The sdA problem – I. Physical properties

@article{Pelisoli2018TheSP,
  title={The sdA problem – I. Physical properties},
  author={Ingrid Pelisoli and S. O. Kepler and Detlev Koester},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2018},
  volume={475},
  pages={2480-2495}
}
The so-called sdA stars are defined by having H-rich spectra and surface gravities similar to hot subdwarf stars, but effective temperature below the zero-age horizontal branch. Their evolutionary history is an enigma: their surface gravity is too high for main sequence stars, but too low for single evolution white dwarfs. They are most likely byproducts of binary evolution, including blue-stragglers, extremely-low mass white dwarf stars (ELMs) and their precursors (pre-ELMs). A small number of… 

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References

SHOWING 1-10 OF 78 REFERENCES

The Physical Nature of Subdwarf A Stars: White Dwarf Impostors

We address the physical nature of subdwarf A-type (sdA) stars and their possible link to extremely low mass (ELM) white dwarfs (WDs). The two classes of objects are confused in low-resolution

What's the nature of sdA stars?

White dwarfs with log g lower than 7.0 are called Extremely Low Mass white dwarfs (ELMs). They were first found as companions to pulsars, then to other white dwarfs and main sequence stars (The ELM

Hot Subluminous Stars

Hot subluminous stars of spectral type B and O are core helium-burning stars at the blue end of the horizontal branch or have evolved even beyond that stage. Most hot subdwarf stars are chemically

New white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12

White dwarfs carry information on the structure and evolution of the Galaxy, especially through their luminosity function and initial-to-final mass relation. Very cool white dwarfs provide insight

Pulsating low-mass white dwarfs in the frame of new evolutionary sequences

Context. Some low-mass white-dwarf (WD) stars with H atmospheres currently being detected in our galaxy, show long-period g(gravity)-mode pulsations, and comprise the class of pulsating WDs called

The age of the Milky Way inner halo

Observations of newly formed white dwarf stars in the halo of the Milky Way are reported and a mathematical relation is developed that links this final stellar mass to the mass of their immediate progenitors, and therefore to the age of the parent population.

Radial-velocity measurements of subdwarf B stars

Subdwarf B (sdB) stars are hot, subluminous stars which are thought to be core-helium burning with thin hydrogen envelopes. The mechanism by which these stars lose their envelopes has been

THE ELM SURVEY. II. TWELVE BINARY WHITE DWARF MERGER SYSTEMS

We describe new radial velocity and X-ray observations of extremely low-mass white dwarfs (ELM WDs, ∼0.2 M☉) in the Sloan Digital Sky Survey Data Release 4 and the MMT Hypervelocity Star survey. We

THE ELM SURVEY. I. A COMPLETE SAMPLE OF EXTREMELY LOW-MASS WHITE DWARFS

We analyze radial velocity observations of the 12 extremely low-mass (ELM), with ⩽0.25 M☉, white dwarfs (WDs) in the MMT Hypervelocity Star Survey. Eleven of the twelve WDs are binaries with orbital

Candidate hypervelocity stars of spectral type G and K revisited

Hypervelocity stars (HVS) move so fast that they are unbound to the Galaxy. When they were first discovered in 2005, dynamical ejection from the supermassive black hole (SMBH) in the Galactic Centre
...