HD 48914 binary system characteristics measured via photometric and radial velocity data

Star system: HD 48914 | Distance from the Sun: 2673 light years

HD 48914, also known as V505 Mon, is an eclipsing binary star system consisting of a Be-shell star—a star surrounded by a shell of gas—and a companion star that has lost much of its outer material. This system demonstrates high-speed rotation and complex interactions between the two stars. By combining new observations from the TESS space mission with existing photometric data—measurements of light brightness over time—and radial velocity data, the physical properties of these stars have been precisely determined.

The primary Be-shell star has a temperature of 16,000 Kelvin and is rotating at a speed of 467 kilometers per second, reaching its centrifugal limit. This means it is spinning as fast as possible without flying apart. It is surrounded by a large decretion disk, a flat, rotating cloud of gas that spreads outward from the star's equator, extending to a radius of approximately 65 solar radii.

The companion star is a contracting hot subdwarf precursor with a temperature of 14,400 Kelvin and a rotational speed of 131 kilometers per second. This companion once donated its own mass to the Be star, resulting in its current partially stripped state. These findings provide a clear model of how mass transfer shapes the evolution of such binary systems, helping explain the high rotational speeds observed in both stellar objects.

Key findings
- The Be-shell star rotates at its centrifugal limit of 467 km/s.
- The companion star rotates at a speed of 131 km/s.
- A large equatorial decretion disk extends to 65 solar radii around the Be star.
- The system shows evidence of past mass transfer from the companion to the primary star.

Scientific study

A Be-shell star rotating at the critical limit and a partially stripped companion in a post-mass-transfer solution for the eclipsing binary V505 Mon (external link)