scholarly journals Discovering new spectroscopic components in visual multiple stars

1999 ◽  
Vol 170 ◽  
pp. 347-353 ◽  
Author(s):  
A.A. Tokovinin
Keyword(s):  
Angular Momentum ◽  
Radial Velocity ◽  
Radial Velocities ◽  
Common Origin ◽  
The Other ◽  
Close Binaries ◽  
Stellar Systems ◽  
Random Combination ◽  
Multiple Stars ◽  
Almost All

AbstractA radial velocity survey of the components of visual multiple stars has been done since 1994 with the correlation radial velocity spectrometer. About 50 spectroscopic sub-systems have been discovered, and a summary of the 30 published orbits is given. Difficulties of measuring the radial velocities of multiple stars are discussed and illustrated by 2 examples. New discoveries will lead to a better understanding of the formation of multiple stellar systems. Close and wide sub-systems can not be considered as a result of independent random combination, but are related by common origin. Almost all close binaries with periods less than 6 days possibly have more distant components which assisted in the formation of close pairs by taking away their angular momentum. On the other hand, among the distant visual tertiary companions the frequency of sub-systems with periods under 100 days is about 3 times higher than for field G dwarfs.

scholarly journals Art. V.—Remarks on the Language of the Amazirghs, commonly called Berebbers

1836 ◽  
Vol 3 (5) ◽  
pp. 106-160
Author(s):  
Jacob Gräberg
Keyword(s):  
Common Origin ◽  
The Other ◽  
The Face ◽  
Almost All ◽  
Social Intercourse ◽  
Different Origin

The original inhabitants of Mount Atlas, and of nearly all the provinces of Maghrib-ul-Aksa, or the present empire of Marocco, are usually divided into two tribes — namely, the Berebbers and the Shelluhhs, both descended from the ancient Mauritanians and Gætulians; perhaps even from the Libyes of Sallust. These two tribes differ essentially from each other; and it is not without reason, that those travellers and geographers, to whom we are indebted for the best information with respect to Marocco, have asserted that the Shelluhhs are not Berebbers. The Moors, or Arabian inhabitants of the country, consider them as two nations of a different origin; as well on account of their manners and the diversity of their natural dispositions, as from the entirely distinct profile of the face, and from their dialects, which differ so much, that they cannot converse together without the aid of an interpreter. Mr. James Grey Jackson, in his Account of the Empire of Marocco, and of the District of Sus, confirms this assertion by a list of words of common use in both languages; and, most certainly, they prove nothing less than a common origin. But such differences, radical or accidental, may be met with in almost all the sister languages. It is, for instance, a curious fact, that the very leading Shelluhh words, which Mr. Jackson quotes as altogether differing from the Berebber, as woman, wife, boy, girl, &c. differ just as much, if not more, in the Swedish, Danish, German, and Dutch languages, which, most undoubtedly, are of one and the same origin. This observation holds good even with respect to the Spanish, Portuguese, and Italian languages. What is more certain, and beyond all doubt, is, that the pretended Berebbers and Shelluhhs live separately and that they bear very little, if any, relation to each other. Although their habitations are sometimes very near, they never have any social intercourse; nor does an instance exist of individuals of one tribe having intermarried with the other.

scholarly journals The Radial Velocities of Galaxies Near NGC 7331

1972 ◽  
Vol 44 ◽  
pp. 376-379 ◽  
Author(s):  
C. R. Lynds
Keyword(s):  
Radial Velocity ◽  
Radial Velocities ◽  
The Other ◽  
Physical Systems

Radial velocity determinations for galaxies in the vicinity of NGC 7331, including the members of ‘Stephan's Quintet’, show clearly a superposition of at least two distinct physical systems. One includes NGC 7331, NGC 7320 (a Quintet member), and NGC 7343, while the other - seven or eight times more distant - contains the four remaining ‘Quintet’ constituents and six of the seven optical ‘companions’ of NGC 7331.

scholarly journals Searching for Earth-mass planets around α Centauri: precise radial velocities from contaminated spectra

2014 ◽  
Vol 14 (2) ◽  
pp. 173-176 ◽  
Author(s):  
Christoph Bergmann ◽  
Michael Endl ◽  
John B. Hearnshaw ◽  
Robert A. Wittenmyer ◽  
Duncan J. Wright
Keyword(s):  
Binary System ◽  
Radial Velocity ◽  
Binary Systems ◽  
Angular Separation ◽  
Radial Velocities ◽  
The Other ◽  
Cross Contamination ◽  
Star System ◽  
Spectroscopic Binary ◽  
Ongoing Project

AbstractThis work is part of an ongoing project which aims to detect terrestrial planets in our neighbouring star system α Centauri using the Doppler method. Owing to the small angular separation between the two components of the α Cen AB binary system, the observations will to some extent be contaminated with light coming from the other star. We are accurately determining the amount of contamination for every observation by measuring the relative strengths of the H-α and NaD lines. Furthermore, we have developed a modified version of a well-established Doppler code that is modelling the observations using two stellar templates simultaneously. With this method we can significantly reduce the scatter of the radial velocity (RV) measurements due to spectral cross-contamination and hence increase our chances of detecting the tiny signature caused by potential Earth-mass planets. After correcting for the contamination we achieve RV precision of ~2.5 m s−1 for a given night of observations. We have also applied this new Doppler code to four southern double-lined spectroscopic binary systems (HR159, HR913, HR7578 and HD181958) and have successfully recovered radial velocities for both components simultaneously.

scholarly journals Frequency of Planets in Binaries

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 16 ◽  
Author(s):  
Mariangela Bonavita ◽  
Silvano Desidera
Keyword(s):  
White Dwarf ◽  
The Other ◽  
Extrasolar Planet ◽  
Stellar Systems ◽  
Orbital Parameters ◽  
Multiple Stars ◽  
Binary Sample ◽  
Data Release ◽  
Formation And Evolution ◽  
Good Agreement

The frequency of planets in binaries is an important issue in the field of extrasolar planet studies because of its relevance in the estimation of the global planet population of our galaxy and the clues it can give to our understanding of planet formation and evolution. Multiple stars have often been excluded from exoplanet searches, especially those performed using the radial velocity technique, due to the technical challenges posed by such targets. As a consequence and despite recent efforts, our knowledge of the frequency of planets in multiple stellar systems is still rather incomplete. On the other hand, the lack of knowledge about the binarity at the time of the compilation of the target samples means that our estimate of the planet frequency around single stars could be tainted by the presence of unknown binaries, especially if these objects have a different behavior in terms of planet occurrence. In a previous work we investigated the binarity of the objects included in the Uniform Detectability sample defined by Fisher and Valenti (2005), showing how more than 20% of their targets were, in fact, not single stars. Here, we present an update of this census, made possible mainly by the information now available thanks to the second Gaia Data Release. The new binary sample includes a total of 313 systems, of which 114 were added through this work. We were also able to significantly improve the estimates of masses and orbital parameters for most of the pairs in the original list, especially those at close separations. A few new systems with white dwarf companions were also identified. The results of the new analysis are in good agreement with the findings of our previous work, confirming the lack of difference in the overall planet frequency between binaries and single stars but suggesting a decrease in the planet frequency for very close pairs.

scholarly journals Are there carbon stars in the Bulge?

1999 ◽  
Vol 191 ◽  
pp. 545-550
Author(s):  
Yuen Keong Ng
Keyword(s):  
Star Formation ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Dwarf Galaxy ◽  
Radial Velocities ◽  
The Other ◽  
Agb Stars ◽  
Carbon Stars ◽  
Other Hand

The Bulge carbon stars have been a mystery since their discovery by Azzopardi et al. (1991), because they are about too faint to be regarded as genuine AGB stars, if located inside the metal-rich Bulge . Part of the mystery can be solved if these carbon stars are related to the Sagittarius dwarf galaxy . They are in that case not old and metal-rich, but young, ∼0.1 Gyr, with SMC-like metallicity (Ng 1998).The σRV = 113 ± 14 km s−1 (Tyson & Rich 1991) radial velocity dispersion of the stars appears to be consistent with Bulge membership. On the other hand, a similar velocity dispersion could be the result from an induced star formation event when the SDG crosses the galactic midplane. It is suggested that the carbon stars are tracers of such an event and that they therefore are located at distances related to the SDG. However, the majority of the carbon stars are not member of the SDG, nor are they similar to the C-stars which are member of the SDG.The radial velocities can be used to determine a possible membership to the SDG. However, they do not give information about the distance of the stars. In particular, if the stars are located at a distance comparable to the SDG. This implies that only the period-luminosity relation (Groenewegen & Whitelock 1996) can be used to distinguish unambiguously if the carbon stars are located at Bulge-like or SDG-like distances. Thus far only carbon stars with reliable periods have been identified at a SDG related distance (Ng & Schultheis 1997; Whitelock 1998).

scholarly journals Statistics Of Multiple Stars

2004 ◽  
Vol 191 ◽  
pp. 7-14 ◽  
Author(s):  
A. Tokovinin
Keyword(s):  
Stability Limit ◽  
Orbital Evolution ◽  
Close Binaries ◽  
Stellar Systems ◽  
Hierarchical Systems ◽  
Momentum Exchange ◽  
Multiple Systems ◽  
Multiple Stars ◽  
Short Period ◽  
Low Mass

AbstractThe statistics of stellar systems of multiplicity three and higher is reviewed. They are frequent, 0.15−0.25 of all stellar systems. Some 700 multiples are expected among the 3383 stars of spectral type F, G, and K within 50 pc, while only 76 of them are actually known. Many (if not all) close binaries have distant tertiary components, indicating that angular momentum exchange within multiple systems was probably critical in forming short-period binaries. The ratio of outer to inner periods in the best-studied nearby multiples and in low-mass pre-main sequence multiples does not exceed 104 at the formation epoch; larger ratios are produced by subsequent orbital evolution. All multiples with well-defined orbits are dynamically stable, the eccentricities of outer orbits obey the empirical stability limit Pout(1 – eout)3/Pin > 5 that is more strict than current theoretical limits. Relative orientation of orbits in triple stars shows some degree of alignment, especially in weakly-hierarchical systems. The statistics support the idea that most multiple stars originated from dynamical interactions in small clusters.

scholarly journals Tracing Hercules in Galactic azimuth with Gaia DR2

2019 ◽  
Vol 632 ◽  
pp. A107 ◽  
Author(s):  
G. Monari ◽  
B. Famaey ◽  
A. Siebert ◽  
O. Bienaymé ◽  
R. Ibata ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Radial Velocity ◽  
Major Axis ◽  
The Other ◽  
Data Release ◽  
Stellar Velocity ◽  
Pattern Speed ◽  
Gaia Dr2 ◽  
Lindblad Resonance ◽  
Exact Origin

The second data release of the Gaia mission has revealed, in stellar velocity and action space, multiple ridges, the exact origin of which is still debated. Recently, we demonstrated that a large Galactic bar with pattern speed 39 km s−1 kpc−1 creates most of the observed ridges. Among these ridges, the Hercules moving group would then be associated with orbits trapped at the co-rotation resonance of the bar. Here we show that a distinctive prediction of such a model is that the angular momentum of Hercules at the Sun’s radius must significantly decrease with increasing Galactocentric azimuth (i.e. when getting closer to the major axis of the bar). We show that this dependence of the angular momentum of trapped orbits on the azimuth on the other hand does not happen close to the outer Lindblad resonance of a faster bar, unless the orbital distribution is still far from phase-mixed, namely for a bar perturbation younger than ∼2 Gyr. Using Gaia DR2 and Bayesian distances from the StarHorse code, and tracing the average Galactocentric radial velocity as a function of angular momentum and azimuth, we show that the Hercules angular momentum changes significantly with azimuth as expected for the co-rotation resonance of a dynamically old large bar.

scholarly journals Do maser stars trace a rotating Galactic bar?

2007 ◽  
Vol 3 (S242) ◽  
pp. 356-360
Author(s):  
H. J. Habing
Keyword(s):  
Radial Velocity ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Small Sample ◽  
Radial Velocities ◽  
Galactic Centre ◽  
Galactic Rotation ◽  
Realistic Potential ◽  
Large Samples ◽  
Almost All

AbstractI have analyzed the radial velocities in two large samples of maser stars that cover the Galactic plane from l = +40deg to l = −40deg through the Galactic Centre. I compare a diagram of longitude versus radial velocity as observed with a diagram obtained from the calculation of orbits in a simple, but realistic potential containing a weak, rotating bar. Almost all stars belong to the Galactic disk but there is a small sample with high velocities close to the Galactic Centre and in the so-called forbidden quadrants. These velocities cannot be explained by a combination of pure Galactic rotation and a modest dispersion in velocity. An acceptable explanation is one in which the stars of this small sample move up and down a rotating Galactic bar.

Starość w nauczaniu św. Bazylego Wielkiego

Vox Patrum ◽  
2011 ◽  
Vol 56 ◽  
pp. 339-348
Author(s):  
Bogdan Czyżewski
Keyword(s):  
Old Age ◽  
Spiritual Maturity ◽  
The Other ◽  
Interesting Aspect ◽  
Other Hand ◽  
Physical Suffering ◽  
Way Of Thinking ◽  
Almost All

Although St. Basil did not live 50 years, the topic of the old age appears in his works quite often. On the other hand, it is clear that Basil does not discuss this issue in one par­ticular work or in the longer argumentation. The fragmentary statements about old age can be found in almost all his works, but most of them can be found in the correspondence of Basil. In this paper we present the most important ad the most interesting aspect of teach­ing of Basil the Great. As these certificates show that the bishop of Caesarea looked at the old age maturely, rationally estimated passage of time, which very often makes a man different. He experienced it, for example as a spiritual and physical suffering, which often were connected with his person. He saw a lot of aspect of the old age, especially its advan­tages – spiritual maturity and wisdom. What is more, he pointed also to passage of time, which leads a man to eternity, which should be prepared to, regardless how old he is. In his opinion fear is not seen opinions of St. Basil present really Christian way of thinking, well-balanced and calm.

scholarly journals Astrometric Radial Velocities From Hipparcos

1998 ◽  
Vol 11 (1) ◽  
pp. 564-564
Author(s):  
D. Dravins ◽  
L. Lindegren ◽  
S. Madsen ◽  
J. Holmberg
Keyword(s):  
Radial Velocity ◽  
High Precision ◽  
Radial Velocities ◽  
Radial Motion ◽  
Spectral Lines ◽  
Parallel Program ◽  
Stellar Surface ◽  
Space Astrometry ◽  
Stellar Motion ◽  
Surface Convection

Abstract Space astrometry now permits accurate determinations of stellar radial motion, without using spectroscopy. Although the feasibility of deducing astrometric radial velocities from geometric projection effects was realized already by Schlesinger (1917), only with Hipparcos has it become practical. Such a program has now been carried out for the moving clusters of Ursa Major, Hyades, and Coma Berenices. Realized inaccuracies reach about 300 m/s (Dravins et al. 1997). Discrepancies between astrometric and spectroscopic radial velocities reveal effects (other than stellar motion) that affect wavelength positions of spectral lines. Such are caused by stellar surface convection, and by gravitational redshifts. A parallel program (Gullberg & Dravins 1997) is analyzing high-precision spectroscopic radial velocities for different spectral lines in these stars, using the ELODIE radial-velocity instrument atHaute-Provence.

Sign in / Sign up

Export Citation Format

Share Document