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.