Omega2 Aquarii
Omega2 Aquarii is a star system in the equatorial constellation of Aquarius. Its name is a Bayer designation that is Latinised from ω2 Aquarii, and abbreviated Omega2 Aqr or ω2 Aqr. The system can be seen with the naked eye as a faint point of light, having an apparent [visual magnitude] of 4.49. The approximate distance to this star,, is known from parallax measurements.
This is a B-type main-sequence star with a stellar classification of B9 V. In 1953, astronomers H. L. Johnson and W. W. Morgan selected it as the Yerkes [spectral classification scheme|MK standard] for stars of class B9.5V. It has an estimated age of 109 million years and is spinning rapidly with a projected rotational velocity of 148 km/s, giving it a rotation period of. The star has 2.6 times the Sun's mass and nearly double the radius of the Sun. It is radiating 37 times the luminosity of the Sun from its photosphere at an effective temperature of, giving it the blue-white hue of a B-type star.
In 1983, this was catalogued as a spectroscopic binary star system with components classed B9V and B9.5V. However, a 2012 survey by R. Chini et al found the star to have a constant radial velocity. There is a companion star at an angular separation of 5.7 arcseconds that shares a common proper motion with the primary. It is an A-type main-sequence star with a visual magnitude of 9.5. This system is among the 100 strongest stellar X-ray sources within of the Sun. It is emitting an X-ray luminosity of ·s−1. The source for this X-ray emission is unknown.