Observations

Nov 13, 2019

Long term programme: searching for new chemically peculiar stars in the southern hemisphere

2019-2-SCI-011

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.

Chemically peculiar Am stars observed by TESS satellite

2019-2-SCI-007

We apply for high-resolution and high-signal-to-noise spectra of chemically peculiar bright Am stars observed by the TESS mission. The detailed analysis of these spectra will allow us to determine atmospheric parameters, chemical composition, and projected rotational velocities of the proposed targets. We will also identify spectroscopic double-lined binary stars in our sample. This information is necessary to fully understand the TESS satellite observations of these stars. The precise photometric time series gathered by TESS will help us answer several questions regarding the incidence of pulsations in Am stars, dependence of pulsation characteristics on atmospheric parameters, chemical abundances, and projected rotational velocities. Moreover, the analysis of the TESS photometric data supplemented with the results of spectroscopic analysis are the necessary ingredients of stellar seismology, the only method allowing us to understand the inner structure of a star.

Surface Chemistry of Peculiar Hot Subdwarfs

2019-1-MLT-003

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.

Nov 12, 2019

Fornax A: optical spectroscopy of multi-phase gas detected in H-alpha and MeerKAT HI observations

2019-2-MLT-002

Fornax A is a group of galaxies (surrounding NGC1316 – a bright radio galaxy) currently falling into the Fornax Cluster. We have recently detected several gas-rich galaxies as well as gaseous features in the group in MeerKAT HI (commissioning) data, and in new H-alpha observations. With optical spectroscopy, we can now probe the ionisation mechanisms of this multi-phase gas to learn more about the transformations in galaxies as well as the interaction with the interstellar medium as the group falls into the cluster.

Long term programme: searching for new chemically peculiar stars in the southern hemisphere

2019-2-SCI-011

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.

HRS spectra of pulsating Algols from TESS

2019-2-SCI-048

Algols are binary (double) stars that “waltz” with each other about their common centre of mass, in very close orbits. While doing so, the stars can transfer material to each other, from time to time. We can learn a lot about the way stars evolve by watching this process occur with telescopes. In this project, we will also explore how these stars vibrate (like musical instruments), to learn more about the physical processes occurring in these stars.

Nov 11, 2019

Polarimetry tests and standards

2016-2-COM-001

Testing the polarimetry modes of the main spectrograph, RSS.

Fornax A: optical spectroscopy of multi-phase gas detected in H-alpha and MeerKAT HI observations

2019-2-MLT-002

Fornax A is a group of galaxies (surrounding NGC1316 – a bright radio galaxy) currently falling into the Fornax Cluster. We have recently detected several gas-rich galaxies as well as gaseous features in the group in MeerKAT HI (commissioning) data, and in new H-alpha observations. With optical spectroscopy, we can now probe the ionisation mechanisms of this multi-phase gas to learn more about the transformations in galaxies as well as the interaction with the interstellar medium as the group falls into the cluster.

Long term programme: searching for new chemically peculiar stars in the southern hemisphere

2019-2-SCI-011

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.

HRS monitoring of yellow symbiotic systems

2019-1-MLT-008

We propose to obtain high resolution (R~40000) high S/N (≳50) spectra for two dozens of so called yellow symbiotic systems using HRS spectrograph in MR mode. The aim of the proposal is to use HRS spectra for the radial velocity monitoring and to measure abundances of chemical elements. Radial velocities will be derived through cross-correlation technique. Abundances will be measured using the spectral synthesis employing the method of standard LTE analysis. We will also look for possible abundance anomalies due to, e.g., former mass transfer pollution. We expect to obtain new information about orbital parameters of these systems. Using it together with new Gaia DR2 distances we are going 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