Accurate mass and radius determinations of a cool subdwarf in an eclipsing binary

Area of Science:

• Astronomy and Astrophysics
• Stellar Evolution

Background:

• Cool subdwarfs are metal-poor, low-mass stars from the early Milky Way.
• Accurate mass and radius measurements for these stars are rare, hindering understanding of low-mass main-sequence stars.

Purpose of the Study:

• To discover and characterize a cool subdwarf star with accurately determined physical parameters.
• To validate theoretical models for low-mass, low-metallicity stars.

Main Methods:

• Discovered an eclipsing binary system (SDSS J235524.29+044855.7) containing a cool subdwarf and a white dwarf.
• Analyzed light-curve and radial-velocity data to determine the cool subdwarf's mass and radius.
• Derived effective temperature and luminosity from spectral energy distribution analysis.

Main Results:

• Successfully determined the mass and radius of the cool subdwarf star.
• Derived its effective temperature and luminosity.
• The determined parameters align with theoretical predictions.

Conclusions:

• The study provides the first accurate mass and radius for a cool subdwarf.
• Results validate theoretical mass-radius-effective temperature-luminosity relations for low-mass, low-metallicity stars.