Delta Circini
Multiple star system with an eclipsing binary and a distant companion.
Delta Circini is a multiple star system in the constellation Circinus, with a combined apparent visual magnitude of +5.09. The system is notable for containing a spectroscopic triple star that includes an eclipsing binary.
Quick Facts
- Apparent visual magnitude
- +5.09
- Distance
- 700 pc (2,300 ly)
- Other designations
- HR 5664, HD 135240
Facts from the source article.
Companions
δ Circini A is a spectroscopic triple star, with two inner components forming an eclipsing binary and an outer component resolved by the VLTI PIONIER instrument. δ Circini B is a 13th magnitude companion nearly an arc-second away; it may be a G5 main sequence star or giant, but physical association is uncertain. HD 135160, a 6th magnitude binary Be star sharing common space motion with δ Circini, lies only 4 arc minutes away, forming a faint naked eye pair.
System properties
The three stars in the Delta Circini A system are all hot and luminous. The brightest, an O8 star just leaving the main sequence, orbits extremely closely with an O9.5 main-sequence companion. Their mutual gravity pulls them into ellipsoidal shapes, and they eclipse each other every 3.9 days, causing a brightness dip of just 0.15 magnitudes. This inner pair is expected to merge in about 1.7 million years, forming a 36.4-solar-mass star that will later explode as a supernova and collapse into a black hole. A third, fainter and cooler B0.5 main-sequence star circles the close binary on a wide, eccentric orbit.
More in Bright Stars by Bayer Designation: Binary and Multiple Stars
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