Observations

Dec 13, 2018

The Lithium Abundance of the Large Magellanic Cloud

2018-2-SCI-006

The creation of the first chemical elements, which took place just minutes after the Big Bang, provides an intimate view of the physical laws that governed our Universe during its first moments. At present, the Standard Model of cosmology and particle physics is unable to fully explain the relative abundance of these primordial elements. In particular, there is a significant disagreement between the measured and predicted abundance of lithium. We propose to conduct a novel survey that will provide a new, reliable measure of the lithium abundance of gas clouds in a nearby galaxy.

Detailled study of CEMP stars identified in the RAVE survey

2017-1-MLT-012

We are observing around 120 stars that are among the oldest in our Galaxy. Determining their chemical composition will allow us to understand what happened during the first billion years of the Universe

Monitoring the line emission in Southern Galactic Be/X-ray binaries

2017-1-MLT-004

Lines arising from the disc of material around Be/X-ray binaries are highly variable on multiple timescales. The variability seen is intimately linked to the mass transfer and resulting X-ray emission seen in such systems, though the details of this link are still not well understood. We are monitoring these lines with SALT/RSS to see how they change during periods of differing X-ray activity and at different points around their orbits.

Dynamics and Star Formation Histories in Groups Hosting Radio Galaxies

2018-1-SCI-046

We are using SALT to understand how the environment in which galaxies reside influences how they evolve.

Magellanic Cloud Nova Shells

2018-2-SCI-014

When novae erupt, the white dwarf in a close binary system ejects about an Earth-mass of hydrogen gas at speeds of a few thousand km/sec. About half of those ejected shells are seen decades later as glowing, expanding blobs of gas, but half are not. We’re surveying the Magellanoc Clouds to determine why some shells become visible, while others don’t.

Observing the Transient Universe

2018-2-LSP-001

This large SALT program is aimed at studying “things that go bang in the night”, namely transient objects in the Universe which either are newly discovered objects, or known objects who suddenly change their appeatance. Such things include binary stars with accreting compact companions, many of them X-ray or gamma ray sources, eruptive stars which suddenly brighten, black holes systems, including active galaxies powered by them, and all manner of explosions including the most energetic of all, gamma ray bursts.

Dec 12, 2018

The Lithium Abundance of the Large Magellanic Cloud

2018-2-SCI-006

The creation of the first chemical elements, which took place just minutes after the Big Bang, provides an intimate view of the physical laws that governed our Universe during its first moments. At present, the Standard Model of cosmology and particle physics is unable to fully explain the relative abundance of these primordial elements. In particular, there is a significant disagreement between the measured and predicted abundance of lithium. We propose to conduct a novel survey that will provide a new, reliable measure of the lithium abundance of gas clouds in a nearby galaxy.

Dark energy tests with quasar monitoring XII

2018-1-MLT-004

Cosmological measurements show that only 5% of the Universe is made up of the well-known atomic matter, while the rest consists of exotic dark matter and even more exotic dark energy. The nature of this dark energy is unknown, physicists proposed hundreds of theories what it might be but the current observational constraints are still consistent with the cosmological constant proposed by Einstein. This is not enough to constrain the physical nature of the dark energy. Thus the goal of the present day cosmology is to detect the departure of the dark energy properties from this constant value. This requires further progress in the currently adopted methods, like the study of the Cosmic Microwave Background, or the Supernova Ia. But it also requires designing new cosmological tools to verify the results, and to achieve even greater accuracy.We propose that quasars can be as good probes of dark energy as Supernova Ia and provide independent distance estimates. Quasars are very luminous centres of active galaxies, which are observed from very large distances. Thanks to the powerful SALT telescope we are able to carry out very accurate observations of quasar emission lines, and from their behaviour, combined with the model of the line emission we developed, we can measure directly the absolute luminosity of every observed quasar, and subsequently to measure distances which are next used in cosmological studies. This in turn constraints the history of the Universe expansion, and the properties of the dark energy which is responsible for accelerated expansion.

Extending the sample of classical Cepheids with accurately determined physical parameters

2018-1-MLT-007

Classical Cepheids are ones of the most important objects in the astrophysics. They are the key objects for the calibration of the distance scale in the universe and determination of the Hubble constant. Yet our knowledge on them was quite poor. Only recently we have started to get to know more about the physical properties of these stars. The breakthrough came with the discovery of classical Cepheids in eclipsing binary systems, which let us determine very precisely such important parameters like mass or size of the star. The observed Cepheid is important because it has the period longer than any other Cepheid in a binary system analyzed before. The wide range of periods of analyzed Cepheids means better sample for statistical analysis.

Asymmetry is Destiny: Wolf-Rayet Binary Stars as GRB Progenitors

2018-2-MLT-005

This program aims to use the recently-commissioned high-precision spectropolarimetry mode of RSS to probe the prodigious mass-loss from certain massive evolved stars known as Wolf-Rayet stars which are in binary systems. These objects are possible progenitors of Gamma-Ray Bursts, which are the most energetic explosions yet known, and can be seen across the entire known universe.