Astronomy:73 Leonis
73 Leonis (n Leonis) is a binary star in the constellation Leo. At a combined apparent magnitude of +5.32,[3] it is faintly visible to the naked eye in ideal conditions. Parallax measurements by the Gaia spacecraft imply a distance of 460 light-years (142 parsecs).[2]
Characteristics
The binary nature of 73 Leonis was initially suggested in 1920, based on spectroscopic observations. The system was confirmed to be a binary by two studies from 1926 and 1928. The most modern determination of the orbital elements, as of 2025, combines spectroscopy, astrometry, and direct observations from interferometry. It finds that the stars orbit with a period of 8.1042 years, an eccentricity of 0.4251, and an inclination of 58.03°. The angular semi-major axis is 45.470 mas, which at the distance of 73 Leonis corresponds to 6.535 astronomical units. Given the relatively high eccentricity, the separation between components varies from 9.322 AU at apoastron to 3.749 AU to periastron. The combined mass of the pair is 4.24±0.37 M☉.[5]
The primary star dominates the energy output of the system.[5] Its spectrum matches a spectral class of K2 III,[4] with the luminosity class III indicating it is a giant star that has exhausted the hydrogen at its core. This star has around 26 times the radius of the Sun, radiating 195 times the Sun's luminosity from its photosphere at an effective temperature of 4,271 K,[8] giving it the orange hue typical of a K-type star.[13]
The secondary star is poorly characterized. It is 3.62 magnitudes fainter than the primary, and based on this difference it is estimated to have a spectral type of F6V, although it was never characterized spectroscopically to accurately determine its spectral type.[5]
References
- ↑ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A XHIP record for this object at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system." (in en). VizieR Online Data Catalog 2237. Bibcode: 2002yCat.2237....0D.
- ↑ 4.0 4.1 4.2 Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series 71: 245. doi:10.1086/191373. Bibcode: 1989ApJS...71..245K.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Mason, Brian D.; Griffin, R. Elizabeth M.; Zavala, R. T.; Hummel, Christian A.; Hurowitz, Haley M.; Hurowitz, Jonathan L.; Hartkopf, William I.; Baines, Ellyn K. et al. (2025-08-04). "Binary Star Orbits. VI. The Interferometric-spectroscopic Binary 73 Leo". The Astronomical Journal 170 (2): 83. doi:10.3847/1538-3881/ade38d. ISSN 0004-6256. Bibcode: 2025AJ....170...83M.
- ↑ 6.0 6.1 Schiavon, Ricardo P. (July 2007). "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations" (in en). The Astrophysical Journal Supplement Series 171 (1): 146–205. doi:10.1086/511753. ISSN 0067-0049. Bibcode: 2007ApJS..171..146S.
- ↑ 7.0 7.1 Feuillet, Diane K.; Bovy, Jo; Holtzman, Jon; Girardi, Léo; MacDonald, Nick; Majewski, Steven R.; Nidever, David L. (2016). "Determining Ages of APOGEE Giants with Known Distances". The Astrophysical Journal 817 (1): 40. doi:10.3847/0004-637X/817/1/40. Bibcode: 2016ApJ...817...40F.
- ↑ 8.0 8.1 8.2 8.3 Hon, Marc; Huber, Daniel; Kuszlewicz, James S.; Stello, Dennis; Sharma, Sanjib; Tayar, Jamie; Zinn, Joel C.; Vrard, Mathieu et al. (2021-10-01). "A "Quick Look" at All-sky Galactic Archeology with TESS: 158,000 Oscillating Red Giants from the MIT Quick-look Pipeline". The Astrophysical Journal 919 (2): 131. doi:10.3847/1538-4357/ac14b1. ISSN 0004-637X. Bibcode: 2021ApJ...919..131H.
- ↑ Cenarro, A. J.; Peletier, R. F.; Sanchez-Blazquez, P.; Selam, S. O.; Toloba, E.; Cardiel, N.; Falcon-Barroso, J.; Gorgas, J. et al. (2007-01-01). "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters" (in en). Monthly Notices of the Royal Astronomical Society 374 (2): 664–690. doi:10.1111/j.1365-2966.2006.11196.x. ISSN 0035-8711. Bibcode: 2007MNRAS.374..664C.
- ↑ 10.0 10.1 De Medeiros, J. R.; Da Silva, J. R. P.; Maia, M. R. G. (2002). "The Rotation of Binary Systems with Evolved Components". The Astrophysical Journal 578 (2): 943. doi:10.1086/342613. Bibcode: 2002ApJ...578..943D.
- ↑ Kordopatis, G.; Schultheis, M.; McMillan, P. J.; Palicio, P. A.; De Laverny, P.; Recio-Blanco, A.; Creevey, O.; Álvarez, M. A. et al. (2023). "Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters of Gaia DR3". Astronomy and Astrophysics 669: A104. doi:10.1051/0004-6361/202244283. Bibcode: 2023A&A...669A.104K.
- ↑ "73 Leonis". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=73+Leonis.
- ↑ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html. Retrieved 2012-01-16.
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