Post on 21-Dec-2015
Photoionization Modeling: the K Lines and Edges of Iron
P. Palmeri (UMH-Belgium)
T. Kallman (GSFC/NASA-USA)
C. Mendoza & M. Bautista (IVIC-Venezuela)
J. Krolik (JHU-USA)
Introduction
• Iron K lines are observed in (almost) all X-ray sources
• First reported in rocket observations of the supernova remnant Cas A
Serlemitsos, et al, 1973
Introduction
• Appear in a relatively unconfused region
• Emitted efficiently over wide range of temperatures and ionization states
• Relativistically broaden and red-shifted lines observed in galactic black hole candidates
Tanaka et al., 1996
Introduction
RXTEEXOSAT
ASCA XMM
Chandra
Astro-E2
Compton
1000 km/s
300 km/s
The world of X-ray observatory is changing:
Atomic Data
• Motivation: they were scarce and not sufficiently accurate especially for the M-shell ions (Fe I-XVII)
• Methods: standard atomic codes, i.e. AUTOSTRUCTURE (Badnell), HFR (Cowan) & BPRM (IP/RmaX Projects)
Atomic Data• L-shell ions (Fe XVIII-XXV) CI: {2s,2p}N+[1s]{2s,2p} N+1+up to double excitations to M-
shellSemi-empirical corrections: compilation of Shirai et al (2000)• M-shell ions (Fe I-XVII)Focus on K-vacancy states produced by removing a 1s
electron from the ground configurationNo experimental energies Ab initio calculationsFew experimental data (wavelengths): Fe X & solid state
Core Relaxation EffectsElectrons in K-vacancy & valence configurations see radically different potentials different orbitals for initial & final states of inner-shell transitions
affects level energies, wavelengths & rates !!!
-increase radiative rates by ~5-10%
-increase KLL rates by ~10%
-no systematic effect on KLM rates
-decrease KMM rates by ~10%
Damping Effect
−+→+ essh NN μμν 11 2
Resonances before K-edge
−− +→ esnps NN 1211 μμ
−− +→ enps N 221 μ
νμ hs N +→ 21
νμ hnps N +→ −121Spectator channels (Damping channels)
Participator channels
Damping Effect: Electron Impact
Withoutdamping
Withdamping
Fe XIX
2p4 3P2 [1s]2p5 3Po2 [1s]2p5 3Po
1 [1s]2p5 3Po0
Line Energy vs. Ionization StageBlue=MakishimaBlack=these studies
Line moves to red near Fe IX
Complicated K linestructure
Edge Energy vs. Ionization Stage
In first row ions, ground level is split by various valence configurations
Blue=MakishimaBlack=these studies
In 2nd and 3rd row ions,Splitting is smaller,Results differ significantlyFrom previous
K/K ratio vs. Ionization Stage
MCDF
Auto-S
HFR
Kaastra-Mewe
Jacobs-Rosznyai experiment
K/K ratio is a potential diagnostic of ionization
Photoionized Plasma Modeling With XSTAR
• Photoionization of a gas by intense external X-ray source (dominant)
• Other processes affecting ionization, excitation & temperature are in equilibrium
Local conditions (ionization fractions, temperature, opacity) parameterized by
=Ionization parameter =4Ionizing flux/gas density
Photoionized Plasma Modeling: Atomic Processes
• Each ion has ~3-30 K-vacancy levels which can be populated by photoionization
• ~4-100 K lines per ion considered in our treatment
Ionization Balance & Temperature
Ionization balance temperature =Ionization parameter=4Ionizing flux/gas density
104<T<108K
Line Emissivity vs. Column Density
1/N decrease marks the Breakdown of the optically thinapproximation
Shift of ionization from high to low will be detectable in reprocessed spectrum
Emissivity averaged over constant density slab with log()=2
Simulated Spectra
XMM Epic PN Astro-E XRS
Assuming log()=2, log(N)=23, 100 mcrab source, tobs= 100 ksec
Conclusions
• Structure of Iron K shell is more complicated than has been previously appreciated, & care is needed to accurately compute useful quantities
• There is a shortage of experimental data needed for accurate spectral modeling especially in intermediate & low ionization stages
• Converging series of damped resonances act to smear absorption edges
• Emission lines contain structure which has diagnostic value, even for low ionization gas