Gamma Circini

Gamma Circini, Latinized from γ Circini, is a star system in the constellation Circinus. It was noted as a double star by Herschel in 1835, who estimated the separation as 1 arc second.[11] It is visible to the naked eye with an apparent visual magnitude of 4.51.[2] Based upon an annual parallax shift of 7.27 mas,[1] it is about 450 light years away.

γ Circini
Location of y Circini (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Circinus
Right ascension  15h 23m 22.64294s[1]
Declination −59° 19′ 14.8131″[1]
Apparent magnitude (V) 4.51[2] (4.94 + 5.73)[3]
Characteristics
Spectral type B5 IV[4] + F8 V[2]
Variable type Be[5]
Astrometry
Radial velocity (Rv)16.90±1.78[6] km/s
Proper motion (μ) RA: −12.97[1] mas/yr
Dec.: −34.24[1] mas/yr
Parallax (π)7.27 ± 0.81[1] mas
Distanceapprox. 450 ly
(approx. 140 pc)
Absolute magnitude (MV)−1.18[7]
Orbit[4]
Period (P)258 yr
Semi-major axis (a)2.576″
Eccentricity (e)0.931
Details
γ Cir A
Mass6.0±0.3[8] M☉
Temperature15,135[9] K
Age63.1±19.6[8] Myr
γ Cir B
Temperature4,786[9] K
Other designations
γ Cir, CPD−58° 5908, HIP 75323, HR 5704, SAO 242463.[10]
γ Cir A: HD 136415
γ Cir B: HD 136416
Database references
SIMBADγ Cir AB
γ Cir A
γ Cir B

This is a wide binary star system and may even be a triple star.[9] The two visible components orbit each other with a preliminary estimated period of 258 years and a large eccentricity of 0.931.[4] As of 2014, the visible components have an angular separation of 0.80 arc seconds on a position angle of 359°.[3]

The primary star, component A, is a B-type subgiant star with a stellar classification of B5 VI.[4] Based upon isochrone curve fitting it is hypothesized to be a pair of matching B5 stars,[9] and is a Be variable with an uncertain maximum.[5] It has an effective temperature of 15,135[9] K and an estimated mass six[8] times that of the Sun. The companion, component B, is an F-type main sequence star with a stellar classification of F8 V.[2] It has an effective temperature of 4,786[9] K.

References
  1. van Leeuwen, F. (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. Buscombe, W.; Barkstrom, B. (1971), "The composite spectrum of gamma Circini", Monthly Notices of the Royal Astronomical Society, 152: 37–45, Bibcode:1971MNRAS.152...37B, doi:10.1093/mnras/152.1.37.
  3. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122: 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22
  4. Malkov, O. Yu.; et al. (2012), "Dynamical masses of a selected sample of orbital binaries", Astronomy & Astrophysics, 546: A69, Bibcode:2012A&A...546A..69M, doi:10.1051/0004-6361/201219774.
  5. Kazarovets, E. V.; et al. (1999). "The 74th Special Name-list of Variable Stars". Information Bulletin on Variable Stars. 4659: 1. Bibcode:1999IBVS.4659....1K.
  6. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  7. 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.
  8. Tetzlaff, N.; et al. (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.
  9. Parsons, Sidney B. (May 2004), "New and Confirmed Triple Systems with Luminous Cool Primaries and Hot Companions", The Astronomical Journal, 127 (5): 2915–2930, Bibcode:2004AJ....127.2915P, doi:10.1086/383546.
  10. "* gam Cir". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-13.
  11. Carette, E.; et al. (April 1995), "γ Circinus: a young visual binary with pre-main-sequence component(s)?", Astronomy and Astrophysics, 296: 139, Bibcode:1995A&A...296..139C.
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