The mass loss and death of massive stars

Lead Research Organisation: Armagh Observatory
Department Name: Astronomy

Abstract

Massive stars are important objects in astronomy for a number of reasons. Because of their brightness (up to a million times that of the Sun), they can be seen out to large distances, offering a glimpse of the Universe in our distant past. Massive stars possess strong outflows, and die spectacularly as supernovae and gamma-ray bursts - the most energetic cosmic explosions since the Big Bang. Due to these outflows and explosions, massive stars are thought to trigger star formation in galaxies throughout the Universe. They are also responsible for the chemical enrichment of the Universe. As the big bang only produced hydrogen and helium, the heavy elements, such as carbon, nitrogen, oxygen - critical for forming life - were synthesised in the cores of massive stars, and are returned to the surrounding medium through mass loss and explosions. The prime goal of the proposed project is to predict the amount of mass loss throughout the Universe, as it is this property that determines the life and death of a massive star. Although the life of solar-type stars is driven by the physical process of hydrogen burning in their cores, the life path of a massive star is largely dominated by mass loss. For instance, an object as massive as 60 times the mass of the Sun, will only end up with 6 times the mass of the Sun before it explodes. The amount of outflow however depends critically on the chemical environment. Our models have been shown to be successful in predicting the mass-loss properties in the Milky Way, but we now wish to extend our models to the early Universe. We will develop, test, and apply the new massive star models to map the strength of the outflow, their path to death, and the way they die. We will determine the final stellar masses and mass boundaries for the formation of neutron stars and black holes. The predictions will be extended to stars representative for conditions in the early Universe, when the cosmos contained no elements heavier than hydrogen and helium, and we will determine whether these objects make neutron stars or black holes and how they explode as supernovae or gamma-ray bursts. Current state-of-the-art models do not take mass-loss into account in a realistic way. Our models use the actual presence of the individual chemical elements - recently been shown to be of paramount importance for objects in the early Universe - and will bring the state-of-the-art to a new level. During the course of the programme, we will predict both the direct chemical enrichment by stellar outflows, and set constraints on their fate. Using both ingredients allows us - for the very first time to provide meaningful predictions for the chemical build-up of the early Universe.

Publications

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Justham Stephen (2014) Luminous Blue Variables and Superluminous Supernovae from Binary Mergers in The Astrophysical Journal

 
Description We found that black hole masses were higher in the early Universe than they are today. We also predicted that energetic gamma-ray bursts (GRBs) were more common at earlier times.
We have discovered that the most massive stars in the Universe have significantly larger rates of mass loss than previously held possible. This will have major consequences for both the stellar upper-mass limit, and the most massive black holes that can be discovered by gravitational waves.
Exploitation Route The prediction that stellar-type black holes are larger in low metallicity environments, representative of the Early Universe,
is of key importance to researchers in gravitational wave research.
Our finding are most suitable for Outreach purposes, as the general public is fascinated by Black Holes.
Sectors Aerospace, Defence and Marine,Education,Culture, Heritage, Museums and Collections,Other

URL http://adsabs.harvard.edu/abs/2013arXiv1302.2021V
 
Description The results of the project have been published in major astronomical and astrophysical journals, such as the Monthly Notices of the Royal Astronomical Society, the Astrophysical Journal, and Astronomy and Astrophyiscs. The results have been presented at major international conferences, such as the General Assembly of the International Astronomical Union (IAU). They have been used for outreach and educational purposes, through talks to e.g. the Irish Amateur Astronomical Society and the supervision of (PhD) students.
First Year Of Impact 2010
Sector Education,Culture, Heritage, Museums and Collections
Impact Types Cultural,Societal

 
Description Acting Director Armagh Planetarium 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Armagh Planetarium attracts >40,000 visitors a year, most of them primary school students.
Through the management of the Planetarium, Dr Vink was able to purchase relevant Digital shows for the Planetarium relevant to the massive star research
performed in Armagh. For instance, Black Holes are very popular with the public.
Year(s) Of Engagement Activity 2015,2016