Mu Velorum

Mu Velorum (μ Vel, μ Velorum) is a binary star system in the southern constellation Vela. The two stars orbit each other with a semi-major axis of 1.437 arcseconds and a period of 116.24 years.[10] (Wulff-Dieter Heintz (1986) lists a period of 138 years with his orbital elements.)[6] The pair have a combined apparent visual magnitude of 2.69,[2] making the system readily visible to the naked eye. From parallax measurements, the distance to this system is estimated to be 117 light-years (36 parsecs).[1] The system is about 360 million years old.[3]

μ Velorum
Location of μ Velorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension  10h 46m 46.17877s[1]
Declination –49° 25′ 12.9244″[1]
Apparent magnitude (V) 2.69[2] (2.7 + 6.4)[3]
Characteristics
Spectral type G5III + G2V[3]
U−B color index +0.57[2]
B−V color index +0.90[2]
Astrometry
Radial velocity (Rv)+6.2[4] km/s
Proper motion (μ) RA: +63.22[1] mas/yr
Dec.: –54.21[1] mas/yr
Parallax (π)27.84 ± 0.38[1] mas
Distance117 ± 2 ly
(35.9 ± 0.5 pc)
Absolute magnitude (MV)−0.06[5]
Orbit[6]
Period (P)138 yr
Semi-major axis (a)1.427″
Eccentricity (e)0.84
Inclination (i)57.0°
Longitude of the node (Ω)59.1°
Periastron epoch (T)1951.1
Argument of periastron (ω)
(secondary)		178.0°
Details
μ Vel A
Mass3.30[7] M☉
Radius13[8] R☉
Luminosity107[3] L☉
Surface gravity (log g)2.75[7] cgs
Temperature5,047[7] K
Rotational velocity (v sin i)6.4[7] km/s
Age360[3] Myr
Other designations
CD−48°5913, HD 93497, HIP 52727, HR 4216, SAO 222321.[9]
Database references
SIMBADdata

The primary component is a giant star with an apparent magnitude of 2.7 and a stellar classification of G5 III.[3] It is radiating about 107 times the luminosity of the Sun from an expanded atmosphere about 13[8] times the Sun's radius. The mass of this star is 3.3[7] times that of the Sun. In 1998, the Extreme Ultraviolet Explorer space telescope detected a strong flare that released an X-ray emission nearly equal to the output of the entire star. The quiescent X-ray luminosity of Mu Velorum A is about 1.7 × 1030 erg s−1.[3]

The fainter companion, Mu Velorum B, is a main sequence star with an apparent magnitude of 6.4[3] and an assigned stellar classification of G2V.[3] However, this classification is suspect. Closer examination of the spectrum suggests the star may actually have a classification of F4V or F5V, which suggests a mass of about 1.5 times the mass of the Sun. Such stars typically do not show a marked level of magnetic activity.[3]

References
  1. 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.
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99), Bibcode:1966CoLPL...4...99J.
  3. Ayres, Thomas R.; Osten, Rachel A.; Brown, Alexander (November 1999), "The Rise and Fall of μ Velorum: A Remarkable Flare on a Yellow Giant Star Observed with the Extreme Ultraviolet Explorer", The Astrophysical Journal, 526 (1): 445–450, Bibcode:1999ApJ...526..445A, doi:10.1086/308001.
  4. Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E.
  5. Cardini, D. (January 2005), "Mg II chromospheric radiative loss rates in cool active and quiet stars", Astronomy and Astrophysics, 430: 303–311, arXiv:astro-ph/0409683, Bibcode:2005A&A...430..303C, doi:10.1051/0004-6361:20041440.
  6. Heintz, W. D. (April 1986), "Orbits of 20 visual binaries", Astronomy and Astrophysics Supplement Series, 64 (1): 1–7, Bibcode:1986A&AS...64....1H. Listed as Ru 155.
  7. Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003), "Lithium and rotation in F and G dwarfs and subgiants", Astronomy and Astrophysics, 409: 251–261, Bibcode:2003A&A...409..251M, doi:10.1051/0004-6361:20031084.
  8. Mullan, D. J.; et al. (May 2006), "A Comparative Study of Flaring Loops in Active Stars" (PDF), The Astrophysical Journal Supplement Series, 164 (1): 173–201, Bibcode:2006ApJS..164..173M, doi:10.1086/502629.
  9. "CCDM J10468-4925AB -- Double or multiple star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-02-03.
  10. Hoffleit, D.; Warren, W. H., Jr. (1987), "The Bright Star Catalogue", Astronomical Data Center Bulletin (5th revised ed.), 1 (4): 285–294, Bibcode:1987ADCBu...1..285H.
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