The visibility of stellar transients in the Galactic Centre
(2024) ASTK03 20232Astrophysics
Department of Physics
- Abstract
- A semi-analytical simulation was developed to evaluate the K-band magnitudes of Red Giants [0.96 - 1.02 M⊙] orbiting the supermassive black hole in the galactic centre. The model assumed star formation between 10-12 Gyrs ago and by following the IMF and applying a random age condition, a stellar population was created. It was established that stars with mK ≤ 16 can be observed and then they become too faint and difficult to observe. The magnitude means that Red Giants on and beyond the Red Clump phase are observable, which means only 12% of a total population of Red Giants can be observed.
Secondly mass transfers between the remnants of a Red Giant and a Red Giant star can happen as the dense core passes through the envelope of the star.... (More) - A semi-analytical simulation was developed to evaluate the K-band magnitudes of Red Giants [0.96 - 1.02 M⊙] orbiting the supermassive black hole in the galactic centre. The model assumed star formation between 10-12 Gyrs ago and by following the IMF and applying a random age condition, a stellar population was created. It was established that stars with mK ≤ 16 can be observed and then they become too faint and difficult to observe. The magnitude means that Red Giants on and beyond the Red Clump phase are observable, which means only 12% of a total population of Red Giants can be observed.
Secondly mass transfers between the remnants of a Red Giant and a Red Giant star can happen as the dense core passes through the envelope of the star. The result will be a ”fuzzball” with observable properties. It showed that larger radius is more important than higher temperature at the region where the envelope is just bound. However after the thermal time scale has passed, the fuzzballs apparent K-band magnitude increases as its luminosity decreases, hence decreasing their observability. This in combination with their cooler temperature and decrease in luminosity would be one way to differentiate them from Red Giants.
It was concluded that if the G2, a stellar gas cloud, orbiting the supermassive black hole is a fuzzball, then it should have a black hole core and be older than 100 000 years since its observed magnitude is higher than expected for the fuzzball model. (Less) - Popular Abstract
- Out there spread all over the night sky are an uncountable amount of stars with a vast range of sizes and properties. They can be redder or they can be bluer, and some are brighter while others can be fainter. The fainter they are, the more difficult they are to observe. The stellar evolution of a star is a long process that can span tens of billions of years. Stars start off in the main sequence phase, where nothing really happens for a few billions of years. The majority of its lifetime is during that stage. When most of its core has been consumed, it becomes more violent, begins to expand and starts changing phase. Turning into a different type of star, and the focus of this paper. Instead of being blueish, it changes colour towards... (More)
- Out there spread all over the night sky are an uncountable amount of stars with a vast range of sizes and properties. They can be redder or they can be bluer, and some are brighter while others can be fainter. The fainter they are, the more difficult they are to observe. The stellar evolution of a star is a long process that can span tens of billions of years. Stars start off in the main sequence phase, where nothing really happens for a few billions of years. The majority of its lifetime is during that stage. When most of its core has been consumed, it becomes more violent, begins to expand and starts changing phase. Turning into a different type of star, and the focus of this paper. Instead of being blueish, it changes colour towards red. Conveniently this phase is named the ”Red Giant phase” They continue to grow over their lifetime, becoming brighter as time passes and can be up to a few hundred times larger than our sun. The larger a Red Giant is, the brighter it is. This makes it also easier to observe on the night sky. Interestingly this will eventually happen to our own sun, until it can’t grow any larger and collapses in on itself.
What will remain is a dense core. Because there are so many stars in the galactic center, sometimes a Red Giant collides with a core, transferring some of its mass to it, creating a large cover around the core called ”fuzzball”. When such a collision happen, the fuzzball could be observable because of its enormous size. By finding out how the fuzzball changes with time, it is possible to also see how its visibility changes.
This academic project centers on the topic of ”The Visibility of Stellar Transients in the Galactic Center.” Our galaxy, the Milky Way circles a Supermassive Black hole in the very center of our galaxy, roughly 8000 parsec away. Although due to the heavy amount of thick dust and gas clouds between us and the center, it is impossible to see with your own eyes. Even with the best telescopes, and imaging in infra red light, it is still difficult to see deep within our galaxy. Unfortunately technology hasn’t advanced far enough for us to simply look towards the center and see these violent Red Giants or fuzzballs without difficulties. It is only at a certain stage of their lifetime we are able to observe them. To find out when, I have implemented a computer simulation. By tracking the stellar evolution of the red giants orbiting the Supermassive Black Hole, we get a set range of different stages they can be in. The closer they are to the end of their lifetime, the brighter it appears to be, and the easier it would be to observe them.
This methodical approach is to learn at what stages Red Giants must be in order to be observable in the Galactic Center, and how such a collision between the Red Giant and a dense core would be observable. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9149411
- author
- Ström, Jonathan LU
- supervisor
-
- Ross Church LU
- organization
- course
- ASTK03 20232
- year
- 2024
- type
- M2 - Bachelor Degree
- subject
- report number
- 2024–EXA221
- language
- English
- id
- 9149411
- date added to LUP
- 2024-03-07 13:03:40
- date last changed
- 2024-03-07 13:03:40
@misc{9149411,
abstract = {{A semi-analytical simulation was developed to evaluate the K-band magnitudes of Red Giants [0.96 - 1.02 M⊙] orbiting the supermassive black hole in the galactic centre. The model assumed star formation between 10-12 Gyrs ago and by following the IMF and applying a random age condition, a stellar population was created. It was established that stars with mK ≤ 16 can be observed and then they become too faint and difficult to observe. The magnitude means that Red Giants on and beyond the Red Clump phase are observable, which means only 12% of a total population of Red Giants can be observed.
Secondly mass transfers between the remnants of a Red Giant and a Red Giant star can happen as the dense core passes through the envelope of the star. The result will be a ”fuzzball” with observable properties. It showed that larger radius is more important than higher temperature at the region where the envelope is just bound. However after the thermal time scale has passed, the fuzzballs apparent K-band magnitude increases as its luminosity decreases, hence decreasing their observability. This in combination with their cooler temperature and decrease in luminosity would be one way to differentiate them from Red Giants.
It was concluded that if the G2, a stellar gas cloud, orbiting the supermassive black hole is a fuzzball, then it should have a black hole core and be older than 100 000 years since its observed magnitude is higher than expected for the fuzzball model.}},
author = {{Ström, Jonathan}},
language = {{eng}},
note = {{Student Paper}},
title = {{The visibility of stellar transients in the Galactic Centre}},
year = {{2024}},
}