New Constraints on Neutron-Capture Nucleosynthesis

Processes

Inese I. Ivans

California Institute of Technology

Hubble Fellows Symposium

April 7, 2005

Lanthanides

Actinides

1

3 4

11 12

19 20 21 22 23 24 25

37 38 4039 41

55

42 43

7456 57 72 73 75

87

62

88

59

9590

58 63

89

60

9491

106105104

61

9392

107 108

96 97

76

67 68666564

10310210199 10098

114113112111110

717069

116115

26 27

44

28

45

77

46

7978

29

47

30

48

80

49

81

31

13

50

82

14 15

32 33

51

8483

17 18

34 35

53

36

5452

8685

118117

5 6

16

87 9 10

2

H

Li

Na Mg

K Ca Sc Ti

Rb Sr Y Zr Nb

V

Cs Ba

Fr

La

Ra Ac

Hf Ta

Ce

W

Pr Nd

Cr Mn

Tc

Re

Th

Fe

Ru

Os

Pa

Co

Rh

Ir

Pm

Ni

Pd

Pt

U

Cu

Np

Au

Ag

Zn

Cd

Fm

Hg

Es

Ga

Sn

Cm

BiPb

PSiAl

In

Bk

Tl

Cf

Sb

Po At Rn

ErHo

S Cl

Ge

Ar

As Se Br

B

Kr

Te I Xe

He

C N O F NeBe

Tm

Md

Yb

No

Lu

Lr

Sm

Pu

Eu

Am

Gd Tb Dy

109

yy

Xx

Mo

A Periodic Table of the Elements

Xx: element symbol; yy: atomic number

BBN CRCR (+/-) neutron-capture

4

(Rolfs & Rodney 1988)

Chart of Nuclides

Solar System Abundance Distribution

=Z+N

(Cowley 1999)=Z+N

Solar System Abundance Distribution

=Z+N

SNeII

SNeIa

O,Mg massiveSi,Ca,Ti

less massive

Th,U

=Z+N

AGB

Sr,Y,Zr Ba,La Pb,Bimassive less massive

Happened very early in Galactic times: some very metal-poor stars are enormously rich in elements created in r -process (eg. [Fe/H] ~-3.1 => 1/1250 [Fe/H]sun)

Sneden, Cowan, Ivans et al 2002

Created in SNe IIMaybeProbablyLikelyPerhaps ...

The site of the rapid neutron-capture process?

Happened over longtimescales and rangeof metallicities andin equal measure inthe disk and halo

• Created in SNe II

MaybeProbablyLikelyPerhaps ...

“universality” of the r-process?

(Cowan, Sneden, Ivans et al 2001)

(Cowan et al 2002)

“universality” of the r-processmaybe not so universal

BD+17o3248 SS-rpoor

agree-mentwith Z<56&/or

heavies

(Rolfs & Rodney 1988)

Lead & bismuth: the end of the line for the s-process

In low mass (1-3Msun) AGB stars,

neutrons: 12C(p,)13N(e+,)13C(,n)16Oseeds: Fe

With decreasing metallicity, n ~ constant Fe decreasing => increasing n/Fe

=> s-process dist’n

(1998 Gallino et al.)

(Ivans et al. submitted)(Ivans et al. submitted)

CS29497-030

Largest [Pb/Fe]to date

First Bi to bemeasured in ametal-poor star

(Ivans et al. submitted)(Ivans et al. submitted)

In Summaryo CS29497-030: first abundance measurement of Bi in a metal-poor staro Bi/Pb in accord with s-process predictionso overall abundance pattern fits that of (r+s) process where s-processing includes r-process pre-enrichmento abundance of Na (and other elements sensitive to the neutron-excess) can be employed to constrain the mass of the AGB progenitor: lower mass stars go through fewer thermal, producing lower abundances of elements sensitive to the neutron excess