Search Publications
Weak lensing shear estimation beyond the shape-noise limit: a machine learning approach
Merten, Julian; Ofek, Eran O.; Springer, Ofer M. +1 more
Weak lensing shear estimation typically results in per galaxy statistical errors significantly larger than the sought after gravitational signal of only a few per cent. These statistical errors are mostly a result of shape noise - an estimation error due to the diverse (and a priori unknown) morphology of individual background galaxies. These erro…
Occurrence rates of small planets from HARPS. Focus on the Galactic context
Mazeh, T.; Zucker, S.; Tal-Or, L. +4 more
Context. The stars in the Milky Way thin and thick disks can be distinguished by several properties such as metallicity and kinematics. It is not clear whether the two populations also differ in the properties of planets orbiting the stars. In order to study this, a careful analysis of both the chemical composition and mass detection limits is req…
Candidate Brown-dwarf Microlensing Events with Very Short Timescales and Small Angular Einstein Radii
Han, Cheongho; Udalski, Andrzej; Lee, Chung-Uk +65 more
Short-timescale microlensing events are likely to be produced by substellar brown dwarfs (BDs), but it is difficult to securely identify BD lenses based on only event timescales ${t}_{{\rm{E}}} because short-timescale events can also be produced by stellar lenses with high relative lens-source proper motions. In this paper, we report three strong …
Effects of density on the oxygen ionization equilibrium in collisional plasmas
Del Zanna, G.; Dufresne, R. P.; Badnell, N. R.
The ion populations most frequently adopted for diagnostics in collisional plasmas are derived from the density independent coronal approximation. In higher density, lower temperature conditions, ionization rates are enhanced once metastable levels become populated, and recombination rates are suppressed if ions recombine into Rydberg levels. As a…
Discovery of a Sirius-like binary system with a very strongly magnetic white dwarf. Binarity among magnetic white dwarfs
Landstreet, John D.; Bagnulo, Stefano
Non-interacting binary systems containing a magnetic white dwarf and a main-sequence star are considered extremely rare, perhaps non-existent. In the course of a search of magnetic fields in high-mass white dwarfs we have discovered a Sirius-like wide binary system composed of a main-sequence G0 star and an M ∼ 1.1 M⊙ white dwarf with a…
Understanding Saturn's interior from the Cassini Grand Finale gravity measurements
Ni, Dongdong
Context. Measurements of Saturn's gravity field by Cassini Grand Finale have been acquired with high precision. It has been demonstrated that the even gravitational harmonics J6-J10 have larger absolute values than the predictions by typical rigid-body interior models. A four-layer structure model, proposed to interpret Juno'…
Discovery of 18 Stars with -3.10 < [Fe/H] < -1.45 in the Sagittarius Dwarf Galaxy
Frebel, Anna; Chiti, Anirudh; Hansen, Kylie Y.
Studies of the early chemical evolution of some larger dwarf galaxies (>107 M⊙) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between -3.08 ≤ [Fe/H] ≤ -1.47 in the Sagittarius dwarf spheroidal g…
Hubble Space Telescope Astrometry in the Orion Nebula Cluster: Census of Low-mass Runaways
Gennaro, Mario; Bellini, Andrea; Strampelli, Giovanni +6 more
We present a catalog of high-precision proper motions in the Orion Nebula Cluster (ONC), based on Treasury Program observations with the Hubble Space Telescope's (HST) ACS/WFC camera. Our catalog contains 2454 objects in the magnitude range of 14.2 < mF775W < 24.7, thus probing the stellar masses of the ONC from ∼0.4 M⊙…
The κ-cookbook: a novel generalizing approach to unify κ-like distributions for plasma particle modelling
Fichtner, H.; Scherer, K.; Lazar, M. +1 more
In the literature different so-called κ-distribution functions are discussed to fit and model the velocity (or energy) distributions of solar wind species, pickup ions, or magnetospheric particles. Here, we introduce a generalized (isotropic) κ-distribution as a 'cookbook', which admits as special cases, or 'recipes', all the other known versions …
Detection of ultra-high-energy gamma rays from the Crab Nebula: physical implications
Aharonian, Felix; Khangulyan, Dmitry; Arakawa, Masanori
The Crab Nebula is an extreme particle accelerator that boosts the energy of electrons up to a few PeV (10^{15} eV), close to the maximum energy allowed theoretically. The physical conditions in the acceleration site and the nature of the acceleration process itself remain highly uncertain. The key information about the highest-energy accelerated …