Observations

Jan 14, 2019

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.

Symbiotic stars – important tracers of late evolutionary stages III

2018-1-MLT-005

We propose a large spectroscopic monitoring of a sample of Magellanic symbiotic stars composed of cold red giant stars and hot white dwarfs, which challenge the binary star evolution models because they do not predict their existence. Our proposed observations will allow us to measure the masses of the two stars in the binary system. They will also help us to understand the formation and evolution of these theoretically impossible although existing binaries.

SALT HRS radial velocity monitoring of post-AGB binary stars

2018-2-MLT-007

We are searching for binary stars in some of the most beautiful stellar remnants in the Galaxy.

Deep Spectroscopy of Compact Massive Starbursts at z~0.5

2018-2-SCI-036

We have discovered a rare population of ultra-compact massive starburst galaxies in the final stages of galaxy mergers. Our aim is to use SALT to obtain high quality spectra of ionized hydrogen emission lines in 18 galaxies. These data will enable us to study powerful gas outflows that are driven by the newly formed stars and supernovae. Our goal is to determine whether the outflows carry away enough gas to halt star formation in these galaxies.

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.

Jan 13, 2019

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.

HRS spectroscopy to unveil the parameters of giants in yellow symbiotic systems

2018-2-SCI-021

We propose to obtain high resolution (R~40000) high S/N (~>50) spectra for 20 of so called yellow symbiotic systems using HRS spectrograph in MR mode. The aim of the proposal is to use the red arm HRS spectra to measure abundances of chemical elements using the spectral synthesis. We will employ the method of standard LTE analysis with use of a hydrostatic model atmospheres. We will also look for possible abundance anomalies due to, e.g., former mass transfer pollution. We will use new information about orbital parameters and Gaia DR2 distances to revise and put new constraints on the physical parameters (temperature, luminosity, abundances) of these giants. It seems be very likely that these objects may turn out to have significantly larger diameters, and so be located at longer distances, be significantly colder and more luminous – the bright giants rather than a normal giants.

Symbiotic stars – important tracers of late evolutionary stages III

2018-1-MLT-005

We propose a large spectroscopic monitoring of a sample of Magellanic symbiotic stars composed of cold red giant stars and hot white dwarfs, which challenge the binary star evolution models because they do not predict their existence. Our proposed observations will allow us to measure the masses of the two stars in the binary system. They will also help us to understand the formation and evolution of these theoretically impossible although existing binaries.

SALT HRS radial velocity monitoring of post-AGB binary stars

2018-2-MLT-007

We are searching for binary stars in some of the most beautiful stellar remnants in the Galaxy.

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.