Blue Stragglers from Primordial Binary Evolution
(2022) ASTK02 20221Lund Observatory - Undergoing reorganization
- Abstract
- Blue stragglers were first discovered as hotter and more luminous than the turnoff in the globular cluster M3. Their presence is typically explained by the interplay between stellar collisions and mass transfer in binary systems. In this thesis, I study blue stragglers produced from primordial binary evolution. This is done by both reproducing individual blue stragglers, to examine the different formation channels in great detail, but also by reproducing blue straggler populations, using a binary population synthesis, to investigate whether the age and/or metallicity of the population have an impact on their relative frequency. Furthermore, the derived relative frequency is compared with observations of the blue stragglers in the open... (More)
- Blue stragglers were first discovered as hotter and more luminous than the turnoff in the globular cluster M3. Their presence is typically explained by the interplay between stellar collisions and mass transfer in binary systems. In this thesis, I study blue stragglers produced from primordial binary evolution. This is done by both reproducing individual blue stragglers, to examine the different formation channels in great detail, but also by reproducing blue straggler populations, using a binary population synthesis, to investigate whether the age and/or metallicity of the population have an impact on their relative frequency. Furthermore, the derived relative frequency is compared with observations of the blue stragglers in the open cluster M67. The results show that primordial binary evolution form blue stragglers at any time during its evolution, but at different rates. Their relative frequency peaks at around 3-5 Gyr and is generally higher at lower metallicities. Furthermore, I show that the initial semi major axis and eccentricity of the binary determine the formation channel of the blue straggler. Also, that the most massive and luminous blue stragglers originate from the coalescence of contact binaries or large-scale mass transfer in close binary systems. The derived relative frequency of blue stragglers from primordial binary evolution was however too low to agree with observations of M67, indicating that the cluster environment likely was partly responsible for shaping the blue straggler population. (Less)
- Popular Abstract
- Something that can significantly affect a person is its environment, and interactions with other people may change a person’s trajectory of life permanently. The same is true for stars. The sun, for example, exists in a place within our galaxy where it is relatively calm. Stars in our neighborhood are far apart from each other and interactions between stars here are rare. The situation is however quite different in globular stellar clusters: spherical collections of stars that are tightly bound by gravity and are present both in the outer and central parts of our galaxy (Camargo and Minniti, 2019). Here, the density of stars is higher and interactions between them are much more likely. These interactions may affect the evolution of the... (More)
- Something that can significantly affect a person is its environment, and interactions with other people may change a person’s trajectory of life permanently. The same is true for stars. The sun, for example, exists in a place within our galaxy where it is relatively calm. Stars in our neighborhood are far apart from each other and interactions between stars here are rare. The situation is however quite different in globular stellar clusters: spherical collections of stars that are tightly bound by gravity and are present both in the outer and central parts of our galaxy (Camargo and Minniti, 2019). Here, the density of stars is higher and interactions between them are much more likely. These interactions may affect the evolution of the stars.
One way to study the effects of these interactions is by looking at blue stragglers. In short, a blue straggler is a star that appears younger than the rest of the stars in the stellar cluster within which they reside. Stars in stellar clusters are believed to have been form out of the same gas cloud, which results in them being born at approximately the same time, hence making the blue stragglers stick out from the rest. Blue stragglers can form by two routes: through stellar collisions or by mass transfer between stars in binary systems: systems with two stars that are gravitationally bound and orbit each other. If the stellar density is high, it becomes more probable that a third star interacts with the binary system which might break it up, thus reducing the possibly for a blue straggler to form. On the other hand, in these environment stellar collisions are more common, which might enhance the blue straggler production.
The aim of my project is to study blue stragglers formed by mass transfer in binary systems in isolation, i.e. where the system is not affected by its environment. I will measure how commonly they form and how long they live. The results can then be compared to the M67 stellar cluster, where a total of 28 blue stragglers have been observed (Hurley et al., 2005), to see whether the derived number of blue stragglers is in agreement with observations, or if it is necessary to include the effects of the cluster environment to match observations. Answering these questions would enable a better understanding of how cluster environments and mass transfer can alter stellar evolution. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9088342
- author
- Desrochers Karlsson, Emilie LU
- supervisor
-
- Ross Church LU
- organization
- alternative title
- Blue stragglers from mass transfer in binary star systems
- course
- ASTK02 20221
- year
- 2022
- type
- M2 - Bachelor Degree
- subject
- keywords
- blue stragglers, binary, stars, binary evolution, mass transfer
- report number
- 2022-EXA189
- language
- English
- id
- 9088342
- date added to LUP
- 2022-08-11 11:45:10
- date last changed
- 2022-08-11 11:45:10
@misc{9088342,
abstract = {{Blue stragglers were first discovered as hotter and more luminous than the turnoff in the globular cluster M3. Their presence is typically explained by the interplay between stellar collisions and mass transfer in binary systems. In this thesis, I study blue stragglers produced from primordial binary evolution. This is done by both reproducing individual blue stragglers, to examine the different formation channels in great detail, but also by reproducing blue straggler populations, using a binary population synthesis, to investigate whether the age and/or metallicity of the population have an impact on their relative frequency. Furthermore, the derived relative frequency is compared with observations of the blue stragglers in the open cluster M67. The results show that primordial binary evolution form blue stragglers at any time during its evolution, but at different rates. Their relative frequency peaks at around 3-5 Gyr and is generally higher at lower metallicities. Furthermore, I show that the initial semi major axis and eccentricity of the binary determine the formation channel of the blue straggler. Also, that the most massive and luminous blue stragglers originate from the coalescence of contact binaries or large-scale mass transfer in close binary systems. The derived relative frequency of blue stragglers from primordial binary evolution was however too low to agree with observations of M67, indicating that the cluster environment likely was partly responsible for shaping the blue straggler population.}},
author = {{Desrochers Karlsson, Emilie}},
language = {{eng}},
note = {{Student Paper}},
title = {{Blue Stragglers from Primordial Binary Evolution}},
year = {{2022}},
}