Ia Hiroya Yamaguchi HarvardSmithsonian Center for Astrophysics MITRIKEN

Ia型超新星の元素合成と その周辺環境 Hiroya Yamaguchi Harvard-Smithsonian Center for Astrophysics (+ MIT/RIKEN)

Problems in the SD scenario 1. No “survivor” 爆発後に伴星が残る(e. g. , Pan+12)はずだが、 その観測事例がない(e. g. , Schaefer+12) but see Di Stefano+12: a survivor should be too dim to detect LMC SNR 0509 -67. 5 (Schaefer+12) SN 2011 fe (Li+11; Shappee+12), SN 1006 (González Hernández+12) Tycho: “Tycho G” was suggested to be the companion by (Ruiz-Lapuente+04) but questioned by Ihara+07; Gonzalez Hernandez+09; etc.

Problems in the SD scenario 2. No presence of CSM “Accretion wind” Kato & Hachisu 94; Hachisu+01 近傍にCSMの存在が期待される Nomoto+82 e. g. , SN 2011 fe (Margutti+12) Hughes+07, Horesh+11, Chomiuk+11, Hancock+11 but see Taddia+12; Patnaude+12 但し、上記シナリオでも最後まで 降着風が続く必要は必ずしもない？

Problems in the SD scenario 3. No signal of hydrogen stripped from a companion SN 2005 am, SN 2005 cf (Leonard+07) SN 2011 fe (Shappee+12) 4. Lack of Super Soft Sources Di Stefano 10, Gilfanov&Bogdan 10, but see Hachisu+10; Wheeler+12 5. Delay Time Distribution (DTD) e. g. , Totani+08; Maoz+10 Recent works seem to be more supportive of the DD scenario, but we should still have an open mind. Can we constrain progenitor’s nature from X-ray observations?

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? Ia (SD) Ia (DD) CC (1987 A) 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 Ia SNRs are more symmetric than CC SNRs (Lopez+09; 11) Ellipticity CC Type Ia Chandra images of Galactic/Magellanic SNRs Doesn’t work for SMC SNRs… Mirror asymmetricity Reflects nature of explosion and/or environment G 344. 7 -0. 1 found to be Type Ia (HY+12) SNR E 0102 -72 (CC) candidate) 0104 -72. 3 (Ia

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 (k. Te ~ hn ~ 0. 1– 10 ke. V, comparable to K-shell potential), so physics is simple Suzaku spectrum of Tycho (Hayato+10) Simple Quiz Artificial features (a sort of bgd) S i S Ar Ca CC (W 49 B) Ia (SN 1006) Mg Ne Fe Ni

X-Ray Spectra of SNRs Absorption for different column density (NH [cm-2]) SN 1006 Large foreground extinction makes O/Ne/Mg emission in W 49 B 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 W 49 B Artificial features (a sort of bgd) S i S Ar Ca W 49 B (CC) Mg Ne 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 k. Te = 5 ke. V Fe 16 + Fe 24+ Fe 26+ Fe 25 + Fe 16+ highly ionized Ion fraction lowly ionized Fe 24+ Fe 25+ Fe 26+ net (cm-3 s) CIE Electron temperature k. Te (ke. V) 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 k. Te = 5 ke. V Fe 16+ highly ionized Fe 24+ Ion fraction lowly ionized net : “ionization age” ne : electron density t : elapsed time since gas was heated Fe 25+ Timescale to reach CIE for ISM t ~ 3 x 104 (ne/1 cm-3)-1 yr Fe 26+ 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 [k. Te = 5 ke. V] 1 x 1010 5 x 1010 1 x 1011 net = 5 x 109 3 x 1011 Fe-K Fe-L blend Full X-ray band 0. 5 10 Magnified spectra in the 6 -7 ke. V band (Fe K emission) C-like Ne-like Ar-like 6. 0 Be-like H-like 7. 0 Observed spectrum (Convolved by Suzaku response) 6. 42 ke. V 6. 44 ke. V 6. 60 ke. V 6. 64 ke. V 6. 67 ke. V

SN 1006: Searching for Fe emission - Prototypical Type Ia SNR, but emission from Fe has never been detected. Beppo. SAX MECS spectrum Fe? Chandra image - Only one possible detection reported by Beppo. SAX - XMM-Newton failed to detect Vink+00 Detected! but weak despite of its Type Ia origin Fe-K centroid ~ 6420 e. V (< Ne-like) … Corresponding net is ~ 1 x 109 cm-3 s Fe 16+ Suzaku spectrum (HY+08) Fe 24+ Fe 25+ Fe 26+

SN 1006: 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 Si 6+ Si 8+ Si 12+ Si 13+ Approx with 2 -net components for Si and S ejecta net 1 ～ 1× 1010 cm-3 s net 2 ～ 1× 109 cm-3 s Si ion fraction @1 ke. V cf. Fe: net ～ 1× 109 cm-3 s

SN 1006: Fullband Spectrum & Abundances Derived abundance ratios compared to the W 7 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 2003 du (Tanaka+10) Color: Si-K Contour: Fe-K Radial profile Si Fe Radius (arcmin) Enclosed mass Decourchelle+01 IME Mazzali+07 56 Ni See also Badenes+06

0509 -67. 5: X-Ray Observations The youngest SNR in the LMC (~400 yr: Rest+08) 12. 8 arcsec Chandra revealed clear shell structure of the ejecta & the western “Fe knot” (Warren+04) – due to off-center ignition (e. g. , Maeda+10)? 15. 2 arcsec 4 pc Suzaku observation (HY 08, Dthesis) - Fe + 一部のSi : net = 3. 5× 109 cm-3 s - その他の元素 : net = 1. 4× 1010 cm-3 s ⇒ Feの電離度はやはり低い！ solid : W 7 (Nomoto et al. 1984) dashed : WDD 3 (Iwamoto et al. 1999) Blue: Old Ejecta Light-blue: Young Ejecta Orange: power-law Green: ISM

0509 -67. 5: X-Ray Observations 12. 8 arcsec 15. 2 arcsec 4 pc 1 D numerical modeling (Badenes+08) 0509 -67. 5 was a bright SN Ia with a Fe yield of ~ 1 M◉

Fe-K diagnostics Type Ia SNRs (e. g. , SN 1006 & 0509 -67. 5): Fe lowly-ionized due to a low ambient density Ejecta stratification with Fe more concentrated toward the center CC SNRs: Ejecta is more mixed, e. g. , Cas A (Hwang+06), G 292+1. 8 (Park+07) Associated with dense CSM/MCs … sometime causes “over-ionization” in plasma e. g. , W 49 B (Ozawa+09), IC 443 (HY+09), HY+12 for review see also an analytical work by Moriya+12 to constrain their progenitors Cr Mn He-like Fe Ka Ni + Fe Kb Fe-K RRC H-like Fe Ozawa+09 Hwang+06 Red: Si Blue: Fe Green: continuum Other SNRs?

Fe-K diagnostics - Type Ia and CC SNRs are clearly separated (Ia always less 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 = 5 x 109 1 x 1010 5 x 1010 1 x 1011

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) RCW 86 (Williams+11) Unique Ia SNR where the presence of a surrounding cavity is suggested. N 103 B (Lewis+03)

DD scenarioの元素合成モデル SNSNR 12 超新星と超新星残骸の融合研究会 (10/15 -17 @国立天文台) 辻本拓司さんの報告より SN Ia-like abundances of Fe-peak elements NGC 1718 age ~2 Gyr, [Fe/H]=-0. 7 [Mg/Fe]=-0. 9± 0. 3 (Colucci et al. 2012) WDD 1, WDD 2 model from Iwamoto et al. 1999 TT & Bekki 2012 Such an extremely low ratio (≤-0. 6) is outside any observed Al-Mg anticorrelations (>-0. 3) as well as by the prediction from nucleosynthesis calculations on any SNe II (>-0. 2). Likely, its birth place is the ejecta of SNe Ia.

DD scenarioの元素合成モデル SNSNR 12 超新星と超新星残骸の融合研究会 (10/15 -17 @国立天文台) 辻本拓司さんの報告より in the scheme of SNe Ia resulting from a 0. 8+0. 6 M⊙ white dwarf merger the explosion of a WD with the mass 0. 8 M⊙ accreting 0. 6 M⊙ matter at the mass accretion rate of 0. 07 M⊙ s-1 a dim SN Ia after spending more than 1 Gyr from the birth subluminous SNe Ia already predicted as a result of the merger of two WDs (Pakmor et al. 2010, 2011) TT & Shigeyama 2012 Mn Ni comment type Fe Cr Slow SN Ia 0. 41 6. 9 x 10 -3 1. 1 x 10 -3 7. 8 x 10 -3 nucleosynthesis caclulation (this study) 2. 5 x 10 -3 1. 5 x 10 -3 8. 9 x 10 -3 prediction from chemical evolution prompt SN Ia 0. 71 1. 7 x 10 -2 7. 1 x 10 -3 5. 9 x 10 -2 WDD 2 model in Iwamoto et al. 1999

Low-Abundance Element in Tycho Suzaku (Tamagawa+09) Good energy resolution and high sensitivity The first discovery of Cr and Mn lines from Type Ia SNRs Detection! Tamagawa+09 Cr and Mn very low abundant elements Cr/Fe ~ Mn/Fe ~ 0. 01, in solar Cr/Fe = 0. 022 Mn/Fe = 0. 014 in Tycho’s SNR Tycho Solar abun. Fe Si O Mn Cr Fe Mn Cr

Neutron-Rich Element in Ia SNRs Cr: Cr 52 Fe (Z=26) → 52 Mn (Z=25) → 52 Cr (Z=24) Mn: Mn 55 Co (Z=27) → 55 Fe (Z=26) → 55 Mn (Z=25) ↑ Parent nuclides synthesized in the explosion Heavy elements which have been detected from Type Ia SNR so far Si S Ar Ca Cr Mn Fe Fe Co Ni O Ne Mg Proton 8 10 12 14 16 18 20 26 27 28 Neutron 8 10 12 14 16 18 20 26 28 28 Unequal numbers of protons and neutrons (neutron excess) ! To synthesize such elements, progenitor should be rich with neutron But, Type Ia progenitor consists mainly of 12 C (Z=6) and 16 O (Z=8) How did the neutron excess in the progenitor originate? ⇒ Found in processes during the progenitor’s evolution!!

Neutron Excess in Ia Progenitors - During the progenitor’s main seq. , C, N, and O which act as catalysts for CNO cycle pile up into 14 N - 14 N is converted to 22 Ne in He-burning phase through the reactions 14 N(a, g)18 F(b+, n)18 O(a, g)22 Ne H-burning: 4 He is eventually synthesized from 4 protons CNO cycle increase! Elements in Type Ia progenitor (WD) C O Ne Proton 6 8 10 Neutron 6 8 12 Increases the neutron excess Slowest reaction - CNO cycle takes place efficiently when C, N, and O are abundant ⇒ Neutron excess (abundance of 22 Ne) becomes larger when the progenitor’s metallicity (initial CNO abundances) is high pp-chain

Mn/Cr Ratio as an Initial Metallicity Tracer During Type Ia SN explosion: 52 Cr and 55 Mn are synthesized together (as 52 Fe and 55 Co) in incomplete Si burning layer (e. g. , Iwamoto+99) - The yield of 55 Mn (neutron-rich nuclide) would be sensitive to the neutron excess due to 22 Ne - 52 Cr is NOT sensitive to neutron excess Mn/Cr ratio is an good tracer of the initial progenitor’s metallicity! 12 C 16 O 22 Ne Mg Si S Ar Ca Cr Mn Fe, Ni Mn and Ni are sensitive to neutron excess!! Badenes+08 noted a correlation b/w Mn/Cr mass ratio and metallicity Z MMn/MCr = 5. 3 x Z 0. 65 For the progenitor of Tycho’s SN, (MMn/MCr = 0. 74± 0. 47) yields a supersolar metallicity - Z = 0. 048 (0. 012－0. 099) - Large uncertainty, but definitely not subsolar (Z<0. 01)

(Cr+Mn)/Fe Sum New Old Tycho Ni/Fe Sum 500 ks Mn/Cr New 400 ks Old 100 ks Tamagawa+08 Tycho & Kepler Deep Obseravations Kepler Tycho Kepler - Mn/Cr ratio は Kepler > Tycho: high metallicity in Kepler? - Keplerは Ni/Fe比が極めて大きい: DD scenario unlikely? Ni/Fe < 0. 3 (Kerkwijk+10) - (Cr+Mn)/Fe は Kepler < Tycho: assuming SD, Kepler is brighter?

Summary - SNe Ia progenitor issue is one of the most intriguing subjects of the recent astrophysics/astronomy. - X-ray observation of SNRs help study stellar/explosive nucleosynthesis (optically-thin, K-shell emission), plus progenitors’ nature (mass loss, metallicity) and environment - Understanding of non-equilibrium in ionization is, however, essential for accurate measurement of element abundances. - Fe emission in Type Ia SNRs is commonly weak, despite a large yield of this element. This is due to low-density ambient and stratified chemical composition. - No evidence of a large cavity expected from an “accretion wind” around Type Ia SNRs, except for RCW 86, constraining progenitor system? ? - Low abundance element in Tycho and Kepler can constrain their progenitors’ nature (not only metallicity but SD/DD)?

W 49 B: Peculiar Ionization State Cr Ejecta is highly ionized to be He-like Fe Ka Mn Ni + Fe Kb Fe-K RRC H-like Fe Radiative recombination continuum Fe 25+ + e- → Fe 24+ + hn … indicates presence of a large fraction of H-like Fe Measured k. Te ~ 1. 5 ke. V Ozawa+09 Fe ion population in a CIE plasma Fe 16+ Fe 24+ Fe 25+ - RRC can be enhanced only when the plasma is recombining (e. g. , photo-ionized plasma) Similar recombining SNRs - IC 443 (HY+09) - SNR 0506 -68 (Broersen+11) - other 3 & a few candidates Temperature (ke. V) “Recombining NEI” in SNRs is not unique => Need to define “recombination age”

W 49 B: 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 2 nd 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)