Serena Repetto, Gijs Nelemans, Peter Jonker and Melvyn ...tauris/NS2014/Repetto_BH-kicks.pdf ·...

Black Hole Kicks:Constraints from Observations

Serena Repetto, Gijs Nelemans, Peter Jonker(Radboud University Nijmegen)

and Melvyn Davies (Lund Observatory)

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Why are BH kicks interesting?

High/Low kick? Which mechanism at play?

Janka’s talk

Kicks affect GW merger rate of BH-BH

Belczynski, Dominik, Repetto et al. arXiv 1208.0358

and number of BHs retained in a globular cluster

Strader et al. 2012

Black Hole Kicks: Constraints from Observations of X-ray binaries

What can observations tell us?

Black-hole X-ray binaries (BH-XRBs)

contain a BH accreting material from a

stellar companion

Credit: Rob Hynes

Jonker & Nelemans 2004

pointed out similarity between

the Galactic distribution of

NS-LMXBs and BH-LMXBs

(see rms-value of distance to

the Galactic plane)

A Population Study of the Galactic distribution ofBH-LMXBs

We simulate a population of

kicked binaries , and we

compare the simulated

distribution with the observed

one

(see Brandt & Podsiadlowski

1995)

Repetto, Davies, Sigurdsson

2012

Cumulative distributions of

height from the Galactic plane

Solid: High Kicks Dashed: Low Kicks


A Population Study of the Galactic distribution ofBH-LMXBs

We simulate a population of

kicked binaries , and we

compare the simulated

distribution with the observed

one

(see Brandt & Podsiadlowski

1995)

Repetto, Davies, Sigurdsson

2012

Cumulative distributions of

height from the Galactic plane

Need High Kicks!


What can we learn from the study of the single sources ?

The main idea is to use all the observational constraints to

uncover the natal kick at birth...

..

1) Use current position in the Galaxy:

Natal kick combines with ΔMSN → Vpec.Vpec has to bee greater than

lower value from kinematics

..

2) Natal kick combines with ΔMSN in changing binary orbital

properties. Which postSN configuration is consistent with the

observed orbital parameters? Trace Binary Evolution

Backwards!


Evolution of a BH-LMXB (M⋆ ≈ M⊙)

..

NK changes orbital properties

.

Orbit shrinks via coupling of tides and

magnetic braking until Roche Lobe Overflow

.

On-going mass transfer

.

Credit: Rob Hynes


..Natal kick chan-

ges binary orbital

properties (a, e, i)

.

Randomize initial

binary properties,

kick and mass-loss,

and calculate postSN

configuration:

(a, e)post

.

Orbit shrinks due

to coupling of

tides and magnetic

braking until RLO

.

On-going

mass transfer

.

Get RLO

configuration:

RLO, masses

.

How to treat cou-

pling? i.e How to link

postSN with RLO?


Coupled effect of tides and Magnetic Braking

..

Angular momentum loss in a non-massive stellar

wind → ω ∼ ω3⋆(Skumanich’s law, see Verbunt &

Zwaan 1981)

We use Hut’s model (1981) of tidal evolution

(, e, ω⋆)

..

We integrate the tidal equations

coupled with magnetic braking:

= |tide = e|tid

ω⋆ = ω⋆|tid + ω⋆|MB


Coupled effect of tides and Magnetic Braking

..

Magnetic Braking spins down the star until

τtides ∼ τMBThe orbit circularizes and the star synchronizes with

the orbital frequency

Tidal torque refills J⋆-reservoir and the orbit shrinks

until RLO


An illustrative example of the coupled evolution

BH-LMXB with a=22 R⊙, e=0.7 and high/low stellar spin:

Synchronization &Cicularization

Dashed:Low SpinSolid: High Spin

Rotation PeriodOrbital Period

..

Thin lines shows the evolution when

neglecting the coupling tides-magnetic braking.

→ Important to consider the coupled evolution!

(Repetto & Nelemans 2014, to be submitted )

..

Implementation: Natal Kick such that

postSN(NK) < mx such that RLO within MS time

Blaauw kick + NK ≥ Space Velocity

Results on minimum Natal Kick⋆

Binary NK (km/s)

Nova Oph 77 460

GS 2000+251 20

A0620-00 10

GRS 1124-68 60

XTE J1118+480 80

GRS 1009-45 50

GRO J0422+32 30

⋆ Repetto & Nelemans 2014 , in prep


What happens when the companion is of high-mass?


High-Mass X-ray binary (M⋆ ≈ 15 M⊙)Unlike the Magnetic Braking case, the wind is massive

(M⋆ ≈ 10−8 M⊙/yr)

..Mass-Loss in a wind widens the orbit

This need not be the case if tidal coupling...

..

Angular momentum loss in terms

of decoupling radius rd = γR⋆

dJ⋆

dt=2

3M⋆ω⋆γ2R2⋆ eω ;

dJ⋆

dt=

d

dt(ω⋆)

this gives the spin-down ω⋆|sd = ω⋆(M⋆, γ)


Magnetic Fields

If star is magnetic→ decoupling radius=magnetospheric radius

What are combinations (B, M⋆) such that τSD =ω⋆

ω⋆< τMS?

Lines at constant Mdot

Wind Braking in a BH-HMXB

Once system achieves synchro., every bit of angular momentum

lost from the star is also lost from the orbit: Wind Braking

Synchronization


Conclusions:

Two ways of getting insights into Black Hole Natal Kicks:

POPULATION STUDY:

Our population study of Galactic BH-LMXBs is consistent

with Black Holes receiving high kicks at birth

SINGLE SOURCES STUDY:

We have developed a fast method to trace backwards the

binary evolution of a BH-LMXB. We find evidence for BHs

receiving intermediate/high kicks in at least some of the

cases.

NEXT: Apply the computational method to BH-HMXBs

Thank You!

Tracing Binary Evolution backwards

□ MASS TRANSFER & DETACHED PHASE

(P,M2,MBH)obs?→ (P,M2,MBH)RLO

?→ (P,M2,MBH)postSN

The shrinkage of the companion drives the shrinkage of the

orbit

Mass-radius relation of companion R2 = Mα2

tells us how

much orbit shrinks

P

Pobs=

�M2

M2,obs

�− 12+ 32α


Maximal postSN orbital separation so that RLO within MS time,

for M⋆ = 1.2 M⊙, MBH = 8 M⊙ as a function of eccentricity:

Rap+

VZtides+GW

0.0 0.2 0.4 0.6 0.80102030405060

e

a max

@R �D


Dashed: Low Spin Solid: High Spin


50 100 150 200 250 3000

5

10

15

20

Natal Kick, km�s

DM

,M�


Serena Repetto, Gijs Nelemans, Peter Jonker and Melvyn ...tauris/NS2014/Repetto_BH-kicks.pdf ·...

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