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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
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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 2
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Spectroscopic codes @ SRON Short history: –1972 Mewe –1975 Mewe-Gronenschild –1985 Mewe-Gronenschild- Van 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
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Need for updates 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 T max log T log rate 4
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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) 5
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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. 6
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Comparison of codes (with Junjie Mao) 7 Wavelength (Å) SPEX V 3.0β ATOMDB V3.0.2 Log T (K) Fe O
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Collisional ionisation (with Igone Urdampilleta) 8
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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 9
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Collisional ionisation for atoms and ions of H to Zn Direct ionization cross section fitting procedure: Relativistic correction (Quarles 1976 and Tinschert et al. 1989): Excitation Autoionization fit (Mewe 1972): where, Ee electron energy I ionisation potential A, B, D, E fit parameters C Bethe constant R relativistic correction
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Examples of fits to collisional ionisation cross sections 11 QI 2 (10 -24 m 2 keV 2 ) 1s 2s Note Dimensionless scaling
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12 QI 2 (10 -24 m 2 keV 2 ) Relativistic correction Note dimensionless scaling I ~ Z 2 for 1s shell H-sequence
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-Cl -Ar -K -Ca -Sc -Ti -V -Cr -Mn -Fe -Co -Ni -Cu -Zn -Cl -Ar -K -Ca -Sc -Ti -V -Cr -Mn -Fe -Co -Ni -Cu -Zn -Cl -Ar -K -Ca -Sc -Ti -V -Cr -Mn -Fe -Co -Ni -Cu -Zn -Cl -Ar -K -Ca -Sc -Ti -V -Cr -Mn -Fe -Co -Ni -Cu -Zn
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-Cl -Ar -K -Ca -Sc -Ti -V -Cr -Mn -Fe -Co -Ni -Cu -Zn
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Radiative recombination (with Junjie Mao) 15
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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 16
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RR Cross Section PI Cross Section Storey&Hummer (1991) PI Cross Section Storey&Hummer (1991) EXACT AUTO STRUCTURE Badnell (2006) AUTO STRUCTURE Badnell (2006) FAC Gu (2003) cf Analytic Free e - distribution Milne relation RR rates Parameterisation 17 R(T) = a 0 T -b0-c0logT (1+a 2 T -b2 ) / (1 + a 1 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 1 D 2 level, still ~15% accuracy 18
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Photoionised plasmas (with Missagh Mehdipour) 19
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Obscuration in NGC 5548 20
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Differences photoionisation models (NGC 5548 obscured case) 22 Ξ = F ion / nkTc
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Total radiative recombination rates 23 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 24
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He-like triplets and absorption (with Missagh Mehdipour) 25
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He-like R-ratio in Active Galactic Nuclei (Seyfert 2 galaxies) 26 Theory: Porquet & Dubau (2000) Landt et al. 2015, observations
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27 1s 2 2s 1s2s( 1 S)2p 2 P1s 2 2s 1s2s( 3 S)2p 2 P w z x,y
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Line broadening 30
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Line broadening Thermal Doppler broadening Turbulent broadening Natural broadening? For Fe-K, FWHM 0.2- 1.0 eV (e.g. Brown et al.) Corresponds to 10-50 km/s Need Voigt profiles 31 Thermal broadening only
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Charge transfer modeling see talk this afternoon by Liyi Gu 33
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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)www.sron.nl/spex 34
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