Rho Leonis

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

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]

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]

  1. ^ a b c d Cite error: The named reference aaa474_2_653 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference gcvs was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference apjs17_371 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference sps1966 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference gcsrv was invoked but never defined (see the help page).
  6. ^ a b c d e f Cite error: The named reference hessmaier was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference koleva2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference ar51_11_920 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Lefèvre was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference HIPCurve was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference aaa499_1_291 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference pm was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference apj591_2 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference radick was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference mcalister was invoked but never defined (see the help page).