Contents • Can Core-collapse Supernova yields explain the abundance pattern of • typical extremely metal poor (EMP) stars ? • Typical abundance of [Fe/H] ~ -3.7 stars (Norris, Ryan, Beers 2001, Depagne 2003) • C-rich EMP stars? • The most iron poor star HE0107-5240 • Other C-rich EMP stars • Black-hole from first supernovae

Exploring Pop III SNe by Pop II abundance Extremely metal poor (EMP) star Formation Single explosion may produce metal- poor stars with [Fe/H]= –4 ~ –2.5[X/Fe]=log(X/Fe) ーlog(X/Fe) （Ryan et al. 1996, Shigeyama & Tsujimoto 1998, Nakamura, Umeda, Nomoto, Thielemann, Burrows 1999) Low mass stars survive until today. The abundance of these stars are determined by the nucleosynthesis of the PopIII SNe. Ｓｈｏｃｋ　Ｗａｖｅ ☆ ☆ ☆ PopIII　　　　　ＳＮ ☆ ☆ ☆ EMP Star Formation

One of the most interesting characters in the abundance of EMP stars: Trends in the Fe-peak elements We havediscussed possible explanations for this trend: (Nakamura, Umeda et al. 1999, ApJ (Umeda & Nomoto 2002, ApJ (Umeda & Nomoto 2003, astro-ph McWilliam et al. 1995, and others

H-R diagram: Metallicity dependence Opacity is smaller for lower metallicity gas. It leads to larger luminosity. Because of the small opacity, radiative force is weak for Pop III and the atmosphere of Pop III does not expand lot. Thus, the radius is small and color is blue (small Teff). Pop III L Pop I Teff Umeda et al.（２０００）

Pop III Star Evolution & NucleosynthesisUmeda & Nomoto (ApJ 2002, Astro-ph/0103241; 9912248) The main energy source for Pop I, II main sequence is the CNO cycle hydrogen burning. In Pop III, there is no CNO elements and the stars contracts until temperature rise sufficiently high for the reaction ３α→12C to operate. Core evolution of Pop III after He burnings are almost same as Pop I, II.

Fe core mass：Metallicity dependence Typically, for lower metallicity, the stellar luminosity is larger and core mass is larger. However, Ｚ＝０ (Pop III) is peculiar and compact. In our model, the Fe core masses of Ｚ＝０andＺ＝Ｚ(=0.02) are quite similar.

Pre-supernova nucleosynthesis (Onion like structure) O He Mass Fraction Fe C-O Si H Mｒ

Ejecta Mass cut Blackhole or Neutron star

Remnant Ejecta Mass Cut Abundance distribution of SNe II after explosive nucleosynthesis Incomplete Si-burning ←Mass Cut Mn Zn, Co↑　Ｃｒ，Ｍｎ ↓

Fe-peak trends can be explained with the hypernova model: Umeda & Nomoto (2003), ApJ submitted, astro-ph/03

Can we explain other abundance Data? Data: Mg – Zn for typical Extremely metal poor (EMP) stars with [Fe/H] ~ < -3.7

*Three EMP stars from Norris, Ryan, Beers (2001):CD-38245, CS22172-002, CS22885-096 -- [Fe/H] = -3.6 ~ - 4Plus [Zn/Fe] (e.g., Primas et al. 2000; Cayrel et al. 2003)Typical abundance pattern of C-un-rich EMP starswith this [Fe/H] [Zn/Fe] Model Obs.

Three modifications from the simplest model

Mixing-fallback or Jet like Explosion?The final yields may be similar:Ejection of Fe-peak elements is possible butFe not over-produced Globally spherical explosion 2D Simulation: Mixing by Rayleigh-Taylor instability Jet-like explosion Ejection of Fe-peak elements are“beamed”. Oxygen JET Fe Oxygen Kifonidis et al. (1999) Maeda et al. (2002)

Umeda & Nomoto 2003 (astro-ph/0308029) Co/Fe, Mn/Fe strongly depend on Ye (electron mole fraction) Ye, during supernova explosion, may be significantly modified due to neutrino processes (e.g., Liebendoerfer et al. 2003) For Ye ~ 0.5003, [Co/Fe] can be as large as observed in hypernova models. In low energy models, [Co/Fe] is smaller than observation for any Ye.

One possibility to enhance Sc and TiLow density model:If the density during explosive burning is lower, α-rich freeze out proceeds more and Sc and Ti abundances are enhanced. All elements butCr can be fitted with slight modification of Ye. Mn, Co Or due to the neutrino process (Yoshida, Umeda & Nomoto, in preparation) Progenitor’s density is artificially reduced to 1/3.

* High energy explosion induced by Jets perpendicular to the accretion disk around a central black hole. * Fe-peak elements can be ejected without over-producing Fe/Mg ratio if the Jets are sufficiently narrow. * Low density explosion may be realized if weak Jets or weak explosion occurs before the MAIN explosion. Consistent view? C.f. Low density progenitor in the very large C/O ratio models (Chieffi & Limongi 2003) -- Na, Ne not over-produced? (Weaver & Woosley 1993; Nomoto et al 1997)

e +- e- Pair Instability Supernovae (PISNe) : ~ 130-300 M stars The stars with this mass range explode and disrupts completely before Fe core formation due to the rapid Oxygen - burning. In the nucleosynthesis of PISNe, the mass fraction of the complete Si- burning products is relatively small, therefore large [Zn/Fe] cannot be realized ⇒ PISNe can’t be dominant in the First Generation (Pop III) stars. (Umeda & Nomoto 2001)

How about PISNe ?: Explosion of130-300 M stars (Umeda & Nomoto 2002, ApJ, 565, 385) Large[Zn/Fe] and [Co/Fe] cannot be realized in the PISN nucleosynthesis

170M, Z=0 After explosion Before explosion Complete Si-burning region is relatively small ⇒　[Zn, Co/Fe] small This result is quite in general, and very hard to avoid. (e.g. Heger et al. 2001)

Cayrel et al. (2003)

Summary We could explain abundance from Mg to Zn in typical EMP stars with high-energy, mixing-fallback, modified Ye, and Low density explosion of ~ 25-130M stars. (Leave >~3M first generation Blackholes) PISN (140-300M) does not fit: [Zn/Fe], [Co/Fe] too small.

Advantages in the Hypernova model for Zn/Fe • There exists another model (Hoffman et al. 1996) though no detailed model and yields have been given • Zn production from very deep layer with very low Ye • The cite may be similar to r-process, but then may be difficult to explain observational homogeneity of [Zn/Fe]? • Observational homogeneity (and no-correlation to r-process elements) may be more easily explained • Hypernova model: Zn production cite is same as Co(Zn, Co - correlation) • Model is simpler: no need for hot bubble, neutrino wind, etc • Ye is not low: no un-wanted elements are simultaneously produced

C-rich EMP stars • The most Fe-poor stars HE0107-5240 Christrieb et al • Other C-rich EMP stars, e.g., • CS22949-037 Norris et al. 2001; Depagne et al. 2002 • CS29498-043 Aoki et al. • CS31062-012 Aoki et al.

The most Fe-poor star:HE0107-5240 • Discovery：Oct 31,2002 (Christrieb et al, Nature) • Red-giant, about 0.8 M • [Fe/H] ~ -5.3 • Quite unusual abundance ratios:e.g., [C/Fe] ~ +4 • Is this star Pop III (first generation) or Second generation? --- Pop III Low mass Star formation is predicted to be inefficient in the typical (simplest?) star formation theory.

Our model Umeda & Nomoto, Nature 422, 871 (2003) • We assume this star was formed in the gas of Pop III SNe. ⇒not very metal poor [C/Fe]~ -1.3, star formation possible • Large C/Fe ratio ←Large amount of Fall-back • Ejected 56Ni mass only ~ 10-5M • Such “faint” SNe has been observed: e.g., SN1997D, SN1999br • A 6M black hole is left Mg/Fe not large ←Mg also needs to be fallen-back (need mixing-fallback or aspherical explosion to eject Fe) :N, Na maybe produced in Low mass EMP stars or in the SN progenitor (Iwamoto, Umeda & Nomoto, in preparation)

Christrieb et al. 2003 (Long paper)

Abundance distribution after explosion Mixing-Fallback region (Almost entire He core) He Mixing-fallback region required for typical EMP stars --- only the Si-burning region O Mg Mr/Ｍ

Other models • HE0107-5240 is a 2nd (or later) generation star • Our model (One SN model) • Two source models: Assuming different origin for N-Na and Mg-Ni. (Schneider et al. 2003 --- PISN (Mg-Ni) + binary (Limongi et al. 2003 --- two Core collapse SNe • One source star (N-Na NOT enhanced and very small [Fe/H])should be discovered (if the first SN induce low mass star formation) • HE0107-5240 is a Pop III (metal free) star (Shigeyama, Tsujimoto, Yoshii 2003) • Assumes all metals have been accreted after its birth • Mg-Ni from interstellar matter & N-Na from binary companion. (So far no evidence for the binary companion) • No-binary star (N-Na NOT enhanced and very small [Fe/H]) should exist

Other C-rich EMP stars(Umeda & Nomoto 2003) *CS22949-037 (Blue:Norris et al. 2001; Red:Depagne et al. 2002) [Fe/H]~ -4.0 C, N, Mg, Si -rich Co, Zn - rich --enriched by High energy supernova N,O under-produced

More massive model 25 ⇒ 30M C/Fe, O/Fe better; N/Fe still underproduced Origin of N: (1)Extra mixing of H into He-rich layer ? (2) CN cycle in EMP stars (C ⇒N transform) Origin of N, Na:(3) H-Mixing in EMP stars? (Iwamoto, Umeda, Nomoto, in preparation) Underproduced ⇒Low density model

Example of a low density model: CS22949-037

CS29498-043 (Aoki et al) Similar abundance with the previous star, but more C/Fe No Co, Zn data (hard to determine energy) Shown is a low energy model Blackhole mass ~ 9M

CS31062-012 (Aoki et al) s-process elements enhanced However, the same model for CS29498-043 (no s-process) fits well. What is the origin of the s-process elements? (binary or self?) Blackhole mass ~ 18M The Blackhole mass is larger for more massive and energetic models.

Nomoto et al. Typical EMP C-rich EMP stars

Summary • Abundance of C-un-rich EMP stars are best reproduced by • High energy core collapse SNe (hypernova), • with mixing-fallback or jet-like explosion • Low density, • (and some modifications of Ye or the effect of neutrino process). • (pair-instabillity SNe with 140-300M are not good --- almost no Co, Zn) • These are likely massive (> ~25M), black-hole (> ~ 3M) forming “hypernova” with accretion disk and Jets. • C-rich Fe-poor stars can be modeled by the 2nd-generation star, formed in the ejecta of“faint”Pop III supernovae, which formed black-holes with M >~ 3-10M.

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