XEUS Con-X artistic impression Abstracts

Workshop talks


Session 1: Plasma Modelling

Susmita Chakravorty (IUCAA)

Impact of sub-keV soft excess on warm absorbers

Soft X-ray spectral features of warm absorbers (WA) are often found in Seyfert 1 galaxies. The ionizing continuum coming from the central engine and which photoionizes the WA, can be optimally modeled to have three spectral components a) the ‘disk blackbody’ at about 10 eV - the spectrum from the accretion disk of the black hole, b) the X-ray powerlaw - representing the dominant component at energies 1 keV and above and c) the soft excess in sub keV - which is seen in most objects after deducting the powerlaw component. We use the thermal equilibrium curves generated by the photoionization code CLOUDY to study the influence of the soft excess component on the nature of the WA.

Our studies show that the nature of the WA is strongly dependent on the chemical composition of the absorbing gas, particularly on the abundance of iron, oxygen and the X-ray group (C, Ne, O, Fe) which have important atomic transitions in the energy range 0.3 - 1.5 keV where the soft excess component is supposed to have maximum effect. One of the popular models for the soft excess component is a blackbody with its temperature lying between 100 - 200 eV. We find that the soft excess component seems to decide the stability properties of the gas at 105 K; the range of ξ/T over which stable warm absorber exists almost doubles if the soft excess luminosity is equal to the luminosity in the powerlaw (0.1 - 10 keV) which is a ratio not unheard of. Even if the soft excess is represented using alternative spectral shapes like the “comptonized reflection” model, the stability properties of the WA do not change significantly.

Randall Smith (SAO)

The Challenges of Plasma Modeling: Current Status and Future Plans

As more high-resolution X-ray spectra become available, the X-ray astrophysics community, including laboratory astrophysicists, observers, and modellers, needs a common storehouse of accurate and complete atomic data that can be easily accessed in order to analyze this data. I will discuss the both the current status and our future plans for atomic codes and data for X-ray astrophysics, along with some mention of the state of the art in other related fields such as fusion research.

Session 2: X-ray Binaries

Laurence Boirin (Strasbourg Observatory)

X-ray spectroscopy of X-ray binaries

I will review X-ray spectroscopic results obtained from Chandra, XMM-Newton and Suzaku observations of X-ray binaries.

Ed Cackett (University of Michigan)

Investigating the Nature of Absorption Lines in the Chandra X-Ray Spectra of the Neutron Star Binary 4U 1820-30

I will discuss Chandra gratings spectra of the neutron star low-mass X-ray binary 4U 1820-30. We study four observations over a range of fluxes to better understand the nature of X-ray absorption lines in neutron star LMXBs. The equivalent widths of the lines are generally consistent between the observations, as expected if these lines originate in the hot interstellar medium. There is apparent variability in the O VIII Ly-alpha line equivalent width providing some evidence that at least some of the O VIII absorption arises within the system. However, the significance is marginal (2.4-sigma), and the lack of variation in the other lines casts some doubt on the reality of the variability. I will show how XSTAR photoionization models can reproduce the observed spectra, but requires an extremely low filling factor. Thus, both the ISM and local absorption origins remain possible.

Elisa Costantini (SRON, Netherlands Institute for Space Research)

The complex gas environment of EXO 0748-676

Thanks to the high energy resolution now available, the complex gaseous environment of X-ray binary systems has been revealed. Here we present the results on a large RGS data-set of EXO 0748-676, a bright dipper. We report the effects of different ionisation mechanisms: photo- and collisional- ionsation, producing both absorption and emission lines. This is the first time that a collisionally ionised gas has been detected in a X-ray binary system. We test different gas geometry and we investigate the possibility of an X-ray-circumbinary disc.

Andy Pollock (ESAC)

The dynamics of the collisionless plasmas in WR140 and other colliding-wind binaries

The orbit of the most brilliant eccentric WC7+O5 colliding- wind binary system WR140 up to the 2009 January periastron passage has given the opportunity to make direct measurements of the collisionless plasma at different phases. The clear differences are compared with the predictions of analytical and numerical models of the physics and dynamics and used to prepare the ground for future measurements of similar systems.

Lara Sidoli (INAF-IASF Milano)

High resolution spectroscopy of the Low Mass X-ray Binary XB1832-330

I will report on the first high spectral resolution observation of the Low Mass X-ray Binary XB1832-330, located in the Galactic globular cluster NGC6652. RGS/XMM-Newton observations are used to search for an anomalous Ne abundance in this X-ray binary, suspected to be an ultra-compact X-ray binary (orbital period less than 1 hour).

Session 3: Active Galactic Nuclei

Stefano Bianchi (Universita' degli Studi di Roma TRE)

A broad-line region origin for the iron Kalpha line in NGC 7213

The X-ray spectrum of NGC 7213 is known to present no evidence for Compton reflection, a unique result among bright Seyfert 1s. The observed neutral iron Kα line, therefore, cannot be associated with a Compton-thick material, like the disc or the torus, but is due to Compton-thin gas, with the broad-line region (BLR) as the most likely candidate. To check this hypothesis, a long Chandra High-Energy Transmission Grating observation, together with a quasi-simultaneous optical spectroscopic observation at the ESO NTT EMMI were performed. We found that the iron line is resolved with a full width at half-maximum (FWHM) = 2400(+1100 -600) km/s, in perfect agreement with the value measured for the broad component of the Hα, 2640(+110 -90) km/s. Therefore, NGC 7213 is the only Seyfert 1 galaxy whose iron Kalpha line is unambiguously produced in the BLR. We also confirmed the presence of two ionized iron lines and studied them in greater detail than before. The resonant line is the dominant component in the Fe XXV triplet, therefore suggesting an origin in collisionally ionized gas. If this is the case, the blueshift of around 1000 km/s of the two ionized iron lines could be the first measure of the velocity of a starburst wind from its X-ray emission.

Rob Detmers (SRON)

X-ray narrow line region variability as a geometry probe: The case of NGC 5548

We study the long time scale variability of the gas responsible for the narrow emission lines in the Seyfert 1 galaxy NGC 5548, in order to constrain the location and geometry of the emitting gas. Using X-ray spectra taken with Chandra LETGS and XMM Newton RGS and combining them with long-term monitoring observations of RXTE, we determine the time scale on which the narrow line emitting gas responds to variations of the continuum flux. This, along with the observed parameters of the O VII forbidden emission line allows us to constrain the location and geometry of the X-ray NLR gas. We conclude that the NLR in NGC 5548 is in the form of an ionization cone, very compact in size, and located between 1 and 5 pc from the central source. We also expand our study to other well-observed Type 1 AGN to determine the geometry and location in those sources.

Doron Chelouche (CITA)

LHC science with AGN

I will show that it may be possible to detect dark matter particles and, at the same time, solve the strong-CP problem of QCD, by looking for unique absorption-like features in the X-ray spectra of AGN.

Dan Evans (MIT Kavli Institute for Astrophysics and Space Research)

Spatially Resolved HETG Spectroscopy of Ionization Cones in Seyfert Galaxies: Detailed Studies of NGC 1068 and NGC 2110

I will review how Chandra HETG spectroscopy provides us detailed diagnostics of the spatially resolved, multiphase narrow-line regions (NLRs) in Seyfert galaxies. The superb energy and spatial resolution of the HETG allows us to probe the ionization state and mechanism along the length of the NLR ‘ionization cone’, and in particular distinguish between the competing roles of AGN photoionization and jet-induced collisional ionization. I will present preliminary results from a new 400-ks HETG GTO observation of NGC 1068, and will argue that the detection of narrow RRC features and He-like triplets suggests that photoionization from the AGN dominates the energetics of these kpc-scale regions. I will also show that additional constraints from VLA, HST, and Chandra imaging of NGC 2110 indicate that jets can also play a significant role in shaping NLR environments. I will finally discuss the consequences of these results for models that link AGN outflows with feedback between accretion and black-hole growth.

Tomer Holczer (Technion)

X-Ray in AGN Outflows - MCG -6-30-15 Multi Components

The X-ray spectrum of many type 1 AGNs (Active Galactic Nuclei) features absorption lines, which are blue- shifted with respect to the AGN rest frame. This is evidence for an ionized wind, which could play an important role in galactic and inter-galactic feedback. Charge states as high as Fe+25 are observed. I will shortly show the method we use to measure ionic column densities, outflow velocity, and how we characterize the broad distribution in ionization parameter - the AMD (Absorption Measure Distribution). I will then present our results for MCG -6-30-15, an AGN with at least two distinct velocity components. I will then talk about what could be a third component with an elusive origin.

Anna Lia Longinotti (M.I.T. Kavli Institute for Astrophysics and Space Research)

Photoionised gas in Seyfert 1 Galaxies revealed through emission lines in high resolution X-ray spectra

I will present the observation of the Seyfert 1 Galaxy Mrk 335 performed by XMM-Newton during an unusually low flux state that unveiled an emission line-rich spectrum in the soft X-ray. Line ratio diagnostics from H-like and He-like ions indicate that the emission lines arise in X-ray photoionised plasma. The physical properties of the line emitting material were derived by comparing the observed line intensities to the simulations performed by the CLOUDY photoionisation code. Different solutions for the electron density and column density of the gas are consistent with the spectral diagnostics, preventing us from uniquely determining the properties of the plasma. However, the location(s) of the X-ray photoionised gas can be constrained to within the inner edge of the Broad Line Region. I will briefly present other Seyfert 1 sources where X-ray photoionised emission lines are possibly located in the Broad Line Region and I will review the implication of these findings in a broader context.

Lance Miller (University of Oxford)

Absorption and wind models of AGN

Recent analysis of long observations of bright, nearby AGN such as MCG-6-30-15 indicate that their 0.5-50 keV spectra may be dominated by the effects of absorption, possibly associated with an accretion disk wind. I shall summarise the key points of these analyses and compare observed spectra with the predictions from 3D Monte-Carlo radiative transfer calculations that model the effects of transmission and scattering through a disk wind.

Katrien Steenbrugge (University of Oxford)

Locating the warm absorber in NGC 4051

I will present a detailed modeling of the Chandra LETGS spectrum taken before, during and after the flux decreased by a factor of 5. The resulting spectral changes and lack thereof allow us to place limits on the location of the warm absorber. Using a previous LETGS spectrum we locate 3 out of the 4 detected absorbers to be between 0.02 and 1 pc.

Tracey Jane Turner (UMBC)

New Results on the Importance of Absorption in Shaping the X-ray Properties of AGN

I discuss the evidence for X-ray absorption by partial-covering gas with high column density and ionization-state in AGN, highlighting recent results from NGC 3516 and 1H 0419-577.

Phil Uttley (University of Southampton)

On the reality of red/blue-shifted narrow lines in X-ray spectra

In recent years there have been many reported detections of highly redshifted or blueshifted narrow spectral lines (both emission or absorption) in the X-ray spectra of active galaxies, but these are all modest detections in terms of their statistical significance. If real, these represent a new and potentially powerful probe of the inner regions of AGN. In this talk we will review the issue of the significance of these detections and, in particular, will discuss the somewhat neglected issue of publication bias in astronomy.

Andy Young (University of Bristol)

High Resolution Spectroscopy of Active Galactic Nuclei

High-resolution X-ray spectroscopy of Active Galactic Nuclei (AGN) and Low-Luminosity AGN (LLAGN) provides a unique probe of the structure and dynamics of accretion flows and ionized obscuring gas. I will discuss Chandra High-Energy Transmission Gratings Spectrometer observations of AGN and LLAGN, and what these can tell us about the nature of their accretion flows.

Session 4: Hot Stars and Planetary Nebulae

Carla Baldovin Saavedra (ISDC/Geneva)

Revealing the properties of the weak-lined TTauri binary HDE 245059 with Chandra HETGS and Keck

We present the Chandra (HETGS) and Keck observations of the young weak-lined T Tauri star HDE 245059 located in the Lambda-Ori star forming region. Our observations in both wavelength regimes have shown that the star is in fact a binary separated by 0.87 arcsec. In the X-rays the plasma properties of both binary components are similar; they show a wide range of plasma temperatures from about 6 to 40 MK dominated by plasma between 8 to 15 MK. The hydrogen column density is low (NH ~ 8x1019 cm-2), probably due to the clearing of the region by a supernova explosion 1 Myr ago. The coronal abundances show an inverse FIP effect, which is also observed in other young active stars. We have obtained line fluxes from the He-like triplets finding no evidence of high density plasma, which is consistent with the absence of accretion in the WTT binary. Furthermore, using the near-infrared photometry and evolutionary models we have also obtained the first estimates for the masses, effective temperatures, and radii for the binary components. According to our study HDE 245059 is 2-3 Myr old, accounting on our estimates the binary has experienced the supernova explosion leaving unchanged its coronal properties.

Ehud Behar (NASA/GSFC; on leave from the Technion, Israel)

Ions Crossing the Contact Discontinuity of an Astrophysical Shock

Contact discontinuities (CDs) of astrophysical shocks are extremely difficult to probe directly. We will present spectroscopic evidence for what we believe is shocked ions (kT ~ 100 eV) crossing the CD and penetrating the un-shocked gas (kT ~ 1 eV). This effect is deduced from the observation of a narrow radiative recombination continuum (RRC) in the X-ray spectrum of the PN BD+30° 3639, indicating bare C ions are recombining with cool electrons at kTe = 1.7 ± 1.3 eV. The RRC flux ratio of C VII to C VI constrains the temperature jump across the CD to ΔkT > 80 eV, providing for the first time direct evidence for the stark temperature disparity between the two sides of an astrophysical CD, and constraining the role of magnetic fields and heat conduction in PNs accordingly.

Ton Raassen (SRON)

The LETG spectrum of delta Ori

The O-giant delta Ori was observed in the wavelength range 5–175 Å by the X-ray detector HRC-S in combination with the grating LETG on-board CHANDRA. We perform a multi-temperature fit and model the differential emission measure (DEM) of the spectrum, resulting in a temperature distribution, emission measures, and elemental abundances. Individual line fluxes and width have been measured. Based on the intercombination and forbidden lines in He-like ions the formation of these ions relative to the stellar surface can be established.

Norbert Schulz (MIT)

Massive Stars in the Orion Trapezium

The Orion Trapezium hosts a variety of very young massive stars in the range between roughly 3 to 45 solar masses. Spatically resolved X-ray spectroscopy with Chandra showed a variety of X-ray production mechanisms which include shocks in line driven winds, magnetically confined plasmas, and various coronal emission patterns. This review discusses spectroscopic signatures of these mechanisms and most recent developments.

Young Sam Yu (Rochester Institute of Technology)

High-resolution X-ray Spectroscopy of the Planetary Nebula BD+30 3639

We present the results of the first X-ray gratings spectroscopy observations of a planetary nebula (PN) – the X-ray-bright, young BD +30°3639. We observed BD +30°3639 for a total of ~300 ks with the Chandra X- ray Observatory's Low Energy Transmission Gratings in combination with its Advanced CCD Imaging Spectrometer (LETG/ACIS-S). The LETG/ACIS results indicate that the X-ray source originates essentially from the present-day stellar wind (Ne/O and C/O are greatly enhanced over solar, while Fe/O is subsolar) and suggest the presence of a range of plasma temperatures from Tx ~ 1.7 MK to 2.9 MK and an intervening absorbing column NH ~ 2.4 x 1021 cm-2. The range of temperatures implied by the plasma model fitting offers the first direct indication of the presence of a temperature gradient within the wind-collision-generated “hot bubble” of a planetary nebula, providing much-needed constraints on wind collision models; while the results for plasma abundances are important in the context of theories of nucleosynthesis during advanced evolutionary stages of intermediate-mass stars.

Session 5: Stellar Coronae, and Solar System

Konrad Dennerl (MPE Garching)

High Resolution X-Ray Spectroscopy of Comets

Remote plasma diagnostics is an important tool for astrophysical studies. In order to fully utilize its power, a detailed knowledge of the properties of the atomic processes which give rise to the observable emission is essential. However, retrieving this information to the necessary accuracy, either by theoretical computation or by laboratory experiments, is often a challenging task. In this context, the X-ray emission of comets provides a welcome opportunity for checking and improving our knowledge of basic atomic quantities. Cometary X-ray emission is the result of charge exchange processes between highly ionized heavy atoms in the solar wind and neutrals in the cometary coma - a textbook example of an interaction between a highly ionized plasma and cold gas far from thermal equilibrium, which takes place in a huge, clean “laboratory” fairly nearby. Thus, cometary X-ray spectra do not only provide information about the elusive properties of the heavy ion content of the solar wind over the solar cycle and in three dimensions, but are also valuable for plasma diagnostics in general.

Manuel Guedel (ETH Zurich)

X-Ray Spectroscopy of Cool Stars: Present View and Future Expectations

X-ray astronomy of cool stars has greatly profited from high-resolution X-ray spectroscopy. Initially concentrating on coronal research, cool star X-ray spectroscopy is now also addressing issues as diverse as accretion physics, interactions of X-rays with circumstellar disks, physics of jets, etc. New spectral features identified in survey work (e.g., systematic abundance anomalies, “soft excess”) as well as from case studies (e.g., anomalous electron densities, absorption anomalies) have provided new input to deeper modeling. However, given the limitations of current instrumentation a new generation of spectrometers will be needed to fully interpret the underlying physics. Apart from reviewing X- ray spectroscopy results from cool stars, I will summarize issues that future X-ray spectrometers should be able to address.

Juergen Schmitt (Hamburger Sternwarte)

High-resolution spectroscopy of cool stars

I will review main results of high-resolution spectroscopy of cool stars with XMM-Newton and Chandra. Spectroscopic determinations of temperature, density and elemental abundances will be discussed and the results for various classes of stars presented. Specific issues discussed include densities of CTTS, the solar and stellar neon problem, CNO abundances of young and evolved stars and the measurement of flare plasma densities.

Session 6: Supernovae, Supernova Remnants, Novae and the ISM

Dan Dewey (MIT)

Velocities and 3D Structure of SNRs Cas A and SN 1987A

I'll review the observations of SNRs Cas A and SN 1987A made with Chandra's HETG (e.g., Lazendic et al. 2006, ApJ, 651, 250; Dewey et al. 2008, ApJ, 676L, 131; Zhekov et al. 2009, arXiv:0810.5313). For both SNRs, the motion of the shocked, emitting plasma can be measured and put into the context of their 3D structure. For SN 1987A I'll also present analyses suggesting very broad emission, of order 6000 km/s FWHM, and speculate on its reality and possible origin.

Frank Haberl (Max-Planck-Institut fuer extraterrestrische Physik (MPE))

X-ray spectroscopy of SN(R)1987A with RGS

Our XMM-Newton monitoring program of the remnant of SN 1987A with yearly observations since January 2007 provided us with EPIC and RGS spectra of unprecedented quality. The soft X-ray light curve shows a significant flattening after 2005. The RGS spectra allow us to study the time evolution of the shock conditions and abundance profiles of, e.g., N, O, Fe and Ne. I'll present the results of a detailed analysis of the available RGS spectra.

Daria Kosenko (Astronomical Institute Utrecht)

Examination Of The X-ray Spectrum Of The SNR 0509-67.5

We discuss XMM-Newton observations of the supernova remnant 0509-67.5 in the Large Magellanic Cloud. EPIC and RGS data were studied extensively using SPEX spectral software package. The analysis allowed us to obtain dynamical properties of the SNR and also plasma conditions in the remnant.

Jan-Uwe Ness (ESAC)

High-Resolution XMM-Newton X-ray spectra of V2491 Cyg probing different stages of evolution

Observations of novae in X-rays have been revolutionised by the capability of Swift to carry out long-term monitoring campaigns on up to sub-daily times scales. The dense X-ray light curves allow us to accurately schedule deeper X-ray observations with Chandra or XMM-Newton. V2491 Cyg is a fast nova, and the bright supersoft source phase lasted only one month. Because of the dense Swift monitoring we were able to schedule two XMM-Newton observations within this period of time, yielding well-exposed RGS spectra, each probing quite different conditions. The XMM-Newton X-ray and UV light curves display a high degree of variability, and I will present grating spectra that were extracted from time periods that correspond to low- and high-flux phases. I will also present similar spectra from other novae for comparison.

Paul Plucinsky (Harvard-Smithsonian Center for Astrophysics)

The SMC SNR 1E0102.2-7219 as a Calibration Standard for X-ray

The flight calibration of the spectral response of CCD instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources typically available. We have been using E0102, the brightest supernova remnant in the Small Magellanic Cloud, to evaluate the response models of the ACIS CCDs on the Chandra X-ray Observatory (CXO), the EPIC CCDs on the XMM-Newton Observatory, the XIS CCDs on the Suzaku Observatory, and the XRT CCD on the Swift Observatory. E0102 has strong lines of O, Ne, and Mg below 1.5 keV and little or no Fe emission to complicate the spectrum. The spectrum of E0102 has been well characterized using high-resolution grating instruments, namely the XMM-Newton RGS and the CXO HETG, through which a consistent spectral model has been developed that can then be used to fit the lower- resolution CCD spectra. Fits with this model are sensitive to any problems with the gain calibration and the spectral redistribution model of the CCD instruments. We have also used the measured intensities of the lines to investigate the consistency of the effective area models for the various instruments around the bright O (570 eV and 654 eV) and Ne (910 eV and 1022 eV) lines. We find that the measured fluxes of the O VII triplet, the O VIII Ly-a line, the Ne IX triplet, and the Ne X Ly-a line generally agree to within +/-10% for all instruments, with 28 of our 32 fitted normalizations within +/-10% of the RGS-determined value. The maximum discrepancies, computed as the percentage difference between the lowest and highest normalization for any instrument pair, are 23% for the O VII triplet, 24% for the O VIII Ly-a line, 13% for the Ne IX triplet, and 19% for the Ne X Ly-a line. If only the CXO and XMM are compared, the maximum discrepancies are 22% for the O VII triplet, 16% for the O VIII Ly-a line, 4% for the Ne IX triplet, and 12% for the Ne X Ly-a line.

Jacco Vink (Astronomical Institute, Utrecht University)

X-ray spectroscopy of supernova remnants

I will present a review of important spectroscopic results concerning supernova remnants. Topics include: shock heating and particle acceleration, and supernova abundances.

Session 7: Clusters of Galaxies and the WHIM

Fabrizio Nicastro (INAF-OAR/UoC)

The WHIM: Current Observational Evidence and Future Prospects with IXO

I will first briefly review the current UV and X-ray evidence for the Warm-Hot Intergalactic Medium (WHIM), and will then discuss future prospects for the study of the missing baryons and the heating and enrichment history of the Universe (feedback), with the International X-Ray Observatory (IXO). I will show detailed WHIM spectral simulations with the IXO dispersive and non-dispersive spectrometers and demonstrate the need for very high-resolution (R>3000) spectroscopy, for accurate WHIM studies.

Jeremy Sanders (Institute of Astronomy, University of Cambridge)

Cool gas in the core of the Centaurus cluster

I will present results from a recent paper, where, with a deep XMM RGS observation of the Centaurus cluster, we manage to detect X-ray emitting material a factor of 10 colder in temperature than in the cluster outskirts. The Fe XVII emission lines are directly seen in the spectrum. In addition I will show XMM RGS results from a new sample of clusters ranging in mass scale, including HCG 62, A1835, A262 and PKS1404.

Rik Williams (Leiden Observatory)

Local X-ray absorption: Galactic corona or IGM?

Deep, high-resolution X-ray spectra of bright AGN have revealed a ubiquitous reservoir of nearby warm-hot gas. However, due to the relatively low velocity resolution of these instruments (compared to UV and optical spectrographs), it is unclear whether these “nearby” absorbers reside in the Galactic halo or farther away, such as in the Local Group or a local intergalactic medium filament. I will show how high- quality data along multiple lines of sight, coupled with ionization balance models, can place constraints on the origin of and physical conditions within these absorbers.

Session 8: Future missions

Jan-Willem den Herder (SRON)

X-ray spectroscopy: opportunities in the future

I will describe technology development for X-ray spectroscopy beyond the currently planned missions including astro-H and IXO as well as potential mission concepts using X-ray spectroscopy.

Kazuhisa Mitsuda (ISAS/JAXA)

The High Resolution X-ray Spectrometer, SXS, on the Astro-H mission

We will present the science and an overview of the the Soft X-ray Spectrometer onboard the Astro-H mission (formerly known as NeXT). The SXS consists of X-ray focussing mirrors and a microcalorimeter array and is developed by international collaboration lead by JAXA and NASA. The effective area of the instrument will be 290 cm2 at 6 keV; by a factor of about two larger than that of the X-ray microcalorimeter on board Suzaku. The baseline detector is a 6x6 format array which covers a 2.8 x 2.8 arcmin2 filed of view, while a larger format array of 8x8 format is being developed. We expect an energy resolution of 6 eV (FWHM) or better at 6 keV. One of the main scientific objectives of the SXS is to determine turbulent and/or macroscopic velocities in the hot gas of clusters of galaxies up to z ~ 1.

Takaya Ohashi (Tokyo Metropolitan University)

DIOS: an X-ray mission to explore missing baryons

A small X-ray mission DIOS (Diffuse Intergalactic Oxygen Surveyor) is proposed to JAXA. It consists of a 4-stage X-ray telescope and an array of TES microcalorimeters cooled by mechanical coolers, with a total weight of about 400 kg. The mission will perform survey observations of warm-hot intergalactic medium using OVII and OVIII emission lines, with an energy coverage up to 1.5 keV and a wide field of view of about 50’ diameter and an energy resolution close to 2 eV FWHM.

Arvind Parmar (ESA), Hideyo Kuneida (Nagoya University), Nicholas White (NASA/GSFC) and the International X-ray Observatory Team

IXO

The International X-ray Observatory (IXO) with the participation of ESA, NASA and JAXA will address many timely science topics including black holes and matter under extreme conditions, galaxy formation, galaxy clusters and cosmic feedback, and the life cycles of matter and energy. The baseline mission implementation consists of a single optic with an effective area of 3 sq m at 1 keV and 5 arc sec resolution, and the instruments include a micro-calorimeter spectrometer array, a wide field imager, a grating spectrometer, a high-time resolution spectrometer and an X-ray polarimeter. This presentation will summarize the current science goals and mission implementation approach based on the on-going NASA, ESA and JAXA design studies.

Norbert Schartel (ESA)

A completely different view of RGS observations: A trial to estimate the intrinsic discovery space

XMM-Newton will celebrate its 10th anniversary in December 2009. With about 300 refereed papers published each year, XMM-Newton is one of the most successful scientific missions of ESA ever. With the launch of XMM-Newton and Chandra for the first time X-ray high resolution spectrometers were made available for the astrophysical community. XMM-Newton has the potential to continue operations for another decade. Based on simple statistical consideration in comparisons to the instrument performance and celestial X-ray sources we try to estimate the potential exploration and discovery space for RGS observations and compare it with the performed observations. We conclude that only about 50% of the potentially interesting targets are observed today.


Workshop posters



Giulio del Zanna (DAMTP Cambridge)

Atomic data for the X-ray plasma modelling - recent advances

The status of atomic data important for the analysis of high-resolution X-ray spectra is briefly described. New calculations of ionization and recombination rates have become available, as well as many new scattering calculations. Atomic data have been made easily accessible but a large amount of work is still needed, in particular in benchmarking the theoretical data, and identify transitions. The latest R-matrix calculations provide for a range of important ions excellent agreement with experimental data, and a range of new density and temperature diagnostics have been found.

Scott Gregory (University of St Andrews)

Multi-wavelength observing of a forming solar-like star

V2129 Oph is a 1.35 solar mass pre-main sequence solar-like star, accreting from a protoplanetary disc. It is known to possess a strong and complex magnetic field. By extrapolating from observationally derived magnetic surface maps, obtained through Zeeman-Doppler imaging, models of V2129 Oph's X-ray emitting corona have been constructed. As this star has never been observed by a modern X-ray satellite, we have used the field extrapolation model to make predictions regarding the global X-ray emission measure, the amount of modulation of X-ray emission we expect to observe, and the density of accretion shocks. In June 2009 we will under take an ambitious multi-wavelength, multi-observing site, and near contemporaneous campaign, combining spectroscopic optical, UV, X-ray, spectropolarimetric and photometric monitoring. This will allow the validity of the 3D field topologies derived via field extrapolation to be throughly examined, and will reveal whether or not magnetic surface mapping can be used to model the spacial distribution of coronal plasma in young stars.

V. Hambaryan (AIU Jena), R. Neuhaeuser (AIU Jena), F. Haberl (MPE), M.M. Hohle (MPE Garching & AIU Jena), A.D. Schwope (Astrophysikalisches Institut Potsdam)

XMM-Newton RGS spectrum of RX J0720.4-3125: Absorption feature at 0.57 keV

We found an absorption feature at 0.57 keV in the co-added RGS spectrum of the isolated neutron star RX J0720.4-3125 with an equivalent width of 1.35 ± 0.3 eV and FWHM ~6.0 eV. The feature was identified with an absorption line of highly ionized oxygen OVII, most probably originating in the ambient medium of RX J0720.4-3125. An extensive investigation with the photo-ionization code CLOUDY indicates the possibility that the optical flux excess observed in the spectrum of RX J0720.4-3125, at least partially may originate in a relatively dense (e.g. nH ~ 108 cm-3) slab, located in the vicinity of the neutron star (e.g. ~ 1010 cm).

Markus M. Hohle (MPE Garching & AIU Jena) & Frank Haberl (MPE)

Variable spectrum of the X-Ray pulsar RX J0720.4-3125

RX J0720.4-31.25 is one of seven radio quiet, isolated neutron stars (often called the magnificent seven) with similar properties discovered during the ROSAT all-sky survey. The X-ray spectrum can be modelled with a blackbody and an gaussian absorption feature. This neutron star does not only show a short periodic variability - its spin period (P=8.3911153s), but also a long term variability in its spectral parameters (see de Vries et al., 2004; Vink et al., 2004; Haberl et al., 2006 and Hohle et al., 2009), i.e. its temperature, size of the emitting area and equivalent width of the absorption feature and a long term variability of its Period. The reason of this behaviour is still unknown, but might be evidence for precession or a glitch event around MJD=52800 days (Haberl et al., 2006 & Kerkwijk et al., 2007). Furthermore, there is an indication for an absorption line from highly ionised oxygen in the RGS spectra (Hambaryan et al., submitted).

Missagh Mehdipour (UCL-MSSL)

XMM-Newton High resolution spectroscopy of NGC 3516

We present a new analysis of the soft and medium X-ray spectrum of the Seyfert 1 galaxy NGC 3516 taken with the RGS and the EPIC-PN camera on board XMM-Newton. We examine four observations (total exposure time of 256 ks) made by XMM-Newton in October of 2006. The source shows significant flux variability between observations. Using the SPEX fitting package, we examine the spectra to uncover how much of the observed variability is due to absorption by the warm absorber regions. The warm absorber is found to consist of three phases of ionisation, two of which have outflow velocities of more than 1000 km/s. The identified absorption lines by the RGS are also presented. Intrinsic changes in the source continuum are found to play a more significant role than previously thought in explaining the observed flux and spectral variability.

Norbert Schulz, Ralf K. Heilmann, Minseung Ahn, David Huenemoerder, Mark L. Schattenburg and the MIT CAT team

High Resolution Soft X-Ray Spectroscopy with a Critical-Angle Transmission Grating Spectrometer

We have developed a new type of soft x-ray diffraction grating. This critical-angle transmission (CAT) grating [1-4] combines the advantages of traditional transmission gratings with those of x-ray reflection gratings which means high efficiency in the direction of grazing-incidence reflection and the use of higher diffraction orders for increased spectral resolution. In addition, grating spectrometers based on CAT gratings are well-suited for co-existence with high-energy focal plane energy-dispersive detectors as planned for the International X-Ray Observatory, since most high-energy X-rays are undeflected and arrive at the telescope focus. We have micro-fabricated 200 nm-period prototypes of the smooth, high-aspect ratio, and sub-micron period structures necessary for efficient CAT gratings. X-ray tests have demonstrated high-efficiency blazing in accordance with theoretical predictions. We will describe the CAT grating principle and design, and discuss how various science questions could benefit from high-resolution up to 5000, high-effective area up to 10,000 cm2 implementations for a CAT grating spectrometer on board of the International X-ray Observatory (IXO).

Jennifer Carter, Steve Sembay and Andrew Read (University of Leicester)

Solar Wind Charge Exchange X-ray emission from the Earth's Magnetosheath

Collisions between solar wind ions and neutral atoms in the Earth's exosphere produce X-ray emission due to the solar wind charge exchange process (SWCX). The X-ray emissivity from SWCX is predicted to be strongest in the Earth's magnetosheath where the solar wind density is most enhanced. SWCX has been detected by the EPIC detectors on XMM-Newton where it appears as a diffuse and variable component of the sky background characterised by strong emission lines from the high charge-state ions within the solar wind. We are performing a systematic search for signatures of SWCX emission in the XMM-Newton archive and we here report on a preliminary study which has detected several new examples. XMM-Newton, however, is not optimised for studying SWCX due to observational constraints and its narrow field of view. We report on two instrument concepts, MagEX and STORM, being developed with collaborators in NASA/GSFC, which have the necessary wide field of view, soft X-ray response and sensitivity to make global studies of the dynamical interaction of the solar wind with the Earth's magnetosheath.

Jiri Svoboda (Astronomical Institute of Academy of Sciences in Prague)

Role of limb brightening in the angular momentum determination of accreting black holes

Angular momentum of an accreting black hole can be determined by careful spectroscopy of the emission and absorption features produced in the inner regions of an accretion disc. We discuss the method employing the relativistic line profiles of iron in the X-ray domain, where the emergent spectrum is blurred by general relativistic effects. Accuracy of the spectra fitting can be affected by inappropriate account of the directional distribution of the disc emission. However, most works so far have avoided this issue by fixing a unique profile of the angular distribution, invariable over the entire range of radii in the disc and energy in the spectral band. An isotropic distribution or a particular limb-darkening law have been frequently assumed, although some calculations of the X-ray reflection suggest that the limb brightening would be more appropriate for the accretion disc surface. By assuming a rotating black hole in the centre of an equatorial accretion disc, we perform numerical radiation-transfer computations to determine the directionality of outgoing X-rays in the 2-10 keV energy band. In order to evaluate the feasibility of future angular measurments and their expected constraints with future X-ray data, we produced a set of artificial spectra using a simple model prescription and preliminary response matrix for the IXO mission. We show how sensitive the results of the black-hole angular momentum determination are to the assumptions about the intrinsic directional distribution of the emitted photons. The results depend on the values of the inclination angle and the spin itself. However, we find that the isotropic directionality reproduces our data to the best precision.

Eleonora Torresi (INAF-IASF Bologna; University of Bologna)

The nuclear environment of 3C 33 as observed by Chandra and XMM-Newton

FRII Narrow Line Radio Galaxies (NLRG) optically classified as High Excitation Galaxies (HEG) share with Seyfert 2s more spectral properties than one could imagine. First of all a heavily absorbed continuum (NH~1023-24 cm-2) related to the bright accretion disk obscured by an oriented thick torus. This is signalled by the presence of a prominent FeKα line and the Compton reflection. At softer energies (0.5-2 keV) a soft unabsorbed tail is often detected. While for Seyfert 2s high resolution spectroscopy led to the interpretation of this excess as produced by extended gas photoionized by the central engine, the origin of the soft X-ray emission in radio galaxies is still matter of debate. At the beginning it was suggested that the soft excess is related to the jet emerging from the edge of the dusty torus. Recently, Chandra and XMM-Newton detected emission-lines produced by photoionized gas on two radio-loud objects, 3C 445 and 3C 234, opening a new way of interptetation of the soft excess. In this poster we present another case: the radio galaxy 3C 33. Although the poor statistics did not allow an RGS analysis, what we obtained with the Chandra ACIS and XMM-Newton PN cameras is encouraging and again points toward the photoionization scenario. The combination of better quality data and high resolution spectroscopy could firmly confirm these results.

Spectroscopy school session abstracts

Ehud Behar (NASA/GSFC and Technion)

Atomic processes in plasmas

The talk will provide a review of the collisional and radiative atomic processes in highly ionized plasmas and describe in general terms how their rates are calculated. The varying importance of these processes under different astrophysical and laboratory plasma conditions will be demonstrated. The mathematical approach to solving for the atomic level populations will be presented for steady state and for transient scenarios. This will elucidate how synthetic spectra are calculated and reveal the diagnostic power of atomic spectra. Several simple examples will be given.

Frits Paerels (Columbia)

Basics of spectroscopy

Basics of spectroscopy from the practical point of view: the kinds of features you see in an high resolution X-ray spectrum, how to tell which processes they derive from, how to apply the curve-of-growth, emission measure analysis etc.. Resolving power (why to use wavelength instead of energy scale), line profiles, equivalent width, signal-to-noise, resonance scattering (nomenclature!). Mainly focussing on the RGS band.

Frank Verbunt (Utrecht)

Spectroscopic techniques

Techniques particular to X-ray spectra: spectral fitting versus traditional optical spectroscopy techniques, binning, techniques for extended sources; the range of spectral fitting packages and what each one is appropriate for.

Andy Pollock (ESAC)

Statistics: Velocity profiles

TBC

Elisa Costantini (SRON)

Introduction to SPEX

Introduction to SPEX, with examples of use, starting with the most basic models (described in some detail).

Exercises 1: Basics of SPEX, stellar spectra

People try SPEX for themselves using pre-prepared data in SPEX format for one type of data, RGS, of one type of source, a star.

Jelle Kaastra (SRON)

Advanced SPEX models: DEM, NEI etc.

Description of more complex SPEX models (e.g. Differential Emission Measure, DEM; Non-Equilibrium Ionisation, NEI); also models often used for the the Fe K band (relativistic and reflection features).

Exercises 2: Clusters, stars and supernovae

Try different types of sources and models: cluster (extended), star (DEM), SNR (NEI)

Randall Smith (SAO)

Plasma codes

Introduce the variety of plasma codes available (e.g. XSTAR, Cloudy, Titan, Mocassin, Mekal/SPEX, etc.) and which astrophysical situations the different codes are applicable to; current status and reliability of the atomic data.

Katrien Steenbrugge (Oxford)

SPEX absorption models

Absorption models (SPEX components slab/xabs/warm/hot); SPEX simulations changing model parameters values, e.g. absorption lines vs edges ..., implications for UV range for the case of AGN; different types of ionisation parameters, use of pressure based ionisation parameter with AGN.

Exercises 3: AGN

AGN RGS spectral modelling.

Frits Paerels (Columbia)

Current and future spectrometers

Comparison RGS/LETGS/HETGS spectra, look forward to Astro-H and IXO (calorimeter, gratings), etc. Design and features of current and future spectrometers (compare observed to simulated calorimeter/gratings spectra); calibration issues to look out for, cross-calibration issues




This page written by Graziella Branduardi-Raymont and Alex Blustin.