SLIDE 1
Neutrino Driven Wind Models Integrated Nucleosynthesis
- 2 Models
- Effects of varying neutrino luminosities
Secondary heating source
- Neutron to seed ratio variation
- Acoustic power
Luke Roberts UCSC w/ Stan Woosley and Rob Hoffman Neutrino Driven - - PowerPoint PPT Presentation
Luke Roberts UCSC w/ Stan Woosley and Rob Hoffman Neutrino Driven - - PowerPoint PPT Presentation
Luke Roberts UCSC w/ Stan Woosley and Rob Hoffman Neutrino Driven Wind Models Integrated Nucleosynthesis 2 Models Effects of varying neutrino luminosities Secondary heating source Neutron to seed ratio variation
SLIDE 2
SLIDE 3
Initial studies found wind to be
promising r‐process site (Woosley et al. 1994)
Wind nucleosynthesis
determined by Ye, s, and tdyn
Proton rich wind may also
contribute to nucleosynthesis
How does standard NDW
nucleosynthesis fit in the context of full stellar models?
Sneden et al. 2007
SLIDE 4
- Neutron and alpha particle
abundances after nucleon recombination:
- Rate of seed production given by:
- Giving a neutron to seed ratio:
dYseed dt ≈ dY12C dt ∝ ρ3Yα
3Yn
Yseed ∝ S f
−3 Ye 2
( )
3Ynτ dyn
⇒ Nn Nseed +10 ∝ S f
3
τ dyn Yn = (1− 2Ye) Yα = Ye /2
Hoffman et al. (1997)
SLIDE 5
Analytic NDW Nucleosynthesis Predictions
Assuming Large neutrino anti‐
neutrino asymmetry required in “standard model”
Likely in N=50
Regime
Lν ∝ T
ν 4
SLIDE 6
Spherically symmetric
Implicit Lagrangian hydrodynamics
Nuclear network for energy generation
Adaptive nuclear network for nucleosynthesis to ~3000 isotopes
Thermal neutrino losses
Integrates ejected nucleosynthesis as mass flows off the grid
Post Newtonian corrections to gravitational potential Kepler massive stellar evolution code (cf. Weaver, Zimmerman, & Woosley 1978) V e l
- c
i t y Entropy Energy Deposition Xheavy Ye
SLIDE 7
Kepler updates for wind models
New neutrino interaction rates
- Coupled to both reaction
networks
- Nucleon capture rates include
first order corrections in the nucleon mass
- Gravitational redshifts
“Lightbulb” transport approximation
- Includes bending of null
geodesics in Schwarzschild geometry
- Different neutrino sphere radii
Mass recycling
Artificial energy deposition
SLIDE 8
Time (s) Mass Loss Rate S/100, Ye, and 10 td Time (s)
<Enu> (MeV) Lnu (1051 erg s-1)
Luminosity histories from Woosley et al. (2004) Original models had successful r-process, but entropies were too high
ν e ν
e
ν µ /τ s
Ye
˙ M τ d
SLIDE 9
Integrated Wind Nucleosynthesis: 20 Msun A Production Factor
Total ejected mass:
18.4 Msun
No significant p‐
process production
Reverse shock
doesn’t affect nucleosynthesis
SLIDE 10
A Production Factor Integrated wind yields combined with yields from 20 Msun model of Woosley & Weaver (1995)
SLIDE 11
A Production Factor Production Factor A Anti-neutrino energy reduced by 15% No weak magnetism corrections
SLIDE 12
Without neutrino interaction corrections With neutrino interaction corrections
SLIDE 13
Fall off at low metallicity Inconsistent with NDW
nucleosynthesis predictions
[Sr/Fe]=0.8 in 20 Msun
model
Evidence for increased SN
fallback at low metallicity?
Lai et al. (2008)
SLIDE 14
Time (s) Mass Loss Rate S/100, Ye, and 10 td Time (s)
<Enu> (MeV) Lnu (1051 erg s-1)
Luminosity histories from Huedepohl et al. (2009) Proton rich throughout, nup-process?
ν e ν
e
ν µ /τ s
Ye
˙ M τ d
SLIDE 15
Total ejected mass: 7.4
Msun
All weighted production
factors at or below one
No significant p‐process
production
Reverse shock not
expected to be strong, doesn’t affect nucleosynthesis
A Production Factor
SLIDE 16
- Temperature structure of the
protoneutron star atmosphere set by:
- Mass loss rate set near surface
- Volumetric energy deposition
source doesn’t effect atmosphere, deposits energy after mass loss rate is set
- Increases entropy of material,
decreases dynamical timescale, conditions more favorable for r- process (Qian & Woosley 96, Suzuki & Nagataki 05)
˙ q
e ≈ ˙
ε
ν
⇒ Tatm ≈ 3 R6
−1/ 3Lν ,51 1/ 6 T ν ,5 MeV 1/ 3
MeV
SLIDE 17
Neutron-to-Seed Ratio Seed Abundance Total Energy Deposition Rate (erg s-1)
˙ q = L0 ρldr2 exp[(r − r
0)/ld ]
ld ≈106cm
Volumetric energy
deposition source with constant damping:
Optimal damping length: Is this reasonable? (see Suzuki & Nagataki 2005)
Ye = 0.44
Conditions at 10 sec in
Woosley (1994) model:
SLIDE 18
L0 ≈ 4 ×1047ergs−1 × E1 1048erg 1.4Msun MNS ρ 1012g/cc × 109cm/s cs
3 RNS
106
6
ω 1000 hz
4
× 1 1+ (ωR/cs)4 /4
Q‐factor < 1
- Must be driven by
accretion
Suzuki & Nagataki argue it is reasonable for high magnetic fields, give Alfven waves and non‐linear damping
Other possibility, purely acoustic power (Qian & Woosley 1996, Burrows et al 2007)
Neutrino damped PNS oscillations (Weinberg & Quatert 2008)
l=1 oscillations have intensity of (see Landau & Lifshitz)
Weinberg & Quatert 2008
SLIDE 19
ld ≈ 2.6 ×106 cm × T MeV
1/2
s 100
1/2 1000 hz
ω0
1/2
P 3εw
1/2
How do these acoustic waves damp? Studied in the context of the solar
corona (see Stein & Schwartz 1973for references)
Steepen into shocks over distance of
- rder the pressure scale height
Energy loss given by weak shock theory
as
Stein & Schwartz 1973
Mach Number - 1 Height (km)
Δs = 2γ(γ −1)cv 3(γ +1)2 m3 dEs dt = −ρTcsΔs(1+ m /2)
Results in a damping length
SLIDE 20
Density (g/cc) Entropy Radius Edot (ergs/g/s) Temperature (K)
T ρ ˙ ε s
Self consistent acoustic
energy input based on weak shock damping length
Atmosphere temperature
still set by neutrino fluxes
Final entropy 285 Dynamical timescale ~2 ms
∂tS + r−2∂r(r2vgS) = −
3 π γ(γ −1)cvρTω S3/ 2
P 3/ 2
SLIDE 21
Abundance Density Temperature Time (s)
ρ T
Reverse Shock Time (s)
SLIDE 22
A Abundance
SLIDE 23
Integrated NDW Nucleosynthesis
- Low mass progenitor wind does not contribute significantly
- Higher mass progenitor consistent with yields from the full star
- Sensitive to uncertain neutrino spectra
- Evolution of N=50 closed shell elements may trace fallback
history
- See arXiv:1004.4916
Secondary Energy Deposition
- Get high neutron to seed ratios for reasonable amount of
energy deposition
- sound waves from PNS oscillations weak shocks
- Volumetric energy deposition at correct radius for r‐process