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Origin of the Excess of High-energy Retrograde Stars in the Galactic Halo
Matsuno, Tadafumi; Aoki, Wako; Suda, Takuma
We report on the very low α-element abundances of a group of metal-poor stars with high orbital energy and with large retrograde motion in the Milky Way halo, whose excess has been reported recently from metallicity and kinematics. We constructed a sample of halo stars with measured abundances and precise kinematics, including ∼880 stars with [Fe/…
207 New Open Star Clusters within 1 kpc from Gaia Data Release 2
Sim, Gyuheon; Lee, Sang Hyun; Ann, Hong Bae +1 more
We conducted a survey of open clusters within 1 kpc from the Sun using the astrometric and photometric data of the Gaia Data Release 2. We found 655 cluster candidates by visual inspection of the stellar distributions in proper motion space and spatial distributions in l-b space. All of the 655 cluster candidates have a well defined main-sequence …
The Foundation Supernova Survey: Measuring Cosmological Parameters with Supernovae from a Single Telescope
Berger, E.; Kirshner, R. P.; Rest, A. +27 more
Measurements of the dark energy equation-of-state parameter, w, have been limited by uncertainty in the selection effects and photometric calibration of z < 0.1 Type Ia supernovae (SNe Ia). The Foundation Supernova Survey is designed to lower these uncertainties by creating a new sample of z < 0.1 SNe Ia observed on the Pan-STARRS system. He…
The Recent Burstiness of Star Formation in Galaxies at z ∼ 4.5 from Hα Measurements
Tacchella, Sandro; Larson, Kirsten L.; Faisst, Andreas L. +2 more
The redshift range z = 4-6 marks a transition phase between primordial and mature galaxy formation in which galaxies considerably increase their stellar mass, metallicity, and dust content. The study of galaxies in this redshift range is therefore important to understanding early galaxy formation and the fate of galaxies at later times. Here, we i…
The Precision of Mass Measurements Required for Robust Atmospheric Characterization of Transiting Exoplanets
Fortney, Jonathan J.; Batalha, Natalie M.; Batalha, Natasha E. +4 more
Two of Transiting Exoplanet Survey Satellite’s major science goals are to measure masses for 50 planets smaller than 4 Earth radii and to discover high-quality targets for atmospheric characterization efforts. It is important that these two goals are linked by quantifying what precision of mass constraint is required to yield robust atmospheric pr…
Coronal Mass Ejections over Solar Cycles 23 and 24
Lamy, P. L.; Gilardy, H.; Floyd, O. +3 more
We present a statistical analysis of solar coronal mass ejections (CMEs) based on 23 years of quasi-continuous observations with the LASCO coronagraph, thus covering two complete Solar Cycles (23 and 24). We make use of five catalogs, one manual (CDAW) and four automated (ARTEMIS, CACTus, SEEDS, and CORIMP), to characterize the temporal evolutions…
Observation-based modelling of magnetised coronal mass ejections with EUHFORIA
Mierla, M.; Rodriguez, L.; Poedts, S. +2 more
Context. Coronal mass ejections (CMEs) are the primary source of strong space weather disturbances at Earth. Their geo-effectiveness is largely determined by their dynamic pressure and internal magnetic fields, for which reliable predictions at Earth are not possible with traditional cone CME models.
Aims: We study two well-observed Earth-dir…
TESS Spots a Compact System of Super-Earths around the Naked-eye Star HR 858
Vanderburg, Andrew; Bieryla, Allyson; Latham, David W. +48 more
Transiting Exoplanet Survey Satellite (TESS) observations have revealed a compact multiplanet system around the sixth-magnitude star HR 858 (TIC 178155732, TOI 396), located 32 pc away. Three planets, each about twice the size of Earth, transit this slightly evolved, late F-type star, which is also a member of a visual binary. Two of the planets m…
Extended stellar systems in the solar neighborhood. I. The tidal tails of the Hyades
Meingast, Stefan; Alves, João
We report the discovery of two well-defined tidal tails emerging from the Hyades star cluster. The tails were detected in Gaia DR2 data by selecting cluster members in the 3D galactocentric cylindrical velocity space. The robustness of our member selection is reinforced by the fact that the sources depict an almost noiseless, coeval stellar main s…
Space Densities and Emissivities of Active Galactic Nuclei at z > 4
Dickinson, M.; Fiore, F.; Castellano, M. +11 more
The study of the space density of bright active galactic nuclei (AGNs) at z > 4 has been subject to extensive effort given its importance in the estimation of cosmological ionizing emissivity and growth of supermassive black holes. In this context we have recently derived high space densities of AGNs at z ∼ 4 and -25 < M 1450 <…