Hosted by the Chandra X-ray Center
Links to Abstracts & Presentations
| Author |
Institution | Title | Presentation | |
|---|---|---|---|---|
| Bryan Armentrout | Catholic University of America | NGC 4151 X-Ray Spectrum Variability: 2000-2007 | ||
| Thomas Ayres | University of Colorado (CASA) | The Fainting of Alpha Cen A | PPT | |
| Ehud Behar | Technion | Highlights from X-ray Grating Spectroscopy | PPT | |
| Stefano Bianchi | Universita' degli Studi di Roma TRE | On the origin of soft X-rays in obscured AGN | PPT | |
| Alex Blustin | UCL Mullard Space Science Laboratory | The mass-energy budget of the ionised outflow in NGC 7469 | PPT | |
| Valentina Braito | JHU/NASA-GSFC | The remarkable soft X-ray emission of the Broad Radio Galaxy3C 445 | PPT | |
| Graziella Branduardi-Raymont | Mullard Space Science Laboratory, UCL | X-ray Spectroscopy of Solar System Objects | ||
| Vadim Burwitz | Max-Planck-Institut fuer extraterrestrische Physik | The complex and variable X-ray spectra of the super-softsource RXJ0513.9-6951 | PPT | |
| Claude Canizares | MIT | Perspectives on the Development of High Resolution X-ray Spectroscopy | ||
| Matthew Carpenter | UC Berkeley Space Sciences Laboratory | Comparison of observed and theoretical Fe L emission from CIEplasmas | PPT | |
| Michael Corcoran | CRESST/USRA/GSFC | X-ray Emission Line Variations in Eta Carinae | ||
| Jean Cottam | NASA Goddard Space Flight Center | High Resolution Spectroscopy with Constellation-X | PPT | |
| D. Michael Crenshaw | Georgia State University | X-ray Grating Spectroscopy of AGN | PPT | |
| Konrad Dennerl | MPE Garching, Germany | X-ray grating spectroscopy of Mars with XMM-Newton/RGS | ||
| Priya Desai | CFA | Capella Grating Data and the Emission Line Project: An Update | PPT | |
| Rob Detmers | SRON Netherlands Institute for Space Research | NGC 5548 Revisited: The lean years | ||
| Daniel Dewey | MIT Kavli Institute | Young, Thin, and on the Move: HETG Observations of SNRs | ||
| Dan Evans | Harvard University | Probing Unification With High-Resolution Spectroscopy of NGC2110 | PPT | |
| Anabela C. Goncalves | Paris-Meudon Observatory (LUTH), France | The impact of the line-of-sight on the estimation of X-rayplasma diagnostics | PPT | |
| Rosario Gonzalez-Riestra | XMM-Newton Science Operations Centre | A Browsing Utility for XMM-Newton RGS spectra | ||
| Ming Gu | Lawrence Livermore National Laboratory | Experimental and Theoretical X-ray Wavelengths of Astrophysical Ions | ||
| Manuel Guedel | Paul Scherrer Institut & ETH Zuerich, Switzerland | X-Ray Spectroscopy of Cool Stars: From Coronal Heating toAccretion | PPT | |
| Ralf Heilmann | M.I.T. | Blazed transmission gratings for soft x-ray spectroscopy | ||
| Tomer Holczer | Technion | Absorption Measure Distribution of Outflows in AGNs | PPT | |
| David Huenemoerder | MIT | Magnetic Activity in Orion's Massive Young Stars | ||
| Jelle Kaastra | SRON | RGS spectroscopy of the Crab nebula | PPT | |
| Timothy Kallman | X-ray Astrophysics Laboratory, NASA/GSFC | Atomic Calculations and Laboratory Measurements | PPT | |
| Vinay Kashyap | SAO | Summarizing Stellar Spectra | ||
| Julia Lee | Harvard | The High Resolution Optical to X-ray Study of the QSO IRAS13349+2438 | ||
| Maurice Leutenegger | Columbia Astrophysics Laboratory | Resonance Scattering in Doppler profiles of $\zeta$ Pup | ||
| Ji Li | MKI |
The non-equilibrium ionization model in ISIS | ||
| Carolin Liefke | Hamburger Sternwarte | Plasma diagnostics of a giant stellar flare | PPT | |
| Anna Lia Longinotti | ESAC, Madrid (Spain) | The variable warm absorber in the Seyfert 1 Galaxy Mrk 841revealed by the RGS | ||
| Antonio Maggio | INAF - Osservatorio Astronomico di Palermo | Benchmark Exercises for stellar X-ray Spectroscopy Testing:initial results | ||
| Herman Marshall | MIT Kavli Institute | Modeling the SS 433 Jet Bends | ||
| Christopher Mauche | Lawrence Livermore Nat'l Lab. | High Spectral Resolution Observations of Cataclysmic Variables | PPT | |
| Michael McCollough | CXC/SAO | Probing the Winds of Cygnus X-3 with the Chandra HETG | ||
| Mariano Mendez | SRON - Netherlands Institute for Space Research | High resolution spectrum of the galactic black-hole binaryGRS 1915+105 | ||
| Kendrah Murphy | Johns Hopkins University | Resolving the Space-Time Around Black Holes | ||
| Joy Nichols | Harvard-Smithsonian Center for Astrophysics | Improved Wavelength Accuracy for Reprocessed Grating Data | ||
| Raanan Nordon | Technion | Large coronal flares and the FIP effect | ||
| Michael Nowak | Massachusetts Institute of Technology | X-ray Binaries in the Era of Chandra and XMM High ResolutionSpectroscopy | PPT | MOV |
| Marina Orio | INAF-Padova (Italy) and U. Wisconsin (USA) | RS Ophiuchi in outburst in X-rays: an ``extreme'' nova. | PPT | |
| John Peterson | Purdue University | X-ray Spectra of Clusters of Galaxies | PPT | |
| Andy Pollock | European Space Agency XMM-Newton SOC | The physics and dynamics of the X-ray plasmas in hot stars | PPT | |
| John Raymond | Center for Astrophysics | High Resolution X-ray Spectra of Accretion Disks | PPT | |
| James Reeves | University of Keele (UK) | AGN outflows, the tip of the iceberg? | PPT | |
| Pedro Rodriguez-Pascual | XMM-Newton SOC | Absorption lines at z=0 in X-ray spectra: a test case for RGSfluxed spectra. | ||
| Jorge Sanz-Forcada | LAEFF-INTA | Coronal abundances of AY Cet and AR Psc | ||
| Norbert S. Schulz | MIT Kavli Institute for Astrophys. & Space Res. | X-Ray Spectroscopy of Cool & Warm Absorbers with Chandra:From Oxygen to Iron | PPT | |
| Randall Smith | JHU & NASA/GSFC | A short review of the talks and posters presented. | PPT | |
| Rebecca Smith | Mullard Space Science Laboratory, UCL | High-res X-ray spectroscopy of AGN Warm Absorbers | PPT | |
| Paola Testa | MIT | Detailed plasma and fluorescence diagnostics of a stellarX-ray flare | PPT | |
| Nolan Walborn | Space Telescope Science Institute | Multiwavelength Systematics of O-Type Spectra | PPT | |
| Q. Daniel Wang | Univ. of Massachusetts, Amherst | X-ray Absorption Line Spectroscopy of the Interste | PPT | |
| Klaus Werner | University of Tuebingen | X-ray Photospheres | PPT | |
| Owen Westbrook | Harvard-Smithsonian Center for Astrophysics | X-Atlas: An Online Archive of Chandra's Stellar HETGObservations | PPT | |
| Jingen Xiang | Harvard College Observatory | The evolving line profiles and dust scattering halo of 4U1624-490 | ||
| Yangsen Yao | MIT Kavli Institute | Searching for the Large Scale Galactic Halo: ObservationsConfront Theories | PPT | |
| Tahir Yaqoob | Johns Hopkins University/ NASA GSFC | HotGAS to go: Outflows, Accretion, Strong Gravity, and the IGM | Andrew Young | MIT / IoA | High Resolution X-ray Spectroscopy of the Low-LuminosityNucleus of M81 |
| Young Sam Yu | Rochester Institute of Technology | Model fitting of high-resolution X-ray Spectroscopy of thePN, BD+30 3639 | PPT | |
Manuel Guedel
X-Ray Spectroscopy of Cool Stars: From Coronal Heating to Accretion
X-ray spectroscopy of cool stars has revealed entirely new phenomenology unknown from solar physics. Extreme coronal temperatures are ubiquitous, but how is the plasma heated? Non-solar patterns in coronal abundances suggest a dependence on the magnetic activity level and on stellar spectral type. Coronal abundance ratios have conversely led to a reconsideration of the standard solar model. Accreting T Tauri stars show suppressed X-ray emission in CCD spectra while grating spectra uncover a ``soft excess''. Are accretion flows interacting with the stellar magnetospheres, and are they producing X-rays in accretion shocks? I will review recent developments with a special emphasis on unsolved problems and the need for future observations (and observatories).
Christopher Mauche
Lawrence Livermore Nat'l Lab.
High Spectral Resolution Observations of Cataclysmic Variables
I will present a review of high spectral resolution - primarily Chandra HETG and LETG - X-ray observations of the various subtypes of cataclysmic variables: (nominally) nonmagnetic dwarf novae and novalike variables and magnetic polars and intermediate polars, concentrating on line-based spectroscopic diagnostics of photoexcitation, high densities, mass-loss, and line and Compton scattering, which provide unique information about the properties of the accretion flows of these semi-detached white dwarf binaries.
Thomas Ayres
The Fainting of Alpha Cen A
Alpha Centauri (G2V + K1V) is the nearest system of solar-like stars. The primary has long been regarded a solar twin. Previous X-ray missions have been able to separate the coronal point sources (14" apart in Y2000), although the orbit now is closing rapidly and since 2006 can only be resolved easily by Chandra. The 25 year X-ray record has revealed striking long term changes in the Alpha Cen coronae, likely related to analogs of the still mysterious solar sunspot cycle. Recent work suggests that the K star is falling into a cycle minimum, while the G star is relapsing following a brief recovery from an unprecedented deep X-ray decline in 2005 that fully challenges our understanding of stellar dynamos. A 120 ks Chandra/LETGS exposure scheduled for early June 2007 will continue the remarkable high-energy narrative of the system, and hopefully will shed some light on the specific physical properties of the dwarf star corona(e) that led to the puzzling anomalous de! clines recorded recently.
Ehud Behar
Highlights from X-ray Grating Spectroscopy
Besides the important but nonetheless anticipated benefits from line-resolved spectra, such as abundance, temperature, and density diagnostics, the grating spectrometers on board Chandra and XMM-Newton have provided a slew of non-standard, perhaps less expected, measurement tools unique to astrophysics. I will highlight a few of my favorite examples, such as: column density in emission, velocity broadening beyond instrumental resolution, distance from hot stars, and direct observation of thermal instability. These methods will be described and the role they may play in facilitating astrophysical discoveries will be discussed.
Stefano Bianchi
Universita' degli Studi di Roma TRE
Oral Presentation
On the origin of soft X-rays in obscured AGN
We present results of a high-resolution soft X-ray (0.2-2 keV) spectroscopic study of a sample of 69 nearby obscured active galactic nuclei (AGN) observed with the reflection grating spectrometer (RGS) on board XMM-Newton. This is the largest sample ever studied with this technique so far. The main conclusions of our study can be summarized as follows: (i) narrow radiative recombination continua are detected in about 36 per cent of the objects in our sample (in 26 per cent their intrinsic width is <=10 eV); (ii) higher order transitions are generally enhanced with respect to pure photoionization, indicating that resonant scattering plays an important role in the ionization/excitation balance. These results support the scenario, whereby the active nucleus is responsible for the X-ray 'soft excess' almost ubiquitously observed in nearby obscured AGN via photoionization of circumnuclear gas. They confirm on a statistical basis the conclusions drawn from the detailed s! tudy of the brightest spectra in the sample. Furthermore, we propose a criterion to statistically discriminate between AGN-photoionized sources and starburst galaxies, based on intensity of the forbidden component of the OVII He$\alpha$ triplet (once normalized to the OVIII Ly$\alpha$) coupled with the integrated luminosity in He- and H-like oxygen lines.
Alex Blustin
UCL Mullard Space Science Laboratory
Oral Presentation
The mass-energy budget of the ionised outflow in NGC 7469
To gain a complete picture of the mass-energy transport in AGN winds, which contain a wide range of ionisation, we need to understand the relationship between the resulting absorption observed in different wavelength bands. Using a 160 ks XMM-Newton RGS spectrum of the Seyfert 1 galaxy NGC 7469, we find that the ionisation parameter of the X-ray absorber in this object ranges between log xi ~0.5-3.5, with the high-ionisation gas outflowing at 580-720 km/s and the low-ionisation gas at 2300 km/s. Comparing these properties with those of the UV absorber, we find that the low-ionisation X-ray phase is probably identical with one of the UV-absorbing phases. We estimate that the X-ray absorbing part of the wind accounts for ~90% of the mass outflow and ~95% of the kinetic luminosity.
Valentina Braito
JHU/NASA-GSFC
Oral Presentation
The remarkable soft X-ray emission of the Broad Radio Galaxy 3C 445
Medium and high resolution X-ray observations of bright nearby Seyferts over the last decade have shown that, beside the Fe emission line complex, the emission below 3 keV presents complex intrinsic absorption/emission features suggesting the presence of photoionized material along the line of sight, responsible for absorption and/or scattering of the X-ray continuum. In contrast, the inner regions of radio-loud AGN are much more poorly studied, because of the relative rarity and distance of these sources. In particular, while weak reflection features were observed in the brightest Broad-Line Radio Galaxies (BLRGs) suggesting the presence of a cold reprocessor, no evidence for absorption or emission at soft X-rays (<2 keV) was detected so far, raising the issue of whether BLRGs contain warm/hot gas at all. Here we present the XMM EPIC spectrum of the BLRG 3C445 which is bound to change the landscape for our understanding of these systems. The EPIC data! show a remarkable X-ray spectrum, with a heavily absorbed (Nh ~ 1e22-1e23 cm^(-2)) power law continuum above 2 keV, a narrow Fe Kalpha line, and possibly strong reflection. A soft excess is present below 2keV over the extrapolation of the hard X-ray power law. Interestingly a host of emission lines is present below 2 keV due to H- and He-like O, Mg, and Si; this is the first time that soft X-ray lines are observed in BLRG and indeed a radio-loud AGN. We attribute the origin of these lines to a photoionized gas, with properties very similar to radio-quiet obscured AGN. Two different ionized media, or a single stratified medium, are required to fit the soft X-ray data satisfactorily. We discuss the possibility that the gas is located in an outflow, particularly interesting in light of jet formation models. The similarity of the X-ray spectrum of 3C445 to Seyferts underscores that the central engines of radio-loud and radio-quiet AGN similarly host both cold AND warm gas! .
Graziella Branduardi-Raymont
Mullard Space Science Laboratory, UCL
Oral Presentation
X-ray Spectroscopy of Solar System Objects
Only over the last few years, with the advent of Chandra and XMM-Newt on observations, we have become able to study in detail the X-ray spectra of so lar system objects other than the Sun, including planets, their satellites, com ets and asteroids. The process of ion charge exchange is now known to play an i mportant role in the solar neighbourhood: grating X-ray spectroscopy is a very effective way of investigating the X-ray line emission it generates, and of res olving it from other emission mechanisms. Among the planets, Venus, the Earth, Mars, Jupiter and Saturn have all been detected in the X-rays and have been st udied in considerable depth. Aurorae have been observed to be powerful sources of X-rays on both Jupiter and the Earth. Jupiter presents probably the most co mplex scenario among the planets: while emission from its low latitude disk has the character of scattered solar X-rays, with a thermal spectrum and typical c oronal emission lines, the auroral soft (! <2 keV) X-rays are most likely produced by ion charge exchange; very recently, an additional high energy component has been revealed by XMM-Newton: this is a ttributed to energetic electron bremsstrahlung, and dominates at energies above 2 keV. The dynamics and energetics of the particles producing the auroral em issions on Jupiter, as well as the nature of the X-rays originating from the di sk of Mars and its exosphere, have been studied with high resolution XMM-Newton spectra. The X-ray emission from the disk of Venus has also been examined with the Chandra LETGS. Results from this novel way of approaching the study of sol ar system objects, via X-ray spectroscopy, will be reviewed and will be shown t o support current models of auroral emission and planetary atmospheres.
Vadim Burwitz
Max-Planck-Institut fuer extraterrestrische Physik
Oral Presentation
The complex and variable X-ray spectra of the super-soft source RXJ0513.9-6951
Super-soft X-ray binaries that accrete close to the Eddington limit are a fascinating class of X-ray sources. The system RXJ0513.9-6951 in the LMC can only be detected during X-ray bright/optically faint states which occur quasi periodically. With a close optical monitoring is was possible to trigger TOO X-ray observations with Chandra and XMM-Newton of RXJ0513.9-6951. The high-resolution X-ray spectra obtained with the Chandra LETGS and XMM-Newton RGS of RXJ0513.9-6951 show very complex features that so far have not been satisfactorily explained. On one hand interpretational difficulties arise from the fact that the spectra seem to be a mixture of optically thick emission from a hot white dwarf atmosphere and optically thin emission coming from a heated corona. On the other hand atomic data are still uncertain and incomplete in the soft X-ray energy range. Therefore theoretical models do not yet exist that can explain all features in the complex spectrum. The obs! erved variability of the total flux and the spectral features provides additional important information and also further challenges for the theoretical modelling of the source. Similar features, though broader, are seen in another LMC super-soft X-ray source Cal 83.
Matthew Carpenter
UC Berkeley Space Sciences Laboratory
Oral Presentation
Comparison of observed and theoretical Fe L emission from CIE plasmas
We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. The variances of line fluxes are measured with bootstrap methods (Efron 1979). Both of these observations are further compared with theoretical predictions of Fe L line fluxes from APED and similar atomic databases.
Jean Cottam
NASA Goddard Space Flight Center
Oral Presentation
High Resolution Spectroscopy with Constellation-X
Constellation-X is an x-ray observatory dedicated to high resolution X-ray spectroscopy, with 100 times the throughput for high resolution spectroscopy of previous x-ray observatories. The primary science objectives for the mission are the study of Black Holes, Dark Energy, Missing Baryons, and the Neutron Star Equation of State. However, the increased capabilities of the Con-X observatory will enable major advances in general astrophysics from solar system objects to distant quasars. I will present the mission science objectives, the instrumentation, and the current mission status.
D. Michael Crenshaw
Georgia State University
Oral Presentation
X-ray Grating Spectroscopy of AGN
I review results derived from CXO and XMM-Newton grating observations of AGN in conjunction with spectroscopic observations at other wavelengths, particularly in the UV. I concentrate on observational constraints obtained on mass outflow detected in both absorption and emission, and dynamical models, such as accretion-disk winds, that satisfy these constraints. I also discuss recent observations of Fe K lines from highly ionized gas in emission and absorption.
Priya Desai
CFA
Oral Presentation
Capella Grating Data and the Emission Line Project: An Update
High resolution X-ray spectroscopy with Chandra of line rich X-ray sources like Capella has given us an opportunity to investigate coronal plasmas in detail. The high accuracy of the observational data motivate the development of accurate spectral models, including the need for new or improved atomic rates and wavelengths. The summed spectra of more than a dozen calibration observations each for the Capella ACIS/HETGS and HRC-S/LETGS help to guide our assessment of the data needs. New atomic data for Fe improve the fits to the observations. We discuss the implications of these results.
Rob Detmers
SRON Netherlands Institute for Space Research
Oral Presentation
NGC 5548 Revisited: The lean years
We present the results of our latest observation of NGC 5548, taken with the Chandra LETGS instrument in 2005. Using the SPEX spectral fitting package, we analyze the spectrum of this AGN, while it is in the lowest state recorded to date (five times lower than previous high-resolution spectra). We detect significant changes in the warm absorber, mostly in the oxygen column densities. Changes in the narrow O VII forbidden emission line, relative to previous observations, allow us to put constraints on where it is formed, near the inner narrow line region. Interestingly, the Iron K line has not reacted to the lower ionizing flux, indicating that the region where the line is formed may be shielded against the ionizing flux.
Daniel Dewey
MIT Kavli Institute
Oral Presentation
Young, Thin, and on the Move: HETG Observations of SNRs
Supernova remnants can be studied with current X-ray slitless spectrometers, e.g, the HETG and LETG on {\it Chandra} and the RGS on {\it XMM-Newton}. Young, ejecta dominated remnants show strong emission from low-density ("thin") plasma in non-equilibrium ionization (NEI). Their bright emission lines and the remnants' small, complex structures allow the dispersed images to retain a large amount of spatial-spectral information. In addition to the usual plasma diagnostics, it is possible to measurement local Doppler shifts, giving kinematic information to constrain 3D geometric models of the remnants and hence the initial SN explosion. General techniques and HETG results for SNRs E0102 and Cas A will be presented. For dessert we have recent HETG GTO observations of SN1987A.
Dan Evans
Harvard University
Oral Presentation
Probing Unification With High-Resolution Spectroscopy of NGC 2110
X-ray grating spectroscopy, combined with high-resolution imaging, are powerful tools for probing the nuclear and circumnuclear environments of Seyfert galaxies. Here, we present HETGS (250 ks) and RGS (60 ks) observations of the Narrow Emission Line Galaxy NGC 2110. The X-ray spectrum of the source is dominated by absorption and fluorescence from neutral material at a large distance (>1 pc) from the supermassive black hole. The excess absorption detected at the Si K and Fe K edges may imply the need for an additional cold absorber. We find tentative evidence for ionized emission, which may be associated with extended X-ray emission that lies 160 pc from the nucleus. Our results indicate that the nucleus of NGC 2110 is inclined at low to intermediate angles with respect to the observer.
Anabela C. Goncalves
Paris-Meudon Observatory (LUTH), France
Oral Presentation
The impact of the line-of-sight on the estimation of X-ray plasma diagnostics
The He-like triplet lines intervene in the computation of R and G line-ratios, which are used as X-ray plasma diagnostics. However, they depend not only on the physics of the ionized gas but also on its geometry. We have estimated the impact of the line-of-sight by computing G and R in fonction of the angular distribution of the flux. We show that they do not convey the same information in type 1 and type 2 AGN. We also compared G and R in the case of thick, stratified media in total pressure equilibrium and in the case of constant density media. We demonstrate that the He-like line-ratios depend on various aspects; their combined effects can have dramatic consequences on the analysis of photoionized media similar to the Warm Absorber in Seyfert 1s or the X-ray emitting gas in Seyfert 2s.
Ming Gu
Lawrence Livermore National Laboratory
Oral Presentation
Experimental and Theoretical X-ray Wavelengths of Astrophysical Ions
Accurate wavelengths of X-ray transitions are indispensible in line identification and plasma diagnostics with high resolution grating spectroscopy, both in emission and absorption. A combination of Ming laboratory experiments and theoretical calculations have provided such crucial data for many astrophysically abundant ions. Here we present the most recent results for oxygen, iron, and nickel ions in the soft x-ray wavelength band. The laboratory measurements carried out on the Lawrence Livermore National Laboratory's electron beam ion traps and theoretical results obtained with the Flexible Atomic Code are compared with each other, and their complementary nature is discussed in detail.
Ralf Heilmann
M.I.T.
Oral Presentation
Blazed transmission gratings for soft x-ray spectroscopy
We have developed a new type of soft x-ray diffraction grating. This critical-angle transmission (CAT) grating combines the advantages of traditional transmission gratings (low mass, relaxed alignment and flatness tolerances) with those of x-ray reflection gratings (high efficiency due to blazing in the direction of grazing-incidence reflection). Prototypes of the smooth, high-aspect ratio, and sub-micron period structures necessary for efficient CAT gratings were micro-fabricated through interference lithography, anisotropic etching of silicon crystals, and critical-point drying. We will describe the CAT grating principle and design and our fabrication results. We expect to have x-ray test results to report in time for the workshop.
Tomer Holczer
Technion
Oral Presentation
Absorption Measure Distribution of Outflows in AGNs
We analyze the Chandra X-ray spectrum obtained with the HETGS grating spectrometer of several AGNs that have rich absorption spectra indicative of an outflow. Absorption from almost all charge states of Fe can be detected, which allows for a detailed reconstruction of the absorption measure distribution ($AMD$), defined as the continuous distribution of column density as a function of ionization parameter. We find a double peaked $AMD$ in all of these objects; Where the minima in column density reside in the same temperature region of $4.5 < \log T < 5$ (K). We interpret these minima as observational evidence for ubiquitous thermal instability in this temperature regime.
Jelle Kaastra
SRON
Oral Presentation
RGS spectroscopy of the Crab nebula
The Crab nebula has been observed with the RGS of XMM-Newton, giving the best high-resolution X-ray spectrum of this extended source. The spectrum can be used to study the interstellar absorption towards the nebula with high signal to noise ratio and good (0.22 Angstrom FWHM) spectral resolution. The edges of N, O, Ne and Fe are well resolved. We find solar abundances for oxygen and nitrogen, and slightly supersolar (1.7) abundances for neon. We discuss the fine structure near the absorption edges of oxygen and iron in relation to the presence of dust in the line of sight.
Timothy Kallman
X-ray Astrophysics Laboratory, NASA/GSFC
Oral Presentation
Atomic Calculations and Laboratory Measurements
Since the launch of Chandra and XMM there has been a great deal of new work on calculating and measuring atomic quantities relevant to the interpretation of astronomical X-ray spectra. I will present a historical overview of progress in this field, together with illustrative examples derived from spectra of compact sources. Shortcomings in the currently available data and modeling tools will also be discussed.
Ji Li
MIT
Oral Presentation
The non-equilibrium ionization model in ISIS
Non-equilibrium ionization is important in a wide range of interesting astrophysical scenarios such as colliding winds in X-ray binaries, outflows in AGNs and shock flows in the IGM. However, no self-consistent non-equilibrium ionization code is conveniently accessible to the astronomical community. We present a self-consistent non-equilibrium ionization code for use within the spectral analysis system ISIS, facilitating direct comparisons with Chandra HETGs observations. The features are investigated and discussed. In addition, we particularly address the possible extension to the photoionization plasma by taking advantage of atomic data and physics from the equilibrium photoionization model of XSTAR.
Carolin Liefke
Hamburger Sternwarte
Oral Presentation
Plasma diagnostics of a giant stellar flare
We present observations of a giant, impulsive X-ray flare on the nearby active M dwarf CN Leo obtained with XMM-Newton. The RGS grating spectra clearly show the flare plasma to be extremely dense, while the plasma emitted in quiescence is close to the low-density limit. EPIC CCD spectra show the Fe K line coming up after the flare onset, but no evidence for nonthermal emission is found during any phase of the flare. We study the temporal evolution of temperature structure and density and assess the abundances of the flaring plasma. An interpretation of the flare in the framework of the chromospheric evaporation scenario will be given.
Antonio Maggio
INAF - Osservatorio Astronomico di Palermo
Oral Presentation
Benchmark Exercises for stellar X-ray Spectroscopy Testing: initial results
In recent years, different teams active in the field of stellar coronal physics have used different approaches for the reduction and analysis of high-resolution X-ray 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). Until recently there was no study available about whether all the different approaches produce compatible results, or whether some (or all) of them lead to biases in the derived 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. To address the above issues we have started the BEXST project, a "hare and hounds exercise" open to the whole community, whose initial results I will present here for the ! first time.
Orio Marina
INAF-Padova (Italy) and U. Wisconsin (USA)
Oral Presentation
RS Ophiuchi in outburst in X-rays: an ``extreme'' nova.
We present long X-rays observations of the recurrent nova RS Ophiuchi, in outburst in February of 2006. Exposures done with different instruments aboard Chandra and XMM-Newton offer an unprecedented view of the evolution of this object that seems to host a very massive CO white dwarf and to be a viable type Ia supernova progenitor. Grating spectra show an accelerated evolution with respect to other novae, with a wind emission line spectrum in the first month, which is cooling and overlapping with an emerging ultra-luminous ultra-hot white dwarf at the end of the fourth week. The white dwarf spectrum becomes then dominant, but is detected for only about 6 weeks. During the transition phase in which the white dwarf spectrum gradually becomes dominant a $\simeq$35 seconds periodicity is detected for part of the time, that disappears completely as mass loss ceases, while the white dwarf is still luminous and burning its residual fuel for more than two weeks. We p! ropose an explanation for this unprecedented and interesting phenomenon.
Herman Marshall
MIT Kavli Institute
Oral Presentation
Modeling the SS 433 Jet Bends
We fit Chandra HETGS spectra obtained for the unusual X-ray binary SS 433. While line strengths and continuum levels hardly change, the jet Doppler shifts show aperiodic variations that probably result from shocks in interactions with the local environment. The X-ray and optical emission line regions are found to be related but not coincident as the optical line emission persists for days while the X-ray emission lines fade in less than 5000 s. The X-ray spectrum of the blue-shifted jet shows over two dozen emission lines from plasma at a variety of temperatures. The emission measure distribution derived from the spectrum can be used to test jet cooling models.
Mariano Mendez
SRON - Netherlands Institute for Space Research
Oral Presentation
High resolution spectrum of the galactic black-hole binary GRS 1915+105
Observations with Chandra and XMM-Newton of several galactic black-hole binaries and AGN show a broad Fe emission line at ~6-7 keV. The interpretation is that the width of the line is due to the strong gravitational field around the black hole. Here I present recent HETGS/Chandra observations of the galactic black hole GRS 1915+105 that appear to show both emission from a relativistic broad line at 6-7 keV, and absorption from photo-ionized gas. The inferred width of the emission Fe line depends on the assumed shape of the underlying continuum spectrum; when the effect of the photo-ionized absorber is taken into account, the line appears to be significantly narrower than otherwise reported. I will also discuss similar results with XMM-Newton on this source and two active galactic nuclei.
Kendrah Murphy
Johns Hopkins University
Oral Presentation
Resolving the Space-Time Around Black Holes
We discuss how high-resolution, time-resolved X-ray spectroscopy can be used to resolve the space-time metric around a black hole. Future instrument ation, such as X-ray calorimeters, will be able to significantly improve the co nstraints on key physical parameters such as the black-hole angular momentum (s pin). However, in order to probe sufficiently small spatial and temporal region s in the vicinity of the black hole, a high degree of accuracy in the calculati on of the geodesics and transfer functions associated with the metric is requir ed. We have found that, to achieve these goals, current schemes that implement these calculations for the Kerr metric must be improved due to unacceptable ina ccuracies, especially in the strong gravity regime. The errors in the current m odels may have escaped attention because of the limited spectral resolution of available X-ray data but would yield incorrect results when applied to higher r esolution data. We present a numerical te! chnique that overcomes this problem and results in a significantly more accura te treatment of photon propagation and relativistic line profiles, in preparati on for the anticipated improvements in X-ray data. With improved X-ray instrum entation and accurate spectral modeling, we will be able to measure the peak en ergies of Fe lines corresponding to the extremes of the orbits of localized fla res (hot spots) close to the black hole. By measuring the energies of the two peaks in the Fe line profile from a hot spot, we will be able to find constrain ts on both the location of the hot spot and the black-hole spin. We use transf er function calculations for the Kerr metric given by Dovciak et al. (2004) to produce theoretical constraints on the hot-spot location and black-hole spin fo r given peak energies and disk inclination angles as a function of uncertaintie s in the other pertinent observable parameters of the system.
Norbert S. Schulz
MIT Kavli Institute for Astrophys. & Space Res.
Oral Presentation
X-Ray Spectroscopy of Cool & Warm Absorbers with Chandra: From Oxygen to Iron
The excellent performance of the X-ray grating spectrometers onboard the Chandra X-ray Observatory have opened a new window for astronomy. X-ray absorption spectroscopy is a prime example for the benefits of high resolving power as provided by the LETG and HETG. The X-ray band $>25~\AA$ is sensitive to K- and L-shell resonance and continuum absorption from O-K to Fe K. X-ray absorbing plasmas are universal and their study is essential to our understanding of the evolution and dynamics of matter. I will review absorption properties of cool and warm plasmas in interstellar media and accreting X-ray sources in terms of densities, temperatures, element abundance, dynamics, spatial distribution, and ionization balance. Future prospects for absorption surveys are discussed as well.
Raanan Nordon
Technion
Oral Presentation
Large coronal flares and the FIP effect
The solar First Ionization Potential (FIP) effect, where low-FIP elements are enriched in the corona relative to the photosphere, has been known for a long while. High resolution observations by Chandra and XMM-Newton have shown that in other stars the effect varies from solar-like FIP effect to an inverse effect (IFIP). This variation has been linked to the coronal flaring activity, switching from FIP, in low activity stars, to IFIP in more active stars. We present a spectral analysis of the largest flares observed by Chandra and XMM-Newton gratings and compare flare relative to quiescence coronal abundances directly, regardless of photospheric or quiescent coronal composition. We find a tendency for a solar-like FIP bias in a large fraction of the flares, which is particularly surprising for the highly active stars whose coronae are believed to be IFIP biased. The remaining sources show no significant FIP bias during the flares. Possible interpretations are discu! ssed.
John Peterson
Purdue University
Oral Presentation
X-ray Spectra of Clusters of Galaxies
We review the X-ray spectra of clusters of galaxies. The high resolution X-ray spectra taken with the Reflection Grating Spectrometers on XMM-Newton exhibit a severe deficit of emission relative to the standard isobaric cooling-flow model, which would be predicted if radiative cooling dominated the energy balance. This result may indicate a sensitive balance between cooling and heating through AGN feedback, or may indicate additional heating or cooling mechanisms are operating in the cores of clusters. We highlight some recent work, which attempts to map the range of plasma temperatures present in the intracluster medium. We also relate the metal enrichment history of clusters of galaxies to the measurements made with X-ray spectra.
Andy Pollock
European Space Agency XMM-Newton SOC
Oral Presentation
The physics and dynamics of the X-ray plasmas in hot stars
Before the advent of the Chandra and XMM-Newton gratings, X-ray astronomy contributed little to the understanding of O stars and Wolf-Rayet stars or the relevant physics. Even though hot stars radiate in X-rays only a tiny fraction of their total luminosities, that has now changed with instruments that are almost perfectly suited to study the physics and dynamics of the supersonic plasmas that constitute hot-star winds. Work on the few single stars - some with strong magnetic fields - and binary systems bright enough to be observed have focussed new attention on the elementary processes involved in the production of radiation from shock waves in collisionless plasmas and its subsequent transfer. Magnetic fields are likely to be of general importance. The long-held promise of abundance measurements of many elements has also started to be fulfilled.
John Raymond
Center for Astrophysics
Oral Presentation
High Resolution X-ray Spectra of Accretion Disks
X-ray spectra from the accretion disks of Cataclysmic Variables, X-ray Binaries and AGN have been measured. They can be used to study the heating of accretion disk coronae and the driving of accretion disk winds. This talk presents an overview of the spectra from the different types of system and the regions where emission lines and absorption lines form.
James Reeves
University of Keele (UK)
Oral Presentation
AGN outflows, the tip of the iceberg?
High resolution X-ray spectroscopy has revealed outflows to be an important phenomenon in AGN, potentially providing the missing link in regulating black hole and bulge mass in galaxies. However most AGN outflows are observed with low velocities (<1000 km/s) and thus represent only a small fraction of the AGN power energetically. Here, evidence for high velocity (~0.1c) outflows in a growing number of AGN is reviewed, from recent XMM-Newton, Chandra and Suzaku observations. In particular, the most compelling evidence for such fast outflows arises from the detection of blue-shifted absorption lines in the iron K-shell band. If confirmed, they may represent an energetically significant fraction of the overall AGN power output. Finally, the prospects for future calorimeter based spectroscopy of AGN outflows will be discussed, which will resolve much of the ambiguity in modeling the iron K band.
Randall Smith
JHU & NASA/GSFC
Oral Presentation
Conference Overview
A short review of the talks and posters presented.
Rebecca Smith
Mullard Space Science Laboratory, UCL
Oral Presentation
High-res X-ray spectroscopy of AGN Warm Absorbers
The current standard model of AGN includes X-ray absorbing and emitting photoionized gas, which appears to be outflowing from the system at hundreds to thousands of kilometres per second. Signatures of these `warm absorbers' are often seen in the high-resolution soft X-ray spectra of AGN and offer clues to the structure, dynamics, elemental composition and ionization of these systems inner regions. We present detailed analyses of soft X-ray spectra from the Seyfert 1 galaxy Markarian 509 and the Narrow Line Seyfert 1 Arakelian 564 obtained with the XMM-Newton RGS. From studies such as these we intend to establish a more detailed picture of the gaseous outflows from the central regions of AGN and in particular to investigate how they are linked to the evolution of AGN and their host galaxy.
Paola Testa
MIT
Oral Presentation
Detailed plasma and fluorescence diagnostics of a stellar X-ray flare
We analyze a Chandra/HETGS observation of the single G-type giant HR 9024, showing a large flare with peak luminosity $L_{\rm X} \sim 10^{32}$ ergs/s. The high flux allows us to examine spectral line and continuum diagnostics at high temporal resolution, to derive plasma parameters. Time-dependent hydrodynamic loop modeling is used to constrain loop morphology and heating. A model of a loop with half-length $L \sim R_{\star}/2$ and impulsive heating, satisfactorily reproduces the observed evolution of temperature and emission measure, as derived from the strong continuum emission. For the first time for stellar flares we can compare predictions from the model with single spectral features, and we find that the model closely matches the observed emission of the hot FeXXV complex at $\sim$1.85\AA. Fe K$\alpha$ fluorescence emission ($\sim$1.94\AA) is detected, and its analysis provides us with an independent diagnostic for the coronal geometry, and therefore with ! a cross-check of the results of the hydrodynamic modeling.
Nolan Walborn
Space Telescope Science Institute
Oral Presentation
Multiwavelength Systematics of O-Type Spectra
Correlated trends among the optical spectral types, UV wind profiles, and X-ray line ionizations of normal O stars will be shown. The relationships between the first two were a surprise to specialists when first demonstrated in the 1980's; that history is now repeating with the current addition of the third. A Chandra program (PI W. Waldron) to fill spectral-type gaps in the archive has enabled a preliminary charting of the X-ray trends. Peculiar objects such as the magnetic stars Theta1 Ori C and Tau Sco are distinct from such trends, just as they were earlier in the optical and/or UV. On the other hand, the normal trends accommodate several objects believed to be colliding-wind binaries, as well as a range of low to moderate interstellar extinctions. These morphological relationships offer significant constraints on astrophysical modeling of the stellar winds and X-ray emission.
Daniel Wang
Univ. of Massachusetts, Amherst
Oral Presentation
X-ray Absorption Line Spectroscopy of the Interste
I will review X-ray grating absorption line spectroscopic studies of the interstellar medium, especially its hot component, in and around the Milky Way. The detection of the X-ray absorption lines produced by OVII, OVIII, NeIX, and Fe XVII, for example, allows for the first time to characterize the spatial, thermal, kinetic, and chemical properties of global hot gas in the Galaxy. In particular, the observed diffuse X-ray emitting/absorbing gas appears primarily in the vicinity (within a few kpc) of the Galactic disk/bulge and is chemically enriched. Therefore, the gas arises primarily from the stellar feedback. I will discuss implications of the results on our understanding the formation and evolution of the Galaxy.
Klaus Werner
University of Tuebingen
Oral Presentation
X-ray Photospheres
A few white dwarfs have effective temperatures high enough to emit detectable soft X-rays. CHANDRA's superb spectral resolution allows for the first time to perform detailed quantitative spectral analysis. We report on observations performed with the LETG and results obtained from atmospheric modeling.
Owen Westbrook
Harvard-Smithsonian Center for Astrophysics
Oral Presentation
X-Atlas: An Online Archive of Chandra's Stellar HETG Observations
We have compiled a database of all stellar observations made with Chandra's High Energy Transmission Grating (HETG) to facilitate the rapid comparison, characterization, and analysis of high-resolution stellar X-ray spectra. This database, known as X-Atlas, is accessible through a web interface with extensive searching and interactive plotting capabilities. For each target, X-Atlas also features predictions of the low-resolution ACIS spectra convolved from the HETG data for comparison with stellar sources in archival ACIS images. X-Atlas offers more than 130 observations of over 65 stars and will be updated as additional observations become public. The atlas is currently expanding to non-stellar point sources and eventually will include Low Energy Transmission Grating data as well.
Young Sam Yu
Rochester Institute of Technology
Oral Presentation
Model fitting of high-resolution X-ray Spectroscopy of the PN, BD+30 3639
We report preliminary results of model fitting of the first X-ray gratings spectrometer observations of a planetary nebula (PN). We have used the Chandra Low Energy Transmission Gratings in combination with its Advanced CCD Imaging Spectrometer (LETG/ACIS) to observe the X-ray-bright, young PN, BD+30 3639, for a total of 300ks. The resulting dispersed LETG/ACIS spectrum of BD+30 3639 displays well-resolved emission lines of H-like C, O and Ne and He-like O and Ne. Lines of Fe and N are weak or absent. Results obtained from fitting APED (Astrophysical Plasma Emission Database) models to this spectrum include accurate determinations of plasma temperature and the key abundance ratios C/O, N/O, Ne/O and Fe/O, which are diagnostic of the origin of the X-ray-emitting gas in planetary nebulae. These results thereby offer clues concerning the production of central ¡°hot bubbles¡± and other important physical mechanisms (such as heat conduction) that govern the shaping
Yangsen Yao
MIT Kavli Institute
Oral Presentation
Searching for the Large Scale Galactic Halo: Observations Confront Theories
Although the existence of the large-scale hot gaseous halos around massive disk galaxies have been theorized for a long time, so far there is very little observational evidence. In this work, we present a differential study of searching for such a halo around our Galaxy. The highly ionized He-like O VII and Ne IX K transition absorption lines have been clearly detected in the spectrum of the low mass X-ray binary 4U 1957+11, which locates $>2$ kpc above the Galactic disk and well off from the Galactic center region. By comparing these line absorptions with those detected in the spectra of LMC X--3 and Mrk 421, we obtained a firm upper limit of the absorption due to the putative Galactic halo and estimated the total mass contained in the halo. These results provide a direct observational test of galaxy formation theories for the first time.
Andrew Young
MIT / IoA
Oral Presentation
High Resolution X-ray Spectroscopy of the Low-Luminosity Nucleus of M81
I will present Chandra High Energy Transmission Grating Spectrometer (HETGS) observations of the Low Luminosity Active Galactic Nucleus (LLAGN) of M81. The HETGS is unique in providing high resolution spectroscopy of the central 1" of M81, including the Fe K bandpass. We detect a range of highly ionized emission lines, many of which are velocity broadened. There is a ~2,500 km/s redshifted Fe XXVI emission line. Fluorescence lines from Fe, Ar and Si indicate the presence of cold, dense material. The Si K alpha line is broadened to FWHM ~1,500 km/s. These observations can be used to study the physical conditions in the LLAGN, such as the ionization mechanism, kinematics and geometry of the accretion flow. I will also discuss how future observations may further enhance our understanding of LLAGN in general.
Bryan Armentrout
Catholic University of America
Poster Presentation
NGC 4151 X-Ray Spectrum Variability: 2000-2007
We present analysis of multiple X-ray observations of NGC 4151, spanning the period 2000-2007. Using the X-ray spectral modeling software XSPEC, the underlying continuum is well-fit by a broken power law and the ionized reflection atable REFLION, attenuated by two absorption columns. The columns were created as mtable grids using the photoionization code CLOUDY, and comprise a low ionization, low column density component, coupled with a higher ionization, high column density feature. While NGC 4151 was in a relatively low state in the investigated time period, the flux of the underlying continuum varied nearly sixfold among the observations. Affects of these variations on the continuum model parameters, as well as on soft X-ray emission lines and radiative recombination continua, are explored.
Valentina Braito
JHU/NASA-GSFC
Poster Presentation
The remarkable soft X-ray emission of the Broad Radio Galaxy 3C 445
We present the XMM spectrum of the BLRG 3C445. The EPIC data show a remarkable X-ray spectrum, with a heavily absorbed power law continuum, a narrow Fe Kalpha line, and possibly strong reflection. Interestingly a host of emission lines is present below 2keV due to H- and He-like O, Mg, and Si. This is the first time that soft X-ray lines are observed in BLRG and indeed a radio-loud AGN. We attribute the origin of these lines to a photoionized gas, with properties similar to radio-quiet obscured AGN. We discuss the possibility that the gas is located in an outflow, particularly interesting in light of jet formation models. The similarity of the X-ray spectrum of 3C445 to Seyferts underscores that the central engines of radio-loud and radio-quiet AGN similarly host both cold and warm gas.
Graziella Branduardi-Raymont
Mullard Space Science Laboratory, UCL
Poster Presentation
X-ray Spectroscopy of Solar System Objects
Chandra and XMM-Newton observations have enabled us to study in detail the X-ray spectra of solar system objects other than the Sun; among the planets, Venus, the Earth, Mars, Jupiter and Saturn have all been detected in the X-rays and have been studied in considerable depth. Aurorae have been observed to be powerful sources of X-rays on both Jupiter and the Earth. The process of ion charge exchange is now known to play an important role in the solar neighbourhood: grating X-ray spectroscopy is a very effective way of investigating the X-ray line emission it generates; recent results will be reviewed and will be shown to support current models of auroral emission and planetary atmospheres.
Michael Corcoran
CRESST/USRA/GSFC
Poster Presentation
X-ray Emission Line Variations in Eta Carinae
Eta Carinae is a binary system composed of an extremely massive luminous blue variable star and a bright companion. Thermal X-ray emission generated where the wind from Eta Car collides with the companion's wind provides unique diagnostics of the mass loss phenomena in both stars. We use variations in resolved X-ray emission lines from HETGS spectra taken around the orbit and concentrating on the approach to periastron passage to constrain the wind-wind interaction, the flow of hot gas along the colliding wind boundary, and the orbital elements of the system.
Konrad Dennerl
MPE Garching, Germany
Poster Presentation
X-ray grating spectroscopy of Mars with XMM-Newton/RGS
The first observation of Mars with XMM-Newton/RGS has provided a wealth of information about the X-ray properties of our neighbouring planet. It has unambiguously demonstrated that this emission is composed of two different components: fluorescent scattering of solar X-rays on neutral molecules in its upper atmosphere, and emission from highly charged ions in its exosphere. The flux ratio in the O$^{6+}$ multiplet proves that these ions are of solar wind origin, interacting with exospheric neutrals by charge exchange. In contrast to the fluorescent radiation, which is observed close to the planet, the spatial distribution of the charge exchange emission appears to be concentrated above the Martian poles, from where it can be traced out to at least 8 Mars radii.
Rosario Gonzalez-Riestra
XMM-Newton Science Operations Centre
Poster Presentation
A Browsing Utility for XMM-Newton RGS spectra
We describe an utility for browsing, visualisation and evaluation of XMM-Newton RGS fluxed spectra (BiRD: "Browsing Interface for RGS Data"). This tool provides access to RGS fluxed spectra homogeneously processed with the most recent versions of both the SAS software and of the calibration files. The BiRD interface allows to select spectra through a variety of parameters, such as date of observation, quality or type of object. It also provides some basic visualization utilities, both for the RGS spectra and spectral images, as well as for the EPIC-pn images taken simultaneously. This tool is available at http://xmm.esac.esa.int/BiRD/
David Huenemoerder
MIT
Poster Presentation
Magnetic Activity in Orion's Massive Young Stars
In the heart if the Orion Nebula Cluster, one of the youngest and nearest star forming regions, is an ensemble of the youngest massive stars we know in the Galaxy. Having a dynamic age of about 300,000 years, it harbors a number of very young and hot ZAMS stars. Recent X-ray studies implied that some of these stars showed coronal type X-ray spectra, but some seemingly not. So far the most compelling cases for magnetic activity in these cases have been made for Theta-1 Ori C and Theta-2 Ori A. As part of our HETG Orion Legacy Project we are in the process of obtaining high quality and highly resolved X-ray spectra from all massive Trapezium stars. We will present spectra and analysis of some of these stars, including line-based spectral characterization of spectra and dynamics.
Vinay Kashyap
SAO
Poster Presentation
Summarizing Stellar Spectra
High-resolution grating spectra of coronal sources contain a tremendous amount of information on the temperature structure and composition of the sources. In general, it requires a painstaking and detailed Emission Measure analysis to extract these parameters from the data. Here, we explore the possibility of summarizing this information in some easily measurable quantities. This is akin to the role played by hardness ratios for low-resolution spectra. Specifically, we measure the ratios of line fluxes in various temperature-, density-, and composition-sensitive lines and compare them to each other and to the underlying continuum. We use as a first test the database of all MEG spectra of cool stars obtained with Chandra to date, and made available via XAtlas (Westbrook et al., 2007). We search for patterns in this high-dimensional space of metrics and report on our capability to group sources according to the measured metrics. This work is carried out as par! t of the XAtlas project (Westbrook, Wolk, Evans, Nichols, Kashyap, Mendrygal, Slavin, Waldron). This research is supported by Chandra Grants GO5-6006 and GO5-6006A and NASA contract NAS8-39073 to the Chandra X-ray Center. HL acknowledges support from NASA/AISRP grant NNG06GF17G.
Julia Lee
Harvard
Poster Presentation
The High Resolution Optical to X-ray Study of the QSO IRAS 13349+2438
We report on a coordinated Chandra HETGS, HST, and ground based optical study at high spectral resolution of the archetypal infrared quasar IRAS 13349+2438; Spitzer IRS observations will also be presented. The implications of our multiwavelength studies will be discussed in the context of the ionization structure and source environment.
Maurice Leutenegger
Columbia Astrophysics Laboratory
Poster Presentation
Resonance Scattering in Doppler profiles of $\zeta$ Pup
We fit the Doppler profiles of the He-like triplet complexes of O VII and N VI in the X-ray spectrum of the O star $\zeta$ Pup, using XMM-Newton RGS data collected over ~400 ks of exposure. We find that they cannot be well fit if the resonance and intercombination lines are constrained to have the same profile shape. However, a significantly better fit is achieved with a model incorporating the effects of resonance scattering, which causes the resonance line to become more symmetric than the intercombination line for a given characteristic continuum optical depth $\tau_*$. We discuss the plausibility of this hypothesis, as well as its significance for our understanding of Doppler profiles of X-ray emission lines in O stars.
Anna Lia Longinotti
ESAC, Madrid (Spain)
Poster Presentation
The variable warm absorber in the Seyfert 1 Galaxy Mrk 841 revealed by the RGS
The Seyfert 1 galaxy Mrk 841 has been observed several times by XMM-Newton yielding five good quality spectra (both EPIC and RGS data) obtained at different epochs. The analysis of all the available observations reveals a complex behaviour in the soft X-ray band. By comparing the RGS exposures obtained in January 2001 to the RGS spectra obtained in 2005, the presence of a variable warm absorber is inferred. The ionisation state of the gas remains at an intermediate level with moderate variation in the ionisation parameter (0.3 dex), correlated with the central source luminosity change, whereas the variability in the column density is much larger, a factor of 5 on a time scale of 4 years. No significant velocity shift of the absorption lines is measured in the RGS data. Remarkably, in 2005 we could measure the recombination line and the Radiative Recombination Continuum (RRC) of OVII. In 2001 the intrinsic luminosity was a factor of two higher and only the line ! is still detected, while the RRC disappeared. This is in agreement with a linear response of the recombining gas to the central flux variations.
Michael McCollough
CXC/SAO
Poster Presentation
Probing the Winds of Cygnus X-3 with the Chandra HETG
We present an analysis of HETG Chandra observations of Cygnus X-3 taken in a soft/high state. Cygnus X-3 is a high mass X-ray binary which has two major states (hard/low and soft/high) and shows correlative activity in the radio. The soft/high state spectra show a rich photoionized spectrum with a large number of H-like and He-like lines. Many of these lines show P-Cygni profiles indicative of the strong outflow from the system. The spectrum also show Radiative Recombination Continuum from which the plasma temperature can be estimated. A discussion and analysis of the spectrum and these features will be given.
Kendrah Murphy
Johns Hopkins University
Poster Presentation
Resolving the Space-Time Around Black Holes
We discuss how high-resolution, time-resolved X-ray spectroscopy can be used to resolve the space-time metric around a black hole. We present a numerical technique that results in significantly more accurate modeling of photon propagation and relativistic line profiles, in preparation for the anticipated improvements in X-ray data. With improved X-ray instrumentation and accurate spectral modeling, we will be able to measure the peak energies of Fe lines corresponding to the extremes of the orbits of localized flares (hot spots) close to the black hole. We use transfer function calculations for the Kerr metric to produce theoretical constraints on the hot-spot location and black-hole spin as a function of uncertainties in the other pertinent observable parameters of the system.
Joy Nichols
Harvard-Smithsonian Center for Astrophysics
Poster Presentation
Improved Wavelength Accuracy for Reprocessed Grating Data
Reprocessing of the Chandra archival data for the years 2000-2005 is nearly complete. A significant improvement in the processing for many of the grating observations is the more accurate position determination for the zeroth order, which results in improved wavelength assignments for the dispersed spectral data. We describe the ISIS software tool FINDZERO which uses the known angles between the readout streak and the heg, meg, and leg spectral arms to locate the zeroth order. FINDZERO was used in the reprocessing to determine the zeroth order position for cases when the standard processing tools give a less accurate result, such as piled-up or instrumentally blocked sources. The newly reprocessed grating data are compared to the previous version of the data and examples of types of sources and methods used by the Validation and Verification Team for determining the zeroth order position are given. Statistics on the fraction of grating observations that wil! l show significant improvement with the reprocessing and keys for the investigator to assess whether an observation is worth re-analysis are also given.
Michael Nowak
Massachusetts Institute of Technology
Poster Presentation
X-ray Binaries in the Era of Chandra and XMM High Resolution Spectroscopy
High resolution X-ray spectroscopy increasingly is being used to probe the components of an accreting binary: the turbulent MHD disk, the inner hot jet/corona, the outer (possibly warped) disk and its hot atmosphere and disk winds. The form of each of these components rely upon spectral state, the nature of the central compact object, and the nature of the secondary. Reflection spectra probe the structure of the jet/corona relative to the thermal disk. Emission line spectra may reveal transitions between cold disk and inner hot flows. The outer atmosphere may be probed via emission lines, while the outer disk edge and incoming accretion stream may be probed via absorption lines. I will review current spectroscopic studies of these topics, as an introduction for subsequent discussions.
Pedro Rodriguez-Pascual
Absorption lines at z=0 in X-ray spectra: a test case for RGS fluxed spectra.
We present a study of absorption lines at z=0 in the spectra of extragalactic sources as a test case for the use of fluxed RGS spectra. The list of observations analysed has been obtained using the filtering capabilities included in the "Browsing Interface for RGS Data". All observations have been reprocessed homogeneously and the spectra binned to a common wavelength scale and according to the spectral resolution of the instrument. The spectra for every source have been normalized and then averaged according to their statistical errors. Finally, standard techniques developed to search for significant absorption features in high resolution optical spectra have been applied.
Jorge Sanz-Forcada
Coronal abundances of AY Cet and AR Psc
The behavior of coronal abundances of active stars have been largely discussed in the last years. Despite of the efforts invested, in most cases the coronal abundances of the star can only be compared hr>Johns Hopkins University/ NASA GSFC Poster Presentation with the photospheric {\em solar} abundances, making difficult to get a state of the art. We report the results of a detailed analysis of the coronal abundance of two active binary systems, AY Cet and AR Psc. We make use of Chandra/LETGS and XMM-Newton/RGS high-resolution spectra to calculate the coronal abundances that we compare to the photospheric abundances of the two stars that we have calculated.
Jingen Xiang
The evolving line profiles and dust scattering halo of 4U 1624-490
We present results based on a 76ks Chandra HETGS observation of the "Big Dipper" 4U 1624-490. Specifically, we will discuss the observed evolving line profiles with phase in the context of the geometry of the system as well as changes in plasma conditions over the 4U 1624-490 binary orbit. In addition, we will show how we have used the associated dust scattering halo to derive a geometric distance of ~15 kpc to this binary, as well as assess location, uniformity and density of ISM dust grains along the line of sight to this source.
Tahir Yaqoob
HotGAS to go: Outflows, Accretion, Strong Gravity, and the IGM
HotGAS (http://hotgas.pha.jhu.edu) contains high-level data products from Chandra HETGS AGN observations. Easy and user-friendly access to reprocessed, multiple format, publishable quality grating products constitute a powerful resource (for research, future mission observation planning, proposals, training), and lend themselves to promote inter-disciplinary and multi-wavelength research. Absorption and emission features can be used to study mass outflows, signatures of the accretion flow down to the strong gravity regime, as well as the IGM. We show some science highlights that are unique to HETG data. We plan to eventually expand the archive to include more Chandra grating observations, and eventually XMM RGS data too. Further in the future HotGAS may not be restricted to AGN only.
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