The inner pair of this system form a well-studied[3]semidetached binary with the orbital plane oriented near the line of sight to the Earth, making it an Algol-typeeclipsing binary. They have an orbital period of just over two days and a semimajor axis of 15 times the radius of the Sun, with the secondary component transferring mass to the hotter primary star.[5] The main eclipse reduces the magnitude of the system to 5.37, while the second eclipse lowers the brightness to magnitude 4.93.[4] Theoretical calculations suggest the donor star began with 7.2 times the mass of the Sun, the current primary at 3.6 solar masses, and their initial orbital period was around 1.35 days.[5]
The third member of this system, component B, lies at an angular separation of 4.4″ from the inner pair with a visual magnitude of 10.2.[8] It shares a common proper motion and similar parallax to the eclipsing pair, and is modelled to be a main sequence star somewhat more massive, hotter, and more luminous than the Sun.[10] Any orbit would require thousands of years.[11]
^ abcdefHilditch, R. W. (April 2005), "Astrophysical parameters for the eclipsing binary u Herculis", The Observatory, 125: 72–81, Bibcode:2005Obs...125...72H
^ abcdefghSaad, Somaya; Nouh, Mohamed (June 2011), "A study of the B+B double-lined eclipsing binary u Her", Bulletin of the Astromical Society of India, 39: 277–287, Bibcode:2011BASI...39..277S.