Asymmetric Dark Matter Imprint on Low-mass Main-sequence Stars in the Milky Way Nuclear Star Cluster

A review of observational searches reveals the following constraints for the constituents of dark halos: (1) Optical searches show that these halos are not for a large fraction of their mass made up of dwarfs of spectral type M5 or earlier. (2) K-band (2.2 μ) searches virtually rule out all H- burning Main Sequence stars. (3) IRAS upper limits are consistent with black dwarfs of any age or Jupiters. (4) The inferred metallicity and M/L variations in the spheroid of NGC 7814 are consistent with the hypothesis that the dark matter consists of low mass objects that formed along with the luminous population II.

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Are sdAs helium core stars?

Open Astronomy ◽

10.1515/astro-2017-0433 ◽

2017 ◽

Vol 26 (1) ◽

Cited By ~ 4

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.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2003.06447.x ◽

2003 ◽

Vol 341 (3) ◽

pp. 805-822 ◽

Cited By ~ 19

Author(s):

M. Pozzo ◽

T. Naylor ◽

R. D. Jeffries ◽

J. E. Drew

Keyword(s):

Main Sequence ◽

Main Sequence Stars ◽

Low Mass

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Response of Low-Mass Main Sequence Stars to Accretion

Effects of Mass Loss on Stellar Evolution - Astrophysics and Space Science Library ◽

10.1007/978-94-009-8500-1_58 ◽

1981 ◽

pp. 401-403

Author(s):

Masayuki Y. Fujimoto ◽

Icko Iben ◽

Stephen A. Becker

Keyword(s):

Main Sequence ◽

Main Sequence Stars ◽

Low Mass

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The Evolutionary Status of the Secondaries of Cataclysmic Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100090394 ◽

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.

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A comparison of the density gradients of main sequence stars obtained by two different methods in different galactic latitudes

Symposium - International Astronomical Union ◽

10.1017/s0074180900000620 ◽

1970 ◽

Vol 38 ◽

pp. 232-235

Author(s):

W. Becker ◽

R. Fenkart

Keyword(s):

Main Sequence ◽

Milky Way ◽

Absolute Magnitude ◽

Galactic Centre ◽

Density Gradients ◽

The Sun ◽

Main Sequence Stars

The Basel Observatory program of the determination of disc- and halo-density gradients for different intervals of absolute magnitude comprises in addition to Milky Way fields several directions, all pointing to Selected Areas near a plane perpendicular to the galactic equator and passing through the sun and the galactic centre. It was started with SA 51 (Becker, 1965) and continued with Sa 57, 54 and 141 (Fenkart, 1967, 1968, 1969).

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921309031731 ◽

2008 ◽

Vol 4 (S258) ◽

pp. 81-94 ◽

Cited By ~ 1

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.

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