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Rho Leonis

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Rho Leonis (ρ Leo) is a binary star in the zodiac constellation of Leo, and, like the prominent nearby star Regulus, is near the ecliptic. With an apparent visual magnitude of 3.9,[4] this star can be readily seen with the naked eye. Spectroscopic measurements give a distance estimate of about 2,930 light-years (900 parsecs) from the Earth.[6] Rho Leonis is an Alpha Cygni-type variable star, showing 0.032 magnitude brightness variations with a period of 3.427 days, in Hipparcos data.[9]

ρ Leonis
Location of ρ Leonis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Leo
Right ascension 10h 32m 48.67168s[1]
Declination +09° 18′ 23.7094″[1]
Apparent magnitude (V) 3.83 - 3.90[2]
Characteristics
Spectral type B1 Iab[3]
U−B color index −0.945[4]
B−V color index −0.153[4]
Variable type α Cyg[2]
Astrometry
Radial velocity (Rv)+42.0[5] km/s
Proper motion (μ) RA: −5.93±0.20[1] mas/yr
Dec.: −3.40±0.11[1] mas/yr
Parallax (π)1.5913 ± 0.3135 mas
Distance2,900±230 ly
(900±70 pc)[6]
Absolute magnitude (MV)−6.19±0.2[6]
Details[6]
Mass19.9±1.0 M☉
Radius28±3 R☉
Luminosity151,000+30,600
−25,500 L☉
Surface gravity (log g)2.87±0.04 cgs
Temperature21,700±200 K
Metallicity [Fe/H]−0.06[7] dex
Rotation26.8 days[8]
Rotational velocity (v sin i)43±5 km/s
Age9.12+0.88
−0.91 Myr
Other designations
47 Leo, HR 4133, BD+10 2166, HD 91316, SAO 118355, FK5 396, HIP 51624.
Database references
SIMBADdata
A light curve for Rho Leonis, plotted from Hipparcos data[10]

This is an enormous star with about 20 times the Sun's mass (M☉) and 28 times the Sun's radius.[6] Its spectrum matches a stellar classification of B1 Iab,[3] with the 'Iab' luminosity class indicating that it is in the supergiant stage of its evolution. Rho Leonis is radiating about 150,000 times the Sun's luminosity at an effective temperature of 21,700 K,[6] giving it the blue-white hue typical of a B-type star. A strong stellar wind is expelling mass from the outer envelope at a rate of 3.5×10−7 M☉ per year, or the equivalent of 1 M☉ every 2.8 million years.[11] The rotation rate is probably about once per 7 days, with an upper limit of 47 days.[8]

Rho Leonis is classified as a runaway star, which means it has a peculiar velocity of at least 30 km s−1 relative to the surrounding stars. It has radial velocity of 42 km s−1 away from the Sun and a proper motion that is carrying it about 1.56 Astronomical Units per year, equivalent to 7 km s−1,[12] in a transverse direction. The star is situated about 2,300 light-years (710 parsecs) above the galactic plane.[13]

Rho Leo is 0.15 degree north of the ecliptic, so it can be occulted by the moon. Unusual light variation during these occultations has been explained as the result of a possible close companion. The companion would be just over one magnitude fainter and separated by 0.01 arcsec.[14] The companion has not been detected by any other means although it should be easily detected with modern observations.[15]

References

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  1. ^ a b c d van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  2. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ^ a b Lesh, Janet Rountree (December 1968). "The Kinematics of the Gould Belt: an Expanding Group?". Astrophysical Journal Supplement. 17: 371. Bibcode:1968ApJS...17..371L. doi:10.1086/190179.
  4. ^ a b c Gutierrez-Moreno, Adelina; et al. (1966). "A System of photometric standards". Publ. Dept. Astron. Univ. Chile. 1: 1–17. Bibcode:1966PDAUC...1....1G.
  5. ^ Wilson, Ralph Elmer (1953). "General Catalogue of Stellar Radial Velocities". Washington. Bibcode:1953GCRV..C......0W.
  6. ^ a b c d e f Weßmayer, D.; Przybilla, N.; Ebenbichler, A.; Aschenbrenner, P.; Butler, K. (2023-09-01). "The blue supergiant Sher 25 revisited in the Gaia era". Astronomy and Astrophysics. 677: A175. arXiv:2308.06164. Bibcode:2023A&A...677A.175W. doi:10.1051/0004-6361/202347253. ISSN 0004-6361.
  7. ^ Koleva, M.; Vazdekis, A. (2012). "Stellar population models in the UV. I. Characterisation of the New Generation Stellar Library". Astronomy & Astrophysics. 538: A143. arXiv:1111.5449. Bibcode:2012A&A...538A.143K. doi:10.1051/0004-6361/201118065. S2CID 53999614.
  8. ^ a b Kholtygin, A. F.; et al. (November 2007). "Microvariability of line profiles in the spectra of OB stars: III. The supergiant ρ LEO". Astronomy Reports. 51 (11): 920–931. Bibcode:2007ARep...51..920K. CiteSeerX 10.1.1.618.7621. doi:10.1134/S1063772907110054. S2CID 121575654.
  9. ^ Lefèvre, L.; Marchenko, S. V.; Moffat, A. F. J.; Acker, A. (November 2009). "A systematic study of variability among OB-stars based on HIPPARCOS photometry". Astronomy and Astrophysics. 507 (2): 1141–1201. Bibcode:2009A&A...507.1141L. doi:10.1051/0004-6361/200912304.
  10. ^ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
  11. ^ Kraus, M.; Borges Fernandes, M.; Kubát, J. (May 2009). "Parameters of galactic early B supergiants. The influence of the wind on the interstellar extinction determination". Astronomy and Astrophysics. 499 (1): 291–299. Bibcode:2009A&A...499..291K. doi:10.1051/0004-6361/200810319.
  12. ^ An Astronomical Unit (AU) is 1.5 × 108 km, while a year is 3.2 × 107 seconds. Thus, 1.56 AU/year = (1.56 AU/yr) × (1.5 × 108 km/AU) / (3.2 × 107 s/yr) = 7 km/s.
  13. ^ Lauroesch, J. T.; Meyer, David M. (July 2003). "Variable Na I Absorption toward ρ Leonis: Biased Neutral Formation in the Diffuse Interstellar Medium?". The Astrophysical Journal. 591 (2): L123–L126. arXiv:astro-ph/0306005. Bibcode:2003ApJ...591L.123L. doi:10.1086/377164. S2CID 119356147.
  14. ^ Radick, R. R.; Africano, J. L.; Flores, M. R.; Klimke, D. A.; Tyson, E. T. (1982). "Cloudcroft occultation summary. II - April 1980-December 1981". The Astronomical Journal. 87: 1874. Bibcode:1982AJ.....87.1874R. doi:10.1086/113277. ISSN 0004-6256.
  15. ^ McAlister, H. A. (1978). "Binary stars unresolved by speckle interferometry". Publications of the Astronomical Society of the Pacific. 90: 288. Bibcode:1978PASP...90..288M. doi:10.1086/130327. ISSN 0004-6280.
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  • Kaler, James B., "Rho Leonis", Stars, University of Illinois, retrieved 2012-01-11
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