Spectroscopic Binaries among Low-Mass Pre-Main Sequence Stars

1989 ◽  
pp. 111-115 ◽  
Author(s):  
Robert D. Mathieu
Keyword(s):  
Main Sequence ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Low Mass

scholarly journals The Mass Distribution of Secondaries to Solar-Type Stars

2004 ◽  
Vol 191 ◽  
pp. 37-40 ◽  
Author(s):  
Helmut A. Abt ◽  
Daryl W. Willmarth
Keyword(s):  
Radial Velocity ◽  
Mass Distribution ◽  
Main Sequence ◽  
Mass Function ◽  
Spectroscopic Binaries ◽  
Orbital Elements ◽  
Main Sequence Stars ◽  
Solar Type ◽  
Low Mass ◽  
Good Agreement

AbstractTwo previous studies of the secondary mass function in spectroscopic binaries by Abt & Levy (1976) and by Duquennoy & Mayor (1991) are shown to be in good agreement if they are both plotted with the same abscissa scale. A new study of 271 main-sequence stars later than F6 V made with a radial-velocity accuracy of ±0.10 km s-1 yielded 10 new sets of orbital elements in addition to the 59 published ones. The resulting secondary mass function is nearly flat and shows that 2.2±1.5% of the primaries have low-mass (0.01–0.10 M⊙) companions. In contrast, the secondary mass function for visual binaries with separations >500 AU fits a van Rhijn function, as was shown previously by Abt and Levy.

scholarly journals Are sdAs helium core stars?

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Ingrid Pelisoli ◽  
S. O. Kepler ◽  
Detlev Koester
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Physical Nature ◽  
Sloan Digital Sky Survey ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
Sky Survey ◽  
Balmer Lines ◽  
Low Mass ◽  
Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

scholarly journals The discovery of low-mass pre-main-sequence stars in Cepheus OB3b

2003 ◽  
Vol 341 (3) ◽  
pp. 805-822 ◽  
Author(s):  
M. Pozzo ◽  
T. Naylor ◽  
R. D. Jeffries ◽  
J. E. Drew
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Low Mass

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 Age-related observations of low mass pre-main and young main sequence stars

2008 ◽  
Vol 4 (S258) ◽  
pp. 81-94 ◽  
Author(s):  
Lynne A. Hillenbrand
Keyword(s):  
Main Sequence ◽  
Rotation Period ◽  
Age Dating ◽  
Main Sequence Stars ◽  
Solar Mass ◽  
Age Related ◽  
Stellar Ages ◽  
Dating Methods ◽  
Low Mass ◽  
Lithium Depletion

AbstractThis overview summarizes the age dating methods available for young sub-solar mass stars. Pre-main sequence age diagnostics include the Hertzsprung-Russell (HR) diagram, spectroscopic surface gravity indicators, and lithium depletion; asteroseismology is also showing recent promise. Near and beyond the zero-age main sequence, rotation period or vsiniand activity (coronal and chromospheric) diagnostics along with lithium depletion serve as age proxies. Other authors in this volume present more detail in each of the aforementioned areas. Herein, I focus on pre-main sequence HR diagrams and address the questions: Do empirical young cluster isochrones match theoretical isochrones? Do isochrones predict stellar ages consistent with those derived via other independent techniques? Do the observed apparent luminosity spreads at constant effective temperature correspond to true age spreads? While definitive answers to these questions are not provided, some methods of progression are outlined.

Behavior of low-mass main-sequence stars in response to accretion

1989 ◽  
Vol 341 ◽  
pp. 306 ◽  
Author(s):  
Masayuki Y. Fujimoto ◽  
Icko, Jr. Iben
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Low Mass

scholarly journals Discovery of Three Very Low Mass Binary Systems: An Adaptive Optics Survey of M6.0–M7.5 Stars

2003 ◽  
Vol 211 ◽  
pp. 257-260
Author(s):  
Nick Siegler ◽  
Laird M. Close ◽  
Eric E. Mamajek ◽  
Melanie Freed
Keyword(s):  
Adaptive Optics ◽  
Binary Systems ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Solar Mass ◽  
Low Mass ◽  
M Stars ◽  
Adaptive Optics System

We have used the adaptive optics system Hōkūpa'a at Gemini North to search for companions from a flux-limited (Ks > 12) survey of 30 nearby M6.0–M7.5 dwarfs. Our observations, which are sensitive to companions with separations > 0.1″ (~ 2.8 AU), detect 3 new binary systems. This implies an overall binary fraction of 9±4% for M6.0–M7.5 binaries. This binary frequency is somewhat less than the 19±7% measured for late M stars and ~ 20% for L stars, but is still statistically consistent. However, the result is significantly lower than the binary fractions observed amongst solar mass main sequence stars (~60%) and early M stars (~35%).

scholarly journals Rotation of Pre-Main Sequence Stars from High S/N Spectroscopy

1988 ◽  
Vol 132 ◽  
pp. 95-98
Author(s):  
J. Bouvier
Keyword(s):  
Stellar Evolution ◽  
Main Sequence ◽  
Spectroscopic Studies ◽  
Main Sequence Stars ◽  
Rotation Rates ◽  
Large Samples ◽  
Stellar Formation ◽  
Low Mass ◽  
Pms Stars ◽  
Large Telescopes

Until 1980, only a handful of low-mass, active pre-main sequence (pms) stars had known rotation velocities (vsini) /1/. Since then, increasingly sensitive detectors coupled to large telescopes led to high–resolution (a few 104) spectroscopic studies of these faint stars (mv = 10–13), with S/N ratio of the order of 100. The measurement of vsini for large samples of pms stars that resulted brought new insights on various pressing questions related to stellar formation and early stellar evolution : how do the rotation rates of pms stars compare with those expected from models of stellar formation ? how does the stellar angular momentum change during pms evolution ? is pms activity linked with rotation as would be expected if activity were triggered by magnetic processes ?

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