SIMBAD references

2018MNRAS.475.2480P - Mon. Not. R. Astron. Soc., 475, 2480-2495 (2018/April-1)

The sdA problem - I. Physical properties.


Abstract (from CDS):

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 ELMs with similar properties to sdAs is known. Other possibilities include metal-poor A/F dwarfs, second generation stars, or even stars accreted from dwarf galaxies. In this work, we analyse colours, proper motions, and spacial velocities of a sample of sdAs from the Sloan Digital Sky Survey to assess their nature and evolutionary origin. We define a probability of belonging to the main sequence and a probability of being a (pre-)ELM based on these properties. We find that 7 per cent of the sdAs are more likely to be (pre-)ELMs than main-sequence stars. However, the spacial velocity distribution suggests that over 35 per cent of them cannot be explained as single metal-poor A/F stars.

Abstract Copyright: © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): binaries: general - stars: evolution - stars: kinematics and dynamics - subdwarfs - white dwarfs

VizieR on-line data: <Available at CDS (J/MNRAS/475/2480): table1.dat table2.dat tablec1.dat>

Simbad objects: 1459

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