Binary stellar systems form a large fraction of the Galaxy's stars. They are useful as laboratories to study the physical processes taking place within stars, and must be correctly taken into account when using observations of stars to study the structure and evolution of the Galaxy. The advent of large-scale spectroscopic and photometric surveys allows us to obtain large samples of binaries which permit characterisations of their populations.

Paper PDF: 

traven_galah_binaries_arxiv.pdf

The latest Gaia data release enables us to accurately identify stars that are more luminous than would be expected on the basis of their spectral type and distance. During an investigation of the 329 best Solar twin candidates uncovered among the spectra acquired by the GALAH survey, we identified 64 such over-luminous stars. In order to investigate their exact composition, we developed a data-driven methodology that can generate a synthetic photometric signature and spectrum of a single star.

Paper PDF: 

GALAH_triple_sun-like.pdf

The Galactic Archaeology with HERMES (GALAH) survey is a large scale, magnitude limited, southern stellar spectroscopic survey providing spectra, stellar parameters and chemical abundances for stars located in different components of the Galaxy. Random selection, based only on object's brightness and its celestial coordinates, implies that a representative set of peculiar stellar types are observed.

Here we focus on carbon enhanced stars which can be identified by peculiar features present in their GALAH spectra.

Paper PDF: 

GALAH_carbon_enhanced_R2.pdf

Symbiotic binaries (SyB) are composed by a red giant (RG) and a degenerate companion, normally a white dwarf (WD) and in a very few cases a neutron star. In most SyB the WD burns steadily at the surface (Teff ~ 10^5 K and L ~ 10^4 Lsun), ionizing the wind from the RG and giving rise to a rich
emission line spectrum. While the burning phase last for 10^2 - 10^3 yrs, the switch-off period during which the WD refuels by accreting from the RG companion lasts for much longer, with a population proportion
SyB-quiet/SyB-loud >> 1.

Paper PDF: 

paper_Munari.pdf

Peculiar spectra and objects to which they belong are relatively abundant among targets of general all-sky surveys such as GALAH. Detection of such objects is important because the automatic evaluation of their stellar and chemical properties might turn out to be very challenging and therefore introduces a complication in achieving scientific goals such as galactic archaeology.

Paper PDF: 

tSNE_paper_team_review.pdf

We present a neural network autoencoder structure that is able to extract the most important latent spectral features from observed spectra and reconstruct a spectrum from those features. Because of the training process, the network is able to reproduce a spectrum of high signal to noise ratio that does not show any spectral peculiarities. Such generated spectra were used to identify various emission features among spectra acquired by multiple surveys using the HERMES spectrograph. Emission features were identified by a direct comparison of the observed and generated spectrum.

Paper PDF: 

galah_emission-line_stars.pdf