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Mu Centauri

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Mu Centauri
Location of μ Centauri (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Centaurus
Right ascension 13h 49m 36.98863s[1]
Declination −42° 28′ 25.4296″[1]
Apparent magnitude (V) +3.42[2] (+2.92 to +3.49)[3]
Characteristics
Spectral type B2V:e[4]
U−B color index −0.854[2]
B−V color index −0.205[2]
Variable type γ Cas[3]
Astrometry
Radial velocity (Rv)+9.1[5] km/s
Proper motion (μ) RA: −24.25[1] mas/yr
Dec.: −18.64[1] mas/yr
Parallax (π)6.45 ± 0.16 mas[1]
Distance510 ± 10 ly
(155 ± 4 pc)
Absolute magnitude (MV)−2.48[6]
Details
Mass9.1±0.2[7] M☉
Radius3.4 × 4.2[8] R☉
Luminosity2,089[9] L☉
Surface gravity (log g)3.95 (3.86–4.33)[8] cgs
Temperature22,410[8] K
Rotational velocity (v sin i)194[10] km/s
Age19.8±1.7[7] Myr
Other designations
μ Cen, CD−41°8172, FK5 508, HD 120324, HIP 67472, HR 5193, SAO 224471
Database references
SIMBADdata

Mu Centauri, Latinized from μ Centauri, is a third-magnitude star in the southern constellation of Centaurus. With the stars ν and φ Centauri, it marks what has been traditionally portrayed as "dextro Latere" (the right side) of the Centaur.[1] The apparent visual magnitude of this star is 3.42,[2] making it one of the brighter members of the constellation. The distance to this star can be estimated directly using parallax measurements, which yield a value of roughly 510 light years (155 parsecs) from Earth.[1]

A visual band light curve for Mu Centauri, plotted from data published by Aguayo et al. (2018)[11]

The spectrum of Mu Centauri is considered to be a standard for a B2 Be star with the stellar classification of B2V:e.[4] The 'e' suffix is used to mark the presence of emission lines, caused by a circumstellar disk of hot gas that was formed from material ejected from the star. Mu Centauri is a pulsating variable star that has multiple non-radial cycles with a primary period of 0.503 days. Three other pulsation cycles have a similar period, while two have a shorter interval of about 0.28 days. It undergoes outburst events that result in the transfer of additional material to the surrounding disk.[12] During these outbursts, the star can experience transient periodicities.[13] Mu Centauri is classified as a Gamma Cassiopeiae type variable star and its brightness varies from magnitude +2.92 to +3.49.[3]

This star is spinning rapidly, with a projected rotational velocity of 194,[10] km s−1 and is completing a full rotation in about 11.615 hours. The equatorial azimuthal velocity is around 85% of the critical velocity where the star would start to break up, resulting a pronounced equatorial bulge that is about 26% wider than the radius at the poles. Because of the oblate spheroidal shape of this star, the polar region is at a higher temperature than the equator—23,000 K versus 17,600 K respectively. Likewise, the gravitational force at the poles is greater than along the equator. The axis of rotation of the star is tilted by an angle of about (19 ± 3)° to the line of sight from the Earth.[9]

At an estimated age of nearly 20 million years,[7] this star is around 55–65% of the way through its evolutionary period on the main sequence of core hydrogen burning stars.[8] It has around nine[7] times the mass of the Sun and four[8] times the Sun's radius, but emits over 2,000[9] times as much energy as the Sun. The outer atmosphere has a mean effective temperature of 22,410 K,[8] giving the star a blue-white hue.[14]

This star is a proper motion member of the Upper Centaurus–Lupus sub-group in the Scorpius–Centaurus OB association, the nearest such co-moving association of massive stars to the Sun.[15]

References

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  1. ^ a b c d e f 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 c d Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
  3. ^ a b c Samus, N. N.; et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. S2CID 125853869.
  4. ^ a b Morgan, W. W; Abt, Helmut A; Tapscott, J. W (1978). "Revised MK Spectral Atlas for stars earlier than the sun". Williams Bay: Yerkes Observatory. Bibcode:1978rmsa.book.....M.
  5. ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick (eds.), "The Revision of the General Catalogue of Radial Velocities", Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30, University of Toronto: International Astronomical Union, Bibcode:1967IAUS...30...57E
  6. ^ 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.
  7. ^ a b c d Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
  8. ^ a b c d e f Zorec, J.; Frémat, Y.; Cidale, L. (October 2005), "On the evolutionary status of Be stars. I. Field Be stars near the Sun", Astronomy and Astrophysics, 441 (1): 235–248, arXiv:astro-ph/0509119, Bibcode:2005A&A...441..235Z, doi:10.1051/0004-6361:20053051, S2CID 17592657
  9. ^ a b c Rivinius, Th.; et al. (April 2001), "Stellar and circumstellar activity of the Be star mu Centauri. III. Multiline nonradial pulsation modeling", Astronomy and Astrophysics, 369: 1058–1077, Bibcode:2001A&A...369.1058R, doi:10.1051/0004-6361:20010185
  10. ^ a b Bernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1). Bibcode:1970CoAsi.239....1B.
  11. ^ Aguayo, G.; Mennickent, R. E.; Granada, A.; Otero, S. (October 2018). "Multi-epoch L-band Spectroscopy of the Be Star μ Centauri Prior to Outburst". The Astronomical Journal. 156 (4): 174. Bibcode:2018AJ....156..174A. doi:10.3847/1538-3881/aad5db. hdl:11336/82431. S2CID 125167180.
  12. ^ Rivinius, Th.; et al. (May 1998), "Stellar and circumstellar activity of the Be star MU Centauri. I. Line emission outbursts", Astronomy and Astrophysics, 333: 125–140, Bibcode:1998A&A...333..125R
  13. ^ Rivinius, Th.; Baade, D.; Štefl, S. (November 2003), "Non-radially pulsating Be stars", Astronomy and Astrophysics, 411 (2): 229–247, Bibcode:2003A&A...411..229R, doi:10.1051/0004-6361:20031285
  14. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
  15. ^ de Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D
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