scholarly journals Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release

2019 ◽  
Vol 490 (4) ◽  
pp. 5088-5102 ◽  
Author(s):  
M Mugrauer
Keyword(s):  
Main Sequence ◽  
Stellar Systems ◽  
Sequence Evolution ◽  
The Sun ◽  
M Dwarfs ◽  
Primary Star ◽  
True Nature ◽  
Quadruple System ◽  
Data Release ◽  
Host Stars

ABSTRACT A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than about 500 pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15  per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4 M⊙ with a peak in their mass distribution between 0.15 and $0.3\, \mathrm{M}_{\odot }$. The companions are separated from the exoplanet host stars by about 20 up to 9100 au, but are found most frequently within a projected separation of 1000 au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.

scholarly journals Unbound Close Stellar Encounters in the Solar Neighborhood

2022 ◽  
Vol 163 (2) ◽  
pp. 44
Author(s):  
Bradley M. S. Hansen
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Radial Distance ◽  
Solar Neighborhood ◽  
Limiting Factors ◽  
Line Of Sight ◽  
The Sun ◽  
Finite Set ◽  
Host Stars ◽  
Migration Event

Abstract We present a catalog of unbound stellar pairs, within 100 pc of the Sun, that are undergoing close, hyperbolic, encounters. The data are drawn from the GAIA EDR3 catalog, and the limiting factors are errors in the radial distance and unknown velocities along the line of sight. Such stellar pairs have been suggested to be possible events associated with the migration of technological civilizations between stars. As such, this sample may represent a finite set of targets for a SETI search based on this hypothesis. Our catalog contains a total of 132 close passage events, featuring stars from across the entire main sequence, with 16 pairs featuring at least one main-sequence star of spectral type between K1 and F3. Many of these stars are also in binaries, so that we isolate eight single stars as the most likely candidates to search for an ongoing migration event—HD 87978, HD 92577, HD 50669, HD 44006, HD 80790, LSPM J2126+5338, LSPM J0646+1829 and HD 192486. Among host stars of known planets, the stars GJ 433 and HR 858 are the best candidates.

scholarly journals Molecular Opacities in Cool Dwarf Stars

1994 ◽  
Vol 146 ◽  
pp. 61-70
Author(s):  
James Liebert
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Small Radius ◽  
The Sun ◽  
M Dwarfs ◽  
Hydrogen Burning ◽  
Dwarf Stars ◽  
Low Mass ◽  
High Space ◽  
Lower Luminosity

The term dwarf stars identifies objects of small radius in the Hertzsprung-Russell (H-R) Diagram, but encompasses more than one phase of stellar evolution. The M dwarfs (type dM) populate the main sequence at the low mass end; these are the coolest core hydrogen-burning stars. They belong generally to the Galactic disk, or Population I, have relatively small space motions with respect to the Sun, and have similar metallicities to the Sun (although perhaps only within a factor of several). In particular, this means that the abundance of oxygen is always greater than that of carbon. The M subdwarfs (sdM) are the Population II counterparts, showing low metallicities and high space motions. Because they have smaller radii, they define a main sequence at lower luminosity than the M dwarfs for a given temperature. Hence the term subdwarf.

scholarly journals Modelling of an Eclipsing RS CVn Binary: V405 And

2011 ◽  
Vol 7 (S282) ◽  
pp. 199-200
Author(s):  
Krisztián Vida ◽  
Katalin Oláh ◽  
Zsolt Kővári
Keyword(s):  
Light Curve ◽  
Main Sequence ◽  
Magnetic Activity ◽  
Light Curves ◽  
Stellar Structure ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Primary Star ◽  
Convective Envelope ◽  
Eclipsing Binary

AbstractV405 And is an ultrafast-rotating (Prot ≈ 0.46 days) eclipsing binary. The system consists of a primary star with radiative core and convective envelope, and a fully convective secondary. Theories have shown that stellar structure can depend on magnetic activity, i.e., magnetically active M-dwarfs should have larger radii. Earlier light curve modelling of V405 And indeed showed this behaviour: we found that the radius of the primary is significantly larger than the theoretically predicted value for inactive main sequence stars (the discrepancy is the largest of all known objects), while the secondary fits well to the mass-radius relation. By modelling our recently obtained light curves, which show significant changes of the spotted surface of the primary, we can find further proof for this phenomenon.

scholarly journals Dynamic study of possible host stars for extrasolar planetary systems

2014 ◽  
Vol 9 (S310) ◽  
pp. 104-105 ◽  
Author(s):  
N. A. Shakht ◽  
L. G. Romanenko ◽  
D. L. Gorshanov ◽  
O. O. Vasilkova
Keyword(s):  
Planetary Systems ◽  
Dynamic Study ◽  
Stellar Systems ◽  
The Sun ◽  
Solar Mass ◽  
Double Stars ◽  
Multiple Stars ◽  
Double And Multiple Stars ◽  
Host Stars

AbstractWe present the stellar systems which consist of double and multiple stars with distances 3.5 ÷ 25 pc from the Sun, belonging to spectral classes F, G, K, M, having masses from 0.3 to 1.5 solar mass and can, in principle, possess planetary systems. On the basis of observations with Pulkovo 65 cm refractor the relative positions of double stars, the parameters of motion, the orbits and also the ephemeris for the nearest epochs have been computed.

scholarly journals Swansong biospheres II: the final signs of life on terrestrial planets near the end of their habitable lifetimes

2014 ◽  
Vol 13 (3) ◽  
pp. 229-243 ◽  
Author(s):  
Jack T. O'Malley-James ◽  
Charles S. Cockell ◽  
Jane S. Greaves ◽  
John A. Raven
Keyword(s):  
Environmental Conditions ◽  
Late Stage ◽  
Cloud Cover ◽  
Main Sequence ◽  
Interaction Model ◽  
Early Earth ◽  
Sequence Evolution ◽  
The Sun ◽  
Upper Limit ◽  
Life On Earth

AbstractThe biosignatures of life on Earth do not remain static, but change considerably over the planet's habitable lifetime. Earth's future biosphere, much like that of the early Earth, will consist of predominantly unicellular microorganisms due to the increased hostility of environmental conditions caused by the Sun as it enters the late stage of its main sequence evolution. Building on previous work, the productivity of the biosphere is evaluated during different stages of biosphere decline between 1 and 2.8 Gyr from present. A simple atmosphere–biosphere interaction model is used to estimate the atmospheric biomarker gas abundances at each stage and to assess the likelihood of remotely detecting the presence of life in low-productivity, microbial biospheres, putting an upper limit on the lifetime of Earth's remotely detectable biosignatures. Other potential biosignatures such as leaf reflectance and cloud cover are discussed.

scholarly journals White dwarfs in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 317-320
Author(s):  
P.-E. Tremblay ◽  
N. Gentile-Fusillo ◽  
J. Cummings ◽  
S. Jordan ◽  
B. T. Gänsicke ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Milky Way ◽  
Mass Function ◽  
Initial Mass Function ◽  
Sequence Evolution ◽  
Atmospheric Parameters ◽  
Stellar Formation ◽  
Formation History ◽  
Data Release

AbstractThe vast majority of stars will become white dwarfs at the end of the stellar life cycle. These remnants are precise cosmic clocks owing to their well constrained cooling rates. Gaia Data Release 2 is expected to discover hundreds of thousands of white dwarfs, which can then be observed spectroscopically with WEAVE and 4MOST. By employing spectroscopically derived atmospheric parameters combined with Gaia parallaxes, white dwarfs can constrain the stellar formation history in the early developing phases of the Milky Way, the initial mass function in the 1.5 to 8 M⊙ range, and the stellar mass loss as well as the state of planetary systems during the post main-sequence evolution.

scholarly journals Using Helioseismic Data to Probe the Hydrogen Abundance in the Solar Core

1990 ◽  
Vol 121 ◽  
pp. 327-340 ◽  
Author(s):  
D. O. Gough ◽  
A. G. Kosovichev
Keyword(s):  
Solar Neutrino ◽  
Particle Physics ◽  
Sound Speed ◽  
Main Sequence ◽  
Neutrino Flux ◽  
Sequence Evolution ◽  
The Sun ◽  
Low Degree ◽  
The Standard Model ◽  
Solar Neutrino Flux

AbstractA procedure for inverting helioseismic data to determine the hydrogen abundance in the radiative interior of the sun is briefly described. Using Backus-Gilbert optimal averaging, the variation of sound speed, density and hydrogen abundance in the energy-generating core is estimated from low-degree p-mode frequencies. The result provides some evidence for there having been some redistribution of material during the sun’s main-sequence evolution. The inversion also suggests that the evolutionary age of the sun is perhaps some 10 per cent greater than the generally accepted value, and that the solar neutrino flux, based on standard nuclear and particle physics, is about 75 per cent of the standard-model value.

scholarly journals Astrometric study of Gaia DR2 stars for interstellar communication

2020 ◽  
Vol 19 (4) ◽  
pp. 308-313
Author(s):  
Naoki Seto ◽  
Kazumi Kashiyama
Keyword(s):  
High Precision ◽  
Main Sequence ◽  
Opening Angle ◽  
Main Sequence Stars ◽  
Extraterrestrial Intelligence ◽  
Data Release ◽  
Interstellar Communication ◽  
Host Stars ◽  
Gaia Dr2 ◽  
Better Than

AbstractWe discuss the prospects of high precision pointing of our transmitter to habitable planets around Galactic main sequence stars. For an efficient signal delivery, the future sky positions of the host stars should be appropriately extrapolated with accuracy better than the beam opening angle Θ of the transmitter. Using the latest data release (DR2) of Gaia, we estimate the accuracy of the extrapolations individually for 4.7 × 107 FGK stars, and find that the total number of targets could be ~107 for the accuracy goal better than 1″. Considering the pairwise nature of communication, our study would be instructive also for SETI (Search for Extraterrestrial Intelligence), not only for sending signals outward.

scholarly journals Distances of Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 109-121 ◽  
Author(s):  
Yervant Terzian
Keyword(s):  
Physical Parameter ◽  
Main Sequence ◽  
Planetary Nebulae ◽  
Variable Stars ◽  
Stellar Systems ◽  
The Sun ◽  
Stellar Clusters ◽  
Main Sequence Stars ◽  
The Universe ◽  
Fundamental Physical

One of the most fundamental physical parameter in astronomy is the distance to the objects we detect in the universe. For many classes of astronomical objects, accurate and proven methods have been developed to determine their distances. Such classes of objects include stars within ∼100 pc from the sun, binary stellar systems, variable stars, stellar clusters, main sequence stars, and other galaxies. It has been, however, more difficult to develop satisfactory methods to determine accurate distances to the more than 1000 planetary nebulae that have been discovered in our galaxy.

Origin of debris disks and the supply of metals in DZ white dwarfs

2007 ◽  
Vol 3 (S249) ◽  
pp. 389-392
Author(s):  
Y. Wang ◽  
R. B. Dong ◽  
D. N. C. Lin ◽  
X. W. Liu
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Dynamical Evolution ◽  
Giant Planets ◽  
Sequence Evolution ◽  
Orbital Eccentricity ◽  
Planetary Bodies ◽  
Compact Disks ◽  
Host Stars ◽  
Gas Drag

AbstractWe discuss the dynamical evolution of minor planetary bodies in the outer regions of planetary systems around the progenitors of DZ white dwarfs. We show that during the planetary-nebula phase of these stars, mass loss can lead to the expansion of all planetary bodies. The orbital eccentricity of the minor bodies, as relics of planetesimals, may be largely excited by the perturbation due to both gas drag effects and nearby gas giant planets. Some of these bodies migrate toward the host star, while others are scattered out of the planetary system. The former have modest probability of being captured by the sweeping secular resonances of giant planets, and induced to migrate toward the host star. When they venture close to their host stars, their orbits are tidally circularized so that they form compact disks where they may undergo further collisionally driven evolution. During the subsequent post main sequence evolution of their host stars, this process may provide an avenue which continually channels heavy elements onto the surface of the white dwarfs. We suggest that this scenario provides an explanation for the recently discovered Calcium line variation in G29-38.

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