Search Publications
Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint
Marchetti, L.; Vaccari, M.; Baker, A. J. +12 more
Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by Agnello & Spiniello (2018) within the Dark Energy Survey public footprints. We have conducted…
A laboratory-based dielectric model for the radar sounding of the martian subsurface
Thomas, Nicolas; Becerra, Patricio; Pommerol, Antoine +2 more
For the last decade, the SHARAD radar on board NASA's Mars Reconnaissance Orbiter, and the MARSIS radar on board ESA's Mars Express, have sounded the surface and subsurface of Mars from orbit to search for and characterise water ice reservoirs. When associated with dielectric models, the regolith composition (in terms of dust, ice and voids) of th…
Probing the fluctuating ultraviolet background using the Hubble Frontier Fields
Dayal, Pratika; Choudhury, Tirthankar Roy
In recent years, the rise in the number of Lyman Break Galaxies detected at high redshifts z ≥ 6 has opened up the possibility of understanding early galaxy formation physics in great detail. In particular, the faint-end slope (α) of the ultraviolet luminosity function (UV LF) of these galaxies is a potential probe of feedback effects that suppres…
The mean rotation rate of Venus from 29 years of Earth-based radar observations
Campbell, Donald B.; Margot, Jean-Luc; Nolan, Michael C. +7 more
We measured the length of the Venus sidereal day (LOD) from Earth-based radar observations collected from 1988 to 2017, using offsets in surface feature longitudes from a prediction based on a 243.0185d period derived from analysis of Magellan mission images over a 487-day interval. We derive a mean LOD over 29 years of 243.0212 ± 0.0006d. Our res…
Direct measurement of stellar angular diameters by the VERITAS Cherenkov telescopes
Benbow, W.; Bird, R.; Brose, R. +54 more
The angular size of a star is a critical factor in determining its basic properties1. Direct measurement of stellar angular diameters is difficult: at interstellar distances stars are generally too small to resolve by any individual imaging telescope. This fundamental limitation can be overcome by studying the diffraction pattern in the…
Current sheets in planetary magnetospheres
Delcourt, Dominique; Zelenyi, Lev; Malova, Helmi +2 more
In this article we aim to highlight the problems related to the structure and stability of the comparatively thin current sheets that were relatively recently discovered by space missions in the magnetospheres of the Earth and planets, as well as in the solar wind. These magnetoplasma structures are universal in collisionless cosmic plasmas and ca…
Asymmetric Mean Metallicity Distribution of the Milky Way’s Disk
An, Deokkeun
I present the mean metallicity distribution of stars in the Milky Way based on photometry from the Sloan Digital Sky Survey. I utilize an empirically calibrated set of stellar isochrones developed in previous work to estimate the metallicities of individual stars to a precision of 0.2 dex for reasonably bright stars across the survey area. I also …
Formation of Transition Alumina Dust around Asymptotic Giant Branch Stars: Condensation Experiments using Induction Thermal Plasma Systems
Tsuchiyama, Akira; Takigawa, Aki; Kim, Tae-Hee +5 more
Mid-infrared spectroscopic observations of oxygen-rich asymptotic giant branch (AGB) stars show the common presence of dust species that have a broad feature at ∼11-12 µm. Chemically synthesized amorphous alumina (Al2O3) is widely accepted as the source of this emission, although it is not obvious that amorphous alumina…
CPD-64°2731: a massive spun-up and rejuvenated high-velocity runaway star
Katkov, I. Y.; Gvaramadze, V. V.; Castro, N. +4 more
We report the results of our study of the high-velocity ({≈ }160 km s^{-1}) runaway O star CPD-64°2731 and its associated horseshoe-shaped nebula discovered with the Wide-field Infrared Survey Explorer. Spectroscopic observations with the Southern African Large Telescope and spectral analysis indicate that CPD-64°2731 is a fast-rotating main-seque…
A survey for high-mass eclipsing binaries
Chini, R.; Hackstein, M.; Pozo Nuñez, F. +4 more
We report results from a search for Galactic high-mass eclipsing binaries. The photometric monitoring campaign was performed in Sloan r and i with the robotic twin refractor RoBoTT at the Universitätssternwarte Bochum in Chile and complemented by Johnson UBV data. Comparison with the SIMBAD data base reveals 260 variable high-mass stars. Based on …