Michael Hammer Advisor: Dr. Lucie Jílkovámhammer/presentations/LEAPS_pptx.pdf · Michael Hammer...

Michael Hammer Advisor: Dr. Lucie Jílková

Professor Simon Portegies Zwart’s Computational ASTrophysics group at LEiden

(CASTLE)

Stellar Flybys:

Example 1 (of 3) No Disk Loss

Kept Particles: (or )

Transferred Particles: (or )

Completely Unbound:

Nothing has been lost. The disk star has kept all of its particles.

Stellar Flybys:

Example 1 (of 3) No Disk Loss



Completely Unbound:

We are too far away!

Stellar Flybys:

Example 2 (of 3) Some Disk Loss



Completely Unbound:

Let’s go closer!

Yay! Some the disk is lost! Do the lost particles end up unbound? Or are they bound to the other star?

Stellar Flybys:

Example 2 (of 3) Some Disk Loss



Completely Unbound:

Let’s go closer!

ZOOM

Stellar Flybys:

Example 3 (of 3) Transfers?



Completely Unbound:

Follow the other star!

Yay! Particles transfer to the other star!

Stellar Flybys:

Example 3 (of 3) Transfers!!



Completely Unbound:

Follow the other star!

ZOOM

My Project

(1) What types of stellar flybys have transferred particles?

(2) How many particles transfer?

(3) What do the new orbits of the transferred particles look like?

General Questions on Transferred Disk Particles

Transferred Disk Particles in Our Solar System (4) How much of our Kuiper Belt is from a different star system?

(5) Are there specific objects (like Sedna) that definitely were transferred from a different star system?

(6) Has a close stellar flyby occurred in our solar system’s past?

Astrophysical MUltipurpose Software Environment

AMUSE solves all problems

Mass: 1 M¤ Radius: 1 R¤ Position: (0, 0, 0) km Velocity: (0, 0, 0) km/s

Mass: 6 × 1024 kg Radius: 6 × 103 m Position: (2, -9, 0) × 0.1 AU Velocity: (28, 7, 0) km/s

ProtoPlanetaryDisk( ) Disk Mass: 10-10 M¤

# of Disk Particles: 106

Surface Density: e-1.0

Particle Set

[# 3]

[# 2]

[# 1]

Run any type of simulation. Run many types of simulations together.

AMUSE solves all problems:

“Like the Borg assimilating the positive characteristics of everybody to become better as a whole.” --- AMUSE Primer (probably Simon…)

①  Gravitational Dynamics, such as (a) Mercury, (b) Huayno, (c) BH-Tree

②  Hydro Dynamics, such as (a) Fi, (b) Athena, (c) Gadget-2

③  Stellar Evolution, such as (a) SeBa, (b) MESA, (c) EV-TWIN

④  Radiative Transfer, such as (a) SimpleX

SIMULATION BY ASSIMILATION

Combine + Synchronize Existing Codes

Simulation Parameters: Investigate Our Solar System’s Past

Fixed Parameters Two Stars (1) The Sun is the star without a disk. ( 1 M¤ )

(2) The disk particles start with circular orbits (3) The disk extends from 10 AU – 100 AU. Flyby Orbit (4) The flyby occurs in the disk plane ( Inclination = 0° ) (5) The flyby has a Parabolic Orbit. Varied Parameters (1) Mass of Star with Disk ( “m” ) (2) Impact Parameter ( “b” ) (Closest Approach of Flyby)

How many disk particles transfer? (1 of 3)

(A): 1% transferred

m = 2.0 M¤

b = 220 AU

Let’s go closer!

And lower the mass of the star with the disk!


(B): 22% transferred

m = 0.5 M¤

b = 140 AU

Let’s go even closer!!!

And keeping lowering the mass of

the star with the disk!!!


(C): 33% transferred!!

m = 0.25 M¤

b = 100 AU

Transferred Particles (as %)

(For 154 simulations)

Mass of Disk Star

Range ( m )

0.1 M¤

to 3 M¤

Impact Parameter Range ( b ) : 40 AU – 300 AU

33%

22%

1%

(A)

(B)

(C)

How often do really close stellar flybys occur?

Use Math! (For UK people, Use Maths!!)

The Sun was born in a cluster.

We care about flybys near the Sun while it was still in its birth cluster.

The cluster only lasts for 1 million years.* In just 1 million years

(for each solar mass star),

less than 1 flyby will occur within 300 AU.

*Adams, F.C. 2010, ARA&A, 48, 47

Probability of a Really Close Stellar Flyby

Across our entire range of simulations

Range of Impact Parameters ( b )

Odds for a Flyby (in 1 000 000 years)

0 – 100 AU (within the disk)

1 in 150

100 – 300 AU (outside the disk)

1 in 33

Range of Impact Parameters ( b )

Odds for a Flyby (in 1 000 000 years)

0 – 300 AU (range of simulations)

1 in 27

In different ranges of simulations

What types of orbits do the

transferred particles have?

(A): 1% transferred

m = 2.0 M¤

b = 220 AU

①  Transfers mostly contained within 100 AU

②  Eccentricities evenly spread from 0.1 – 0.8

③  This is the exception!



(B): 22% transferred

m = 0.5 M¤

b = 140 AU

①  There are some very high eccentricities > 0.8

②  Most of the orbits have about the same “orientation” angle.



(C): 33% transferred!!

m = 0.25 M¤

b = 100 AU

①  There are some very high eccentricities > 0.8

②  Most of the orbits have about the same “orientation” angle.

Explaining Sedna

This is Sedna.

The Search for Sedna (with ‘q’ )

Closest Approach ( q )

Ecce

ntri

city

( e

cc )

Objects in Outer Solar System*

‘Biden’

*Trujillo, C.A & Sheppard, S.S. Nature 507, 471-474 (2014)

The Search for Sedna (with ‘q’ )


Ecce

ntri

city

( e

cc )

Objects in Outer Solar System*

‘Biden’

‘Biden’

Sedna


m = 0.25 M¤

b = 100 AU

[33%]


The Search for Sedna (with ‘omega’ )

Semi-major axis ( a )

“Orb

it O

rien

tatio

n”

( om

ega

) Objects in Outer Solar System*

‘Biden’

110° (out of 360°)


m = 0.25 M¤

b = 100 AU

[33%]

110° (out of 360°)

The Search for Sedna (with ‘omega’ )


“Orb

it O

rien

tatio

n”

( om

ega

) Objects in Outer Solar System*

‘Biden’

‘Biden’ Sedna


m = 0.25 M¤

b = 100 AU

[33%]


Conclusions

(1) Stellar flybys that are close enough to induce particles to transfer are very rare.

(2) Flybys grazing the edge of another star’s disk can cause up to 40% of particles to transfer.

(3) But many of the transfers have very high eccentricities ( > 0.9 ).

General Conclusions on Transferred Disk Particles

Transferred Disk Particles in Our Solar System (4) At most, only a small % of our Kuiper Belt can be transfers.

(5) If a stellar flyby happened in the past, it could have placed objects like Sedna in their current orbits.

(6) If that is true, where are the even more eccentric particles?

Thank you! Thanks to Leiden University and the Sterrewacht for hosting the LEAPS

program and bringing me to the Netherlands!

Thanks to Lucie for selecting me for this project and advising me throughout the

summer!

Thanks to CASTLE!

Thanks to anyone who showed up for any of today’s LEAPS symposium. Thanks to everyone for a great summer!

Thanks to Benne and Catherine for running the LEAPS program!

The Forgotten Slides

②  Input (and output) not standardized

Problems with Existing Simulation Codes

⑦ Some codes are written in Fortran

①  (too many) Different programming languages used

④ Only handles specific problem (not adaptable)

⑤ Difficult to combine different simulation codes

⑥ Difficult to reuse code for different purposes

③  (very) Poor documentation

Transferred Particles (as %)

(For 154 simulations) in 3D!

Mass of Disk Star

Range ( m )

0.1 M¤

to 3 M¤ Impact Parameter Range ( b ) : 300 AU – 40 AU

Michael Hammer Advisor: Dr. Lucie Jílkovámhammer/presentations/LEAPS_pptx.pdf · Michael Hammer...

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