Atomic data: state of the art and
future perspectives
Jelle Kaastra
with Ton Raassen, Liyi Gu, Junjie Mao, Igone Urdampilleta,
Missagh Mehdipour
SRON & Leiden University
Introduction
• X-ray emitting plasmas everywhere:
– Solar system to cosmic web filaments
• Broad range environments & physical conditions:
– collisional ionised, photo-ionised, transiently ionised
• High resolution X-ray spectroscopy key to understand
these sources
• Next year launch ASTRO-H with SXS calorimeter
• Old models not always most up to date atomic physics
• Need tool to model these different sources with same,
consistent set atomic parameters
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Spectroscopic codes @ SRON
• Short history:
– 1972 Mewe
– 1975 Mewe-Gronenschild
– 1985 Mewe-GronenschildVan den Oord
– 1990 Meka
– 1994 Mekal
– 1992 SPEX
• 1992 Version 1
• 2001 Version 2
• 2015 Version 3 (expected release December)
• Evolution from plasma model to full astrophysical model
including data analysis (fitting), plotting & diagnostic output
• Example: Mewe code
(still core present SPEX
models) approximates
radiative recombination
contribution to lines by
local power-law
• Okay for CIE but:
• Large deviations for
recombining / ionising
plasma
log rate 
Need for updates
Tmax
log T 
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Requirements for updates
• Code must allow options for fast calculation yet
accurate enough
•  Minimise number of mathematical operations
& data storage for the cross sections/rates
•  follow original strategy of Mewe: simple,
accurate & fast approximations, but more
accurate & complete than before
• Restrict to Z ≤ 30 (astrophysically most relevant)
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Updates to atomic data
• For full model, need updates of many
processes:
– Collisional & photo-ionisation cross sections
– Transition probabilities
– Auto-ionisation rates
– Recombination rates
– Line energies
– Etc.
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Comparison of codes
(with Junjie Mao)
SPEX V 3.0β
ATOMDB V3.0.2
Fe
Log T (K)
Wavelength (Å)
O
Wavelength (Å)
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Collisional ionisation
(with Igone Urdampilleta)
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Motivation
•
•
•
•
•
•
In the past, several compilations
Recent one: Dere 2007
Almost always give total ionisation rates
Subshells needed for inner-shell line emission
New data published since 2007
 Revisit collisional ionisation rates
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Collisional ionisation for atoms and ions
of H to Zn
Direct ionization cross section fitting procedure:
where,
Ee electron energy
I ionisation potential
A, B, D, E fit parameters
C Bethe constant
R relativistic correction
Relativistic correction (Quarles 1976 and Tinschert et al. 1989):
Excitation Autoionization fit (Mewe 1972):
QI2 (10-24 m2keV2)
Examples of fits to collisional
ionisation cross sections
2s
1s
 Note
Dimensionless scaling 
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QI2 (10-24 m2keV2)
I ~ Z2 for 1s shell H-sequence
 Note dimensionless scaling 
Relativistic
correction 
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-Cl
-Ar
-K
-Ca
-Sc
-Ti
-V
-Cl
-Ar
-K
-Ca
-Sc
-Ti
-V
-Cr
-Mn
-Fe
-Co
-Ni
-Cu
-Zn
-Cr
-Mn
-Fe
-Co
-Ni
-Cu
-Zn
-Cl
-Ar
-K
-Ca
-Sc
-Ti
-V
-Cl
-Ar
-K
-Ca
-Sc
-Ti
-V
-Cr
-Mn
-Fe
-Co
-Ni
-Cu
-Zn
-Cr
-Mn
-Fe
-Co
-Ni
-Cu
-Zn
-Cl
-Ar
-K
-Ca
-Sc
-Ti
-V
-Cr
-Mn
-Fe
-Co
-Ni
-Cu
-Zn
Radiative recombination
(with Junjie Mao)
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Radiative recombination
• Need individual rates to different excited
shells for calculation of line spectrum
• Also need cooling rate associated to the
recombination (kinetic energy captured
electron averaged over the recombination
rate)
• Start with hydrogen-like systems
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FAC Gu (2003)
PI Cross
Section
Storey&Hummer
(1991)
Milne
relation
RR Cross
Section
cf
AUTO STRUCTURE
Badnell (2006)
Free edistribution
RR rates
Parameterisation
R(T) = a0 T-b0-c0logT (1+a2T-b2) / (1 + a1 T-b1)
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Fitting accuracy
• Vast majority:
accurate within
few %
• Very limited
number outliers
• Usually
unimportant
transitions
• Example: C I n=5
1D level, still
2
~15% accuracy
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Photoionised plasmas
(with Missagh Mehdipour)
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Obscuration in NGC 5548
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1
0.8
0.6
0.4
0.2
0
Transmission
WA 2002
WA 2013
Obscurer nr. 1 2013
Obscurer nr. 2 2013
Total obscurer 2013
Total obscurer + WA 2013
1
2
5
10
Restframe wavelength (Å)
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Differences photoionisation models
(NGC 5548 obscured case)
Ξ = Fion / nkTc
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Total radiative recombination rates
• Seaton approximation: simple analytic
form for low to intermediate T
• Fails at higher T
• Previously widely used (e.g. Arnaud &
Rothenflug 1985 balance)
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Effects of update for photoionised
plasmas
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He-like triplets and absorption
(with Missagh Mehdipour)
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He-like R-ratio in Active Galactic Nuclei
(Seyfert 2 galaxies)
Landt et al. 2015,
observations
Theory: Porquet & Dubau (2000)
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1s22s1s2s(1S)2p 2P
1s22s1s2s(3S)2p 2P
z
w
x,y
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Line broadening
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Line broadening
• Thermal Doppler
broadening
• Turbulent broadening
• Natural broadening?
• For Fe-K, FWHM 0.21.0 eV (e.g. Brown et
al.)
• Corresponds to 10-50
km/s
•  Need Voigt profiles
Thermal broadening only
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Charge transfer modeling
see talk this afternoon by Liyi Gu
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Conclusions
• Astrophysical sources sometimes found in
remarkable areas of parameter space
• New X-ray missions like ASTRO-H (launch
2016) demand more detail & accuracy (but
also Chandra & XMM-Newton benefit)
• Work in progress: update atomic parameters
in X-ray spectral models to account for this
• SPEX ( www.sron.nl/spex ) Version 3 will
contain these updates (release late 2015)
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