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The third realization of the International Celestial Reference Frame by very long baseline interferometry
Charlot, P.; Lambert, S.; Bourda, G. +17 more
A new realization of the International Celestial Reference Frame (ICRF) is presented based on the work achieved by a working group of the International Astronomical Union (IAU) mandated for this purpose. This new realization follows the initial realization of the ICRF completed in 1997 and its successor, ICRF2, adopted as a replacement in 2009. Th…
Unresolved stellar companions with Gaia DR2 astrometry
Everall, Andrew; Brown, Anthony G. A.; Belokurov, Vasily +9 more
For stars with unresolved companions, motions of the centre of light and that of mass decouple, causing a single-source astrometric model to perform poorly. We show that such stars can be easily detected with the reduced χ2 statistic, or renormalized unit weight error (RUWE), provided as part of Gaia DR2. We convert RUWE into the amplit…
The XMM-Newton serendipitous survey. IX. The fourth XMM-Newton serendipitous source catalogue
Motch, C.; Page, M. J.; Ballet, J. +28 more
Context. Sky surveys produce enormous quantities of data on extensive regions of the sky. The easiest way to access this information is through catalogues of standardised data products. XMM-Newton has been surveying the sky in the X-ray, ultra-violet, and optical bands for 20 years.
Aims: The XMM-Newton Survey Science Centre has been producin…
The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager
Vial, J. -C.; Zhang, X.; Peter, H. +146 more
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the "connection science" between solar activity and the heliosphere…
Rapid Reionization by the Oligarchs: The Case for Massive, UV-bright, Star-forming Galaxies with High Escape Fractions
Conroy, Charlie; Tacchella, Sandro; Naidu, Rohan P. +3 more
The protagonists of the last great phase transition of the universe - cosmic reionization - remain elusive. Faint star-forming galaxies are leading candidates because they are found to be numerous and may have significant ionizing photon escape fractions (fesc). Here we update this picture via an empirical model that successfully predic…
The milky way total mass profile as inferred from Gaia DR2
Grand, Robert J. J.; Gómez, Facundo A.; Fattahi, Azadeh +7 more
We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of baryons induces a contraction of the dark matter (DM) distribution in the inner regions, r ≲ 20 kpc. We provi…
Design and Operation of the ATLAS Transient Science Server
Rest, A.; Smartt, S. J.; Stalder, B. +19 more
The Asteroid Terrestrial impact Last Alert System (ATLAS) system consists of two 0.5 m Schmidt telescopes with cameras covering 29 square degrees at plate scale of 1.86 arcsec per pixel. Working in tandem, the telescopes routinely survey the whole sky visible from Hawaii (above $\delta \gt -50^\circ $ ) every two nights, exposing four times per ni…
Universal bolometric corrections for active galactic nuclei over seven luminosity decades
Maiolino, R.; Fiore, F.; Bianchi, S. +12 more
Context. The AGN bolometric correction is a key element for understanding black hole (BH) demographics and computing accurate BH accretion histories from AGN luminosities. However, current estimates still differ from each other by up to a factor of two to three, and rely on extrapolations at the lowest and highest luminosities.
Aims: Here we …
The biggest splash
Grand, Robert J. J.; Fattahi, Azadeh; Belokurov, Vasily +4 more
Using a large sample of bright nearby stars with accurate Gaia Data Release 2 astrometry and auxiliary spectroscopy we map out the properties of the principle Galactic components such as the 'thin' and 'thick' discs and the halo. We confirm previous claims that in the Solar neighbourhood, there exists a large population of metal-rich ([Fe/H] > …
On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
Fontaine, G.; Bergeron, P.; Bédard, A. +1 more
As they evolve, white dwarfs undergo major changes in surface composition, a phenomenon known as spectral evolution. In particular, some stars enter the cooling sequence with helium atmospheres (type DO) but eventually develop hydrogen atmospheres (type DA), most likely through the upward diffusion of residual hydrogen. Our empirical knowledge of …