Classification of SN Progenitors Optical obs of SNe Classification is relatively straightforward - Spectrum (historically well established) - Luminosity (56Ni 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? Ia (SD) Ia (DD) CC (1987A) SNe Ia: nuclear reaction energy ~ 1051 erg SNe CC: gravitational energy ~ 1053 erg 99% neutrino + 1% kinetic (~ 1051 erg) => transformed to thermal energy (X-ray luminosity) Morphology of SNRs CC SNRs are more asymmetric than Ia SNRs (Lopez+09;11) CC 0104-72.3 Ellipticity E0102-72 Type Ia Chandra images of Galactic/Magellanic SNRs Doesn’t work for SMC SNRs… (Lopez+12) Mirror asymmetricity Reflects nature of explosion and/or environment? G344.7-0.1 found to be Type Ia (HY+12) SNR E0102-72 (CC) 0104-72.3 (Ia candidate) 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 (kTe ~ hn ~ 0.1–10 keV, comparable to K-shell potential), so physics is simple YOU LOSE Simple Quiz m9(^Д^) Suzaku spectrum of Tycho (Hayato+10) Artificial features (a sort of bgd) Ia (SN1006) Mg Ne S i S Ar Ca CC (W49B) Fe Ni X-Ray Spectra of SNRs Absorption for different column density (NH [cm-2]) SN1006 Large foreground extinction makes O/Ne/Mg emission in W49B weak Note: although we use NH 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 W49B Artificial features (a sort of bgd) Mg Ne S i S Ar Ca W49B (CC) Fe Ni 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 kTe = 5 keV Fe16+ highly ionized Ion fraction lowly ionized Fe24+ + Fe24+ Fe26+ Fe25+ CIE Fe25+ Fe26+ net (cm-3 s) Fe16 Electron temperature kTe (keV) net : “ionization age” ne : electron density t : elapsed time since gas was heated Non Equilibrium in Ionization (NEI) Fe ion population in NEI plasma for kTe = 5 keV Fe16+ highly ionized ne : electron density t : elapsed time since gas was heated Fe24+ Ion fraction lowly ionized net : “ionization age” Fe25+ Fe26+ Timescale to reach CIE for ISM t ~ 3 x 104 (ne/1 cm-3)-1 yr net (cm-3 s) 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. Non Equilibrium in Ionization (NEI) How does ionization age affect a spectrum? How can we measure ionization age? Model spectra of Fe emission [kTe = 5 keV] 1x1010 5x1010 1x1011 net = 5x109 3x1011 Fe-K Fe-L blend Full X-ray band 0.5 10 Magnified spectra in the 6-7 keV band (Fe K emission) C-like Ne-like Ar-like 6.0 Be-like He-like H-like 7.0 Observed spectrum (Convolved by Suzaku response) 6.42 keV 6.44 keV 6.60 keV 6.64 keV 6.67 keV SN1006 (Type Ia SNR) W49B (CC SNR) Artificial features (a sort of bgd) S i S Ar Ca Fe Ni Mg HY+2008, Uchida+, in prep. Ne Ozawa+2009 SN1006: Searching for Fe emission - Prototypical Type Ia SNR, but emission from Fe has never been detected. BeppoSAX MECS spectrum Fe? Chandra image - Only one possible detection reported by BeppoSAX - XMM-Newton failed to detect Vink+00 Detected! but weak despite of its Type Ia origin Fe-K centroid ~ 6420eV (< Ne-like) … Corresponding net is ~ 1 x 109 cm-3 s Fe16+ Suzaku spectrum (HY+08) Fe24+ Fe25+ Fe26+ SN1006: Multiple net Components in Si broad feature Mg Si S C~O-like He-like Reverse shock heats from outer region Outer ejecta = highly ionized Inner ejecta = lowly ionized Si6+ Si8+ Si12+ Si13+ Approx with 2-net components for Si and S ejecta net1 ～ 1×1010 cm-3 s net2 ～ 1×109 cm-3 s Si ion fraction @1keV cf. Fe: net ～ 1×109 cm-3 s SN1006: Fullband Spectrum & Abundances Derived abundance ratios compared to the W7 model of Nomoto+84 Fe Outer ejecta HY+08 Inner ejecta ISM (w/ solar abundance) Outer ejecta (net ~ 1010 cm-3 s) Inner ejecta (net ~ 109) Non-thermal (synchrotron) Suggests stratified composition with Fe toward the SNR center, which results in the lowly-ionized (thus weak) Fe emission Ejecta Stratification in Type Ia SN/SNRs XMM image of Tycho SN 2003du (Tanaka+10) Color: Si-K Contour: Fe-K Radial profile Si Fe Radius (arcmin) Enclosed mass Decourchelle+01 IME Mazzali+07 56Ni See also Badenes+06 SN1006 (Type Ia SNR) W49B (CC SNR) Artificial features (a sort of bgd) S i S Ar Ca Fe Ni Mg HY+2008, Uchida+, in prep. Ne Ozawa+2009 W49B: Peculiar Ionization State Cr Ejecta is highly ionized to be He-like He-like Fe Ka Mn Radiative recombination continuum Fe25+ + e- → Fe24+ + hn … indicates presence of a large fraction of H-like Fe Ni + Fe Kb Fe-K RRC H-like Fe Measured kTe ~ 1.5 keV Ozawa+09 Fe ion population in a CIE plasma Fe16+ Fe26+ Fe24+ Fe25+ - 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 Temperature (keV) “Recombining NEI” in SNRs is not unique => Need to define “recombination age” W49B: Possible Progenitor Explosion in dense CSM Shimizu+12 - Numerical (Shimizu+12) - Analytical, more progenitororiented (Moriya 12) blast wave Blast wave breakout into ISM BW speed becomes faster and expand adiabatically, resulting in rapid cooling with “frozen” ionization state reverse shock 2nd reverse shock Type II-P or IIn could be a progenitor of a recombining SNR (Moriya 12) RSG case (vw ~ 10 km/s) WR case (vw ~ 1000 km/s) 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? Fe-K diagnostics - Type Ia and CC SNRs are clearly separated (CC more ionized) Type Ia - Luminosity of both groups are distributed in the similar range. CC Can be explained by ionization (and temperture, density effects) --- Measuring ionization state is essential for measuring element abundances!! (HY+, in prep.) net = 5x109 1x1010 5x1010 1x1011 3x1011 Fe-K diagnostics Ionization ages expected if the SNRs have evolved in uniform ISM with typical density Type Ia CC Hachisu+01 (HY+, in prep.) 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 Badenes+07 Evidence of cavity/CSM in Ia SNRs Kepler (Reynolds+07) RCW86 (Williams+11) Unique Ia SNR where the presence of a surrounding cavity is suggested N103B (Lewis+03) 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??