73 Leonis

This article is about n Leonis and is not to be confused with η Leonis.
73 Leonis
Observation data
Epoch J2000      Equinox J2000
Constellation Leo[1]
Right ascension 11h 15m 51.8801s[2]
Declination +13° 18′ 27.235″[2]
Apparent magnitude (V) +5.32[3]
Characteristics
Evolutionary stage giant[4] + main sequence[5]
Spectral type K2 III[4] + F6V[5]
B−V color index +1.19[6]
Astrometry
Radial velocity (Rv)+14.51±0.01[5] km/s
Proper motion (μ) RA: +7.895 mas/yr[2]
Dec.: −10.518 mas/yr[2]
Parallax (π)7.0432±0.1980 mas[2]
Distance460 ± 10 ly
(142 ± 4 pc)
Absolute magnitude (MV)−0.58[6]
Orbit[5]
Period (P)8.10420±0.00059 yr
Semi-major axis (a)45.470±0.058 mas
(6.535 AU)
Eccentricity (e)0.42510±0.00096
Inclination (i)58.03±0.16°
Longitude of the node (Ω)283.410±0.076°
Periastron epoch (T)2006.2870±0.0011
Argument of periastron (ω)
(secondary)		332.7±4.9°
Semi-amplitude (K1)
(primary)		9.400±0.013 km/s
Details
73 Leo A
Mass1.55[7] M☉
Radius25.5±3.9[8] R☉
Luminosity195±58[8] L☉
Surface gravity (log g)2.02[7] cgs
Temperature4,271±85[8] K
Metallicity [Fe/H]−0.10[9] dex
Rotation2,963 days[10]
Rotational velocity (v sin i)1.9[10] km/s
Age2.7±0.6[11] Gyr
Other designations
n Leonis, BD+14°2367, HD 97907, HIP 55016, HR 4365, WDS J11159+1318, TYC 861-1283-1[12]
Database references
SIMBADdata

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

  1. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
  2. ^ a b c d e Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ^ a b Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". VizieR Online Data Catalog. 2237. Bibcode:2002yCat.2237....0D.
  4. ^ a b c Keenan, Philip C.; McNeil, Raymond C. (1989). "The Perkins catalog of revised MK types for the cooler stars". Astrophysical Journal Supplement Series. 71: 245. Bibcode:1989ApJS...71..245K. doi:10.1086/191373. S2CID 123149047.
  5. ^ a b c d e f g 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.; Williams, Stephen J.; Matson, Rachel A. (2025-08-04). "Binary Star Orbits. VI. The Interferometric-spectroscopic Binary 73 Leo". The Astronomical Journal. 170 (2): 83. Bibcode:2025AJ....170...83M. doi:10.3847/1538-3881/ade38d. ISSN 0004-6256.
  6. ^ a b Schiavon, Ricardo P. (July 2007). "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations". The Astrophysical Journal Supplement Series. 171 (1): 146–205. arXiv:astro-ph/0611464. Bibcode:2007ApJS..171..146S. doi:10.1086/511753. ISSN 0067-0049.
  7. ^ a b 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. arXiv:1511.04088. Bibcode:2016ApJ...817...40F. doi:10.3847/0004-637X/817/1/40.
  8. ^ a b c d Hon, Marc; Huber, Daniel; Kuszlewicz, James S.; Stello, Dennis; Sharma, Sanjib; Tayar, Jamie; Zinn, Joel C.; Vrard, Mathieu; Pinsonneault, Marc H. (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. arXiv:2108.01241. Bibcode:2021ApJ...919..131H. doi:10.3847/1538-4357/ac14b1. ISSN 0004-637X.
  9. ^ Cenarro, A. J.; Peletier, R. F.; Sanchez-Blazquez, P.; Selam, S. O.; Toloba, E.; Cardiel, N.; Falcon-Barroso, J.; Gorgas, J.; Jimenez-Vicente, J.; Vazdekis, A. (2007-01-01). "Medium-resolution Isaac Newton Telescope library of empirical spectra - II. The stellar atmospheric parameters". Monthly Notices of the Royal Astronomical Society. 374 (2): 664–690. arXiv:astro-ph/0611618. Bibcode:2007MNRAS.374..664C. doi:10.1111/j.1365-2966.2006.11196.x. ISSN 0035-8711.
  10. ^ a b 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. arXiv:astro-ph/0207288. Bibcode:2002ApJ...578..943D. doi:10.1086/342613.
  11. ^ Kordopatis, G.; Schultheis, M.; McMillan, P. J.; Palicio, P. A.; De Laverny, P.; Recio-Blanco, A.; Creevey, O.; Álvarez, M. A.; Andrae, R.; Poggio, E.; Spitoni, E.; Contursi, G.; Zhao, H.; Oreshina-Slezak, I.; Ordenovic, C.; Bijaoui, A. (2023). "Stellar ages, masses, extinctions, and orbital parameters based on spectroscopic parameters of Gaia DR3". Astronomy and Astrophysics. 669: A104. arXiv:2206.07937. Bibcode:2023A&A...669A.104K. doi:10.1051/0004-6361/202244283.
  12. ^ "73 Leonis". SIMBAD. Centre de données astronomiques de Strasbourg.
  13. ^ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on 2013-12-03. Retrieved 2012-01-16.
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