Astronomy:Mu Centauri

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Short description: Variable star in the constellation Centaurus
Mu Centauri
Centaurus constellation map.svg
Red circle.svg
Location of μ Centauri (circled)
Observation data
Equinox J2000.0]] (ICRS)
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[1] mas
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
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

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. doi:10.1051/0004-6361:20078357. Bibcode: 2007A&A...474..653V. 
  2. ↑ 2.0 2.1 2.2 2.3 Gutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement 15: 459, doi:10.1086/190168, Bibcode: 1968ApJS...15..459G 
  3. ↑ 3.0 3.1 3.2 Samus, N. N. et al. (2017). "General Catalogue of Variable Stars". Astronomy Reports. 5.1 61 (1): 80–88. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  4. ↑ 4.0 4.1 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, doi:10.1134/S1063773712050015, Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 7.2 7.3 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, doi:10.1111/j.1365-2966.2010.17434.x, Bibcode: 2011MNRAS.410..190T 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 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, doi:10.1051/0004-6361:20053051, Bibcode: 2005A&A...441..235Z 
  9. ↑ 9.0 9.1 9.2 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, doi:10.1051/0004-6361:20010185, Bibcode: 2001A&A...369.1058R 
  10. ↑ 10.0 10.1 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. doi:10.3847/1538-3881/aad5db. Bibcode: 2018AJ....156..174A. https://iopscience.iop.org/article/10.3847/1538-3881/aad5db/pdf. Retrieved 31 July 2022. 
  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, doi:10.1051/0004-6361:20031285, Bibcode: 2003A&A...411..229R 
  14. ↑ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html, 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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