scholarly journals K2-280 b – a low density warm sub-Saturn around a mildly evolved star

2020 ◽  
Vol 497 (4) ◽  
pp. 4423-4435
Author(s):  
Grzegorz Nowak ◽  
Enric Palle ◽  
Davide Gandolfi ◽  
Hans J Deeg ◽  
Teruyuki Hirano ◽  
...  
Keyword(s):  
Solar System ◽  
Photometric Data ◽  
Joint Analysis ◽  
Low Density ◽  
Eccentric Orbit ◽  
Velocity Measurements ◽  
Detailed Characterization ◽  
Iron Abundance ◽  
Current Sample

ABSTRACT We present an independent discovery and detailed characterization of K2-280 b, a transiting low density warm sub-Saturn in a 19.9-d moderately eccentric orbit (e = $0.35_{-0.04}^{+0.05}$ ) from K2 campaign 7. A joint analysis of high precision HARPS, HARPS-N, and FIES radial velocity measurements and K2 photometric data indicates that K2-280 b has a radius of Rb = 7.50 ± 0.44 R⊕ and a mass of Mb = 37.1 ± 5.6 M⊕, yielding a mean density of ρb = $0.48 _{ - 0.10 } ^ { + 0.13 }$ ${\rm g\, cm^{-3}}$. The host star is a mildly evolved G7 star with an effective temperature of Teff = 5500 ± 100 K, a surface gravity of $\log \, g_{\star }$ = 4.21 ± 0.05 (cgs), and an iron abundance of [Fe/H] = ${0.33}\, {\pm }\, {0.08}$ dex, and with an inferred mass of M⋆ = 1.03 ± 0.03 M⊙ and a radius of R⋆ = 1.28 ± 0.07 R⊙. We discuss the importance of K2-280 b for testing formation scenarios of sub-Saturn planets and the current sample of this intriguing group of planets that are absent in the Solar system.

scholarly journals A multiplanet system of super-Earths orbiting the brightest red dwarf star GJ 887

Science ◽  
2020 ◽  
Vol 368 (6498) ◽  
pp. 1477-1481 ◽  
Author(s):  
S. V. Jeffers ◽  
S. Dreizler ◽  
J. R. Barnes ◽  
C. A. Haswell ◽  
R. P. Nelson ◽  
...  
Keyword(s):  
Solar System ◽  
Equilibrium Temperature ◽  
The Sun ◽  
Habitable Zone ◽  
Dwarf Star ◽  
Velocity Measurements ◽  
Detailed Characterization ◽  
Photometric Variability ◽  
Orbital Periods

The closet exoplanets to the Sun provide opportunities for detailed characterization of planets outside the Solar System. We report the discovery, using radial velocity measurements, of a compact multiplanet system of super-Earth exoplanets orbiting the nearby red dwarf star GJ 887. The two planets have orbital periods of 9.3 and 21.8 days. Assuming an Earth-like albedo, the equilibrium temperature of the 21.8-day planet is ~350 kelvin. The planets are interior to, but close to the inner edge of, the liquid-water habitable zone. We also detect an unconfirmed signal with a period of ~50 days, which could correspond to a third super-Earth in a more temperate orbit. Our observations show that GJ 887 has photometric variability below 500 parts per million, which is unusually quiet for a red dwarf.

scholarly journals Mass and metallicity distribution of parent AGB stars of presolar SiC

2020 ◽  
Vol 644 ◽  
pp. A8
Author(s):  
S. Cristallo ◽  
A. Nanni ◽  
G. Cescutti ◽  
I. Minchev ◽  
N. Liu ◽  
...  
Keyword(s):  
Solar System ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Detailed Characterization ◽  
Mixing Processes ◽  
Capture Process ◽  
Metallicity Distribution

The vast majority (≳90%) of presolar SiC grains identified in primitive meteorites are relics of ancient asymptotic giant branch (AGB) stars, whose ejecta were incorporated into the Solar System during its formation. Detailed characterization of these ancient stardust grains has revealed valuable information on mixing processes in AGB interiors in great detail. However, the mass and metallicity distribution of their parent stars still remains ambiguous, although such information is crucial to investigating the slow neutron-capture process, whose efficiency depends on mass and metallicity. Using a well-known Milky Way chemo-dynamical model, we followed the evolution of the AGB stars that polluted the Solar System at 4.57 Gyr ago and weighted the stars based on their SiC dust productions. We find that presolar SiC in the Solar System predominantly originated from AGB stars with M ∼ 2 M⊙ and Z ∼ Z⊙. Our finding well explains the grain-size distribution of presolar SiC identified in situ in primitive meteorites. Moreover, it provides complementary results to very recent papers that characterized parent stars of presolar SiC.

Characterization of machined polystyrene foam

1989 ◽  
Vol 47 ◽  
pp. 372-373
Author(s):  
C. W. Price ◽  
E. F. Lindsey ◽  
R. M. Franks ◽  
M. A. Lane
Keyword(s):  
Surface Finish ◽  
Cell Walls ◽  
Surface Structures ◽  
Efficient Technique ◽  
Low Density ◽  
Polystyrene Foam ◽  
Planar Surfaces ◽  
Machining Characteristics

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.

Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

2020 ◽  
Author(s):  
Wallace Derricotte ◽  
Huiet Joseph
Keyword(s):  
Chemical Potential ◽  
Reaction Force ◽  
Intramolecular Proton Transfer ◽  
Intermediate Energy ◽  
Force Analysis ◽  
Activation Energy Barrier ◽  
Detailed Characterization ◽  
Proton Transfers ◽  
Reaction Force Constant

The mechanism of isomerization of hydroxyacetone to 2-hydroxypropanal is studied within the framework of reaction force analysis at the M06-2X/6-311++G(d,p) level of theory. Three unique pathways are considered: (i) a step-wise mechanism that proceeds through formation of the Z-isomer of their shared enediol intermediate, (ii) a step-wise mechanism that forms the E-isomer of the enediol, and (iii) a concerted pathway that bypasses the enediol intermediate. Energy calculations show that the concerted pathway has the lowest activation energy barrier at 45.7 kcal mol<sup>-1</sup>. The reaction force, chemical potential, and reaction electronic flux are calculated for each reaction to characterize electronic changes throughout the mechanism. The reaction force constant is calculated in order to investigate the synchronous/asynchronous nature of the concerted intramolecular proton transfers involved. Additional characterization of synchronicity is provided by calculating the bond fragility spectrum for each mechanism.

Characterization of Low Density Glass Filled Epoxies

2003 ◽  
Author(s):  
Matthew J. Quesenberry ◽  
Phillip H. Madison ◽  
Robert E. Jensen
Keyword(s):  
Low Density

DETAILED CHARACTERIZATION OF EUROPA'S RIDGE MORPHOLOGY

2016 ◽  
Author(s):  
Janelle A.F. Heitmeier ◽  
◽  
Emily S. Martin ◽  
Jordan M. Bretzfelder ◽  
D. Alex Patthoff ◽  
...  
Keyword(s):  
Detailed Characterization

The Problem of Divine Hiddenness

2018 ◽  
Author(s):  
Michael C. Rea
Keyword(s):  
Problem Of Evil ◽  
Philosophical Discussion ◽  
Detailed Characterization ◽  
The Past ◽  
Divine Hiddenness ◽  
The Problem Of Evil ◽  
The Relationship

This chapter provides a detailed characterization of the various meanings of the term “divine hiddenness,” carefully and rigorously articulates the version of the problem of divine hiddenness that has dominated contemporary philosophical discussion for the past twenty-five years, and then explains the relationship between that problem and the problem of evil.

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

Impulsivity and Drug Addiction: A Neurobiological Perspective

2012 ◽  
Author(s):  
Trevor Robbins
Keyword(s):  
Drug Addiction ◽  
Conceptual Analysis ◽  
Animal Studies ◽  
Reaction Time Task ◽  
Compulsive Behavior ◽  
Self Administration ◽  
Detailed Characterization ◽  
Cocaine Seeking ◽  
Serial Reaction

A conceptual analysis of the impulsivity construct in behavioral and neurobiological terms is followed by an analysis of its causal role in certain forms of drug addiction in both human and animal studies. The main focus of this chapter is on a rat model of impulsivity based on premature responding in the five-choice serial reaction time task and a more detailed characterization of this phenotype in neurobehavioral, neurochemical, and genetic terms. Evidence is surveyed that high impulsivity on this task is associated with the escalation subsequently of cocaine self-administration behavior and also with a tendency toward compulsive cocaine seeking. Novelty reactivity, by contrast, is associated with the enhanced acquisition of self-administration, but not with the escalation of intravenous self-administration of cocaine or the development of compulsive behavior associated with cocaine seeking. These results indicate that the vulnerability to stimulant addiction may depend on different factors, as expressed through distinct presumed endophenotypes. These observations help us further to dissociate various aspects of the impulsivity construct in neural as well as behavioral terms.

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