Xi Lupi
Xi Lupi is a triple star system in the southern constellation of Lupus. Its main identifier is a Bayer designation that is Latinized from ξ Lupi, and abbreviated Xi Lup or ξ Lup. The combined apparent magnitude is 4.56, making it faintly visible to the naked eye. The system is located at from Earth, and is a member of the Upper Scorpius sub-group of the nearby Sco OB2 association.
Characteristics
This is a hierarchical triple system. It consists on the binary star ξ1 Lup and the star ξ2 Lup; both form a visual binary separated by 10.2" in the sky, or 660 astronomical units at their distance. The components of ξ1 Lup, named ξ1 Lup A and B, are separated by about the same distance Earth is from Sun, the orbital period is an estimated 200 days, although the observed separation is merely a projected separation and the whole orbit has not been observed.ξ1 Lup has a combined stellar classification of A3 V, and its primary and secondary components have, respectively, 2.0 and 1.65 times the mass of the Sun, radii 2.0 and 1.6 times solar and effective temperatures of 8,650 and 7,850 K.
ξ2 Lup has a stellar classification of B9 V, matching a B-type main-sequence star. It has twice the mass of the Sun, 1.74 times the Sun's radius, is 23 times more luminous and has an effective temperature of 9,550 K. It spins rapidly with a projected rotational velocity of. The star has a peculiar velocity of relative to its neighbors, and is probably a runaway star.
The system is currently about 500 million years old. When ξ1 Lup A evolves into an AGB star, it will likely engulf component Ab, but given the orbit of the system is unknown, it may be more distant, and survive its companion's AGB phase. Assuming the Aa-Ab separation is correct, the system will likely end as a triple white dwarf system; few of such system have been observed so far.