54 Leonis

54 Leonis is a binary star[12] system in the zodiac constellation of Leo, located around 321[3] light years from the Sun. It is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 4.30.[13] As of 2017, the pair had an angular separation of 6.60″ along a position angle of 113°.[14] They have a physical separation of around 533 AU (79,700 Gm).[9]

54 Leonis

Observation data Epoch J2000.0      Equinox
Constellation	Leo
54 Leo A
Right ascension	10^h 55^m 36.80266^s[1]
Declination	+24° 44′ 59.0440″[1]
Apparent magnitude (V)	4.477[2]
54 Leo B
Right ascension	10^h 55^m 37.24836^s[3]
Declination	+24° 44′ 56.5478″[3]
Apparent magnitude (V)	6.29[4]
Characteristics
54 Leo A
Spectral type	A0 V[5]
B−V color index	+0.001[5]
54 Leo B
Spectral type	A2 Vn[5]
B−V color index	+0.07[4]
Astrometry
54 Leo A
Radial velocity (Rv)	−0.49±0.98[6] km/s
Proper motion (μ)	RA: −78.057[1] mas/yr Dec.: −16.520[1] mas/yr
Parallax (π)	9.8275 ± 0.3537[1] mas
Distance	330 ± 10 ly (102 ± 4 pc)
Absolute magnitude (MV)	–0.29[7]
54 Leo B
Radial velocity (Rv)	1.30±0.92[6] km/s
Proper motion (μ)	RA: −75.374[3] mas/yr Dec.: −18.595[3] mas/yr
Parallax (π)	10.1748 ± 0.0569[3] mas
Distance	321 ± 2 ly (98.3 ± 0.5 pc)
Details
54 Leo A
Mass	2.4+0.44 −0.36[8] M☉
Radius	2.88[9] R☉
Surface gravity (log g)	3.5±0.25[8] cgs
Temperature	9000±500[8] K
Rotational velocity (v sin i)	185[10] km/s
Age	411+137 −168[8] Myr
54 Leo B
Radius	2.59[9] R☉
Rotational velocity (v sin i)	250±20[9] km/s
Other designations
54 Leo, BD+25 2314, CCDM J10556+2445, HIP 53417, Struve 1487[11]
54 Leo A: HD 94601, HR 4259, SAO 81583
54 Leo B: HD 94602, HR 4260, SAO 81584
Database references
SIMBAD	data

The magnitude 4.477[2] primary, designated component A, is an A-type main-sequence star with a stellar classification of A0 V,[5] which indicates it is generating energy through hydrogen fusion at its core. It has a high rate of spin, showing a projected rotational velocity of 185 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 8% larger than the polar radius.[10] The star is roughly 411[8] million years old with 2.4[8] times the mass of the Sun and about 2.88[9] times the Sun's radius.

The fainter magnitude 6.29[4] secondary, component B, is a smaller A-type main-sequence star with a class of A2 Vn.[5] The 'n' suffix indicates wide "nebulous" lines due to rapid rotation. It is spinning with an even higher projected rotational velocity of 250[9] km/s. The star has about 2.59[9] times the Sun's radius.

Asteroid 729 Watsonia occulted HIP 53417 on March 3, 2013 at 01:48.[15]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, 355: L27, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862.
3. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
4. Fabricius, C.; et al. (2002), "The Tycho double star catalogue", Astronomy and Astrophysics, 384: 180–189, Bibcode:2002A&A...384..180F, doi:10.1051/0004-6361:20011822
5. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
6. Becker, Juliette C.; et al. (April 2015), "Extracting Radial Velocities of A- and B-type Stars from Echelle Spectrograph Calibration Spectra", The Astrophysical Journal Supplement Series, 217 (2): 13, arXiv:1503.03874, Bibcode:2015ApJS..217...29B, doi:10.1088/0067-0049/217/2/29, S2CID 33968873, 29.
7. Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000), "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases", Astronomy and Astrophysics, 361: 614–628, Bibcode:2000A&A...361..614P
8. Gullikson, Kevin; et al. (2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 40, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065.
9. Howe, K. S.; Clarke, C. J. (January 2009), "An analysis of v sin (i) correlations in early-type binaries", Monthly Notices of the Royal Astronomical Society, 392 (1): 448–454, Bibcode:2009MNRAS.392..448H, doi:10.1111/j.1365-2966.2008.14073.x
10. Belle, G. T. (2012), "Interferometric observations of rapidly rotating stars", The Astronomy and Astrophysics Review, 20 (1): 51, arXiv:1204.2572, Bibcode:2012A&ARv..20...51V, doi:10.1007/s00159-012-0051-2, S2CID 119273474.
11. "54 Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-02-05.
12. 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, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
13. 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, S2CID 119257644.
14. Mason, Brian D.; et al. (December 2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, U. S. Naval Observatory, Washington D.C., 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
15. Pier Paolo Ricci (29 November 2012). Almanacco astronomico 2013 Astronomical almanac 2013. Lulu.com. pp. 322–. ISBN 978-1-291-21157-3.