scholarly journals Chemically Peculiar Stars Among Spectroscopic Binaries – Revisited

1993 ◽  
Vol 138 ◽  
pp. 137-142 ◽  
Author(s):  
Wilhelm Seggewiss
Keyword(s):  
Relative Frequency ◽  
Main Sequence ◽  
Statistical Investigation ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Eccentric Orbits ◽  
Peculiar Stars ◽  
Orbital Periods ◽  
Chemically Peculiar Stars ◽  
The Masses

AbstractThis paper presents a new statistical investigation of peculiar A-type stars (Am, Ap, Hg-Mn) among spectroscopic binary (SB) stars. The relative frequency of Am (CP 1) stars is 55% in the spectral range A1 to A6 of main-sequence stars. The Ap (CP 2) stars amount to 15% in the range B9 to A2. The Hg-Mn stars are concentrated to the spectral types B8 to AO and reach a relative frequency of 23%. The Am SB stars have the shortest orbital periods and the smallest eccentricities (30% circular) whereas the Ap SB stars show a strong tendency to long periods and highly eccentric orbits (only 10% circular). The masses of the Am stars agree with the masses of non-peculiar SB stars of corresponding spectral type.

scholarly journals A Spectroscopic and Photometric Survey for Pre-Main Sequence Binaries

2001 ◽  
Vol 200 ◽  
pp. 165-168 ◽  
Author(s):  
Eike W. Guenther ◽  
Viki Joergens ◽  
Ralph Neuhäuser ◽  
Guillermo Torres ◽  
Natalie Stout Batalha ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Current State ◽  
Short Period ◽  
Velocity Variations ◽  
The Masses ◽  
Stellar Masses ◽  
Crucial Test

We give here an overview of the current state of our survey for pre-main sequence spectroscopic binaries. Up to now we have taken 739 spectra of 250 pre-main sequence stars. We find that 8% of the stars show significant radial velocity variations, and are thus most likely spectroscopic binaries. In addition to the targets showing radial velocity variations, 6% of the targets are double-lined spectroscopic binaries i.e., the total fraction of spectroscopic binaries is expected to be about 14%. All short-period SB2s are monitored photometrically in order to search for eclipses. An eclipsing SB2 would allow the direct measurement of the masses of both stellar components. Measurements of the stellar masses together with determinations of the stellar radii are a crucial test of evolutionary tracks of pre-main sequence stars.

scholarly journals Surveys of Spectroscopic Binaries at the Center for Astrophysics

1992 ◽  
Vol 135 ◽  
pp. 110-118
Author(s):  
D.W. Latham
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Eccentric Orbits ◽  
Binary Formation ◽  
Wide Range ◽  
Formation And Evolution ◽  
Better Than

Abstract For more than a decade we have been measuring stellar radial velocities with three almost identical digital speedometers on telescopes in Arizona and Massachusetts. By now we have accumulated nearly 100,000 measurements with a typical precision of better than 1 km s-1. One of the main scientific applications has been surveys of binaries in several different stellar environments, to study the frequency and orbital characteristics of binaries in a variety of stellar populations. A main goal is to confront theories of binary formation and evolution with observational results. With various collaborators we have investigated the binary populations among pre-main-sequence stars, in the Hyades and M67 open clusters, and in the Carney-Latham proper-motion sample. Thus, we have data for coeval samples of binaries covering a wide range of ages. One result is clear evidence for evolution of binary orbits. The orbital period at which there is a transition from circular to eccentric orbits gets longer for older samples of binaries, presumably due to tidal circularization. Another result is that the frequency of binaries does not seem to depend on the stellar population. Binaries are just as common among the oldest stars in the halo of our Galaxy as among the younger stars in the disk.

Main Sequence Abundances: Observational Aspects

1988 ◽  
Vol 108 ◽  
pp. 2-2
Author(s):  
Jun Jugaku
Keyword(s):  
Chemical Composition ◽  
Effective Temperature ◽  
Main Sequence ◽  
Theoretical Models ◽  
Current Data ◽  
Main Sequence Stars ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
F Stars

AbstractAlthough once it was thought that main-sequence stars are remarkably homogeneous with respect to their chemical composition, the upper main-sequence stars (30000 > Te > 7000) show a variaety of chemically peculiar stars besides the so-called normal stars. Those include the Am, Ap, λ Bootis, He-deficient, and He-rich stars. This review summarizes the current data, which are necessary to construct and test the theoretical models of these stars. In the second half of the review we concentrate on Li. In the lower main-sequecnce stars abundances of Li have been determined in hundreds of stars. Some of the remarkable results are: (1) A uniform upper abundance value irrespective of stellar effective temperature, (2) abundance gap in the F stars of the Hyades, and (3) increasing depletion with smaller stellar mass for the Hyades.

scholarly journals Pulsars in Globular Clusters

2007 ◽  
Vol 3 (S246) ◽  
pp. 291-300 ◽  
Author(s):  
Scott M. Ransom
Keyword(s):  
Equation Of State ◽  
Neutron Stars ◽  
Globular Clusters ◽  
Main Sequence ◽  
Galactic Disk ◽  
Nuclear Density ◽  
Millisecond Pulsars ◽  
Eccentric Orbits ◽  
The Masses ◽  
Current Record

AbstractGlobular clusters produce orders of magnitude more millisecond pulsars per unit mass than the Galactic disk. Since the first cluster pulsar was uncovered 20 years ago, at least 138 have been identified – most of which are binary millisecond pulsars. Because their origins involve stellar encounters, many of the systems are exotic objects that would never be observed in the Galactic disk. Examples include pulsar-main sequence binaries, extremely rapid rotators (including the current record holder), and millisecond pulsars in highly eccentric orbits. These systems are allowing new probes of the interstellar medium, the equation of state of material at supra-nuclear density, the masses of neutron stars, and globular cluster dynamics.

scholarly journals 29. Stellar Spectra

1982 ◽  
Vol 18 (1) ◽  
pp. 343-360 ◽  
Author(s):  
W.K. Bonsack
Keyword(s):  
Stellar Evolution ◽  
Working Group ◽  
Main Sequence ◽  
Symbiotic Stars ◽  
Be Stars ◽  
Stellar Spectra ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
Ap Stars

During the interval covered by this report, Commission 29 has sponsored or cosponsored the following IAU meetings: Symposium 98 on “Be Stars,” Munich, FRG, April 1981; Colloquium 59, “Effects of Mass-Loss on Stellar Evolution,” Trieste, Italy, September 1980; and Colloquim 70, “The Nature of Symbiotic Stars,” Haute-Provence, France, August 1981. In addition, Commission 29, through its Working Group on Ap Stars, collaborated in the organization of the 23rd Liege International Astrophysical Symposium on Upper Main-Sequence Chemically Peculiar Stars. Several IAU symposia and colloquia proposed for 1982 and 1983 are also cosponsored by Commission 29.

scholarly journals The Evolutionary Status of the Secondaries of Cataclysmic Binaries

1983 ◽  
Vol 72 ◽  
pp. 257-262
Author(s):  
H. Ritter
Keyword(s):  
Probability Distribution ◽  
Main Sequence ◽  
The Other ◽  
Initial Mass ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Main Sequence Stars ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Orbital Periods

ABSTRACTIt is shown that the secondary components of cataclysmic binaries with orbital periods of less than ~10 hours are indistinguishable from ordinary low-mass main-sequence stars and that, therefore, they are essentially unevolved. On the other hand, it is shown that, depending on the mass ratio of the progenitor system, the secondary of a cataclysmic binary could be significantly evolved. The fact that nevertheless most of the observed secondaries are essentially unevolved can be accounted for by assuming that the probability distribution for the initial mass ratio is not strongly peaked towards unity mass ratio.

scholarly journals Masses of the components of SB2 binaries observed with Gaia – V. Accurate SB2 orbits for 10 binaries and masses of the components of 5 binaries

2020 ◽  
Vol 496 (2) ◽  
pp. 1355-1368
Author(s):  
J-L Halbwachs ◽  
F Kiefer ◽  
Y Lebreton ◽  
H M J Boffin ◽  
F Arenou ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Binary Stars ◽  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Orbital Elements ◽  
Evolved Stars ◽  
The Individual ◽  
The Masses ◽  
Stellar Masses ◽  
Selection Of

ABSTRACT Double-lined spectroscopic binaries (SB2s) are one of the main sources of stellar masses, as additional observations are only needed to give the inclinations of the orbital planes in order to obtain the individual masses of the components. For this reason, we are observing a selection of SB2s using the SOPHIE spectrograph at the Haute-Provence observatory in order to precisely determine their orbital elements. Our objective is to finally obtain masses with an accuracy of the order of one per cent by combining our radial velocity (RV) measurements and the astrometric measurements that will come from the Gaia satellite. We present here the RVs and the re-determined orbits of 10 SB2s. In order to verify the masses, we will derive from Gaia, we obtained interferometric measurements of the ESO VLTI for one of these SB2s. Adding the interferometric or speckle measurements already published by us or by others for four other stars, we finally obtain the masses of the components of five binary stars, with masses ranging from 0.51 to 2.2 solar masses, including main-sequence dwarfs and some more evolved stars whose location in the HR diagram has been estimated.

scholarly journals Discovery of Secular Evolution of the Atmospheric Abundances of Ap Stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 365-366
Author(s):  
J. D. Bailey ◽  
J. D. Landstreet ◽  
S. Bagnulo
Keyword(s):  
Main Sequence ◽  
Chemical Abundance ◽  
Mixing Processes ◽  
Chemical Tracers ◽  
Secular Evolution ◽  
Abundance Patterns ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars ◽  
Ap Stars

AbstractThe stars of the middle main-sequence have relatively quiescent outer layers, and unusual chemical abundance patterns may develop in their atmospheres, revealing the action of such subsurface phenomena as gravitational settling and radiatively driven levitation of trace elements, and their competition with mixing processes such as turbulent diffusion. We report the discovery of the time evolution of such chemical tracers through the main-sequence lifetime of magnetic chemically peculiar stars.

scholarly journals Circumstellar Disks and Star Formation

1992 ◽  
Vol 9 ◽  
pp. 377-380
Author(s):  
L. Hartmann ◽  
M. Gomez ◽  
S.J. Kenyon
Keyword(s):  
Star Formation ◽  
Spectral Region ◽  
Main Sequence ◽  
Circumstellar Disks ◽  
Central Star ◽  
Disk Accretion ◽  
Main Sequence Stars ◽  
Excess Emission ◽  
Infrared Spectral ◽  
The Masses

Results from the IRAS satellite showed that many pre-main sequence stars exhibited unexpectedly large fluxes in the infrared spectral region. Several studies have shown that the simplest and most satisfying explanation of this excess emission is that it arises in optically-thick, dusty, circumstellar disks (Rucinski 1985; Adams, Lada, and Shu 1987, 1988; Kenyon and Hartmann 1987; Bertout, Basri, and Bouvier 1988; Basri and Bertout 1989). The masses of these disks are estimated to range between 10-3M⊙ to 1M⊙ (Beckwith et al. 1990; Adams et al. 1990), large enough that disk accretion may have a significant effect on the evolution of the central star. Indeed, Mercer-Smith, Cameron, and Epstein (1984) suggested that stars are essentially completely accreted from disks, rather than formed from quasi-spherical accretion (Stabler 1983, 1988).

scholarly journals HST/STIS analysis of the first main sequence pulsar CU Virginis

2019 ◽  
Vol 625 ◽  
pp. A34 ◽  
Author(s):  
J. Krtička ◽  
Z. Mikulášek ◽  
G. W. Henry ◽  
J. Janík ◽  
O. Kochukhov ◽  
...  
Keyword(s):  
Radio Emission ◽  
Main Sequence ◽  
Flux Distribution ◽  
Mass Loss Rate ◽  
Rotational Period ◽  
Uv Spectrum ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemically Peculiar Stars

Context. CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. Aims. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. Methods. We used our own far-UV and visual photometric observations supplemented with the archival data to improve the parameters of the quasisinusoidal long-term variations of the rotational period. We predict the flux variations of CU Vir from surface abundance maps and compare these variations with UV flux distribution. We searched for wind, auroral, and interstellar lines in the spectra. Results. The UV and visual light curves display the same long-term period variations supporting their common origin. New updated abundance maps provide better agreement with the observed flux distribution. The upper limit of the wind mass-loss rate is about 10−12 M⊙ yr−1. We do not find any auroral lines. We find rotationally modulated variability of interstellar lines, which is most likely of instrumental origin. Conclusions. Our analysis supports the flux redistribution from far-UV to near-UV and visual domains originating in surface abundance spots as the main cause of the flux variability in chemically peculiar stars. Therefore, UV and optical variations are related and the structures leading to these variations are rigidly confined to the stellar surface. The radio emission of CU Vir is most likely powered by a very weak presumably purely metallic wind, which leaves no imprint in spectra.

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