Sep 19, 2019

SALT HRS radial velocity monitoring of post-AGB binary stars


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

Observing the Transient Universe


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.

Sep 18, 2019

TESSting the interior structures of supernova progenitors


Just as we know the interior structure of the Earth from the analysis of earthquakes, astronomers use stellar oscillations – “starquakes” to sound the inner life of the stars. Very precise measurements, such as from the upcoming NASA mission TESS, are required for this effort. The present project uses stellar spectral from SALT to characterize some targets for TESS, stars which are highly interesting because they are tomorrow’s supernovae.

Monitoring candidate Be+white dwarf binaries in the Magellanic Clouds


We are obtaining spectra of a new class of very massive, hot and energetic binaries that contain amassive star with a disk around it, and a white dwarf of high mass that appears to be sporadicallyigniting nuclear fusion.

Magellanic Clouds Nova Shells/Imaging and Spectroscopy


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 Magellanic Clouds to determine why some shells become visible, while others don’t.

Searching for new chemically peculiar stars in the southern hemisphere


We aim at looking for new chemically peculiar stars (CPs) among southern late B-type stars. The region of the Main Sequence centered on early A and late B stars, also referred to as the “tepid stars”, represents an ideal laboratory to study a wide variety of physical processes that are at work in most stellar types. These processes include radiation driven diffusion, differential gravitational settling, and magnetic fields. While their observable manifestation is particularly prominent in tepid stars, some or all of them do play a significant role in the physics, formation, and evolution of most stars. Among the tepid stars, one identifies chemically peculiar objects, that have characteristic surface abundance patterns, strength and structure of the magnetic field, rotation, and multiplicity. For instance, the classical magnetic Bp-Si stars and the HgMn stars result from different formation and evolution scenarios. Their study allows to gain insight into the above-mentioned physical processes.

SALT HRS radial velocity monitoring of post-AGB binary stars


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

Spectroscopic observations of four candidate post-binary interaction products


Spectroscopic observations of four candidate post-binary interaction products

Sep 17, 2019

Long period near-contact giant eclipsing binary candidates


Very little is known about binary star mergers. In 2008, a binary star that merged to become a single star, V1309 Scorpii, was observed. We have identified several similar binary stars which may comprise two red giant stars that are on the brink of merging – they orbit each other so closely that they are almost touching. Spectroscopic observations of some of these objects will be made using SALT, with the aim of measuring the masses of the stars and so confirming their nature. These observations will give us the opportunity to identify and characterise binary mergers before they merge, allowing us to advance our understanding of so-called red novae.

Surface Chemistry of Peculiar Hot Subdwarfs


Stars approaching the end of their lives expand and, in many cases, exchange material with close companions. This has a radical effect on their evolution and surface composition, producing a zoo of rare but highly exotic stars. By exploring the propertiesof thes pathological cases, we are endeavouring to understand the ways in which stars exhange matter and evolve towardstheir final fate as white dwarfs or supernovae. The stars in this programme are perfect examples — many of them have completelylost their surface hydrogen, for reasons still to be explained. These observations will tell us about the abundances of otherelements — previously we have discovered huge overabundances of exotic species such as lead and zirconium, and will explore how some of these stars may vary over time.