Motivation:

A Brief History of the Universe

`

Cosmic Dark Age

(after recombination)

time

What WeFind Today

What theBig Bang

made…

(The primordial abundance pattern)Brian Fields (2002, priv. com.)

(The solar abundance pattern)Lodders (2003)

(Pop III star yields)Heger & Woosley (2010)

Frebel et al. (2005)

© Alexander Heger Hubble Deep Field

http://www.astro.psu.edu/users/tabel/Homepage/transparencies/c.eps

Setting the Stage:

Pre-SupernovaEvolution and

Nucleosynthesis(Recap)

Once formed, the evolution of a star is governed by gravity: continuing contraction

to higher central densities and temperatures

Evolution of central density and temperature of 15 MꙨ

and 25 MꙨ stars

Nuclear Burning Stages

net nuclear energy generation (burning + neutrino losses)

net nuclear energy loss (burning + neutrino losses)

convection semiconvectiontotal mass of star(reduces by mass loss)ra

dia

tiv

e e

nv

elo

pe

(blu

e g

ian

t)

convective envelope (red super giant)

H b

urn

ing

He

bu

rnin

g

C b

urn

ing

(rad

iati

ve)

C s

hel

lb

urn

ing

Ne O

burning

C shell burning

OO O O shell burning

Si

Si

Fuel MainProduct

SecondaryProduct

T(109 K)

Time(s)

Main Reaction

Innermostejecta

r-processνp-process

- >10? 1 (n,γ), β−

Si, O 56Ni iron group >4 0.1 (α,γ)

O Si, S Cl, Ar,K, Ca 3 - 4 1 16O + 16O

O, Ne O, Mg, Ne Na, Al, P 2 - 3 5 (γ,α)

p-process11B, 19F,

138La,180Ta2 - 3 5 (γ ,n)

ν-process 5 (ν, ν’), (ν, e-)

Explosive Nucleosynthesisin supernovae from massive stars

Eje

cted

“m

etal

s”

Naoki Yoshida:

● stars● massive stars● very massive stars● very very massive stars● very very very massive stars● very very very very massive stars● very very very very very massive stars● very very very very very very massive stars● very very very very very very very massive stars● very very very very very very very very massive stars

“Beers Scale”

adopted from Beers and Christlieb

+ stars that do not enter hydrostatic burning

Open Questions

Eta Car – a really big star in our galaxy today

Nathan Smith, 2007, First Stars III

Mass Loss due to Giant Eruptions?

How do the most massive stars evolve?

● Reduced mass loss on the main sequence followed by LBV & giant eruptions?

● What are these eruptions? (physics, number, recurrence)

● When do they occur? (internal evolution stage?)

● How do we model these eruptions?● Pulsational Pair-Instability Supernovae (PPSN)?

Initial Rotation of Massive Stars

Pop I/II

Pop III

star disk

Mass Loss due to Critical Rotation

ANGULAR MOMENTUM

mass

● How important is mass loss due to critical (or fast) rotation? ● How do we quantify mass loss and angular momentum loss?● How does it effect our stellar models?

(Langer, Meynet, Maeder, Hirschi,...)

(Yoon et al. 2012)

Nucleosynthesis in Low-Mass

Core CollapseSupernovae

Low-Mass Pre-SN Structure

z9.6

u8.1

Mueller, Janka, Heger (2012, in prep.)

Explosion of Low-Mass SN

2D simulation with neutrino transport and core cooling

Explosion driven by convection not SASI

Explosion starts fast as accretion drops very rapidly

n-Rich Ejecta Low-Mass SN

-> May produce elements below 1st r-process peak

Mueller, Janka, Heger (2012, in prep.)

z9.6A

R-Process in Low-Mass SN

r-precess initiated for explosion with a few times 0.1 B

z9.6a

R-Process in Low-Mass SNr-precess initiated for explosion with a few times 0.1 B

z9.6b



z9.6B



Impact of rotation on s-process element production in very-metal-poor massive stars.

C Chiappini et al. Nature 472, 454-457 (2011)

doi:10.1038/nature10000

Supernova Progenitor Masses

(Smartt 2009)

Presupernova stars for Type IIp and II-L

Solid Line: Salpeter IMF with 16.5 M

Θ cutoff

Dotted Line: Salpeter IMF with 35 M

Θ cutoff

► Exclude stars with M

initial > 20 M

Θ as

Type IIP/IIL progenitors at 95% confidence level?

Nucleosynthesis in

Massive Pop III Stars

Supernovae, Nucleosynthesis, & Mixing

SN + mixing SN, no mixing

Pop III NucleosynthesisElemental Yieldsas a function of initial mass

non-rotating stars

120 stellar masses

“complete” reaction network

normalized to Mg

RESULTS:e.g.,Production of 7Li by neutrino interaction in very compact stellar envelope!

Mg yield (ejecta mass fraction)

20 30 40 50

Heger & Woosley (2010)

What Can Nucleosynthesis

Do for Us?

Reconstruction of the IMF

primordial stars form,nucleosynthesis ejected

ejecta incorporated in low-Z halo stars

find low-Z halo stars(HERES, SEGUE, …)

measure abundances(VLT, KECK, …)

compare abundances to primordial star

nucleosynthesis library

obtain IMF of population of progenitor stars

Frebel, priv. com. (2007)

http://www.astro.psu.edu/users/tabel/Homepage/transparencies/c.eps

Umeda & Nomoto, Nature, 422, 871, (2003)

25 solar mass star, Pop III0.3 B, mildly mixed8x10-6 solar masses iron

Comparison to Observational DataThe most iron-poor star

Heger & Woosley (2010)

different explosion energies

The second most iron-poor star

~1/1000 solar metallicity stars

Fit to Caffau Star10.6 MꙨ

0.9 B

Vo et al. (2012 in prep)

Reconstruction of the IMF

Vo et al. (2012 in prep)

Pair-InstabilitySupernovae

PISNPCSN hypernovaepair production SNe

}PSN

pulsational pair-instability SNe ➞ PPSN

A Good Name?

Nucleosynthesis in

Pair-InstabilitySupernovae

Initial mass: 150MꙨ

expl

osio

n en

ergy

/ B

approximate

E expl

Fe-richFe-poor

•Low neutron excess from CNO -> 22Ne in helium burning

•No extended stable period of carbon and oxygen burning where weak interactions might increase the neutron excess

ProblemPair-Instability Supernovae do

not reproduce the abundances as observed in very metal poor halo stars!

The IMF or the First Stars – and hence how they come to pass – still remains elusive without observational data

Summary● Uncertainties in Fates of the First Stars largely come from

uncertainties in their initial properties: mass, rotation, binarity

● Significant uncertainty also exists in the modeling of the stellar physics of primordial stars – very massive stars in general, but particularly, as with all theory, if there is no experimental (observational) constrain

● Stellar forensics, determining abundance patterns of what the first stars left behind, may be our best tool in the near future (e.g., constraints on pair-SNe)

the first stars - konan...

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