DS Andromedae (often abbreviated to DS And) is an eclipsing binary star in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Andromeda and a member of the open cluster

NGC 752 NGC 752 (also known as Caldwell 28) is an open cluster in the constellation Andromeda (constellation), Andromeda. The cluster was discovered by Caroline Herschel in 1783 and cataloged by her brother William Herschel in 1786, although an object th ...

. Its maximum apparent visual magnitude is 10.44, but drops down to 10.93 during the main eclipse and to 10.71 during the secondary one.

System

The primary star has a spectral classification F3IV-V, matching the evidence for a star that is evolving off the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

and is expanding its radius. The secondary is thought to be a main sequence star with spectral type G0. It is not visible in the spectrum of DS Andromedae, but the temperature and spectral type can be estimated from the difference in brightness of the two components, determined from the eclipses. The two components are modelled to have apparent magnitudes of 10.62 and 12.47 respectively. The age of DS Andromedae appears to be very close to the hook at the end of main sequence phase of evolution and has just reached the

subgiant branch A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution of ...

. Its age can be determined at from the NGC 752 main sequence turnoff and this allows its physical properties to be accurately calculated. It appears to be not quite filling its roche lobe and no mass transfer has taken place between the two stars; they are evolving as isolated stars.

Variability

The light curve of DS Andromedae shows a main eclipse when the secondary star passes in front of the primary, and a

secondary eclipse A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

when the opposite occurs. This cycle repeats with a periodicity slightly over one day. Since the system is almost exactly edge-on the secondary eclipse is total, and allows the determination of the spectral type of the secondary component. The primary eclipse is annular as the smaller secondary passes in front of the hotter brighter primary. It is classified as an Algol variable (detached) star in the General Catalogue of Variable Stars, but is sometimes considered to be a

β Lyrae variable Beta Lyrae variables are a class of close binary stars. Their total brightness is variable because the two component stars orbit each other, and in this orbit one component periodically passes in front of the other one, thereby blocking its light. ...

(contact).

References

{{DEFAULTSORT:DS Andromedae Andromeda (constellation) Andromedae, DS BD+37 435 J01574604+3804284 Beta Lyrae variables G-type main-sequence stars F-type subgiants