Search Publications
An extended halo around an ancient dwarf galaxy
Erkal, Denis; Jerjen, Helmut; Frebel, Anna +7 more
The Milky Way is surrounded by dozens of ultrafaint (<105 L⊙) dwarf satellite galaxies1-3. They are the remnants of the earliest galaxies4, as confirmed by their ancient5 and chemically primitive6,7 stars. Simulations8-10 suggest that these systems formed within extend…
Interacting dark energy in a closed universe
Di Valentino, Eleonora; Melchiorri, Alessandro; Mena, Olga +2 more
Recent measurements of the Cosmic Microwave Anisotropies power spectra measured by the Planck satellite show a preference for a closed universe at more than $99 {{\ \rm per\ cent}}$ confidence level (CL). Such a scenario is however in disagreement with several low redshift observables, including luminosity distances of Type Ia supernovae. Here we …
The population of M dwarfs observed at low radio frequencies
Callingham, J. R.; Shimwell, T. W.; Vedantham, H. K. +12 more
Coherent low-frequency (≲200 MHz) radio emission from stars encodes the conditions of the outer corona, mass-ejection events and space weather1-5. Previous low-frequency searches for radio-emitting stellar systems have lacked the sensitivity to detect the general population, instead largely focusing on targeted studies of anomalously ac…
Fundamental relations for the velocity dispersion of stars in the Milky Way
Lewis, Geraint F.; Ting, Yuan-Sen; Huber, Daniel +35 more
We explore the fundamental relations governing the radial and vertical velocity dispersions of stars in the Milky Way, from combined studies of complementary surveys including GALAH, LAMOST, APOGEE, the NASA Kepler and K2 missions, and Gaia DR2. We find that different stellar samples, even though they target different tracer populations and employ…
Solar oxygen abundance
Carlsson, Mats; Reiners, Ansgar; Bergemann, Maria +10 more
Motivated by the controversy over the surface metallicity of the Sun, we present a re-analysis of the solar photospheric oxygen (O) abundance. New atomic models of O and Ni are used to perform non-local thermodynamic equilibrium (NLTE) calculations with 1D hydrostatic (MARCS) and 3D hydrodynamical (Stagger and Bifrost) models. The Bifrost 3D MHD s…
A stripped-companion origin for Be stars: clues from the putative black holes HR 6819 and LB-1
El-Badry, Kareem; Quataert, Eliot
HR 6819 is a bright (V = 5.36), blue star recently proposed to be a triple containing a detached black hole (BH). We show that the system is a binary and does not contain a BH. Using spectral decomposition, we disentangle the observed composite spectra into two components: a rapidly rotating Be star and a slowly rotating B star with low surface gr…
CHEOPS observations of the HD 108236 planetary system: a fifth planet, improved ephemerides, and planetary radii
Guterman, P.; Alonso, R.; Deleuil, M. +106 more
Context. The detection of a super-Earth and three mini-Neptunes transiting the bright (V = 9.2 mag) star HD 108236 (also known as TOI-1233) was recently reported on the basis of TESS and ground-based light curves.
Aims: We perform a first characterisation of the HD 108236 planetary system through high-precision CHEOPS photometry and improve t…
Discovery of magnetic fields along stacked cosmic filaments as revealed by radio and X-ray emission
Vazza, F.; West, J. L.; Galvin, T. J. +5 more
Diffuse filaments connect galaxy clusters to form the cosmic web. Detecting these filaments could yield information on the magnetic field strength, cosmic ray population, and temperature of intercluster gas; yet, the faint and large-scale nature of these bridges makes direct detections very challenging. Using multiple independent all-sky radio and…
Milky Way spiral arms from open clusters in Gaia EDR3
Castro-Ginard, A.; Jordi, C.; Luri, X. +7 more
Context. The physical processes driving the formation of Galactic spiral arms are still under debate. Studies using open clusters favour the description of the Milky Way spiral arms as long-lived structures following the classical density wave theory. Current studies comparing the Gaia DR2 field stars kinematic information of the solar neighbourho…
The X-SHOOTER Lyman α survey at z = 2 (XLS-z2) I: what makes a galaxy a Lyman α emitter?
Hayes, Matthew; Schaerer, Daniel; Sobral, David +9 more
We present the first results from the X-SHOOTER Lyman α survey at z = 2 (XLS-z2). XLS-z2 is a deep spectroscopic survey of 35 Lyman α emitters (LAEs) utilizing ≈90 h of exposure time with Very Large Telescope/X-SHOOTER and covers rest-frame Ly α to H α emission with R ≈ 4000. We present the sample selection, the observations, and the data reductio…