Astronomy:31 Leonis
Coordinates: 
10h 07m 54s, +09° 59′ 51″
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Leo |
| Right ascension | 10h 07m 54.2701s[1] |
| Declination | +09° 59′ 51.025″[1] |
| Apparent magnitude (V) | 4.39[2] |
| Characteristics | |
| Spectral type | K3.5 IIIb Fe-1:[3] |
| B−V color index | 1.447[4] |
| Astrometry | |
| Radial velocity (Rv) | +39.84±0.20[5] km/s |
| Proper motion (μ) | RA: −82.021[1] mas/yr Dec.: −64.844[1] mas/yr |
| Parallax (π) | 11.0209 ± 0.1661[1] mas |
| Distance | 296 ± 4 ly (91 ± 1 pc) |
| Absolute magnitude (MV) | −0.39[2] |
| Details | |
| Radius | 33.9+0.7 −0.71[6] R☉ |
| Luminosity | 283±9[6] L☉ |
| Surface gravity (log g) | 1.42[6] cgs |
| Temperature | 4066±28[6] K |
| Metallicity [Fe/H] | −0.02[7] dex |
| Rotational velocity (v sin i) | 5.1[4] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
31 Leonis, also named Yunü,[9] is a binary star[10] system in the equatorial constellation of Leo. The system is visible to the naked eye in unresolved form, having a combined apparent visual magnitude of 4.39.[2] An estimated distance of around 300 light years is obtained from the annual parallax shift of 11.02 mas as seen from Earth's orbit.[1] At the current distance, interstellar extinction between Earth and 31 Leo diminished the apparent brightness by 0.12 magnitudes.[6] It is moving away from the Sun with a radial velocity of +39.8 km/s.[5]
The primary member of 31 Leonis, component A, is an evolved K-type red giant[11] with a stellar classification of K3.5 IIIb Fe-1:,[3] where the suffix notation indicates an underabundance of iron in the spectrum. It has expanded to 34 times the Solar radius and is radiating around 283 times the Sun's luminosity from its photosphere at an effective temperature of 4,066 K.[6] The magnitude 13.6 secondary, component B, lies at an angular separation of 7.9 arcseconds, as of 2008.[10]
This star has the traditional Chinese name Yunü (御女); it is in the middle of the southernmost stars of the Xuanyuan (轩辕) constellation (ο Leonis and ρ Leonis). The IAU Working Group on Star Names approved the name Yunü for this star on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names.[9]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 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.
- ↑ 2.0 2.1 2.2 Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters 38 (5): 331, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A.
- ↑ 3.0 3.1 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.
- ↑ 4.0 4.1 Massarotti, Alessandro et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 Hipparcos Giants and the Role of Binarity", The Astronomical Journal 135 (1): 209–231, doi:10.1088/0004-6256/135/1/209, Bibcode: 2008AJ....135..209M.
- ↑ 5.0 5.1 de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics 546: 14, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 Baines, Ellyn K.; Clark III, James H.; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01), "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble", The Astronomical Journal 166 (6): 268, doi:10.3847/1538-3881/ad08be, ISSN 0004-6256, Bibcode: 2023AJ....166..268B.
- ↑ Piau, L. et al. (February 2011), "Surface convection and red-giant radius measurements", Astronomy and Astrophysics 526: A100, doi:10.1051/0004-6361/201014442, Bibcode: 2011A&A...526A.100P.
- ↑ "31 Leo". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=31+Leo.
- ↑ 9.0 9.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/.
- ↑ 10.0 10.1 Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society 389 (2): 869–879, doi:10.1111/j.1365-2966.2008.13596.x, Bibcode: 2008MNRAS.389..869E.
- ↑ Wood, Brian E. et al. (October 2016), "Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars", The Astrophysical Journal 829 (2): 13, doi:10.3847/0004-637X/829/2/74, 74, Bibcode: 2016ApJ...829...74W.
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