scholarly journals Introductory Remarks on Spectroscopic Parameters

1973 ◽  
Vol 18 ◽  
pp. 73-76
Author(s):  
Helmut A. Abt
Keyword(s):  
Positive Result ◽  
Spectral Type ◽  
Spectroscopic Data ◽  
Main Sequence ◽  
Multiple Star ◽  
Spectroscopic Parameters ◽  
Multiple Systems ◽  
Visual Systems

I hope that you will excuse a relative newcomer to this field and a spectroscopist for presenting his views, which may be somewhat different than those of others. I would like to enumerate the aims of research on visual systems and the needs of the field, particularly for spectroscopic data, as I see them.I. Aims of Multiple-Star Astronomy. (1). Statistics of multiple systems. We would like to know the fraction of stars that are visually double, triple, etc. and in each case as a function of spectral type. For instance, is the frequency of visual doubles the same for Population II stars as for Population I stars? Or are the frequencies of visual doubles the same for stars off the main sequence as for their antecedents on the main sequence? For such information a negative result on duplicity is as important as a positive result, i.e. we wish to know which stars are not seen to be visually double as well as which ones are seen as doubles.

scholarly journals Pre-main sequence multiple systems

2010 ◽  
Vol 6 (S270) ◽  
pp. 41-44
Author(s):  
Hervé Bouy
Keyword(s):  
Main Sequence ◽  
Eclipsing Binaries ◽  
Observational Constraints ◽  
Evolutionary Models ◽  
Multiple Star ◽  
Multiple Systems ◽  
Stellar Radius ◽  
Stellar Formation ◽  
Powerful Approach ◽  
Special Case

AbstractIt is now well established that the majority of young stars are found in multiple systems, so that any theory of stellar formation must account for their existence and properties. Studying the properties of multiple star systems therefore represents a very powerful approach to place observational constraints on star formation theories. Additionally, multiple systems offer other advantages. They provide the most accurate and unambiguous way to measure masses, using orbital fitting and Kepler's laws, and even the stellar radius in the special case of eclipsing binaries. They also allow to compare the properties of 2 coeval objects with different masses, providing important tests for the evolutionary models.

scholarly journals Stellar 5 min Oscillations

1983 ◽  
Vol 66 ◽  
pp. 469-486
Author(s):  
Jørgen Christensen-Dalsgaard ◽  
Søren Frandsen
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Total Flux ◽  
The Sun ◽  
Major Fraction ◽  
Main Sequence Stars ◽  
Red Supergiants

AbstractEstimates are given for the amplitudes of stochastically excited oscillations in Main Sequence stars and cool giants; these were obtained using the equipartition between convective and pulsational energy which was originally proposed by Goldreich and Keeley. The amplitudes of both velocity and luminosity perturbation generally increase with increasing mass along the Main Sequence as long as convection transports a major fraction of the total flux, and the amplitudes also increase with the age of the model. The 1.5 Mʘ ZAMS model, of spectral type F0, has velocity amplitudes ten times larger than those found in the Sun. For very luminous red supergiants luminosity amplitudes of up to about 0ṃ.1 are predicted, in rough agreement with observations presented by Maeder.

scholarly journals The Hipparcos Double and Multiple Star Solutions

1998 ◽  
Vol 11 (1) ◽  
pp. 539-541
Author(s):  
F. Mignard
Keyword(s):  
Detailed Data ◽  
Multiple Star ◽  
Multiple Systems ◽  
Multiple Stars ◽  
Different Types ◽  
Hipparcos Catalogue ◽  
Double And Multiple Stars

Abstract The Hipparcos Catalogue provides general astrometric and photometric information on double and multiple stars in specific fields of the main Catalogue and detailed data on the components in the various sections of a dedicated annex: the Double and Multiple Systems Annex (DMSA). Overall statistics of these solutions are presented for the 13211 entries of this annex and the different types of solutions are outlined.

scholarly journals Interferometric Investigations of Eclipsing Binaries as a Key to an Improved Distance Scale

2006 ◽  
Vol 2 (S240) ◽  
pp. 496-498
Author(s):  
K. Shabun ◽  
A. Richichi ◽  
U. Munari ◽  
A. Siviero ◽  
B. Pacsysnki
Keyword(s):  
Spectral Type ◽  
Effective Temperature ◽  
Binary Systems ◽  
Angular Separation ◽  
Eclipsing Binaries ◽  
Multiple Systems ◽  
Long Baseline ◽  
Global Calibration ◽  
Empirical Calibration ◽  
Full Solution

AbstractBinary and multiple systems constitute one of the main tools for obtaining fundamental stellar parameters, such as masses, radii, effective temperatures and distances. One especially fortunate, and at the same time rare, occurrence is that of double-lined eclipsing binaries with well-detached components. In this special case, it is possible to obtain a full solution of all orbital and stellar parameters, with the exception of the effective temperature of one star, which is normally estimated from spectral type or derived from atmospheric analysis of the spectrum. Long-baseline interferometry at facilities such as the ESO VLTI is beginning to have the capability to measure directly the angular separation and the angular diameter of some selected eclipsing binary systems, and we have proposed such observations with the AMBER instrument. In particular, we aim at deriving directly the effective temperature of at least one of the components in the proposed system, thereby avoiding any assumptions in the global solution through the Wilson–Devinney method. We will also obtain an independent check of the results of this latter method for the distance to the system. This represents the first step towards a global calibration of eclipsing binaries as distance indicators. Our results will also contribute to the effective temperature scale for hot stars. The extension of this approach to a wider sample of eclipsing binaries could provide an independent method to assess the distance to the LMC. The observations will extend accurate empirical calibration to spectral type O9 – B0.

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 The Census of Exoplanets in Visual Binaries: Population Trends from a Volume-Limited Gaia DR2 and Literature Search

2021 ◽  
Vol 8 ◽  
Author(s):  
Clémence Fontanive ◽  
Daniella Bardalez Gagliuffi
Keyword(s):  
Planetary Systems ◽  
Multiple Star ◽  
Multiple Systems ◽  
Binary Separation ◽  
Extensive Search ◽  
Short Period ◽  
Massive Component ◽  
Low Mass ◽  
Cool Gas ◽  
Gaia Dr2

We present results from an extensive search in the literature and Gaia DR2 for visual co-moving binary companions to stars hosting exoplanets and brown dwarfs within 200 pc. We found 218 planet hosts out of the 938 in our sample to be part of multiple-star systems, with 10 newly discovered binaries and 2 new tertiary stellar components. This represents an overall raw multiplicity rate of 23.2 ± 1.6 % for hosts to exoplanets across all spectral types, with multi-planet systems found to have a lower stellar duplicity frequency at the 2.2-σ level. We found that more massive hosts are more often in binary configurations, and that planet-bearing stars in multiple systems are predominantly observed to be the most massive component of stellar binaries. Investigations of the multiplicity of planetary systems as a function of planet mass and separation revealed that giant planets with masses above 0.1 MJup are more frequently seen in stellar binaries than small sub-Jovian planets with a 3.6-σ difference, a trend enhanced for the most massive (>7 MJup) short-period (<0.5 AU) planets and brown dwarf companions. Binarity was however found to have no significant effect on the demographics of low- mass planets (<0.1 MJup) or warm and cool gas giants (>0.5 AU). While stellar companion mass appears to have no impact on planet properties, binary separation seems to be an important factor in the resulting structure of planetary systems. Stellar companions on separations <1000 AU can play a role in the formation or evolution of massive, close-in planets, while planets in wider binaries show similar properties to planets orbiting single stars. Finally, our analyses indicate that numerous stellar companions on separations smaller than 1–3 arcsec likely remain undiscovered to this date. Continuous efforts to complete our knowledge of stellar multiplicity on separations of tens to hundreds of AU are essential to confirm the reported trends and further our understanding of the roles played by multiplicity on exoplanets.

scholarly journals Photometric Study of two Southern Algol Type Binaries

1989 ◽  
Vol 107 ◽  
pp. 376-376
Author(s):  
K. D. Abhyankar ◽  
M. L. Vyas
Keyword(s):  
Spectroscopic Data ◽  
Main Sequence ◽  
Light Curves ◽  
The Other ◽  
Main Sequence Star ◽  
Photometric Study ◽  
The Absolute ◽  
Better Than ◽  
Absolute Dimensions

Complete UBV light-curves of RR-Lep and RX-Hya have been obtained during 1983-87 seasons. Preliminary elements were computed using modified Wellmann’s method. With these parameters as inputs Wilson-Devinney program was executed for Blue and Yellow passbands simultaneously in detached and semi-detached modes for both the systems. The semidetached mode fitted better than the other solution for both the systems. For RR-Lep, the absolute dimensions were computed by assuming the primary to be a slightly evolved main sequence star. For RX-Hya, the absolute dimensions were computed using Struve’s spectroscopic data. The following table gives all the elements for both the systems. The secondaries of both the systems are overluminous for their masses suggesting that they have lost considerable mass.

scholarly journals The Gaia ultracool dwarf sample – II. Structure at the end of the main sequence

2019 ◽  
Vol 485 (3) ◽  
pp. 4423-4440 ◽  
Author(s):  
R L Smart ◽  
F Marocco ◽  
L M Sarro ◽  
D Barrado ◽  
J C Beamín ◽  
...  
Keyword(s):  
Main Sequence ◽  
Absolute Magnitude ◽  
Proper Motions ◽  
Work Package ◽  
Large Area ◽  
Training Set ◽  
Multiple Systems ◽  
Sky Surveys ◽  
Notable Increase ◽  
Complete Catalogue

ABSTRACT We identify and investigate known late M, L, and T dwarfs in the Gaia second data release. This sample is being used as a training set in the Gaia data processing chain of the ultracool dwarfs work package. We find 695 objects in the optical spectral range M8–T6 with accurate Gaia coordinates, proper motions, and parallaxes which we combine with published spectral types and photometry from large area optical and infrared sky surveys. We find that 100 objects are in 47 multiple systems, of which 27 systems are published and 20 are new. These will be useful benchmark systems and we discuss the requirements to produce a complete catalogue of multiple systems with an ultracool dwarf component. We examine the magnitudes in the Gaia passbands and find that the GBP magnitudes are unreliable and should not be used for these objects. We examine progressively redder colour–magnitude diagrams and see a notable increase in the main-sequence scatter and a bivariate main sequence for old and young objects. We provide an absolute magnitude – spectral subtype calibration for G and GRP passbands along with linear fits over the range M8–L8 for other passbands.

scholarly journals The Subdwarf Eclipsing Binary LB3459 (AA Dor)

1982 ◽  
Vol 69 ◽  
pp. 455-456
Author(s):  
R.W. Hilditch ◽  
Graham Hill ◽  
D. Kilkenny
Keyword(s):  
Light Curve ◽  
Observational Data ◽  
Spectroscopic Data ◽  
Main Sequence ◽  
Primary Component ◽  
Curve Analysis ◽  
Current Status ◽  
Evolutionary Models ◽  
Light Curve Analysis ◽  
Normal Composition

A review was presented of the currently available observational data on this evolved system, namely, uvby photometry (Kilkenny et al. 1978; paper II) radial velocities (Kilkenny et al. 1981; paper III) and a non-LTE atmosphere analysis of the primary component (Kudritski et al. 1981). Kudritski et al. conclude that T(pr) = 40000 ± 2500°K and log g = 5.3 ± 0.2 and from the spectroscopic data and light curve analysis (papers II, III) derive masses and radii for the primary and secondary components of M(pr) ≃ 0.25 M⊙, M(sec) ≃ 0.04 M⊙, R(pr) ≃ 0.16R⊙, R(sec) ≃ 0.09R⊙ respectively. Thus the primary component is a normal sd0 star whilst the secondary component is a most enigmatic object, perhaps a normal composition degenerate dwarf but of too low a mass to be on the main sequence, perhaps an evolved degenerate object but then the radius is too large. The published evolutionary models for this system (Paczynski 1980; Conti et al 1981) do not adequately describe its current status.

scholarly journals Accuracy of Spectral Classification

1983 ◽  
Vol 62 ◽  
pp. 118-119
Author(s):  
Helmut A. Abt
Keyword(s):  
Spectral Type ◽  
Quantitative Information ◽  
Spectral Lines ◽  
Spectral Classification ◽  
Signal To Noise ◽  
Independent System ◽  
Visual Systems ◽  
Other Information

A knowledge of the spectral types of visual components is still basic to most intensive studies of visual systems. Although there are photoelectric techniques that give good quantitative information on certain classes of stars, the only way at present to identify most classes of stars, from mercury-manganese stars to barium stars, is by obtaining their spectra. The spectra can be obtained from objective prisms, slit spectrographs, or spectrum scans, but the important things are that they (1) show a large portion of the spectra, preferrably in the blue-violet for most classes of stars, (2) have sufficient resolution and signal-to-noise to identify many spectral lines, and (3) be standardized as an independent system. The last is important because if spectral type standards are changed so that they will agree with other information, such as colors, we lose the benefits of a comparison, such as deriving interstellar reddening.

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