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The total stellar halo mass of the Milky Way
Belokurov, Vasily; Sanders, Jason L.; Deason, Alis J.
We measure the total stellar halo luminosity using red giant branch (RGB) stars selected from Gaia data release 2. Using slices in magnitude, colour, and location on the sky, we decompose RGB stars belonging to the disc and halo by fitting two-dimensional Gaussians to the Galactic proper motion distributions. The number counts of RGB stars are con…
The strong gravitational lens finding challenge
Kneib, J. -P.; Bertin, E.; Jullo, E. +34 more
Large-scale imaging surveys will increase the number of galaxy-scale strong lensing candidates by maybe three orders of magnitudes beyond the number known today. Finding these rare objects will require picking them out of at least tens of millions of images, and deriving scientific results from them will require quantifying the efficiency and bias…
A comprehensive three-dimensional radiative magnetohydrodynamic simulation of a solar flare
Cheung, M. C. M.; De Pontieu, B.; Sainz Dalda, A. +11 more
Solar and stellar flares are the most intense emitters of X-rays and extreme ultraviolet radiation in planetary systems1,2. On the Sun, strong flares are usually found in newly emerging sunspot regions3. The emergence of these magnetic sunspot groups leads to the accumulation of magnetic energy in the corona. When the magneti…
Late-time UV Observations of Tidal Disruption Flares Reveal Unobscured, Compact Accretion Disks
Brown, Thomas M.; Fruchter, Andrew S.; Stone, Nicholas C. +3 more
The origin of thermal optical and UV emission from stellar tidal disruption flares (TDFs) remains an open question. We present Hubble Space Telescope far-UV (FUV) observations of eight optical/UV-selected TDFs 5-10 yr post-peak. Six sources are cleanly detected, showing point-like FUV emission ({10}41.5{--42.5} {erg} {{{s}}}-1
Abundance to age ratios in the HARPS-GTO sample with Gaia DR2. Chemical clocks for a range of [Fe/H]
Chaplin, W. J.; Moya, A.; Davies, G. R. +8 more
Aims: The purpose of this work is to evaluate how several elements produced by different nucleosynthesis processes behave with stellar age and provide empirical relations to derive stellar ages from chemical abundances.
Methods: We derived different sets of ages using Padova and Yonsei-Yale isochrones and HIPPARCOS and Gaia parallaxes fo…
The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass
Emsellem, Eric; Liu, Chengze; Cuillandre, Jean-Charles +25 more
Using deep, high-resolution optical imaging from the Next Generation Virgo Cluster Survey, we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 105 ≲ {\text{}}{M}* /{\text{}}{M}⊙ ≲ 1012. The nucleation fraction reac…
The Atmospheric Circulation of Ultra-hot Jupiters
Tan, Xianyu; Komacek, Thaddeus D.
Recent observations of ultra-hot Jupiters with dayside temperatures in excess of 2500 K have found evidence for new physical processes at play in their atmospheres. In this work, we investigate the effects of the dissociation of molecular hydrogen and recombination of atomic hydrogen on the atmospheric circulation of ultra-hot Jupiters. To do so, …
The ice composition in the disk around V883 Ori revealed by its stellar outburst
Johnstone, Doug; Lee, Jeong-Eun; Aikawa, Yuri +6 more
Complex organic molecules (COMs), which are the seeds of prebiotic material and precursors of amino acids and sugars, form in the icy mantles of circumstellar dust grains1 but cannot be detected remotely unless they are heated and released to the gas phase. Around solar-mass stars, water and COMs only sublimate in the inner few uc(au) o…
Gaia Data Release 2 distances and peculiar velocities for Galactic black hole transients
Maccarone, Thomas J.; Gandhi, Poshak; Rao, Anjali +2 more
We report on a first census of Galactic black hole X-ray binary (BHXRB) properties with the second data release (DR2) of Gaia, focusing on dynamically confirmed and strong candidate BH transients. Gaia DR2 provides five-parameter astrometric solutions including position, parallax and proper motion for 11 out of a sample of 24 systems. Distance est…
The shape of the Galactic halo with Gaia DR2 RR Lyrae. Anatomy of an ancient major merger
Belokurov, Vasily; Iorio, Giuliano
We use the Gaia DR2 RR Lyrae sample to gain an uninterrupted view of the Galactic stellar halo. We dissect the available volume in slices parallel to the Milky Way's disc to show that within ∼30 kpc from the Galactic centre the halo is triaxial, with the longest axis misaligned by ∼70° with respect to the Galactic x-axis. This anatomical procedure…