Related papers: US 708 - An unbound hyper-velocity subluminous O s…

We predict that there is a population of low-luminosity dwarf galaxies orbiting within the halo of the Milky Way that have surface brightnesses low enough to have escaped detection in star-count surveys. The overall count of stealth…

We describe the serendipitous discovery in the spectroscopic data of the Sloan Digital Sky Survey of a star-like object, SDSSJ103913.70+533029.7, at a heliocentric radial velocity of +1012 km/s. Its proximity in position and velocity to the…

We derive new constraints on the mass of the Milky Way's dark matter halo, based on a set of halo stars from SDSS as kinematic tracers. Our sample comprises 2401 rigorously selected Blue Horizontal-Branch (BHB) halo stars drawn from SDSS…

We present observations and analyses of seven Galactic O stars of type O6 and earlier. Analyses are carried out using NLTE plane-parallel, hydrostatic models as well as NLTE spherical models with mass-loss. With detailed calculations for…

We report on the discovery of a high velocity B star, HD 69686. We estimate its space velocity, distance, surface temperature, gravity, and age. With these data, we are able to reconstruct the trajectory of the star and to trace it back to…

We confirm, quantify, and provide a table of the coherent velocity substructure of the Milky Way disk within 2 kpc of the Sun towards the Galactic anticenter, with 0.2 kpc resolution. We use the radial velocities of ~340,000 F-type stars…

The tremendous tidal force that is linked to the supermassive black hole (SMBH) at the center of our galaxy is expected to strongly subdue star formation in its vicinity. Stars within 1" from the SMBH thus likely formed further from the…

NGC 1851 is an intriguing Galactic globular cluster, with multiple stellar evolutionary sequences, light and heavy element abundance variations and indications of a surrounding stellar halo. We present the first results of a spectroscopic…

Hypervelocity stars (HVSs) are a natural consequence of the presence of a massive nuclear black hole (Sgr A*) in the Galactic Center. Here we use the Brown et al. sample of unbound and bound HVSs together with numerical simulations of the…

We present an examination of the metallicity distribution function of the outermost stellar halo of the Galaxy based on an analysis of both local (within 4 kpc of the Sun, ~16,500 stars) and non-local (~21,700 stars) samples. These samples…

This work presents a new detection of H$_2$ absorption arising in a high velocity cloud (HVC) associated with either the Milky Way or the Large Magellanic Cloud (LMC). The absorber was found in an archival Far Ultraviolet Spectroscopic…

We measure the circular velocity curve $v_{\rm c}(R)$ of the Milky Way with the highest precision to date across Galactocentric distances of $5\leq R \leq 25$ kpc. Our analysis draws on the $6$-dimensional phase-space coordinates of…

AIMS: We selected the bluest object, WISE~J0725$-$2351, from Luhman's new high proper motion (HPM) survey based on observations with the Wide-field Infrared Survey Explorer (WISE) for spectroscopic follow-up observations. Our aim was to…

We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We firstly use a large sample of 860 Galactic halo RRLab stars and derive…

We analyse the structure of the local stellar halo of the Milky Way using $\sim$ 60000 stars with full phase space coordinates extracted from the SDSS--{\it Gaia} catalogue. We display stars in action space as a function of metallicity in a…

Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. In this paper, we present an analysis of spectroscopic observations of individual stars from one such…

The hypervelocity stars recently found in the Galactic halo are expelled from the Galactic center through interactions between binary stars and the central massive black hole or between single stars and a hypothetical massive binary black…

PG 1002+506 is found to be a Be star, one of two so far found by the Palomar-Green survey. Its spectrum is classified as a B5 +/- 1 Ve, with Teff = 14,900 +/- 1200, log g = 4.2 +/- 0.2, and v sin i = 340 +/- 50 km/s. At b = +51 degrees, its…

The mass assembly history of the Milky Way can inform both theory of galaxy formation and the underlying cosmological model. Thus, observational constraints on the properties of both its baryonic and dark matter contents are sought. Here we…

We use Hubble Space Telescope imaging to measure the absolute proper motion of the hypervelocity star (HVS) HE 0437-5439, a short-lived B star located in the direction of the Large Magellanic Cloud (LMC). We observe (\mu_\alpha,…