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Constraining progenitors of SNRs using X-ray morphology and spectra

Constraining progenitors of SNRs using X-ray morphology and spectra. Hiroya Yamaguchi Harvard-Smithsonian Center for Astrophysics. Classification of SN Progenitors. Optical obs of SNe. Classification is relatively straightforward - Spectrum (historically well established)

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Constraining progenitors of SNRs using X-ray morphology and spectra

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  1. Constraining progenitors of SNRs using X-ray morphology and spectra Hiroya Yamaguchi Harvard-Smithsonian Center for Astrophysics

  2. Classification of SN Progenitors Optical obs of SNe Classification is relatively straightforward - Spectrum (historically well established) - Luminosity (56Ni yield) X-ray obs of SNRs Ia (SD) 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 (DD) CC (1987A) SNeIa: nuclear reaction energy ~ 1051 erg SNe CC: gravitational energy ~ 1053 erg 99% neutrino + 1% kinetic (~ 1051 erg) => transformed to thermal energy (X-ray luminosity)

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

  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 (kTe ~ hn ~ 0.1–10 keV, comparable to K-shell potential), so physics is simple YOU LOSE m9(^Д^) Suzaku spectrum of Tycho (Hayato+10) Simple Quiz S Si Fe Ar Ca Artificial features (a sort of bgd) Ni CC (W49B) Ia (SN1006) Mg Ne

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

  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 Fe24+ Fe26+ Fe16+ Fe25+ Fe ion population in NEIplasma for kTe = 5 keV highly ionized lowly ionized Fe16+ CIE Fe24+ Fe25+ Ion fraction Electron temperature kTe (keV) net: “ionization age” ne: electron density t: elapsed time since gas was heated Fe26+ net (cm-3s)

  7. Non Equilibrium in Ionization (NEI) net: “ionization age” ne: electron density t: elapsed time since gas was heated highly ionized lowly ionized Timescale to reach CIE for ISM t ~ 3 x 104 (ne/1 cm-3)-1 yr As for ejecta… Fe ion population in NEIplasma for kTe = 5 keV Time when the masses of swept-up ISM and ejecta becomes comparable Fe16+ Fe24+ Fe25+ Ion fraction 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. Fe26+ net (cm-3s)

  8. 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] net = 5x1091x1010 5x1010 1x10113x1011 Fe-K Fe-L blend Full X-ray band 0.5 10 Magnified spectra in the 6-7 keV band (Fe K emission) He-like Be-like C-like Ne-like Ar-like H-like 6.0 7.0 Observed spectrum (Convolved by Suzaku response) 6.60 keV 6.67 keV 6.44 keV 6.42 keV 6.64 keV

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

  10. SN1006: Searching for Fe emission • Prototypical Type Ia SNR, but emission from Fe has never been detected. - Only one possible detection reported by BeppoSAX - XMM-Newton failed to detect BeppoSAX MECS spectrum Fe? Chandra image 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+ Fe24+ Suzaku spectrum (HY+08) Fe25+ Fe26+

  11. 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 Si8+ Si6+ Approx with 2-net components for Si and S ejecta net1～ 1×1010 cm-3 s net2～ 1×109 cm-3 s cf. Fe: net ～ 1×109 cm-3 s Si12+ Si13+ Si ion fraction @1keV

  12. SN1006: Fullband Spectrum & Abundances Derived abundance ratios compared to the W7 model of Nomoto+84 Outer ejecta Fe 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

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

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

  15. W49B: Peculiar Ionization State Ejecta is highly ionized to be He-like Radiativerecombination continuum Fe25+ + e- → Fe24+ + hn … indicates presence of a large fraction of H-like Fe He-like Fe Ka Cr Mn Ni + Fe Kb Fe-K RRC H-like Fe Measured kTe ~ 1.5 keV Ozawa+09 Fe ion population in a CIE plasma Fe26+ Fe16+ 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”

  16. W49B: Possible Progenitor Explosion in dense CSM Shimizu+12 - Numerical (Shimizu+12) - Analytical, more progenitor- oriented (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 orIIn could be a progenitor of a recombining SNR (Moriya 12) RSG case (vw ~ 10 km/s) WR case (vw ~ 1000 km/s)

  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 and CCSNRs are clearly separated (CC more ionized) - Luminosity of both groups are distributed in the similar range. Type Ia CC Can be explained by ionization (and temperture, density effects) --- Measuring ionization state is essential for measuring element abundances!! (HY+, in prep.) net = 5x1091x1010 5x1010 1x10113x1011

  19. 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 IaSNRs Badenes+07

  20. Evidence of cavity/CSM in IaSNRs Kepler (Reynolds+07) RCW86 (Williams+11) Unique Ia SNR where the presence of a surrounding cavity is suggested 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 IaSNRs 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 IaSNRs, except for RCW86, constraining progenitor • system??

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