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On the Origin of Hypervelocity Stars

Wahlberg Jansson, Karl LU (2010) In Lund Observatory Examensarbeten ASTK01 20101
Lund Observatory
Abstract
Hypervelocity stars (HVSs) are stars located in the Galactic halo travelling with extremely high speeds. They are produced when a binary approches the supermassive black hole (SMBH) in the Galactic Center (GC) and gets tidally broken up. In this process one of the stars is ejected with high velocity.

The angle between the velocity of the incoming binary and the velocity of the ejected HVS is almost 180◦. Lu et al. (2010) claims that all the HVSs come from two distinctive existing disks of stars by stating that the planar structure of the stars is preserved since
the deflection angle is 180◦.

I derive different properties of HVSs, e.g. the deflection angle and the break-up radii as functions of the SMBH mass, the initial velocity... (More)
Hypervelocity stars (HVSs) are stars located in the Galactic halo travelling with extremely high speeds. They are produced when a binary approches the supermassive black hole (SMBH) in the Galactic Center (GC) and gets tidally broken up. In this process one of the stars is ejected with high velocity.

The angle between the velocity of the incoming binary and the velocity of the ejected HVS is almost 180◦. Lu et al. (2010) claims that all the HVSs come from two distinctive existing disks of stars by stating that the planar structure of the stars is preserved since
the deflection angle is 180◦.

I derive different properties of HVSs, e.g. the deflection angle and the break-up radii as functions of the SMBH mass, the initial velocity of the binary, the ejection velocity, the closest approach of the binary, the binary separation, the stellar radii and the stellar masses. I also discuss what happens to the other star in the binary and the future of the HVSs.

I test the results of Lu et al. (2010) by trying to find combinations of two planes that have a better fit than their results. I also use a larger sample of stars than they do and also I consider the effects of the Galactic potential on the trajectories of the HVSs.

My conclusions are that there exist many more combinations of two planes that fit the origin of the HVSs better than the two existing disks so it is not really possible to claim that the HVSs come from these two disks.

In the final section I discuss what happens if you change some parameters, the SMBH mass and the binary separation, and also how you could extend the project in the future, e.g. if you add post-Newtonian effects and if there is an assymmetric dark matter halo in the Milky Way. (Less)
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author
Wahlberg Jansson, Karl LU
supervisor
organization
course
ASTK01 20101
year
type
M2 - Bachelor Degree
subject
publication/series
Lund Observatory Examensarbeten
report number
2010-EXA43
language
English
id
2171581
date added to LUP
2011-10-03 16:17:39
date last changed
2011-10-03 16:17:39
@misc{2171581,
  abstract     = {Hypervelocity stars (HVSs) are stars located in the Galactic halo travelling with extremely high speeds. They are produced when a binary approches the supermassive black hole (SMBH) in the Galactic Center (GC) and gets tidally broken up. In this process one of the stars is ejected with high velocity. 

The angle between the velocity of the incoming binary and the velocity of the ejected HVS is almost 180◦. Lu et al. (2010) claims that all the HVSs come from two distinctive existing disks of stars by stating that the planar structure of the stars is preserved since
the deflection angle is 180◦. 

I derive different properties of HVSs, e.g. the deflection angle and the break-up radii as functions of the SMBH mass, the initial velocity of the binary, the ejection velocity, the closest approach of the binary, the binary separation, the stellar radii and the stellar masses. I also discuss what happens to the other star in the binary and the future of the HVSs.

I test the results of Lu et al. (2010) by trying to find combinations of two planes that have a better fit than their results. I also use a larger sample of stars than they do and also I consider the effects of the Galactic potential on the trajectories of the HVSs.

My conclusions are that there exist many more combinations of two planes that fit the origin of the HVSs better than the two existing disks so it is not really possible to claim that the HVSs come from these two disks.

In the final section I discuss what happens if you change some parameters, the SMBH mass and the binary separation, and also how you could extend the project in the future, e.g. if you add post-Newtonian effects and if there is an assymmetric dark matter halo in the Milky Way.},
  author       = {Wahlberg Jansson, Karl},
  language     = {eng},
  note         = {Student Paper},
  series       = {Lund Observatory Examensarbeten},
  title        = {On the Origin of Hypervelocity Stars},
  year         = {2010},
}