Massive runaway stars: probes for stellar physics and dynamics - PowerPoint PPT Presentation

Massive runaway stars: probes for stellar physics and dynamics Mathieu Renzo Collaborators: E. Zapartas, S. E. de Mink, Y. G¨ otberg, S. Justham, R. J. Farmer, R. G. Izzard, S. Toonen, D. J. Lennon, H. Sana, E. Laplace, S. N. Shore, F . Evans ...

What is a runaway star? Runaway stars Tail of the velocity distribution Blaauw 61 v 3D [ km s − 1 ] Hipparcos velocity distribution for young ( � 50 Myr) stars, Tetzlaff et al. 11, 2 see also Zwicky 57, Blaauw, 93, Gies & Bolton 86, Leonard 91, Renzo et al. 19a, 19b

What is a runaway star? Runaway stars Tail of the velocity distribution Blaauw 61 Fraction per type O: ∼ 10 − 20 % Be: ∼ 13 % v 3D [ km s − 1 ] Hipparcos velocity distribution for young ( � 50 Myr) stars, Tetzlaff et al. 11, 2 see also Zwicky 57, Blaauw, 93, Gies & Bolton 86, Leonard 91, Renzo et al. 19a, 19b

Two ways to produce fast massive stars Binary supernova disruption Dynamical ejection from cluster Massive runaway origins ... ... is there a problem ? 3

Most common massive binary evolution Credits: ESO, L. Calc ¸ada, M. Kornmesser, S.E. de Mink 4

Spin up, pollution, and rejuvenation The binary disruption shoots out the accretor Spin up: Packet ’81, Cantiello et al. ’07, de Mink et al. ’13 Pollution: Blaauw ’93 Rejuvenation: Hellings ’83, Schneider et al. ’15

What exactly disrupts the binary? 86 + 11 − 22 % of massive binaries are disrupted Ejecta impact (Tauris & Takens 98, Liu et al. 15) Loss of SN ejecta (Blaauw ’61) Renzo et al. 19b, Kochanek et al. 19, 6 Eldridge et al. 11, De Donder et al. 97

What exactly disrupts the binary? 86 + 11 − 22 % of massive binaries are disrupted Ejecta impact (Tauris & Takens 98, Liu et al. 15) SN Natal kick (Shklovskii 70, Katz 75, Janka 13, 17) Loss of SN ejecta (Blaauw ’61) Renzo et al. 19b, Kochanek et al. 19, 6 Eldridge et al. 11, De Donder et al. 97

Do BHs receive kicks ? NO YES ⇒ most remain together with ⇒ most are single and we can’t their widowed companion see them... 7

Do BHs receive kicks ? NO YES ⇒ most remain together with ⇒ most are single and we can’t their widowed companion see them... ...but we can see the “widowed” companions 7

A way to constrain BH kicks with Gaia Massive runaways mass function ( v ≥ 30 km s − 1 , M ≥ 7 . 5 M ⊙ ) 1.0 Probability × 10 5 0.0 # stars 1.0 0.0 1.0 0.0 0 10 20 30 40 50 60 70 M dis [ M ⊙ ] Mass 8 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

A way to constrain BH kicks with Gaia Massive runaways mass function ( v ≥ 30 km s − 1 , M ≥ 7 . 5 M ⊙ ) 1.0 Probability × 10 5 0.0 # stars 1.0 0.0 BH momentum kick ( σ kick = 265 km s − 1 , fiducial) 1.0 0.0 0 10 20 30 40 50 60 70 M dis [ M ⊙ ] Mass 8 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

A way to constrain BH kicks with Gaia Massive runaways mass function ( v ≥ 30 km s − 1 , M ≥ 7 . 5 M ⊙ ) 1.0 Probability × 10 5 0.0 BH: σ kick = 100 km s − 1 NS: σ kick = 265 km s − 1 # stars 1.0 (no fallback for BH) 0.0 BH momentum kick ( σ kick = 265 km s − 1 , fiducial) 1.0 0.0 0 10 20 30 40 50 60 70 M dis [ M ⊙ ] Mass 8 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

A way to constrain BH kicks with Gaia Massive runaways mass function ( v ≥ 30 km s − 1 , M ≥ 7 . 5 M ⊙ ) BH kick=NS kick ( σ kick = 265 km s − 1 ) 1.0 (no fallback) Probability × 10 5 0.0 BH: σ kick = 100 km s − 1 NS: σ kick = 265 km s − 1 # stars 1.0 (no fallback for BH) 0.0 BH momentum kick ( σ kick = 265 km s − 1 , fiducial) 1.0 0.0 0 10 20 30 40 50 60 70 M dis [ M ⊙ ] Mass 8 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

Kicks do not change companion velocity 86 + 11 − 22 % of massive binaries are disrupted v dis ≃ v orb 2 before the SN SN Natal kick (Shklovskii 70, Katz 75, Janka 13, 17) Renzo et al. 19b, Kochanek et al. 19, 9 Eldridge et al. 11, De Donder et al. 97

Velocity distribution: Runaways Velocity respect to the pre-explosion binary center of mass 10 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

Velocity distribution: Walkaways Velocity respect to the pre-explosion binary center of mass 11 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

Velocity distribution: Walkaways Under-production of runaways because mass transfer widens the binaries and makes the secondary more massive Velocity respect to the pre-explosion binary center of mass 11 Numerical results publicly available at: Renzo et al. 19b http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A66

Summary of ejection mechanisms Binary SN disruption • Ejects initially less massive star • Requires SN kick • Final v ≃ v orb 2 • Most binaries are disrupted • Leaves binary signature fast rotation, He/N enrichment, lower apparent age 12

Outline Binary supernova disruption Dynamical ejection from cluster Massive runaway origins ... ... is there a problem ? 13

Dynamical ejection from cluster N-body interactions (typically) least massive thrown out. Binaries matter... • Cross section ∝ a 2 ≫ R 2 ∗ • (Binding) Energy reservoir Poveda et al. 67 ...but don’t necessarily leave imprints! Credits: C. Rodriguez

Typical outcome of dynamical interactions Fast runaway (the least massive of the three) Tighter and more massive binary e.g., Fujii & Portegies-Zwart 11 15

The most massive runaways known M = 137 . 8 + 27 . 5 − 15 . 9 M ⊙ − 69 ◦ 00 ′ VFTS72 M = 97 . 6 + 22 . 2 − 23 . 1 M ⊙ 02 ′ VFTS682 Declination (J2000) 04 ′ 06 ′ VFTS16 R136 08 ′ M = 91 . 6 + 11 . 5 − 10 . 5 M ⊙ 39 m 00 s 30 s 38 m 00 s 30 s 5 h 37 m 00 s Right Ascension (J2000) 16 Renzo et al. 19a Lennon et al. (incl. MR), 18

The most massive runaways known M = 137 . 8 + 27 . 5 − 15 . 9 M ⊙ − 69 ◦ 00 ′ VFTS72 M = 97 . 6 + 22 . 2 − 23 . 1 M ⊙ 02 ′ VFTS682 Declination (J2000) 04 ′ 06 ′ VFTS16 R136 08 ′ M = 91 . 6 + 11 . 5 − 10 . 5 M ⊙ 39 m 00 s 30 s 38 m 00 s 30 s 5 h 37 m 00 s Right Ascension (J2000) 16 Renzo et al. 19a Lennon et al. (incl. MR), 18

The most massive runaways known M = 137 . 8 + 27 . 5 − 15 . 9 M ⊙ − 69 ◦ 00 ′ VFTS72 M = 97 . 6 + 22 . 2 − 23 . 1 M ⊙ 02 ′ VFTS682 v 2D = 93 ± 15 km s − 1 Declination (J2000) 04 ′ 06 ′ VFTS16 R136 08 ′ M = 91 . 6 + 11 . 5 − 10 . 5 M ⊙ v 2D = 80 ± 11 km s − 1 39 m 00 s 30 s 38 m 00 s 30 s 5 h 37 m 00 s Right Ascension (J2000) 16 Renzo et al. 19a Lennon et al. (incl. MR), 18

The most massive runaways known M = 137 . 8 + 27 . 5 − 15 . 9 M ⊙ − 69 ◦ 00 ′ VFTS72 v 2D = 38 ± 17 km s − 1 M = 97 . 6 + 22 . 2 − 23 . 1 M ⊙ 02 ′ VFTS682 v 2D = 93 ± 15 km s − 1 Declination (J2000) 04 ′ 06 ′ VFTS16 R136 08 ′ M = 91 . 6 + 11 . 5 − 10 . 5 M ⊙ v 2D = 80 ± 11 km s − 1 39 m 00 s 30 s 38 m 00 s 30 s 5 h 37 m 00 s Right Ascension (J2000) 16 Renzo et al. 19a Lennon et al. (incl. MR), 18

Outline Binary supernova disruption Dynamical ejection from cluster Massive runaway origins ... ... is there a problem ? 17

Known ejection mechanisms Binary SN disruption Cluster ejections • Ejects initially less massive star • Happen early on, before SNe • Requires SN kick • Can produce faster stars • Final v ≃ v orb • Least massive thrown out 2 • Most binaries are disrupted • Gaia hint: high efficiency dynamical ejection • Leaves binary signature fast rotation, He/N enrichment, ...Binaries are still important! but might lower apparent age not leave signature 18

Known ejection mechanisms Binary SN disruption Cluster ejections • Ejects initially less massive star • Happen early on, before SNe • Requires SN kick • Can produce faster stars • Final v ≃ v orb • Least massive thrown out 2 • Most binaries are disrupted • Gaia hint: high efficiency dynamical ejection • Leaves binary signature fast rotation, He/N enrichment, ...Binaries are still important! but might lower apparent age not leave signature Relative efficiency ? ∼ 2 3 of runaways from binaries Hoogerwerf et al. 01 18

O type stars runaway fraction # runaways # all stars ≃ Theoretical consensus from Observational claims: (regardless of origin) binaries: ∼ 10 % 0 . 5 + 2 . 1 − 0 . 5 % ∼ 2 3 from binaries Renzo et al. 19b, De Donder et al. 97, Eldridge et al. 11, Hoogerwerf et al. 01 Kochanek et al. 19 19

O type stars runaway fraction # runaways # all stars ≃ Theoretical consensus from Observational claims: (regardless of origin) binaries: ∼ 10 % 0 . 5 + 2 . 1 − 0 . 5 % 0 1 . a l t ∼ 2 e 3 from binaries i k s n Renzo et al. 19b, De Donder et al. 97, Eldridge et al. 11, l i i J Hoogerwerf et al. 01 Kochanek et al. 19 Is it really a problem? • Frame of reference to measure v • Biases in favor of runaways • Gaia hint: high efficiency dynamical ejection 19 • Binary prediction sensitive to SFH