Search Publications
The origin of the Gaia phase-plane spiral
Binney, James; Schönrich, Ralph
A simple model is presented of the formation of the spiral in the (z, vz) phase plane of solar-neighbourhood stars that was recently discovered in Gaia data. The key is that the frequency Ωz at which stars oscillate vertically depends on angular momentum about the z-axis in addition to the amplitude of the star's vertical osc…
The internal rotation of globular clusters revealed by Gaia DR2
van der Marel, R. P.; Bellini, A.; Libralato, M. +5 more
Line-of-sight kinematic studies indicate that many Galactic globular clusters have a significant degree of internal rotation. However, three-dimensional kinematics from a combination of proper motions (PMs) and line-of-sight velocities are needed to unveil the role of angular momentum in the formation and evolution of these old stellar systems. He…
The evolution of surface magnetic fields in young solar-type stars II: the early main sequence (250-650 Myr)
Donati, J. -F.; Petit, P.; Vidotto, A. A. +6 more
There is a large change in surface rotation rates of sun-like stars on the pre-main sequence and early main sequence. Since these stars have dynamo-driven magnetic fields, this implies a strong evolution of their magnetic properties over this time period. The spin-down of these stars is controlled by interactions between stellar and magnetic field…
Evidence for a variable Ultrafast Outflow in the newly discovered Ultraluminous Pulsar NGC 300 ULX-1
Fabian, A. C.; Pinto, C.; Bachetti, M. +5 more
Ultraluminous pulsars are a definite proof that persistent super-Eddington accretion occurs in nature. They support the scenario according to which most Ultraluminous X-ray Sources (ULXs) are super-Eddington accretors of stellar mass rather than sub-Eddington intermediate mass black holes. An important prediction of theories of supercritical accre…
Retrieval of planetary and stellar properties in transmission spectroscopy with AURA
Madhusudhan, Nikku; Apai, Dániel; Rackham, Benjamin V. +1 more
Transmission spectroscopy provides a powerful probe of the atmospheric properties of transiting exoplanets. To date, studies of exoplanets in transit have focused on inferring their atmospheric properties such as chemical compositions, cloud/haze properties, and temperature structures. However, surface inhomogeneities in the host stars of exoplane…
Age as a major factor in the onset of multiple populations in stellar clusters
Martocchia, S.; Dalessandro, E.; Salaris, M. +16 more
It is now well established that globular clusters (GCs) exhibit star-to-star light-element abundance variations (known as multiple populations, MPs). Such chemical anomalies have been found in (nearly) all the ancient GCs (more than 10 Gyr old) of our Galaxy and its close companions, but so far no model for the origin of MPs is able to reproduce a…
Cluster mass calibration at high redshift: HST weak lensing analysis of 13 distant galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey
Simon, P.; Schrabback, T.; Foley, R. J. +26 more
We present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (zmedian = 0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide…
Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge*
Casey, Andrew R.; Erkal, Denis; Belokurov, Vasily +9 more
We report the discovery of a nearby dwarf galaxy in the constellation of Hydrus, between the Large (LMC) and the Small Magellanic Clouds (SMC). Hydrus 1 is a mildly elliptical ultrafaint system with luminosity MV ∼ -4.7 and size 53 ± 3 pc, located 28 kpc from the Sun and 24 kpc from the LMC. From spectroscopy of ∼30 member stars, we mea…
Halo substructure in the SDSS-Gaia catalogue: streams and clumps
Myeong, G. C.; Evans, N. W.; Belokurov, V. +2 more
We use the Sloan Digital Sky Survey (SDSS)-Gaia Catalogue to identify six new pieces of halo substructure. SDSS-Gaia is an astrometric catalogue that exploits SDSS data release 9 to provide first epoch photometry for objects in the Gaia source catalogue. We use a version of the catalogue containing 245 316 stars with all phase-space coordinates wi…
Intracluster light at the Frontier - II. The Frontier Fields Clusters
Trujillo, Ignacio; Montes, Mireia
Multiwavelength deep observations are a key tool to understand the origin of the diffuse light in clusters of galaxies: the intracluster light (ICL). For this reason, we take advantage of the Hubble Frontier Fields (HFF) survey to investigate the properties of the stellar populations of the ICL of its six massive intermediate redshift (0.3 < z …