This is a spectroscopic binary, which is a type of binary star system in which the two stars are so close together that they have not been individually resolved with a telescope. The pair orbit each other with a period of about 196 days and an eccentricity of nearly 0.5.[7] The combined spectrum of this pair matches a star with a stellar classification of B1.5 III.[3] The 'III' luminosity class indicates the presence of a giant star that has exhausted the supply of hydrogen at its core and is in a late evolutionary stage.
A light curve for Kappa Scorpii, adapted from Lomb and Shobbrook (1975)[10]
The primary component of the pair, κ Sco A, is a variable star of Beta Cephei type. It is undergoing radial pulsations with a dominant frequency of 4.99922 cycles per day, or 4.8 hours per cycle. There are overlapping secondary pulsation frequencies of about 4.85 and 5.69 cycles per day.[11] This star has about 17 times the mass of the Sun and is nearly 7 times the Sun's radius.[7] The effective temperature of the outer envelope is 23,400 K,[7] giving it a blue-white hue. It is rotating rapidly, with an estimated period of only 1.9 days and an axis of rotation that is inclined by about 40° to the line of sight from the Earth.[7]
The secondary component, κ Sco B, is smaller than the primary, but still much larger than the Sun. It has about 12 times the mass of the Sun and nearly six times the Sun's radius.[7] The effective temperature of 18,800 K[7] is also higher than the Sun's, which is at 5,778 K.
^ abHouk, Nancy (1978), "Michigan catalogue of two-dimensional spectral types for the HD star", Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 3. Declinations -40.0° to -26.0°, 3, Ann Arbor: Dept. of Astronomy, University of Michigan: distributed by University Microfilms International, Bibcode:1982mcts.book.....H
^ abGutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
^Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
^Bernacca, P. L.; Perinotto, M. (1970), "A Catalogue of Stellar Rotational Velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B
^Uytterhoeven, K.; et al. (March 2005), "Disentangling component spectra of κ Scorpii, a spectroscopic binary with a pulsating primary. II. Interpretation of the line-profile variability", Astronomy and Astrophysics, 432 (3): 955–967, Bibcode:2005A&A...432..955U, doi:10.1051/0004-6361:20041444, hdl:2066/32420
