Search Publications
Detection of a variable ultrafast outflow in the narrow-line Seyfert 1 galaxy PG 1448+273
Fabian, A. C.; Reynolds, C. S.; Pinto, C. +4 more
Relativistically blueshifted absorption features of highly ionized ions, the so-called ultrafast outflows (UFOs), have been detected in the X-ray spectra of a number of accreting supermassive black holes. If these features truly originate from accretion disc winds accelerated to more than 10 per cent of the speed of light, their energy budget is v…
A thirty-four billion solar mass black hole in SMSS J2157-3602, the most luminous known quasar
Fan, Xiaohui; Wolf, Christian; Bian, Fuyan +3 more
From near-infrared spectroscopic measurements of the Mg II emission line doublet, we estimate the black hole (BH) mass of the quasar, SMSS J215728.21-360215.1, as being (3.4 ± 0.6) × 1010 M⊙ and refine the redshift of the quasar to be z = 4.692. SMSS J2157 is the most luminous known quasar, with a 3000 Å luminosity of (4.7 ± …
Exploring Effects on Magnifications due to Line-of-Sight Galaxies in the Hubble Frontier Fields
Keeton, Charles R.; Raney, Catie A.; Brennan, Sean
Cluster lensing has become an important tool in the search for high redshift galaxies through its ability to magnify sources. In order to determine the intrinsic properties of these galaxies, lensing mass models must be constructed to determine the magnification of the images. These models are traditionally two-dimensional, focusing on the mass wi…
Constraining planet formation around 6-8 M⊙ stars
Hermes, J. J.; Gänsicke, Boris T.; Kennedy, Grant M. +4 more
Identifying planets around O-type and B-type stars is inherently difficult; the most massive known planet host has a mass of only about $3\, \mathrm{M}_{\odot }$ . However, planetary systems which survive the transformation of their host stars into white dwarfs can be detected via photospheric trace metals, circumstellar dusty and gaseous discs, a…
A fresh look at the RR Lyrae population in the Draco dwarf spheroidal galaxy with Gaia
Garofalo, Alessia; Clementini, Gisella; Muraveva, Tatiana +1 more
We present a catalogue of 285 RR Lyrae stars (RRLs) in the Draco dwarf spheroidal (dSph) galaxy, obtained by combining data from a number of different surveys including the Data Release 2 (DR2) of the European Space Agency cornerstone mission Gaia. We have determined individual distances to the RRLs in our sample using for the first time a Gaia G-…
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…
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…
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 …
The pulsation properties of λ bootis stars I. the southern TESS sample
Paunzen, E.; Huber, D.; Bedding, T. R. +2 more
We analyse TESS light curves for 70 southern λ Boo stars to identify binaries and to determine which of them pulsate as δ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of λ Boo stars pulsate as δ Sct variables, which is about twice that of normal stars over the same parameter sp…