Observations

Aug 14, 2017

Chromospheric Variability from Ultracool Dwarfs

2017-1-MLT-008

Some of the smallest stars have strong magnetic fields that heat small bright regions on their otherwise cool surfaces. Those bright hot regions can be seen by looking at spectra of these stars – they create a strong emission line. We plan to take repeated spectra of the emission lines of these small stars to see how those small, bright regions – and the magnetic fields that cause them – change over the course of a few hours, days, weeks, and months. The different variations over these different time periods will indicate whether these stars are more like the sun or Jupiter.

Unveiling powerful “hidden” black holes: redshifts and characteristics of WISE-selected obscured quasars

2017-1-SCI-056

We are searching for powerful, supermassive black holes in galaxies that are hidden behind dense obscuring clouds of gas and dust and so have been mysterious and difficult find in the past. New infrared observations with the Wide-Field Infrared Survey Explorer (WISE) satellite have allowed us to observe the “heat” from dust heated up by the radiation coming from these powerful black holes, and so identify many thousands of possible hidden supermassive black holes. Observations with SALT will allow us to confirm that these are really black holes, by looking for telltale fluorescent light produced by the black hole lighting up the gas in the their galaxy, and will tell us how far away in the Universe these objects are.

Completing RINGS: the RSS Imaging spectroscopy Nearby Galaxy Survey (Phase II)

2017-1-SCI-022

We will measure the orbital speeds of hydrogen gas cloudsin nearby galaxies like our own Milky Way, and we will use them to derive the total mass distribution of each system. By comparing this mass to those of the gas and the stars in each system, we can map its dark matter content. Our main scientific goal is to compare this dark matter content to theoretical models developed from computer simulations of the evolution of the Universe: are our observationsconsistent with predictions from the standard cosmological model input into the simulations, or is our understanding of cosmology and/or galaxy formation incomplete?

Masses, Orbits, and Merger Rates of Double White Dwarfs

2017-1-SCI-052

Measuring the orbits of double white dwarfs.

Spectroscopic investigation of southern lambda Boo – type stars.

2017-1-SCI-010

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.

Further unravelling the mysterious J1917

2017-1-SCI-025

From analysing the light variations of J1917 we see that the star is not stable, and in fact changes in a way that is not predicted by theory. The observations with SALT will allow us to determine if the star is in a multiple system, which is one of the solutions to the problem of J1917’s light variations.

2017-1 Activity in close-in planet hosts: establishing a homogeneous database

2017-1-SCI-044

We are observing stars with planets orbiting very close to them. Some of these planets complete an orbit around their star in about a day. This means the planets are heated and pulled by the star’s gravity and magnetic field. We are looking at the signatures of that in emission from calcium in the outer layers of the star’s atmosphere.

HRS study of long-period eclipsing binaries: towards the true mass-luminosity relation

2017-1-MLT-001

Study of long-period eclipsing binaries

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

2017-1-MLT-010

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

SALT Supernova Followup

2017-1-MLT-002

Observations of supernovae, near and far.