1. Pop III Black-hole-forming supernovae and Abundance pattern of Extremely Metal Poor Stars Hideyuki Umeda (梅田秀之) Dept. of Astronomy Univ.of Tokyo work with Prof.K. Nomoto

2. 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 HE
Other C-rich EMP stars
Black-hole from first supernovae

3. 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 ~ – [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

4. One of the most interesting characters in the abundance of EMP stars: Trends in the Fe-peak elements
We have discussed
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

5. 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）

6. Pop III Star Evolution & Nucleosynthesis Umeda & 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.　

7. 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.

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

9. Ejecta
Mass cut
Blackhole
or Neutron star

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

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

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

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

14. Three modifications from the simplest model

15. Mixing-fallback or Jet like Explosion
Mixing-fallback or Jet like Explosion? The final yields may be similar: Ejection of Fe-peak elements is possible but Fe 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)

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

17. One possibility to enhance Sc and Ti Low 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 but Cr 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.

18. Consistent view? * 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.
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)

19. 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)

20. How about PISNe ?: Explosion of 130-300 M stars
(Umeda & Nomoto 2002, ApJ, 565, 385)
Large [Zn/Fe] and [Co/Fe] cannot be realized in
the PISN nucleosynthesis

21. 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)

22. Cayrel et al. (2003)

23. 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 ~ M stars. (Leave >~3M
first generation Blackholes)
PISN ( M) does not fit:
[Zn/Fe], [Co/Fe] too small.

24. 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
Advantages in the Hypernova model for Zn/Fe

25. C-rich EMP stars The most Fe-poor stars HE0107-5240 Christrieb et al
Other C-rich EMP stars, e.g.,
CS Norris et al. 2001; Depagne et al. 2002
CS Aoki et al.
CS Aoki et al.

26. 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.

27. 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)

28. Christrieb et al. 2003 (Long paper)

29. He O Abundance distribution after explosion Mg
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

30. 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 PISN (Mg-Ni) + binary (Limongi et al 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)
HE 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

31. Other C-rich EMP stars (Umeda & Nomoto 2003)
*CS (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

32. C/Fe, O/Fe better; N/Fe still underproduced
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

33. Example of a low density model: CS22949-037

34. No Co, Zn data (hard to determine energy) Shown is a low energy model
CS (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

35. CS31062-012 (Aoki et al) s-process elements enhanced
However, the same model for CS (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.

36. Nomoto et al.
Typical EMP
C-rich EMP stars

37. 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 M 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.