Eta Muscae

Eta Muscae is a multiple[8][9] star system in the southern constellation of Musca. It is visible to the naked eye as a faint, blue-white hued point of light with an apparent visual magnitude of 4.79.[2] The system is located around 406 light years away from the Sun.[5] It is a member of the Lower Centaurs Crux subgroup of the Sco OB2 stellar association of co-moving stars.[10]

Eta Muscae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Musca
Right ascension 13h 15m 14.94123s[1]
Declination −67° 53′ 40.5276″[1]
Apparent magnitude (V) 4.79[2]
Characteristics
Spectral type B8V + sim. + K9.4XR? + A0p[3] or B7III + B7III[4]
B−V color index −0.078±0.003[2]
Variable type eclipsing binary
Astrometry
Radial velocity (Rv)−8.1±7.4[2] km/s
Proper motion (μ) RA: +30.207[1] mas/yr
Dec.: +17.921[1] mas/yr
Parallax (π)7.1001 ± 0.1924[1] mas
Distance405.7[5] ly
(124.4[5] pc)
Absolute magnitude (MV)−0.81[5]
Orbit[6]
Period (P)2.3963161 d
Semi-major axis (a)14.11±0.15 R☉
Eccentricity (e)0.00
Inclination (i)77.40°
Semi-amplitude (K1)
(primary)		145.35±0.20 km/s
Semi-amplitude (K2)
(secondary)		145.38±0.20 km/s
Details[6]
Eta Mus Aa
Mass3.30±0.04 M☉
Radius2.14±0.02 R☉
Luminosity223.77[2] (combined) L☉
Surface gravity (log g)4.293±0.005 cgs
Temperature12,700±100 K
Rotational velocity (v sin i)34±2 km/s
Eta Mus Ab
Mass3.29±0.04 M☉
Radius2.13±0.04 R☉
Surface gravity (log g)4.298±0.005 cgs
Temperature12,550±300 K
Rotational velocity (v sin i)44±2 km/s
Other designations
η Mus, CPD−67° 2224, FK5 493, HD 114911, HIP 64661, HR 4993, SAO 252224, WDS J13152-6754A[7]
Database references
SIMBADdata

The two main components of this system form a double-lined spectroscopic binary[11] with a period of 2.4 days in a circular orbit.[6][10] They are a detached eclipsing binary with a spectral type of B8V and a brightness that dips by 0.05 magnitude once per orbit.[12] This pair consists of two components of similar mass and type.[3]

Further away from the primary system are stars of magnitude 7.3 and 10, designated Eta Muscae B and C. It is unclear if these stars are gravitationally–bound to the main pair. Evidence for an additional component has been found with a 30-year cycle in the orbital behavior of the main pair.[8] The data suggests an orbital eccentricity of 0.29 for this suspected component, Eta Muscae D.[13]

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. S2CID 18759600.
  2. 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.
  3. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  4. Hube, Douglas P. (1970). "The radial velocities of 335 late B-type stars". Memoirs of the Royal Astronomical Society. 72: 233. Bibcode:1970MmRAS..72..233H.
  5. Hubrig, S.; et al. (June 2001). "Search for low-mass PMS companions around X-ray selected late B stars". Astronomy and Astrophysics. 372: 152–164. arXiv:astro-ph/0103201. Bibcode:2001A&A...372..152H. doi:10.1051/0004-6361:20010452. S2CID 17507782.
  6. Eker, Z.; et al. (May 2014). "The Catalogue of Stellar Parameters from the Detached Double-Lined Eclipsing Binaries in the Milky Way". Publications of the Astronomical Society of Australia. 31: 23. arXiv:1403.1583. Bibcode:2014PASA...31...24E. doi:10.1017/pasa.2014.17. S2CID 119238300. e024.
  7. "eta Mus". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-26.
  8. Butland, R. J.; Budding, E. (2011). "Another component in the multiple system Eta Mus". Commissions 27 and 42 of the IAU Information Bulletin on Variable Stars (6004).
  9. Medici, A.; Hubrig, S. (January 2000). "Triple System epsilon Vol and Quadruple System eta Mus: the Mass Ratio in Close Binary Systems". Information Bulletin on Variable Stars. 4827: 1. Bibcode:2000IBVS.4827....1M.
  10. Hensberge, H.; et al. (April 5–10, 2003). Lépine, Jacques; Gregorio-Hetem, Jane (eds.). η Muscae: a multiple system with a PMS component. Open Issues in Local Star Formation. Proceedings of the Ouro Preto Colloquium, Brazil. Astrophysics and Space Science Library. 299. Kluwer Academic Publishers, Dordrecht. Bibcode:2003ASSL..299P...8H.
  11. Buscombe, W.; Morris, Pamela M. (1961). "Three southern spectroscopic binaries". Monthly Notices of the Royal Astronomical Society. 123 (2): 183. Bibcode:1961MNRAS.123..183B. doi:10.1093/mnras/123.2.183.
  12. Zasche, P.; et al. (2009). "A catalog of visual double and multiple stars with eclipsing components". The Astronomical Journal. 138 (2): 664–79. arXiv:0907.5172. Bibcode:2009AJ....138..664Z. doi:10.1088/0004-6256/138/2/664. S2CID 17089387.
  13. Blackford, M. G.; et al. (June 2016). "The AD binary in the multiple system eta Mus". Information Bulletin on Variable Stars. 6171: 1. Bibcode:2016IBVS.6171....1B.
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