Formation rate of LB-1 like systems through dynamical interactions

Ataru Tanikawa (The University of Tokyo, Japan)

Collaborators: M. S. Fujii, T. Kinugawa, J. Kumamoto

Innovative Area Gravitational Wave Physics and Astronomy: Genesis The Third Annual Area Symposium

Konan University, Kobe, Japan, 11th Feb. 2020

Binary evolution and star cluster in A03 group

Ataru Tanikawa (The University of Tokyo, Japan)

Collaborators: M. S. Fujii, T. Kinugawa, J. Kumamoto, K. Takahashi,

H. Umeda, T. Yoshida

Innovative Area Gravitational Wave Physics and Astronomy: Genesis The Third Annual Area Symposium

Konan University, Kobe, Japan, 11th Feb. 2020

ContentsOpen cluster

Open cluster

• BH-BH formation in open clusters (Kumamoto et al. 2018; 2020; Kumamoto’s poster 8)

• Formation of LB-1 (Tanikawa et al. 2019)

• Stellar evolution tracks (Tanikawa et al. 2019)Binary evolution and star cluster

Open clusters• Dense stellar clusters

•

•

•

Moc ∼ 10 − 104M⊙

ρoc ∼ 1 − 104M⊙pc−3

ρdisk,solar ∼ 0.1M⊙pc−3Pleiades (© NASA, ESA, AURA/Caltech Palomar Obsevatory)

BH-BH formation

Kumamoto et al. (2018, MNRAS, 486, 3942), (see also Di Carlo, Giacobbo, Mapelli et al. 2019, MNRAS, 487, 2947)

Mass distribution• The and distributions are consistent with LIGO/Virgo observations.

• stars contribute to low-mass mergers ( ) .

• High-mass mergers ( ) come from

stars formed at the present day.

M1 q

Z ∼ Z⊙

M1 ∼ 10M⊙

M1 ∼ 30M⊙

Z ∼ 0.1Z⊙

Kumamoto et al. (2020, arXiv:2001.10690)

Z ∼ 0.1Z⊙

Z ∼ Z⊙

LB-1 system• B-type star - BH

•

• But, many studies have raised doubts on the presence (e.g. Eldridge et al. 2019; Adbul-Masih et al. 2019; Safarzadeh et al. 2019; El-Badry, Quataert 2020; Irrgang et al. 2020).

8M⊙ 70M⊙

a ∼ 1 au, e ∼ 0.03, Z ∼ Z⊙

BH + accretion disk70M⊙

B-type star8M⊙

😀

Hα

He I etc.

Liu et al. (2019)

BH

B-type star

Formation scenario

Tanikawa et al. (2019, arXiv:1912.04509)

Formation rate• Formation rate:

• Collision rate:

•

•

• Surviving rate:

•

NLB1 ∼ 0.1 (·Ncoll

3 × 10−8yr−1 ) ( Psurv

0.1 ) ( TB

40Myr )·Ncoll = ·NPIgap

ΓnHe

ΓeHe∼ 3 × 10−8 [yr−1]

·NPIgap ∼ 2 × 10−6 (fPIgap

0.002 ) ( ρoc

104M⊙pc−3 ) ( η20

0.003M−1⊙ ) ( foc

0.2 ) (·Mmw

2M⊙yr−1 ) [yr]

ΓnHe

ΓeHe∼ 10−2 (

N1,nHe /N1,eHe

2 ) (M12,nHe /M12,eHe

2 ) (R12,nHe /R12,eHe

0.01 )

Psurv = tKH/tcoll,life,max ∼ 0.1 ( tcoll,life,max

0.2Myr )−1

tKH ∼ 2 × 104 ( Mcoll

70M⊙ )2

( Rcoll

100R⊙ )−1

( Lcoll

105L⊙ )−1

[yr]

MS star Naked He star

LB-1

Merge or CECollapse

Circularized

Di Carlo, Mapelli et al. (2019, arXiv:1911.01434)

Stellar evolution trackMS

He star

Naked He star

BH

BH

BH

BH

MS

MS

MS

MS

He star

BH

BH

Binary evolution Dense stellar cluster

Fitting formulae• Fitting formulae

• Based on the Bonn model

• Coupled with SSE, BSE, and NBODY

• Support for

• Extreme metal poor stars down to

• Massive stars up to

• To be open sources within this year

log(Z /Z⊙) = − 8

M ∼ 1300M⊙

Tanikawa et al. (2019, arXiv:1906.06641)

Summary• Open clusters are one of promising formation sites of merging BH-BHs (Kumamoto et al. 2019, MNRAS, 486, 3942; 2020, arXiv:2001.10690)

• The LB-1 system cannot be formed in open clusters (Tanikawa et al. 2019, arXiv:1912.04509).

• Evolution tracks for massive or EMP stars will be soon available on SSE, BSE, and NBODY codes (Tanikawa et al. 2019, arXiv:1906.06641).