M Dwarfs at Lower z Distances

Twelve years ago, during the International Summer Course at Lagonissi, Bart Bok (1966) presented a paper “Desiderata for Future Galactic Research”. He pointed to the importance of studies in the galactic polar caps which would allow us, as he hoped, to determine some basic data for galactic structure.The significance of his statements was demonstrated already in the following years when the gradual increase of our knowledge of the objects in the solar neighbourhood was suddenly interrupted by new observational data from which diverging conclusions have been drawn. Never before have such controversial opinions on problems in the vicinity of the sun been so eagerly discussed: A formerly unknown numerous population of low-velocity red dwarfs, the mass density resulting from stars three times that formerly thought, a remarkably increased luminosity function - yes or no? Obviously, the controversies have smoothed down again during the last months. But what is the situation after this troubled period? Which problems are still unsolved? Which promising programmes will be proposed? I think this Joint Discussion is justified in 1976!

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A Population Discriminant in M-Dwarf Spectra

Symposium - International Astronomical Union ◽

10.1017/s0074180900008974 ◽

1976 ◽

Vol 72 ◽

pp. 205-205 ◽

Cited By ~ 2

Author(s):

W. P. Bidelman ◽

W. G. Smethells

Keyword(s):

Southern Hemisphere ◽

High Velocity ◽

Gradual Increase ◽

Tangential Velocity ◽

M Dwarfs ◽

Low Velocity ◽

Band Ratio ◽

Slight Tendency ◽

Objective Prism ◽

M Dwarf

The CaH bands in the λ 6385 region of the spectra of M dwarfs have long been known; they become visible in the late K's and show a gradual increase in strength to later types. However, Greenstein and Eggen have noted that there is a substantial strengthening of all the hydride bands, including CaH, in high-velocity dwarfs (notably G95-59), and one of us (W.P.B.) has also seen this effect in suitable Warner and Swasey Observatory objective-prism plates of the rather low-velocity subdwarfs Ross 730 and 731. In a recent southern-hemisphere survey with the Curtiss Schmidt, Smethells has discovered nearly 200 late K and early M dwarfs, for all of which estimates of CaH-band strength were made. He found a considerable variation of the CaH-band strength in stars of the same (TiO-band) spectral type, and a slight tendency for the CaH/TiO band ratio to increase with increasing tangential velocity. A fuller account of this work will appear elsewhere.

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Galactic Mass Density in the Vicinity of the Sun

Highlights of Astronomy ◽

10.1017/s1539299600002938 ◽

1977 ◽

Vol 4 (2) ◽

pp. 33-33

Author(s):

M. Joeveer ◽

J. Einasto

Keyword(s):

Observational Data ◽

Total Mass ◽

Mass Density ◽

Solar Neighbourhood ◽

Interstellar Matter ◽

The Sun ◽

Number Density ◽

Stellar Component ◽

The Mean

It is possible to estimate the galactic mass density in the solar neighbourhood either directly by summing up the mass densities of individual subsystems of stars and interstellar matter or indirectly from dynamical considerations.Observational data on the number density of visible stars lead to mutually consistent results on the stellar component of the mass density. The mean of different estimates is ⍴stars=0.052±0.010 Mʘpc−3. By adding the probable contributions of intrinsically faint undetected objects and of interstellar matter the value ⍴=0.09±0.02 Mʘpc−3 has been obtained for the total mass density.

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Probabilistic Oblique Impact Analysis of Functionally Graded Plates – A Multivariate Adaptive Regression Splines Approach

European Journal of Computational Mechanics ◽

10.13052/ejcm2642-2085.30234 ◽

2021 ◽

Author(s):

P. K. Karsh ◽

Bindi Thakkar ◽

R. R. Kumar ◽

Vaishali ◽

Sudip Dey

Keyword(s):

Material Properties ◽

Mass Density ◽

Plate Thickness ◽

Functionally Graded ◽

Multivariate Adaptive Regression Splines ◽

Low Velocity Impact ◽

Fe Model ◽

Low Velocity ◽

Velocity Impact ◽

Mars Model

Purpose: To investigate the probabilistic low-velocity impact of functionally graded (FG) plate using the MARS model, considering uncertain system parameters. Design/methodology/application: The distribution of various material properties throughout FG plate thickness is calculated using power law. For finite element (FE) formulation, isoparametric elements with eight nodes are considered, each component has five degrees of freedom. The combined effect of variability in material properties such as elastic modulus, modulus of rigidity, Poisson’s ratio, and mass density are considered. The surrogate model is validated with the FE model represented by the scatter plot and the probability density function (PDF) plot based on Monte Carlo simulation (MCS). Findings: The outcome of the degree of stochasticity, impact angle, impactor’s velocity, impactor’s mass density, and point of impact on the maximum value of contact force (CFmax ), plate deformation (PDmax), and impactor deformation (IDmax ) are determined. A convergence study is also performed to determine the optimal number of the constructed MARS model’s sample size. Originality/value: The results illustrate the significant effects of uncertain input parameters on FGM plates’ low-velocity impact responses by employing a surrogate-based MARS model.

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A microvariability study of nearby M dwarfs from the Western Italian Alps: Status update

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311021077 ◽

2010 ◽

Vol 6 (S276) ◽

pp. 525-526

Author(s):

Mario Damasso ◽

Andrea Bernagozzi ◽

Enzo Bertolini ◽

Paolo Calcidese ◽

Paolo Giacobbe ◽

...

Keyword(s):

Italian Alps ◽

M Dwarfs ◽

Red Dwarfs ◽

Typical Period ◽

Low Mass ◽

M Stars ◽

Rocky Planets ◽

Long Term Survey

AbstractSmall ground-based telescopes can effectively be used to look for transiting rocky planets around nearby low-mass M stars, as recently demonstrated for example by the MEarth project. Since December 2009 at the Astronomical Observatory of the Autonomous Region of Aosta Valley (OAVdA) we are monitoring photometrically a sample of red dwarfs with accurate parallax measurements. The primary goal of this ‘pilot study’ is the characterization of the photometric microvariability of each target over a typical period of approximately 2 months. This is the preparatory step to long-term survey with an array of identical small telescopes, with kick-off in early 2011. Here we discuss the present status of the study, describing the stellar sample, and presenting the most interesting results obtained so far, including the aggressive data analysis devoted to the characterization of the variability properties of the sample and the search for transit-like signals.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2673 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5088-5102 ◽

Cited By ~ 4

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.

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PROBLEM OF SUPER-STRONG MAGNETIC FIELDS ON THE SUN: BRIEF CHRONOLOGY AND NEW OBSERVATIONAL DATA

Odessa Astronomical Publications ◽

10.18524/1810-4215.2018.31.144560 ◽

2018 ◽

Vol 31 (0) ◽

pp. 152-158 ◽

Cited By ~ 2

Author(s):

V. G. Lozitsky ◽

V. B. Yurchyshyn ◽

K. Ahn ◽

H. Wang ◽

N. I. Lozitska

Keyword(s):

Magnetic Fields ◽

Observational Data ◽

The Sun ◽

Strong Magnetic Fields

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Molecular Opacities in Cool Dwarf Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100021242 ◽

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.

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