Pulsational Pair Instability The reason why these black holes cant - - PowerPoint PPT Presentation

Pulsational Pair Instability

The reason why these black holes can’t come from stars

Mathieu Renzo

Pair-instability SNe are the best understood supernovae

see Fowler & Hoyle 1964, Rakavy & Shaviv 1967, Barkat et al. 1968, Fraley 1968, Glatzel et al. 1985, Woosley et al. 2002, 2007, Langer et al. 2007, Chatzopoulos et al. 2012, 2013, Yoshida et al. 2016, Woosley 2017, 2019, Leung et al. 2019, etc...

Radiation pressure dominated: Ptot ≃ Prad MHe 32 M⊙

Renzo, Farmer et al. 2020b

He cores computed with Γ1

def

=

• ∂ ln P

∂ ln ρ

• s

γ γ → e+ e−

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

Renzo, Farmer et al. 2020b

The pair-instability BH mass gap

The distribution of stellar BH masses

3

Renzo, Farmer, et al. 2020b

The distribution of stellar BH masses

GW190521.1

3

(Some events missing) Renzo, Farmer, et al. 2020b

How robust are these predictions?

Metallicity? Small effect

4

Focus on lower edge of the gap Farmer, Renzo et al. 2019

Metallicity shift

∆ max{MBH} ∼7%

• ver 2.5 orders of magnitude

Comparable or smaller effects: mixing, resolution, winds, nuclear reaction network size, etc..

Treatment of time-dependent convection? Not the edge

5

Matters for least massive PPI, not for the most massive BH progenitors

Renzo, Farmer et al. 2020a

Can rotation move the gap? Barely...

6

Rotation ⇒ bigger MHe ⇒ can increase the rates

Chatzopoulos et al. 2012, 2013

Rotation stabilizes only for very extreme assumption:

• No core-envelope coupling
• large initial rotation
• low Z (≃ no winds)

⇐

• nly ∼20% shift of instability

4% for “realistic” coupling

Marchant & Moryia 2020 see also Glatzel et al. 1985

The only known large uncertainty

Nuclear reaction rates

The most important reaction 12C(α, γ)16O reaction rate

7

Change in C/O ratio ⇒ different C-shell behavior GW can constrain nuclear rates with the gap...

...if other channels don’t pollute it too much Farmer, Renzo et al. 2020, see also Takahashi 2018, Farmer, Renzo et al. 2019

The most important reaction 12C(α, γ)16O reaction rate

7

Change in C/O ratio ⇒ different C-shell behavior GW can constrain nuclear rates with the gap...

...if other channels don’t pollute it too much Farmer, Renzo et al. 2020, see also Takahashi 2018, Farmer, Renzo et al. 2019

MBH ≃ 85 M⊙ requires decreasing rate by ∼2.5 σ

Possible ways to bridge the gap

Does binarity move the gap?

Can isolated binary evolution “pollute” the gap?

8

With unlimited accretion, some binary BHs can enter the gap...

van Son et al., incl. MR, 2020

Can isolated binary evolution “pollute” the gap?

8

... but those entering the gap don’t merge within 13.7 Gyr

van Son et al., incl. MR, 2020

Can isolated binary evolution “pollute” the gap?

8

... but those entering the gap don’t merge within 13.7 Gyr

Mass accretion leads to orbital widening

even with the most optimistic assumptions:

• 1% systems with Mtot 90 M⊙
• No systems with Mtot > 100 M⊙

van Son et al., incl. MR, 2020

Possible ways to bridge the gap

The speculative stellar merger scenario

Post main-sequence + main sequence merger

9

Population synthesis assumptions not quite backed up by detailed models

di Carlo et al. 2019, 2020a,b, see also Kremer et al. 2020 Mapelli et al. 2020

• Mass loss (and rejuvenation)?

Assumed zero

• Loss of envelope at core-collapse?

Because of ν losses – Assumed zero see Nadhezin 1980, Lovegrove & Woosley 2013

• Need dynamics to pair with 2nd BH

⇐

Requires nuclear cluster and/or AGN disk?

Possible ways to bridge the gap

Beyond standard-model physics ?

Effectively change the cooling during He core burning

10

Choplin et al. 2017

Other possibilities:

• dark photons
• other axions
• change G
• ν magnetic moment
• extra dimensions

Croon et al. 2020a, see also Croon et al. 2020b, Sakstein et al. 2020

Affects C/O ratio, T − ρ structure, decrease Prad/Ptot

Conclusions

PISN are the theoretically best understood SNe

11

although observationally elusive

• PISN BH mass gap

very robust prediction

• BH formation after PPI

poorly understood

• Accretion in isolated binary

does not shift the gap

• Populating the gap requires

non-stellar (2nd gen. +) BHs

• r

new physics TODO: detailed binary evolution models of PPI

Backup slides

The 12C(α, γ)16O ends He core burning

More 12C ⇒ C shell burning delays 16O ignition to higher ρ

Core Collapse Pulsations Pair Instability SNe Reduced Median Enhanced Helium shell Center Carbon Off-center Carbon Explosive Oxygen Center Oxygen (A) (B) (C) (D) (E) No remnant

Farmer, Renzo et al. 2020

Convection during the pulses quenches the PPI mass loss

Renzo, Farmer et al. 2020a

Amount of mass lost per pulse

20 40 ∆Mtot [M⊙] 1st 2nd 3rd fit 30 35 40 45 50 55 MCO [M⊙] 10−3 10−2 10−1 100 101 ∆Mpulse [M⊙] Larger cores

⇐ More energetic pulses ⇐ More mass loss

(and longer delays)

Renzo, Farmer et al. 2020b

Summary of EM transients

Renzo, Farmer et al. 2020b

Chirp mass distribution – weighted by LIGO’s sensitivity

(Fishbach & Holtz 2017) Marchant, Renzo,et al. 2019

dN dMBH ∝ M−2.35 BH

q ≥ 0.5

(motivated by LVC 2016)

Chirp Mass [M⊙]

Winds, mixing, ν physics? Also small effects

30 40 50 60 70 CO core mass (MCO [M⊙]) 10 20 30 40 50 Black hole mass (MBH [M⊙])

Core Collapse Pulsations Pair Instability

˙ M = 0 N&L η = 0.1 N&L η = 1.0 H η = 0.1∗ T η = 0.1 T η = 1.0

30 40 50 60 70 CO core mass (MCO [M⊙]) 10 20 30 40 50 Black hole mass (MBH [M⊙])

Core Collapse Pulsations Pair Instability

νr − 3∆ νr − 2∆ νr − 1∆ ν∗

r

νr + 1∆ νr + 2∆ νr + 3∆ sin2 θW = 0.2319∗ sin2 θW = 0.23867 sin2 θW = 0.2223

30 40 50 60 70 CO core mass (MCO [M⊙]) 10 20 30 40 50 Black hole mass (MBH [M⊙])

Core Collapse Pulsations Pair Instability

αMLT = 1.5 αMLT = 1.6 αMLT = 1.7 αMLT = 1.8 αMLT = 1.9 αMLT = 2.0∗ fov = 0.00 fov = 0.01∗ fov = 0.05

Farmer, Renzo et al. 2019