2. Classification of SN Progenitors Optical obs of SNe Classification is relatively straightforward - Spectrum (historically well established) - Luminosity ( 56 Ni yield) X-ray obs of SNRs Classification (Ia/CC) is (was) controversial in many SNRs - Similar X-ray luminosity - Morphology? SNRs can be spatially resolved, strong advantage of X-ray - Spectrum? SNe Ia: nuclear reaction energy ~ 10 51 erg SNe CC: gravitational energy ~ 10 53 erg 99% neutrino + 1% kinetic (~ 10 51 erg) Ia (SD) Ia (DD) CC (1987A) => transformed to thermal energy (X-ray luminosity)

3. Type Ia CC Ellipticity Mirror asymmetricity Morphology of SNRs CC SNRs are more asymmetric than Ia SNRs (Lopez+09;11) G344.7-0.1 found to be Type Ia (HY+12) Chandra images of Galactic/Magellanic SNRs Reflects nature of explosion and/or environment? SNR E0102-72 (CC) 0104-72.3 (Ia candidate) Doesn’t work for SMC SNRs… (Lopez+12) 0104-72.3 E0102-72

4. X-Ray Spectra of SNRs Advantage - Optically thin (self absorption is almost negligible, but see Miyata+08) - K-shell emission from He- & H-like atoms (kT e ~ h ~ 0.1–10 keV, comparable to K-shell potential), so physics is simple SiSi S Ar Ca Fe Ni Mg Ne Artificial features (a sort of bgd) Simple Quiz CC (W49B) Ia (SN1006) YOU LOSE m9(^Д^) Suzaku spectrum of Tycho (Hayato+10)

5. X-Ray Spectra of SNRs SiSi S Ar Ca Fe Ni Mg Ne Artificial features (a sort of bgd) W49B (CC) Large foreground extinction makes O/Ne/Mg emission in W49B weak Absorption for different column density (N H [cm -2 ]) SN1006 W49B Note: although we use N H to describe the column, what we measure in X-rays is the column of metals Yet, weakness of Fe emission in SN 1006 (Ia SNR) is puzzling => Understanding of NEI is essential

6. Non Equilibrium in Ionization (NEI) Pre-shocked metals in ISM/ejecta are almost neutral (unionized) Shock-heated electrons gradually ionize atoms by collision, but ionization proceeds very slowly compared to heating Fe ion population in NEI plasma for kT e = 5 keV n e t (cm -3 s) Ion fraction Fe 24+ Fe 25+ Fe 26+ Fe 16+ lowly ionized highly ionized Fe 24+ Fe 25+ Fe 26+ Fe 16 + Electron temperature kT e (keV) CIE n e t : “ionization age” n e : electron density t : elapsed time since gas was heated

7. Non Equilibrium in Ionization (NEI) Fe ion population in NEI plasma for kT e = 5 keV n e t (cm -3 s) Ion fraction Fe 24+ Fe 25+ Fe 26+ Fe 16+ lowly ionized highly ionized n e t : “ionization age” n e : electron density t : elapsed time since gas was heated Timescale to reach CIE for ISM t ~ 3 x 10 4 (n e /1 cm -3 ) -1 yr As for ejecta … Time when the masses of swept-up ISM and ejecta becomes comparable Ionization state for the ejecta becomes almost “frozen” after an SNR evolved. Ionization age for the ejecta strongly depends on the initial CSM density rather than its age.

8. Non Equilibrium in Ionization (NEI) Full X-ray band Magnified spectra in the 6-7 keV band (Fe K emission) Fe-L blend Fe-K Observed spectrum (Convolved by Suzaku response) n e t = 5x10 9 1x10 10 5x10 10 1x10 11 3x10 11 Ar-like Ne-like C-like Be-like He-like Model spectra of Fe emission [kT e = 5 keV] How does ionization age affect a spectrum? How can we measure ionization age? H-like 6.42 keV 6.44 keV 6.60 keV 6.64 keV 6.67 keV 6.07.0 0.510

9. SiSi S Ar Ca Fe Ni Mg Ne Artificial features (a sort of bgd) Ozawa+2009 HY+2008, Uchida+, in prep. SN1006 (Type Ia SNR) W49B (CC SNR)

10. SN1006: Searching for Fe emission Fe? BeppoSAX MECS spectrum Chandra image - Prototypical Type Ia SNR, but emission from Fe has never been detected. - Only one possible detection reported by BeppoSAX - XMM-Newton failed to detect Vink+00 Suzaku spectrum (HY+08) Detected! but weak despite of its Type Ia origin Fe-K centroid ~ 6420eV (< Ne-like) … Corresponding n e t is ~ 1 x 10 9 cm -3 s Fe 24+ Fe 25+ Fe 26+ Fe 16+

11. SN1006: Multiple n e t Components in Si Approx with 2- n e t components for Si and S ejecta n e t 1 ～ 1×10 10 cm -3 s n e t 2 ～ 1×10 9 cm -3 s cf. Fe: n e t ～ 1×10 9 cm -3 s Si ion fraction @1keV Si 12+ Si 13+ Si 6+ Si 8+ C~O-like He-like Mg Si broad feature S Reverse shock heats from outer region Outer ejecta = highly ionized Inner ejecta = lowly ionized

12. SN1006: Fullband Spectrum & Abundances ISM (w/ solar abundance) Outer ejecta ( n e t ~ 10 10 cm -3 s) Inner ejecta ( n e t ~ 10 9 ) Non-thermal (synchrotron) Fe Derived abundance ratios compared to the W7 model of Nomoto+84 Outer ejecta Inner ejecta Suggests stratified composition with Fe toward the SNR center, which results in the lowly-ionized (thus weak) Fe emission HY+08

13. Ejecta Stratification in Type Ia SN/SNRs XMM image of Tycho Radius (arcmin) Radial profile Fe Si Color: Si-K Contour: Fe-K Decourchelle+01 Mazzali+07 IME 56 Ni Enclosed mass SN 2003du (Tanaka+10) See also Badenes+06

14. SiSi S Ar Ca Fe Ni Mg Ne Artificial features (a sort of bgd) Ozawa+2009 HY+2008, Uchida+, in prep. SN1006 (Type Ia SNR) W49B (CC SNR)

15. W49B: Peculiar Ionization State - RRC can be enhanced only when the plasma is recombining (e.g., photo-ionized plasma) Similar recombining SNRs - IC443 (HY+09) - SNR 0506-68 (Broersen+11) - other 3 & a few candidates “Recombining NEI” in SNRs is not unique => Need to define “recombination age” Cr Mn He-like Fe K  Ni + Fe K  Fe-K RRC H-like Fe Ozawa+09 Ejecta is highly ionized to be He-like Radiative recombination continuum Fe 25+ + e - → Fe 24+ + h … indicates presence of a large fraction of H-like Fe Measured kT e ~ 1.5 keV Temperature (keV) Fe 24+ Fe 25+ Fe 26+ Fe 16+ Fe ion population in a CIE plasma

16. W49B: Possible Progenitor blast wave 2nd reverse shock reverse shock Blast wave breakout into ISM BW speed becomes faster and expand adiabatically, resulting in rapid cooling with “frozen” ionization state Shimizu+12 Explosion in dense CSM - Numerical (Shimizu+12) - Analytical, more progenitor- oriented (Moriya 12) RSG case ( v w ~ 10 km/s)WR case ( v w ~ 1000 km/s) Type II-P or IIn could be a progenitor of a recombining SNR (Moriya 12)

17. Fe-K diagnostics Extreme cases have been shown SN1006: Type Ia SNR, Fe lowly-ionized due to a low ambient density and ejecta stratification with Fe more concentrated toward the center W49B: CC SNR, Fe over-ionized (recombining), possibly due to interaction with high-density CSM … and inhomogeneous ejecta structure? Red: Si Blue: Fe Green: continuum Other SNRs?

18. Fe-K diagnostics Type Ia CC - Type Ia and CC SNRs are clearly separated (CC more ionized) - Luminosity of both groups are distributed in the similar range. (HY+, in prep.) n e t = 5x10 9 1x10 10 5x10 10 1x10 11 3x10 11 Can be explained by ionization (and temperture, density effects) --- Measuring ionization state is essential for measuring element abundances!!

19. Fe-K diagnostics Type Ia CC (HY+, in prep.) Ionization ages expected if the SNRs have evolved in uniform ISM with typical density Hachisu+01 Badenes+07 If the SD scenario is the case, a large, low-density cavity is expected around the progenitor No evidence of an “accretion wind” and a resultant cavity but for a few Type Ia SNRs

20. Evidence of cavity/CSM in Ia SNRs RCW86 (Williams+11) Unique Ia SNR where the presence of a surrounding cavity is suggested Kepler (Reynolds+07) N103B (Lewis+03)

21. Summary - X-ray observation of SNRs is one of the best methods to study stellar/explosive nucleosynthesis. (optically-thin, K-shell emission) - Understanding of non-equilibrium in ionization is, however, essential for accurate measurement of element abundances. - Fe emission in Type Ia SNRs is commonly weak due to low-density ambient and stratified chemical composition. - In CC SNRs, on the other hand, Fe is highly ionized, sometime overionized, possibly due to initial CSM interaction. - No evidence of a large cavity expected from an “accretion wind” around Type Ia SNRs, except for RCW86, constraining progenitor system??