The ESA Gaia astrometric mission and deep photometric surveys have revolutionized our knowledge of the Milky Way. There are many ongoing efforts to search these data for substructure to find evidence of individual accretion events that built up the Milky Way and its halo. One of these newly identified features, called Nyx, was announced as an accreted stellar stream traveling in the plane of the disk.

Paper PDF: 

Nix_on_Nyx.pdf

We explore the fundamental relations governing the radial and vertical velocity dispersions of stars in the Milky Way. We determine stellar age estimates from combined studies of complementary surveys including GALAH, LAMOST, APOGEE, and the NASA Kepler and K2 missions, and obtain parallax and proper motion from {\it Gaia} DR2. We find that stellar samples from these surveys, even though they target different tracer populations and employ a variety of age estimation techniques, follow the same set of fundamental relations.

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veldisp_mw.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

Gaia DR2 has revealed substructures in the phase space distribution of stars in the Milky Way. In particular, ridge like structures can be seen in the (R,V_phi) plane and asymmetric arches in (V_R, V_phi) plane. We show that the ridges are also clearly present when the (R,V_phi) plane is mapped by , ,, <|z|>,[Fe/H] and [alpha/Fe]. The last three maps suggest that stars along the ridges lie preferentially close to the Galactic midplane (|z|<0.2 kpc), and, have metallicity and alpha elemental abundance similar to that of the Sun.

Paper PDF: 

Linking_ridges__arches_and_vertical_waves_in_the_kinematics_of_the_Milky_Way.pdf

Context: If the Galaxy is axisymmetric and in dynamical equilibrium, we expect negligible fluctuations in the residual line-of-sight velocity field. However, non-axisymmetric structures like a bar, spiral arms and merger events can generate velocity fluctuations. Recent results using the APOGEE survey claim significant fluctuations in velocity for stars in the mid plane (|z|<0.25 kpc) out to 5 kpc and suggest that the dynamical influence of the Milky Way's bar extends out to the Solar neighborhood.

Paper PDF: 

Khanna_velfluc_MW.pdf

We present a study using the second data release of the GALAH survey of stellar parameters and elemental abundances of 15 pairs of stars identified by Oh et al. They identified these pairs as potentially co-moving pairs using proper motions and parallaxes from Gaia DR1. We find that 11 very wide (>1 pc) pairs of stars do in fact have similar Galactic orbits, while a further four claimed co-moving pairs are not truly co-orbiting.

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sty3042.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