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Observations of Disequilibrium CO Chemistry in the Coldest Brown Dwarfs
Fortney, Jonathan J.; Marley, Mark S.; Freedman, Richard S. +10 more
Cold brown dwarfs are excellent analogs of widely separated, gas giant exoplanets, and provide insight into the potential atmospheric chemistry and physics we may encounter in objects to be discovered by future direct imaging surveys. We present a low-resolution, R ∼ 300, M-band spectroscopic sequence of seven brown dwarfs with effective temperatu…
Neutron-capture elements in dwarf galaxies. III. A homogenized analysis of 13 dwarf spheroidal and ultra-faint galaxies
Hansen, C. J.; Skúladóttir, Á.; Grebel, E. K. +3 more
Context. We present a large homogeneous set of stellar parameters and abundances across a broad range of metallicities, involving 13 classical dwarf spheroidal (dSph) and ultra-faint dSph (UFD) galaxies. In total, this study includes 380 stars in Fornax, Sagittarius, Sculptor, Sextans, Carina, Ursa Minor, Draco, Reticulum II, Bootes I, Ursa Major …
Nebular spectra of 111 Type Ia supernovae disfavour single-degenerate progenitors
Kochanek, C. S.; Galbany, L.; Kumar, S. +15 more
We place statistical constraints on Type Ia supernova (SN Ia) progenitors using 227 nebular-phase spectra of 111 SNe Ia. We find no evidence of stripped companion emission in any of the nebular-phase spectra. Upper limits are placed on the amount of mass that could go undetected in each spectrum using recent hydrodynamic simulations. With these nu…
Reviving old controversies: is the early Galaxy flat or round?. Investigations into the early phases of the Milky Way's formation through stellar kinematics and chemical abundances
Bonifacio, P.; Caffau, E.; Spite, M. +4 more
We analysed a set of very metal-poor stars, for which accurate chemical abundances have been obtained as part of the ESO Large Program "First stars" in the light of the Gaia DR2 data. The kinematics and orbital properties of the stars in the sample show they probably belong to the thick disc, partially heated to halo kinematics, and to the accrete…
Completeness of the Gaia verse II: what are the odds that a star is missing from Gaia DR2?
Everall, Andrew; Boubert, Douglas
The second data release of the Gaia mission contained astrometry and photometry for an incredible 1692 919 135 sources, but how many sources did Gaiamiss and where do they lie on the sky? The answer to this question will be crucial for any astronomer attempting to map the Milky Way with Gaia DR2. We infer the completeness of Gaia DR2 by exploiting…
Radial Evolution of Coronal Mass Ejections Between MESSENGER, Venus Express, STEREO, and L1: Catalog and Analysis
Lugaz, N.; Winslow, R. M.; Salman, T. M.
Our knowledge of the properties of coronal mass ejections (CMEs) in the inner heliosphere is constrained by the relative lack of plasma observations between the Sun and 1 AU. In this work, we present a comprehensive catalog of 47 CMEs measured in situ measurements by two or more radially aligned spacecraft (MESSENGER, Venus Express, STEREO, Wind/A…
The Solar Orbiter Heliospheric Imager (SoloHI)
St. Cyr, O. C.; Plunkett, S. P.; Lamy, P. L. +45 more
Aims: We present the design and pre-launch performance of the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently scheduled for launch in 2020.
Methods: The goal of this paper is to provide details of the SoloHI instrument concept, design, and pre-fligh…
A stripped helium star in the potential black hole binary LB-1
Geier, S.; Heber, U.; Irrgang, A. +2 more
Context. The recently claimed discovery of a massive (MBH = 68-13+11 M⊙) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution.
Aims: A crucial aspect for the determination of the mass of the unseen bla…
Double White Dwarf Merger Products among High-mass White Dwarfs
Toonen, Silvia; Cheng, Sihao; Cummings, Jeffrey D. +1 more
Double white dwarf (double-WD) binaries may merge within a Hubble time and produce high-mass WDs. Compared to other high-mass WDs, the double-WD merger products have higher velocity dispersion because they are older. With the power of Gaia data, we show strong evidence for double-WD merger products among high-mass WDs by analyzing the transverse-v…
Velocity substructure from Gaia and direct searches for dark matter
Belokurov, Vasily; Evans, N. Wyn; Myeong, GyuChul +2 more
Data from the Gaia satellite show that the solar neighborhood of the Milky Way's stellar halo is imprinted with substructure from several accretion events. Evidence of these events is found in "the shards," stars clustering with high significance in both action space and metallicity. Stars in the shards share a common origin, likely as ancient sat…