Dec 13, 2017

Systematic radial velocity monitoring of likely intermediate period post-AGB binaries


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

Dec 12, 2017

Simultaneous observations of HD42659 — The only roAp star in a binary


We will measure the movement of two stars relative to each other to determine if the motion affects short period pulsations.

Dark energy tests with quasar monitoring XI


Cosmology is a science that is extensively investigating the evolution of the Universe by delving into its large-scale structure. Thanks to years of various observations and theoretical efforts, we know that only 5% of the Universe is made up of the well-known atomic matter, while the rest consists of exotic dark matter and dark energy. The presence of the dark energy is the most important puzzle of the present-day cosmology. Its existence and properties should be thus confirmed by many independent methods. Quasars – very luminous centres of active galaxies, which are observed from even very large distances – can serve as important probes of the Universe geometry at redshifts above 1. The key factor here is precise distance measurements to far-away galaxies, which give us evidence that the universal expansion accelerates, so there must be something that pushes it up. For measuring distances, supernovae type Ia have been successfully used as standard candles, but it turns out that also quasars can be as good probes of dark energy by providing independent distance estimates. Thanks to the powerful SALT telescope we are able to carry out very accurate observations of quasar emission lines, and from their behaviour we can then measure distances which are next used in cosmological studies.

Intermediate mass black holes or very massive stars in star-forming galaxies


We are looking for intermediate mass black holes or very massive stars in star-forming galaxies



Everything in the universe warps space – even you, right now, are warping the space around you. This is too tiny to see in everyday objects but entire galaxies are big enough for the warps to be measurable. You can see the warps if you have a chance alignment of a foreground and a background galaxy: the background looks warped and stretched and magnified because of the warped space around the foreground galaxy. However, finding these alignments of foreground and background galaxies has been tricky. We have made a breakthrough and discovered an extremely efficient method of finding these chance alignments of galaxies using the Herschel infrared space telescope. Some galaxies appear to be unexpectedly bright in infrared light, and this is because of the magnification from a foreground galaxy. Our project on SALT aims to measure the distances to these foreground galaxies, so we can work out the geometry of the lenses and make inferences about the geometry of the Universe, the shape of the invisible dark matter, and shed light on why the expansion of the Universe is accelerating.

The Search for New Ultracompact Binary Star Systems in the OmegaWhite Survey IV


Identifying new ultracompact binary star systems through their spectral characteristics

Spectroscopic investigations of Cepheids and stars belonging to Galactic open clusters and associations


Spectroscopic investigations of Cepheids and stars belonging to Galactic open clusters and associations

High-quality spectroscopy to confirm the record-low metallicity of a LSB J0110-0000 in a nearby void


High-quality spectroscopy to confirm the record-low metallicity of a LSB in a nearby void

Dec 11, 2017

Bright southern lambda Boo – type stars


When talking about stars, we very often refer to the Sun which is the most extensively studied star in the sky. In the Universe, however, there are plenty of stars. Some are cooler than the Sun, others are hotter, but for most of them the elemental abundance of the constituent material is very close to solar. There are, however, exceptions. Among stars that are hotter than the Sun, there is a small group of stars called lambda Boo type which are chemically peculiar. Their peculiarity is characterised by moderate to high- surface underabundances of heavy elements like magnesium, aluminium, manganese, nickel or iron and near-solar abundances of carbon, nitrogen, oxygen and sulphur. The origin of these anomalies is not clear. It is generally accepted that lambda Boo stars are young and that their chemical peculiarities result from accretion of metal-poor material from the interstellar medium or from the interaction of the star with protoplanetary disks or planets. However, there is no agreement which of these two theories is correct. We do not know if the chemical peculiarities are limited to the surface or continue into the depth of the stars, and we are not sure if the lambda Boo phenomenon is limited to young stars, as suggested by a lot of observational evidence.The keys to the understanding of the origin, structure, and evolutionary status of lambda Boo stars lie in the studies of high-resolution, high signal-to-noise spectroscopic observations and high-precision photometric data that are planned in this proposal. Our spectroscopic observations will be used by us to derive detailed pattern of abundances of chemical elements in lambda Boo stars. Those will then be used as an input in asteroseismic analysis of the photometric observations which will be delivered by the TESS space mission within a few years.Our study will allow us not only to address the questions of the origin and composition of lambda Boo stars, but also investigate larger problems of formation and evolution of stars , and interactions between stars, planets, and planetary disks.

The Origin and Fate of Very Fast Rotators among Evolved Massive Stars


We will study the consequences of rotation on the determination of mass loss rates, and on the description and onset of clumping.