 20771

Poster Abstract

The importance of dielectronic satellites as temperature diagnostics in solar and tokamak soft X-ray spectra is well known, but the satellites in question most generally used are those near the 1s2-1s2p lines of He-like ions. These suffer from spectral confusion with other He-like ion lines to the long-wavelength side of the resonance line, notably the forbidden line ( 1s2\,1S0 - 1s2s\,3S1). Relatively little attention has been paid to satellites on the long-wavelength side of 1s2-1snp lines of He-like ions in solar spectra, yet their temperature dependence (approximately T-1) is identical to the 1s2-1s2p satellites and (owing to the absence of an equivalent forbidden line) there is no spectral confusion. This paper identifies recent solar flare observations of these satellites and their importance for temperature information. RESIK, a high-resolution spectrometer flying on the Russian Coronas-F spacecraft, has made observations of Si XII and S XIV satellites near the (He-like) Si XIII and S XV 1s2-1s3p, 1s2-1s4p and 1s2-1s2p. Comparison of the measured ratios for Si and temperatures derived from the GOES satellites confirm the T-1 dependence of their intensities relative to the He-like ion lines. In addition, spectra from the RHESSI solar flare mission, which observes solar flare thermal spectra with broad-band resolution at wavelengths less than 4~\AA\ (photon energies > 3~keV), includes a peak at 6.7 keV which is largely due to Fe XXV 1s2-1s2p lines and satellites. In addition, RHESSI observes a feature at 8.1 keV which for T-20MK is made up of 1s2-1snp (n>2) lines of Fe XXV but for lower temperatures the largest contributors are the satellites to these lines. The importance of these satellites has only recently been realized through investigations with the CHIANTI atomic database and code. In this paper, we will give results comparing their predicted intensities with measurements of the Si lines made by RESIK and the Fe-line complexes made by RHESSI.

 Ionization of the Post-Shock Gas in the Wolf-Rayet Colliding-Wind Binary WR140

*Andy Pollock, **M.F. Corcoran, ***I.R. Stevens, ****P.M. Williams,

Apartado 50727
Villafranca del Castillo
28080 Madrid, Spain


***University of Birmingham, England.

**** ROE, Scotland

The textbook Wolf-Rayet WC7+O4.5 colliding-wind binary WR140 went through the periastron passage of its 8-year eccentric binary orbit in early 2001 as the two stars made their closest approach. Chandra grating observations made when the collisionless-shock-produced X-rays were at their brightest gave the opportunity to study the velocity profile of lines, all of which were resolved and blue-shifted. These measurements constrain the flow of hot gas and where different ions were made. The lower velocity widths of cool ions imply a plasma that was not in equilibrium. The expected variation of ionization balance with binary separation probably accounts for hitherto puzzling variations in the strength of the 6.7 keV Fe lines observed years ago with ASCA.

 X-Ray Satellites Spectra in the La1 Region

Surendra Poonia

Central Arid Zone Research Institute, India
Surendra Poonia,
Division of Natural Resources and Environment, Central Arid Zone Research Institute,
Jodhpur - 342 003, Rajasthan, India

Poster Abstract

The X-ray satellite spectra arising due to 2p3/2-13x-1-3x-13d-1 (x = s, p, d) transition array, in elements with Z = 40 to 92, have been calculated. While the energies of various transitions of the array have been determined by using available HFS data on 1s-1-2p-13x-1 and 2p3/2-1-3x-1,3x'-1 Auger transition energies and their relative intensities have been estimated by considering cross - sections of singly ionized 2x-1 (x = s, p) states and then of subsequent Coster-Kronig and shake off processes. The calculated spectra have been compared with the measured satellite energies in La1 spectra. Their intense peaks have been identified as the observed satellite lines. It has been established that six satellites observed in the La1 region of the X-ray spectra of various elements and named a3, a4, a5, a¢, aix and ax in order of increasing energy are mainly emitted by 2p3/2-13d-1-3d-2 transitions.


The He-Like Triplet Ratios as Powerful Plasma Diagnostic Tools

Delphine Porquet

MPI-Extraterrestrische Physik
P.O. Box 1312
Garching bei Munchen, 85741 Germany

With the advent of the new generation of X-ray satellites (Chandra and XMM-Newton), X-ray spectroscopy with unprecedented spectral resolution for extra-solar objects is now possible for the first time. In particular, the He-like line triplet ratios are powerful diagnostic tools for a variety of plasmas such as collisional (e.g., stellar coronae), and/or photo-ionized (e.g., Active Galactic Nuclei) plasmas. I will show how the triplet line ratios can be used to infer the density, the electron temperature (and ionization processes) of the plasma. I will review the advantages and limitations of these diagnostics and as well the perspectives with Astro-E2 and Constellation X.


Atomic Processes, Theories, and Data For X-Ray Astronomy

Anil Pradhan

Department of Astronomy
The Ohio State University
Columbus, OH 43210

A review of theoretical approximations and experiments for atomic data will be presented. The Close Coupling R-matrix method affords an ab initio and self-consistent treatment of atomic processes on a large-scale: electron impact excitation, photoionization, electron-ion recombination (including both 'radiative' and 'dielectronic' recombination), and transition probabilities. Agreement between experiments and R-matrix results for electron-ion recombination cross sections show that it is possible to calculate rates to 10-20% accuracy, and that there are no significant shortcomings. However, comparison with the distorted wave method and its variants is hampered by lack of availability of detailed cross sections, transition probabilities, and rates for individual atomic transitions over all temperature/density regimes of interest. Such a comparison of fundamental atomic parameters is essential to not only benchmark theories and experiments, but also to ascertain the validity of neglecting or treating indirectly atomic effects such as resonances, fine structure, plasma conditions, etc. Atomic database efforts, including data computed but not yet publicly available, will also be addressed.

X-ray Diagnostics of Ionizing Plasmas in Collisionless Shocks

Cara E. Rakowski

Harvard-Smithsonian CfA
60 Garden Street, MS 70
Cambridge, MA 02138

The energy distributions of electrons and ions from thermal to cosmic-ray populations behind a collisionless shock are still under investigation. Anything from pure thermal populations with mass-proportional heating to efficient cosmic-ray acceleration may occur. The primary goal of X-ray observations at the shock front has been to diagnose the post-shock electron temperature, and hope to see signatures of the ion temperatures and any high energy tails. There are many complications to this endeavor: The X-ray emission peaks well behind the shock front, so that the immediate post-shock electron temperature must be inferred from the current temperature. The timescale for this extrapolation must be deduced from how far out of equilibrium the ionization state is. The accuracy of measuring an ionization timescale from the X-ray spectrum depends strongly on our knowledge of the ionization and recomb! ination rates (including DR) as well the emission processes. However, lines that are only strong in a rapidly ionizing plasma could provide a separate proof of non-equilibrium conditions distinct from diagnostics that are indicative of the temperature or ion fractions. Currently, most atomic calculations have focused on either equilibrium or photo-ionizing plasmas. Less attention has been paid to transitions that would only be common in a low density collisionally ionizing plasma, such as radiative decays from high energy states created by inner-shell ionization. In this talk I will present examples of both traditional temperature and ion fraction diagnostics as well as lines that would be undetectable in anything other than a rapidly ionizing plasma.

 Analysis of a XMM-Newton Spectrum of the Extremely Hot White Dwarf in Nova V4743 Sgr

Thomas Rauch, K. Werner, M. Orio

Bamberg Observatory
Sternwartstrasse 7
96049 Bamberg, Germany

Poster Abstract

Classical novae occur in close binary systems (main-sequence star + white dwarf). V4743\,Sgr is a very fast nova exhibiting a X-ray spectrum which is consistent with a view on the optically thick atmosphere of an extremely hot white dwarf. It exhibits strong absorption features of the C\,V, C\,VI, N\VI, N\,VII, and O\,VII resonance lines indicating an effective temperature of about 600\,000\,K.

We present preliminary results of a spectral analysis by means of line-blanketed non-LTE atmosphere models of a XMM-Newton RGS-1 spectrum of V4743\,Sgr, taken about half a year after its outburst.

 X-ray Diagnostics of Astrophysical Plasmas

John Raymond

Harvard-Smithsonian Center for Astrophysics
60 Garden Street
Cambridge, MA 02138

This is a brief historical overview of X-ray diagnostics and of the general codes that predict thermal X-ray emission spectra. It will discuss the general approaches behind different
X-ray models and the general ideas behind line ratio diagnostics for density, temperature and optical depth. It will also discuss some of the things that might be added to the codes and the level of accuracy available.


A Primer on Atomic Theory Calculations (for X-Ray Astrophysicists)

Francis Robicheaux

Auburn University
206 Allison Lab
Auburn, AL 36849

I will give an overview of different types of atomic calculations with an emphasis on how the methods work. The focus will be on the methods that are mostly used to generate data for plasma physics. The topics might include atomic structure, photo-ionization/auto-ionization, electron scattering, and heavy particle scattering. The methods might include classical trajectory Monte Carlo, perturbation theory, and configuration interaction/close coupling. I will describe how the different methods work and describe the strengths and limitations of the different methods.

 Compton Scattering in Fluorescent Fe K Line Profiles

Agata Rozanska and Jerzy Madej

Nicolaus Copernicus Astronomical Center
Bartycka 18,
00-716 Warsaw, Poland

I plan to present recent progress in modeling of X-ray illuminated atmospheres, where radiative transfer of both:external radiation and self radiation of affected gas, is precisely computed. Also, I will describe wide variety of modeled spectra calculated by our group for
different physical parameters of gas.

In models of atmosphere in hydrostatic equilibrium the equation of transfer includes terms which represent emission of the fluorescent Fe Ka and Fe Kb lines, up-scattered on free electrons by multiple Compton scattering process. Modeled spectra exhibit distinct Compton shoulders from red side of line recently observed by Bianchi et al. 2002, Watanabe et al. 2003.

 Ionization and Recombination: Laboratory Measurements and Observational Consequences

Daniel Wolf Savin

Columbia Astrophysics Laboratory
550 West 120th Street
MC 5247
New York, NY 10027

Reliably interpreting spectra from both photoionized and electron-ionized cosmic sources requires an accurate understanding of the ionization balance and the underlying atomic collision processes which produce the ionization structure. Uncertainties in ionization balance calculations hamper our ability to model cosmic sources and affect our ability to infer reliably their properties. Of particular importance are accurate rate coefficients for electron impact ionization (EII) and dielectronic recombination (DR) . I will review the astrophysical implications due to current uncertainties in EII and DR and discuss our ongoing laboratory work aimed to remove these uncertainties.

 Grating Emission Line Analysis in Cataclysmic Variables

Eric M. Schlegel, V. Rana, TIFR, K. P. Singh, TIFR, P. Barrett, STScI

Smithsonian Astrophysical Observatory
60 Garden Street, Mail Stop 4
Cambridge, MA 02138

Poster Abstract

We describe the analysis of the emission lines detected in the grating observations of cataclysmic variables. In contrast to the approach of the Mukai et al. (2002) paper describing the CV spectra as either 'cooling flows' or 'photoionized', we fit each line individually and examine the global behavior. We compare our results to the global fitting approaches of Mukai et al. as well as those adopting multiple-temperature component models.

 X-ray K Band Absorption of Ionized and Molecular Oxygen in the ISM

Norbert S. Schulz, A. Juett, D. Chakrabarty

MIT Center for Space Research
70 Vassar Str., Bldg. 37
Cambridge, MA 02139

The interstellar medium (ISM) is composed of gas and dust in various phases that contains both compact clouds and diffuse gas components. Despite years of study, questions still remain as to the relationship between these components. High-resolution X-ray observations from the Chandra X-ray Observatory and future observatories now offer a new window with which to study the ISM through K band absorption studies. We review the current status of the treatment of photoelectric absorption specifically with respect to oxygen. This includes atomic oxygen as well as oxygen bound in molecules. These predictions are then compared with measurements obtained with the Chandra/HETGS and the XMM-Newton/RGS with the emphasis on signatures from OI, II, and CO, CO2, and O2. Consequences for ISM studies are discussed.


The Remarkable Soft X-Ray Emission in NGC 4151 -Does It Still Look Like a Seyfert 2?

Nicholas J. Schurch, R. S. Warwick, R. E. Griffiths

Carnegie Mellon University
Dept. of Physics,
5000 Forbes Avenue
Pittsburgh, PA, 15213

There is growing evidence that the extended soft X-ray emission observed in nearby heavily obscured AGN are dominated by of photoionized emission lines that originate in low temperature (~40,000 K) gas in the extended Narrow Line Region (NLR). We present the results of the most recent XMM-Newton observations of NGC 4151, focussing on the RGS spectrum of NGC 4151 and comparing the results from the new observation with the previous observations. The soft X-ray emission in NGC 4151 is extremely rich in emission lines and radiative recombination continua but, in contrast with the earlier observations, the new data do show some evidence for underlying continuum emission. We associate this with intrinsic changes in the environment of the AGN. The emission line spectra are modeled in terms of photoionized and photoexcited gas in the extended NLR of the source and accurately define the ionization state and outflow velocity of the material in the ionization cones of this source.

 High-Energy High-Resolution X-Ray Spectroscopy

Eric Silver

Harvard-Smithsonian Center for Astrophysics
60 Garden Street
Cambridge, MA 02138

Nuclear line astrophysics provides a direct probe of the details of one of the most violent events in the universe­ a supernova explosion that expels the heavy elements in the ISM from the nuclear furnace in which they were created. Because of its production deep in the stellar core and 60 year half-life, 44Ti provides a key diagnostic of supernova explosions. By using a high resolution microcalorimeter optimized to measure the hard x-ray emission at 68 keV from the chain of 44Ti decay products, one can determine the extent and velocity distribution of the 44Ti emitting region. Details of the spectrometer and simulated results will be resented.


Modelling the X-Ray Spectra of High Velocity Outflows from Quasars

Stuart A. Sim

Imperial College London
Astrophysics Group
Blackett Laboratory
Prince Consort Road
SW7 2AZ London, UK

High velocity outflows from supermassive black holes have been invoked to explain the recent identification of strong absorption features in the hard X-ray spectra of several quasars. New 2-D Monte Carlo radiative transfer calculations utilising indivisible energy packet quanta and Lucy's recently developed macro atom approach have been performed to synthesise X-ray spectra from such outflows. The results of these computations will be presented to show that simple, parametric bi-conical outflow models with plausible choices for the wind parameters predict spectra that are in good qualitative agreement with observations. Particular attention will be given to the bright quasar PG1211+143 for which constraints on the geometry and mass-loss rate of a possible outflow will be discussed subject to the limitations of the currently available observational data.

 What is the Origin of the Soft Excess in AGN?

Malgorzata A. Sobolewska, Chris Done

Copernicus Astronomical Center
Bartycka 18
00-716 Warsaw, Poland

We investigate the nature of the soft excess observed in AGN using XMM-Newton data of the low redshift, optically bright quasar PG1211+143, and the Narrow Line Seyfert 1 galaxy 1H0707-495. We test whether the soft excess below 1 keV and the sharp spectral drop around 7 keV are better explained by the reflection-dominated model, complex absorption model, partial covering model, or models including a seperate spectral component. We discuss the advantages and disadvantages of these different approaches.


X-Ray Spectroscopy of Multi-Phase Hot Gas in and Around Galaxies

David Strickland

Johns Hopkins University
Dept. of Physics and Astronomy,
Johns Hopkins University,
3400 N. Charles St.
Baltimore, MD 21218

Poster Abstract

Both analytical and hydrodynamical models for stellar wind-blown bubbles, superbubbles blown by clusters of massive stars, and starburst-driven superwinds predict complex X-ray differential emission integral distributions [EI(T)] that are not well approximated as one or two temperatures, or even simple functions such as Gaussians. Furthermore, it is possible that the hot gas in not in ionization equilibrium, different scenarios predicting either ionizing or recombining plasmas.

Accurately recovering EI(T) and the ionization state from X-ray spectra is vital in order to accurately determine the gas-phase abundances in these objects. I will present a few example realistic theoretical EI(T) distributions for bubbles and superwinds, demonstrate the level of systematic errors to be expected from fitting Chandra or XMM-Newton spectra with the standard simple model, and also consider the efficacy of high-resolution plasma diagnostics in the presence of complex EI(T) distributions.

 Cygnus X-3: A Study of the Bepposax Spectra

Anna Szostek

N. Copernicus Astronomical Center
ul. Bartycka 18
00-716 Warszawa, Poland

Poster Abstract:

BeppoSAX data constitute a compromise between the high energy resolution of narrow band data collected by Chandra and broad band low resolution RXTE data.

Using the BeppoSAX data, we present an attempt to model the broad band continuum (~1-200 keV) together with discrete spectral features in the high mass X-ray binary system Cygnus X-3. The continuum modeled by hybrid plasma comptonization is modified by the strongly ionized plasma of stellar wind coming from the Wolf Rayet companion star. Discrete absorption and emission spectral features are modeled with the XSTAR table models. The model has been applied to hard and soft state phase resolved spectra.

 High Resolution X-ray Spectroscopy of SN 1006

Jacco Vink

SRON National Institute for Space Research
Utrecht, 3584CA The Netherlands

I will discuss spectroscopic aspects of the remnant of SN 1006. SN 1006 has received a lot of attention over the last decade, mainly because of the X-ray synchrotron emission from its shell. However, the thermal emission of SN 1006 is equally interesting, as it is a remnant with one of the lowest known ionization ages (log (ne t) ~ 9.3), i.e. it is very much out of collisional ionization equilibrium. As a result there is relatively little emission from H-like ions, some elements, notably Si, have not even reached the He-like ionization state. The low ionization state has considerable consequences for the debate about whether the shocked iron abundance is high or not, which is of interest because SN 1006 is likely to have been a Type Ia event, which are thought to produce ~0.5 Msun of Fe. The low ionization age has also interesting consequences for the electron-ion temperature equilibration. I will address these topics using results obtained with high resolution XMM-Newton/RGS data, but in addition I will also show the prospects for observation of SN 1006 and other remnants with future spectroscopic missions, such as Astro-E2 and Constellation-X/Xeus.


Chandra HETGS Observations of B Supergiants

Wayne L. Waldron

L-3 Communications Government Services, Inc.
1801 McCormick Drive, Suite 170
Largo, MD 20774

The X-ray emission from OB stars is believed to arise from a distribution of stellar wind shocks. However, analyses of HETGS data from OB stars indicate that there are some problems with this interpretation and HETGS observations of B supergiants can be used to help resolve these issues. Observations of B supergiants extend our understanding of the UV flux dependence of He-like f/i emission line ratios by providing measurements at lower UV flux levels. The diversity in B supergiant wind properties as compared to other OB stars allows us to probe different distributed X-ray source models and test (over a broader range in OB stellar effective temperatures) the developing concept that the observed He-like X-ray emission lines from OB stars are emerging from their associated X-ray continuum optical depth unity radii. We present the first HETGS observation of an early B supergiant, Epsilon Orionis (B0 Ia), and compare the X-ray emission line characteristics, X-ray locations, and the distribution of X-ray temperatures with other OB star results.

 Diffuse Hot Gas Under X-Ray Absorption Line Spectroscopy

Daniel Q. Wang, Yangsen Yao

University of Massachusetts Amherst
Astronomy Dept.
Amherst, MA 01003

We will review our study of diffuse hot gas, based on both Chandra and XMM-Newton grating spectroscopic observations. In particular, we will report the results from our recent 100 ksec TOO observation of LMC X-3. The OVII absorption line by the Galactic gas is clearly detected, with an equivalent width comparable to those seen in the spectra of AGNs. In addition, we have systematically analyzed archival data on both Galactic X-ray binaries and AGNs, which has led to the detection of various absorption lines (O~VII Kalaph, O~VII Kbeta and/or O~VIII~Kalpha). We have also conducted comparisons with diffuse X-ray emission and far UV OVI line observations to estimate or tightly constrain the spatial, kinematic, and thermal properties of the gas. We will also discuss the implications of the results for the understanding of the Galactic gaseous halo and the warm/hot intergalactic medium.


Turning Cool Star X-ray Spectra Upside Down

Klaus Werner, J.J. Drake

University of Tuebingen
Institut fuer Astronomie und Astrophysik
Sand 1
Tuebingen, D-72076 Germany

H1504+65 is a young white dwarf with a temperature of 200,000K and is the hottest post-AGB star ever analysed with detailed model atmospheres. Chandra LETG+HRC-S spectra have revealed the richest X-ray absorption line spectrum recorded from a stellar photosphere to date. The line forming regions in this extremely hot photosphere produce many transitions in absorption that are also observed in emission in cool star coronae. We have performed a detailed comparison of Chandra spectra of H1504+65 with those of Procyon and alpha Cen A and B. State of the art non-LTE model spectra for the hot white dwarf have enabled us to identify a wealth of absorption lines from highly ionised O, Ne and Mg. In turn, these features have allowed us to identify coronal lines whose origins were hitherto unknown.

 Atomic Data for the Atmospheres of Strongly Magnetized Neutron Stars

M. Klews, *K. Werner, G. Wunner

*University of Tuebingen
Institut fuer Astronomie und Astrohysik
Sand 1
Tuebingen, D-72076 Germany

Calculations of synthetic spectra of strongly magnetized neutron stars are bedeviled by the lack of data for atoms in intense magnetic fields. While the behavior of hydrogen and helium has been investigated in detail, complete and reliable data for heavier elements, in particular iron, are still missing. Since neutron stars are formed by the collapse of the iron cores of massive stars, it may be assumed that their atmospheres contain an iron plasma. We have developed a new method for the fast computation of wave-lengths and oscillator strengths for medium-Z atoms and ions, up to iron, at neutron star magnetic field strengths. The method is a parallelized multi-configuration Hartree-Fock approach based on finite-element and B-spline techniques. It turns out that typically 15 finite elements are suffcient to calculate energies to within a relative accuracy of 10-5 in 4 or 5 iteration steps using B-splines of 6th order, with parallelization speed-ups of 20 on a 26-processor machine. Results will be presented for the energies of the ground states and excited levels and for the transition strengths of astrophysically relevant atoms and ions in the range Z = 2 . . . 26 in different ionization stages.


 Developments in Soft X-Ray Spectral Modelling for Fusion

A D Whiteford, N R Badnell, R Barnsley, I H Coffey,
M G O'Mullane, H P Summers and K-D Zastrow

Department of Physics
University of Strathclyde
107 Rottenrow
Glasgow, G73 5DH UK

High resolution x-ray spectroscopy instrumentation currently in use in fusion and planned for ITER briefly reviewed. The main part of the talk will focus on the diagnostic analysis in magnetically confined fusion plasmas with attention drawn both to the methodology in common with that in astrophysics and to points of departure -- such as species, transport, high density and the role of neutral hydrogen. Comment is also made on the state of high quality theoretical collision data from a fusion perspective and how it can support rigorous error analysis of better spectroscopic measurements.


The Absorption Line Spectroscopy of Hot Galactic Interstellar Medium

Yangsen Yao, Q. Daniel Wang

University of Massachusetts, Amherst
710 North Pleasant Street
Amherst, MA 01003

We have studied the large-scale hot interstellar medium (HISM) in the Galaxy, based on the X-ray absorption line spectroscopy of X-ray binaries. The data are obtained from the Chandra grating spectrometer archive. The observations, though not optimized for such a study, have led to the significant detection of Ne~IX Ka absorption lines in the spectra of seven X-ray binaries. Three of these spectra also show evidence for absorptions by O VII KaKb and/or O~VIII~Ka. The detected absorption lines are consistent with an origin in the diffuse HISM. We have implemented an accurate line profile model in XSPEC to account for line saturation and to facilitate a joint analysis of multiple line detections. The average temperature of the absorbing gas is ~ 106.3 K (assuming a collisional ionization equilibrium) and the average hot gas density is ~4.2 x 10-3 cm-3.


Outflows, Accretion Disks & the IGM: High Resolution Chandra & XMM Spectroscopy of AGN

*Tahir Yaqoob, B. McKernan, U. Padmanabhan, P. Serlemitsos, I. George, J. Turner, J. Reeves

*Johns Hopkins University
Physics Astronomy
3400 N. Charles St.
Baltimore, MD 21218

We discuss the principal new results which have emerged from over five years of high resolution X-ray spectroscopy of Active Galactic Nuclei with Chandra and XMM. The picture emerging from measurments of absorption and emission lines, both from the soft X-ray band and the Fe K band is one which is more complex than anticipated during the ASCA era and provides important new clues on the dynamics and physical state of circumnuclear matter, as well as the putative accretion disk, and in some cases the IGM. The current data provide a tantalizing glimpse into an even richer phenomenology which will likely be uncovered by Astro-E2 and future missions. We show some simulations illustrating how Astro-E2 will resolve some key dengeneracies in the cuurent data and therefore provide unique constraints on the ionization structure and kinematics of matter in the central engine of AGN.