GCIRS 16SW, also known as S97, is a

contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overconta ...

star located in the

Galactic Center The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact ra ...

. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an

eclipsing binary 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 w ...

varying in brightness by 0.35 magnitudes at

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

wavelengths. GCIRS 16SW Celestia

GCIRS 16SW orbits

Sagittarius A* Sagittarius A* ( ), abbreviated Sgr A* ( ), is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, ...

at approximately 19,000 AU, with a period of approximately 1,270 years. At the stars' estimated mass of about 50 solar masses, they are predicted to have a lifespan of about 4 million years, indicating that the system formed within of Sagittarius A*, instead of having migrated inward from a greater distance. GCIRS 16SW was classified as a candidate luminous blue variable on the basis of its spectrum and physical properties. This was before it was identified as an eclipsing binary, but it is still treated as a candidate LBV. Each star is strongly distorted by the gravity of the other star. The polar radius is calculated to be , while the radius along the direction of orbital motion is . The radius along the line joining the two stars is , while the separation of the centres of the two stars is . A calculation of properties treating the binary as a single star gave an effective temperature of . The secondary component is found to have a temperature 96% of that of the primary. However, these temperatures yield a luminosity over a million times that of the sun, uncomfortably close to the Eddington luminosity for each star, and it is suspected the actual temperatures are slightly lower.

References

{{DEFAULTSORT:GCIRS 16SW Sagittarius (constellation) Wolf–Rayet stars Eclipsing binaries