Omicron Leonis (ο Leonis, abbreviatedOmicron Leo,ο Leo) is amultiple star system in the constellation ofLeo, west ofRegulus, some 130light-years from theSun, where it marks one of the lion's forepaws. The position of this system near theecliptic means it is subject tolunar occultation.[7]
It consists of abinary pair, designated Omicron Leonis A and anoptical companion, Omicron Leonis B.[8] A's two components are themselves designated Omicron Leonis Aa (officially namedSubra/ˈsuːbrə/, the traditional name for the system)[9][10] and Ab.
ο Leonis (Latinised toOmicron Leonis) is the star'sBayer designation. The designations of the two constituents asOmicron Leonis A andB, and those ofA's components—Omicron Leonis Aa andAb—derive from the convention used by the Washington Multiplicity Catalog (WMC) formultiple star systems, and adopted by theInternational Astronomical Union (IAU).[11]
It bore the traditional nameSubra, from the Arabic زبرةzubra (upper part of the back), originally applied to Delta and Theta Leonis.[12]
In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entiremultiple systems.[14] It approved the nameSubra for the component Omicron Leonis Aa on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[10]
The two members of the spectroscopic pair have similar brightnesses, but are very different stars: the primary is given thetype F8-G0IIIgiant; and the secondary is a type A7mdwarf.[15] Their combinedapparent magnitude is +3.52.
The visible companion, component B, is a much fainter star that has increased its separation from about anarc-minute to one and a half arc-minutes in the 350 years since it was first measured.[8] It is an 11th-magnitude star a little more massive and hotter than the Sun, but much further away than the spectroscopic pair.[16]
^abcDucati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system".CDS/ADC Collection of Electronic Catalogues.2237: 0.Bibcode:2002yCat.2237....0D.
^abcdGallenne, A.; Mérand, A.; Kervella, P.; Graczyk, D.; Pietrzyński, G.; Gieren, W.; Pilecki, B. (2023-04-01). "The Araucaria project: High-precision orbital parallaxes and masses of binary stars. I. VLTI/GRAVITY observations of ten double-lined spectroscopic binaries".Astronomy and Astrophysics.672: A119.arXiv:2302.12960.Bibcode:2023A&A...672A.119G.doi:10.1051/0004-6361/202245712.ISSN0004-6361.
^Herr, Richard B. (April 1969). "Identification List of Spectroscopic and Eclipsing Binaries Subject to Occultations by the Moon".Publications of the Astronomical Society of the Pacific.81 (479): 105.Bibcode:1969PASP...81..105H.doi:10.1086/128748.
^Kunitzsch, Paul; Smart, Tim (2006).A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub.ISBN978-1-931559-44-7.
^Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets".arXiv:1012.0707 [astro-ph.SR].
