Workshop scientific programme
Posters abstracts
| Session 2: Stellar Coronae |
2-1 Elena Franciosini (INAF/Osservatorio Astronomico di Palermo)
XMM-Newton Spectroscopy of Hyades Stars
We present the results of XMM-Newton observations of two Hyades stars: the giant theta1 Tau and the solar-type star VB 50. From the analysis of RGS and EPIC spectra we derive the temperature structure and chemical abundances of the coronae of the two stars.
2-2 Antonio Maggio (INAF/Osservatorio Astronomico di Palermo)
XMM RGS Observations of X-ray Luminous G-type Stellar Coronae
We present results from the analysis of the XMM RGS X-ray spectra of 31 Com and HD 283572, two G-type stars in very different evolutionary phases, but with equally high X-ray luminosity. Similarities and differences in the inferred properties of their coronae are discussed.
2-3 Roberto Pallavicini (Osservatorio Astronomico di Palermo)
The complex RGS spectrum of sigma Orionis
We present an XMM observation of the sigma Orionis cluster obtained as part of the GTO time. In addition to the EPIC image, which shows the presence of about 250 sources, mostly low-mass PMS stars belonging to the cluster, a high statistics RGS spectrum is obtained for the central star sigma Ori (O9 V). The RGS spectrum is dominated by lines around 5 MK. We present a detailed analysis of the RGS spectrum and we discuss the possible contamination by nearby sources in the central area of the cluster.
2-4 Jorge Sanz-Forcada (Osservatorio Astronomico di Palermo)
The Longest X-ray Observation of AB Dor
A set of XMM observations of AB Dor (K1 V-IV) has been collected totalling more than 400 ks. The resulting spectrum is analyzed in order to obtain the Emission Measure Distribution, abundances and electron density of this well known young star. The results are compared to those obtained with other instruments.
2-5 Beate Stelzer (MPE Garching/Osservatorio Astronomico di Palermo)
Castor A and Castor B Resolved in a Simultaneous Chandra and XMM-Newton Observation
No text provided.
2-6 Beate Stelzer (MPE Garching/Osservatorio Astronomico di Palermo)
The XMM-Newton View of TW Hya
No text provided.
| Session 3: Hot Stars | |||||||
3-1 Stan Owocki (University of Delaware/University of Glasgow)
X-rays from Magnetically Confined Wind Shocks in Hot Stars
Hot star winds can emit soft X-rays from shocks originating from instrinsic instabilities in the radiative driving. But harder X-rays more like arise from stronger shocks resulting from magnetically confined or channelled wind outflow. I will describe recent MHD simulations of this process done in our research group, and summarize the status of our ongoing efforts to use these simulations to model the observed X-ray emission from several hot stars.
3-2 Andy Pollock (ESA/Vilspa)
Doppler Shifts and Absorption in the X-ray Spectra of WR140 near the 2001 Periastron Passage
The bright colliding-wind binary WR140 (WC7+O4-5) went through the periastron passage of its eccentric 8-year orbit in early 2001. The Chandra HETG spectra taken a few weeks before show prominent resolved emission lines whose Doppler shifts map the flow of a gas not obviously in a state of equilibrium ionisation. The heavy absorption present in the post-periastron spectra is clearly from the WC star although simple models drawn up from popular abundance schemes do not fit the data very well.
3-3 Patrick Wojdowski (MIT)
A Determination of the Temperature Distribution of HD 206267 Using Single-Ion Spectral Models
We have obtained a high-resolution X-ray spectrum of the triple O star system HD 206267 with Chandra HETGS for the purpose of studying the properties and dynamics of the system's stellar wind. The spectrum contains emission lines from hydrogen and helium-like oxygen, neon, and magnesium, helium-like silicon and the iron L-shell ions XVII, XVIII, and XIX. We have fit this spectrum with a combination of emission-line spectra of the individual ions at the temperatures at which the populations of the ions peak. From this fit we derive a temperature differential emission measure distribution which is non-zero only below ~8MK. An analysis of the emission line profiles in which optically thick line emission is properly accounted for is ongoing.
| Session 4: X-ray Binaries, Pulsars, Novae | |||||||
4-1 Agnieszka Majczyna (Copernicus Astronomical Center, Warsaw)
Ratio of Colour and Effective Temperatures in X-ray Burst Spectra
We present model atmospheres and theoretical spectra for X-ray bursters. Our models include the effects of Compton scattering on free electrons. The atmospheres have compositions that are mixtures of hydrogen, helium, and iron. For our models the ratio of colour temperature, T_c, to effective temperature, T_eff, is in the range 1.2 - 1.8. This ratio depends on T_eff, surface gravity, and iron abundance. For fixed T_eff and surface gravity, models with non-zero iron abundance exhibit values of T_c/T_eff that are slightly lower than pure hydrogen-helium models.
| Session 5: Supernova Remnants | |||||||
5-1 Jean Ballet (SAp, CEA Saclay)
RGS Spectrum of Kepler's SNR
We present our attempts to model the RGS spectrum of Kepler's SNR, in conjunction with the EPIC spectrum and image. The source is bright, but extended (about 3 arcminutes across). The EPIC image is not the same in the O K lines as in the Fe L and Si K lines. We model individual lines and the spectrum globally, attempting to measure Doppler shifts and broadening.
| Session 6: Active Galactic Nuclei and IGM | |||||||
6-1 Stefano Bianchi (Universita' degli Studi Roma Tre)
Chandra Detection of the Iron Compton Shoulder in the Circinus Galaxy
We report on the detection of the iron line Compton shoulder with a flux of about 20 % the line core in the Chandra HEG spectrum of the Circinus Galaxy. This feature is predicted on theoretical grounds as arising from Compton scattering of the fluorescent line photons in optically thick matter, and the observed flux and width are fully consistent with Monte Carlo simulations, which are also presented here.
6-2 Graziella Branduardi-Raymont (UCL/MSSL)
XMM-Newton Spectroscopy of the Seyfert 1.9 / NEL Galaxy NGC 7314
Preliminary analysis of the XMM-Newton observation of NGC 7314 shows that rapid variability in the 0.2 - 12 keV flux of this object is not associated with spectral changes. A significant amount of warm absorption is required to explain the complexity of the X-ray spectrum at low energies. The continuum and Fe K line emission are best explained by reflection and fluorescence in cold gas at some distance from the active nucleus, far out in the accretion disk or in a molecular torus.
6-3 Elena Jimenez Bailon (LAEFF/INTA)
The Nuclear XMM-Newton Spectrum of the Seyfert 2 Galaxy NGC 1808
No text provided.
6-4 Steven Fuerst (UCL/MSSL)
Transfer of Line Emission from Accreting Black Holes
Observations of emission lines provide the opportunity to probe the extreme environment around black holes. We calculate line profiles from accretion disks including the effects of resonant absorption by relativistic media, as the photons propagate through the curved space-time.
6-5 Agata Rozanska (Copernicus Astronomical Center, Warsaw)
The Origin of Emission and Absorption Features in Ton S180 Chandra Observations
We present a new interpretation of the Ton S180 spectrum obtained by the Chandra Imaging Spectrometer. Several narrow absorption lines and a few emission disk lines have been successfully fitted to the data. We have not found any significant edges accompanying line emission. Therefore, we propose the interpretation of lines consistent with the paper recently written by Krolik (2002), where the warm absorber is strongly inhomogeneous. Such situation is possible in so called multi-phase medium, where regions with different ionization states, densities and temperatures may coexist in thermal equilibrium under constant pressure. We present theoretical spectra of radiation transfered by a stratified cloud with constant pressure (not density) computed by code 'titan' in plane parallel approximation. Such models fully explain the lack of edges in the spectrum of Ton S180 and put new constrains on the structure of the warm absorber.
6-6 Tracey Jane Turner (NASA/GSFC and UMBC)
The X-ray Spectrum of NGC 3516
Narrow emission features, probably redshifted iron lines, have recently been reported by us in the spectrum of NGC 3516 during an XMM/Chandra observation. We now discuss the properties of the warm absorber and the shape of the X-ray continuum in this source during the same observation.
| Session 7: Clusters of Galaxies | |||||||
7-1 Martin Still (NASA/GSFC)
Gas Dynamics in the Cluster Core of Abell 2597
In common with many of the galaxy clusters observed by XMM-Newton, the RGS fails to detect significant emission from gas below 1 keV. This is in contrast to the expected temperature profiles of the standard cooling flow picture. Among numerous models of heating, mixing and reprocessing that have been invoked to remove 1 keV gas, galaxy mergers in the core of the cluster are expected to at least partially stifle the flow. Chandra imaging of structure in clusters has provided some evidence for mergers, but in Abell 2597 we find a discrepancy between the redshift of the cooling gas and the surrounding halo of 1600 +/- 300 km/s, indicating that the cluster is not relaxed. We find a OM-UV source in the core, too bright to be the result of star formation from cooling flow material. The position of this source, slightly removed from the cD galaxy, supports the merger idea.
| Session 8: Instrumentation/Data Analysis | |||||||
8-1 John C. Houck (MIT)
ISIS: The Interactive Spectral Interpretation System
ISIS, the Interactive Spectral Interpretation System, is designed to facilitate the interpretation and analysis of high resolution X-ray spectra. It also supports analysis of lower resolution data, such as CCD spectra, via standard instrument response matrices; all XSPEC spectral models are available. In one package, ISIS combines functions to query a database of atomic data and plasma emission models with functions to manipulate and measure high resolution spectral data. These tools simplify low level operations such as file input, data plotting and database search and retrieval, allowing users to concentrate on higher level analysis issues. ISIS is programmable and extensible, meaning that users can write new functions to simplify repetitive analysis tasks and can extend the ISIS command set by adding those functions (or even user-supplied C programs) as new commands. S-Lang, the interpreted language which provides these features, also provides array-based mathematical functions which greatly simplify common analysis operations. ISIS is free software, written in ANSI-C and is intended to be portable across most Unix operating systems. For more information, see the ISIS web page at http://space.mit.edu/CXC/ISIS. This software was developed by the MIT Center for Space Research under contract SV1-61010 from the Smithsonian Institution.
8-2 Jan-Uwe Ness (Hamburger Sternwarte)
Modelling the NeIX Triplet with Chandra Using HEG, MEG, and LETGS
The He-like NeIX triplet around 13A is severely blended by Fe lines in ionization stages XVIII to XXI. Especially the weak intercombination line cannot easily be disentangled, but is important for measurements of the plasma density at around 4MK. We use the HEG calibration data of Capella (155 ksec co-added) in order to show that the line database APEC can handle the blending even for the difficult case of Capella quite well. The blending lines are identified and a procedure is introduced how data with lower resolution (MEG, LETGS, and RGS) can still be good for useful measurements.
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