Search Publications
Architectures of exoplanetary systems - I. A clustered forward model for exoplanetary systems around Kepler's FGK stars
Ford, Eric B.; Ragozzine, Darin; He, Matthias Y.
Observations of exoplanetary systems provide clues about the intrinsic distribution of planetary systems, their architectures, and how they formed. We develop a forward modelling framework for generating populations of planetary systems and `observed' catalogues by simulating the Kepler detection pipeline (SysSim). We compare our simulated catalog…
A giant exoplanet orbiting a very-low-mass star challenges planet formation models
Schmitt, J. H. M. M.; Rebolo, R.; del Burgo, C. +179 more
Surveys have shown that super-Earth and Neptune-mass exoplanets are more frequent than gas giants around low-mass stars, as predicted by the core accretion theory of planet formation. We report the discovery of a giant planet around the very-low-mass star GJ 3512, as determined by optical and near-infrared radial-velocity observations. The planet …
Discovery of an equal-mass `twin' binary population reaching 1000 + au separations
Tian, Haijun; Duchêne, Gaspard; Rix, Hans-Walter +2 more
We use a homogeneous catalogue of 42 000 main-sequence wide binaries identified by Gaia to measure the mass ratio distribution, p(q), of binaries with primary masses 0.1 < M1/M⊙ < 2.5, mass ratios 0.1 ≲ q < 1, and separations 50 < s/au < 50 000. A well-understood selection function allows us to constrain p(q) i…
Spatially Resolved Stellar Kinematics of the Ultra-diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, and Cold Dark Matter Halo Fits
van Dokkum, Pieter; Forbes, Duncan A.; Romanowsky, Aaron J. +8 more
We present spatially resolved stellar kinematics of the well-studied ultra-diffuse galaxy (UDG) Dragonfly 44, as determined from 25.3 hr of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion within the half-light radius is {σ }1/2={33}-3+3 km s-1, lower than what we had infe…
The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science
Geha, M.; Bechtol, K.; Allam, S. +30 more
We introduce the southern stellar stream spectroscopy survey (S5), an on-going program to map the kinematics and chemistry of stellar streams in the southern hemisphere. The initial focus of S5 has been spectroscopic observations of recently identified streams within the footprint of the dark energy survey (DES), with the eve…
The first view of δ Scuti and γ Doradus stars with the TESS mission
Reese, D. R.; Niemczura, E.; Handberg, R. +63 more
We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilize the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung-Russell diagram using Gaia DR2 data. Included within our sample are the epon…
The Galactic WC and WO stars. The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors
Hamann, W. -R.; Oskinova, L. M.; Sander, A. A. C. +4 more
Wolf-Rayet stars of the carbon sequence (WC stars) are an important cornerstone in the late evolution of massive stars before their core collapse. As core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type Ib/c supernovae. Their stro…
Super-efficient Electron Acceleration by an Isolated Magnetic Reconnection
Vaivads, A.; Xu, Y.; Fu, H. S. +1 more
Magnetic reconnection—the process typically lasting for a few seconds in space—is able to accelerate electrons. However, the efficiency of the acceleration during such a short period is still a puzzle. Previous analyses, based on spacecraft measurements in the Earth’s magnetotail, indicate that magnetic reconnection can enhance electron fluxes up …
PHIBSS2: survey design and z = 0.5 - 0.8 results. Molecular gas reservoirs during the winding-down of star formation
Lutz, D.; Wuyts, S.; Förster Schreiber, N. M. +29 more
Following the success of the Plateau de Bure high-z Blue Sequence Survey (PHIBSS), we present the PHIBSS2 legacy program, a survey of the molecular gas properties of star-forming galaxies on and around the star-formation main sequence (MS) at different redshifts using IRAM's NOrthern Extended Millimeter Array (NOEMA). This survey significantly ext…
The Galactic disc in action space as seen by Gaia DR2
Rix, Hans-Walter; Coronado, Johanna; Trick, Wilma H.
The quality and quantity of 6D stellar position-velocity measurements in the second Gaia data release's radial velocity sample (DR2/RVS) allow us to study small-scale structure in the orbit distribution of the Galactic disc beyond the immediate Solar neighbourhood. We investigate the distribution of orbital actions (JR, Lz, J…