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 Radiation pressure dominated: P tot ≃ P rad M He � 32 M ⊙ 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, Renzo, Farmer et al. 2020b 2013, Yoshida et al. 2016, Woosley 2017, 2019, Leung et al. 2019 , etc...

γ γ → e + e − def � � ∂ ln P = Γ 1 ∂ ln ρ s He cores computed with 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 (Some events missing) GW190521.1 3 Renzo, Farmer, et al. 2020b

How robust are these predictions?

Metallicity? Small effect Focus on lower edge of the gap Metallicity shift ∆ max { M BH } ∼ 7% over 2.5 orders of magnitude Comparable or smaller effects: mixing, resolution, winds, nuclear reaction network size, etc.. 4 Farmer, Renzo et al. 2019

Treatment of time-dependent convection? Not the edge Matters for least massive PPI, not for the most massive BH progenitors 5 Renzo, Farmer et al. 2020a

Can rotation move the gap? Barely... Rotation ⇒ bigger M He ⇒ 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) ⇐ only ∼ 20% shift of instability Marchant & Moryia 2020 � 4% for “realistic” coupling 6 see also Glatzel et al. 1985

The only known large uncertainty Nuclear reaction rates

The most important reaction 12 C ( α , γ ) 16 O reaction rate 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 7 Farmer, Renzo et al. 2020, see also Takahashi 2018, Farmer, Renzo et al. 2019

The most important reaction 12 C ( α , γ ) 16 O reaction rate Change in C/O ratio ⇒ different C-shell behavior M BH ≃ 85 M ⊙ requires decreasing rate by ∼ 2 . 5 σ GW can constrain nuclear rates with the gap... ...if other channels don’t pollute it too much 7 Farmer, Renzo et al. 2020, see also Takahashi 2018, Farmer, Renzo et al. 2019

Possible ways to bridge the gap Does binarity move the gap?

Can isolated binary evolution “pollute” the gap? With unlimited accretion, some binary BHs can enter the gap... 8 van Son et al. , incl. MR, 2020

Can isolated binary evolution “pollute” the gap? ... but those entering the gap don’t merge within 13.7 Gyr 8 van Son et al. , incl. MR, 2020

Can isolated binary evolution “pollute” the gap? ... 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 M tot � 90 M ⊙ • No systems with M tot > 100 M ⊙ 8 van Son et al. , incl. MR, 2020

Possible ways to bridge the gap The speculative stellar merger scenario

Post main-sequence + main sequence merger Population synthesis assumptions not quite backed up by detailed models • 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 2 nd BH ⇐ Requires nuclear cluster and/or AGN disk? di Carlo et al. 2019, 2020a,b, 9 see also Kremer et al. 2020 Mapelli et al. 2020

Possible ways to bridge the gap Beyond standard-model physics ?

Effectively change the cooling during He core burning Choplin et al. 2017 Other possibilities: • dark photons • other axions • change G • ν magnetic moment • extra dimensions Affects C/O ratio, T − ρ structure, decrease P rad / P tot 10 Croon et al. 2020a, see also Croon et al. 2020b, Sakstein et al. 2020

Conclusions

PISN are the theoretically best understood SNe 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 (2 nd gen. +) BHs or new physics TODO: detailed binary evolution models of PPI 11

Backup slides

The 12 C ( α , γ ) 16 O ends He core burning More 12 C ⇒ C shell burning delays 16 O ignition to higher ρ Helium shell Center Carbon Off-center Carbon Explosive Oxygen Center Oxygen Reduced Core Collapse Median Pulsations No remnant Pair Enhanced Instability SNe (A) (B) (C) (D) (E) 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 ∆ M tot [ M ⊙ ] 1 st 2 nd 3 rd 40 fit 20 0 Larger cores ⇐ 10 1 More energetic pulses ∆ M pulse [ M ⊙ ] 10 0 ⇐ 10 − 1 More mass loss (and longer delays) 10 − 2 10 − 3 30 35 40 45 50 55 M CO [ M ⊙ ] 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) dM BH ∝ M − 2 . 35 dN BH q ≥ 0 . 5 (motivated by LVC 2016) Chirp Mass [ M ⊙ ] Marchant, Renzo, et al. 2019

Winds, mixing, ν physics? Also small effects Core Pair Core Pair Pulsations Pulsations 50 50 Collapse Instability Collapse Instability Black hole mass (M BH [M ⊙ ]) Black hole mass (M BH [M ⊙ ]) 40 40 30 30 20 20 ν r − 3∆ ν r + 2∆ ν r − 2∆ ν r + 3∆ sin 2 θ W = 0 . 2319 ∗ 10 10 ν r − 1∆ ˙ H η = 0 . 1 ∗ M = 0 ν ∗ sin 2 θ W = 0 . 23867 N&L η = 0 . 1 T η = 0 . 1 r sin 2 θ W = 0 . 2223 ν r + 1∆ N&L η = 1 . 0 T η = 1 . 0 0 0 30 40 50 60 70 30 40 50 60 70 CO core mass (M CO [M ⊙ ]) CO core mass (M CO [M ⊙ ]) Core Pair Pulsations 50 Collapse Instability Black hole mass (M BH [M ⊙ ]) 40 30 20 α MLT = 1 . 5 α MLT = 2 . 0 ∗ α MLT = 1 . 6 f ov = 0 . 00 10 α MLT = 1 . 7 f ov = 0 . 01 ∗ α MLT = 1 . 8 f ov = 0 . 05 α MLT = 1 . 9 0 30 40 50 60 70 Farmer, Renzo et al. 2019 CO core mass (M CO [M ⊙ ])