Astronomy:AX Circini

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Short description: Binary star system in the constellation Circinus
AX Circini
Observation data
Equinox J2000.0]] (ICRS)
Constellation Circinus
Right ascension  14h 52m 35.25324s[1]
Declination −63° 48′ 35.4172″[1]
Apparent magnitude (V) 5.91[2] (5.69–6.19)[3]
Characteristics
Spectral type F8 II + B6 V[4]
U−B color index +0.2[5]
B−V color index +0.8[5]
Variable type δ Cep[6]
Astrometry
Radial velocity (Rv)−20.9±4.6[7] km/s
Proper motion (μ) RA: −4.779[1] mas/yr
Dec.: −5.108[1] mas/yr
Parallax (π)1.7449 ± 0.3450[1] mas
Distanceapprox. 1,900 ly
(approx. 600 pc)
Absolute magnitude (MV)−3.37[8]
Orbit[9]
Period (P)6,532±25 d
Eccentricity (e)0.19±0.02
Longitude of the node (Ω)231±8°
Periastron epoch (T)2,448,500±60 JD
Semi-amplitude (K1)
(primary)		10.0±0.5 km/s
Details
AX Cir A
Mass11.56[10] M☉
Radius45.68[1] R☉
Luminosity2,050[9] L☉
Surface gravity (log g)2.00[11] cgs
Temperature5,443±21[11] K
Metallicity [Fe/H]−0.05[12] dex
Rotational velocity (v sin i)7.4±0.4[13] km/s
AX Cir B
Mass5.57[10] M☉
Other designations
26 G. Cir, AX Cir, CD−63° 1029, HD 130701/2, HIP 72773, HR 5527, SAO 252928, WDS J14526-6349AB[14]
Database references
SIMBADdata
Light curve of AX Circini recorded by NASA's Transiting Exoplanet Survey Satellite (TESS)

AX Circini is a binary star[4] system in the southern constellation of Circinus. It has a nominal magnitude of 5.91,[2] which is bright enough to be visible to the naked eye. Based upon an annual parallax shift of 1.7 mas,[1] it is located roughly 1,900 light-years from the Earth. The system is moving closer with a heliocentric radial velocity of −21 km/s.[7]

This is a spectroscopic binary with an orbital period of 17.88 years and an eccentricity of 0.19.[9] A binary companion was first suspected in 1960, as the spectrum was considered to be composite and there is an ultraviolet excess. The companion was confirmed in 1982, and it was resolved using long baseline interferometry in 2014[4] and 2015.[15] The system has an a sin i value of 6.05 astronomical unit|AU, where a is the semimajor axis and i is the (unknown) orbital inclination.[4]

The primary, component A, is a yellow-white-hued bright giant with a stellar classification of F8 II,[16] and it is a classical Cepheid variable.[11] The combined apparent magnitude of the system ranges from 5.69 to 6.19 over 5.273 days.[3] The secondary companion, component B, is a main-sequence star with a class of B6 V and an absolute magnitude of about −0.12.[4]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G.  Gaia DR2 record for this source at VizieR.
  2. ↑ 2.0 2.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  3. ↑ 3.0 3.1 Klagyivik, P.; Szabados, L. (September 2009). "Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes". Astronomy and Astrophysics 504 (3): 959–972. doi:10.1051/0004-6361/200811464. Bibcode: 2009A&A...504..959K. 
  4. ↑ 4.0 4.1 4.2 4.3 4.4 Gallenne, A. et al. (January 2014), "Multiplicity of Galactic Cepheids from long-baseline interferometry. II. The Companion of AX Circini revealed with VLTI/PIONIER", Astronomy & Astrophysics 561: 5, doi:10.1051/0004-6361/201322883, L3, Bibcode: 2014A&A...561L...3G 
  5. ↑ 5.0 5.1 Lloyd Evans, T (1968). "The frequency of Cepheid binaries". Monthly Notices of the Royal Astronomical Society 141: 109–142. doi:10.1093/mnras/141.1.109. Bibcode: 1968MNRAS.141..109L. 
  6. ↑ Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports 61 (1): 80. doi:10.1134/S1063772917010085. Bibcode: 2017ARep...61...80S. 
  7. ↑ 7.0 7.1 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, doi:10.1051/0004-6361/201219219, A61, Bibcode: 2012A&A...546A..61D. 
  8. ↑ Evans, Nancy Evans; Bond, Howard E; Schaefer, Gail H; Mason, Brian D; Karovska, Margarita; Tingle, Evan (2013). "Binary Cepheids: Separations and Mass Ratios in 5 M ☉ Binaries". The Astronomical Journal 146 (4): 93. doi:10.1088/0004-6256/146/4/93. Bibcode: 2013AJ....146...93E. 
  9. ↑ 9.0 9.1 9.2 Petterson, O. K. L.; Albrow, Michael D.; Cottrell, P. L.; Fokin, A. (May 2004). "A spectroscopic study of southern binary Cepheids". in Kurtz, Donald W.; Pollard, Karen R.. Variable Stars in the Local Group, IAU Colloquium 193, Proceedings of the conference held 6-11 July, 2003 at Christchurch, New Zealand. 310. San Francisco: Astronomical Society of the Pacific. p. 403. Bibcode: 2004ASPC..310..403P. 
  10. ↑ 10.0 10.1 Tokovinin, A. (2008). "Comparative statistics and origin of triple and quadruple stars". Monthly Notices of the Royal Astronomical Society 389 (2): 925–938. doi:10.1111/j.1365-2966.2008.13613.x. Bibcode: 2008MNRAS.389..925T. 
  11. ↑ 11.0 11.1 11.2 Usenko, I. A. et al. (July 2011). "Spectroscopic studies of Cepheids (S Cru, AP Pup, AX Cir, S TrA, T Cru, R Mus, S Mus, U Car) and semiregular bright supergiants (V382 Car, HD 75276, R Pup) in the southern hemisphere". Astronomy Letters 37 (7): 499–507. doi:10.1134/S1063773711070061. Bibcode: 2011AstL...37..499U. 
  12. ↑ Luck, R. E. et al. (August 2011). "The Distribution of the Elements in the Galactic Disk. II. Azimuthal and Radial Variation in Abundances from Cepheids". The Astronomical Journal 142 (2): 12. doi:10.1088/0004-6256/142/2/51. 51. Bibcode: 2011AJ....142...51L. 
  13. ↑ Ammler-von Eiff, Matthias; Reiners, Ansgar (June 2012), "New measurements of rotation and differential rotation in A-F stars: are there two populations of differentially rotating stars?", Astronomy & Astrophysics 542: A116, doi:10.1051/0004-6361/201118724, Bibcode: 2012A&A...542A.116A. 
  14. ↑ "26 Cir". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=26+Cir. 
  15. ↑ Gallenne, A. et al. (July 2015). "Robust high-contrast companion detection from interferometric observations. The CANDID algorithm and an application to six binary Cepheids". Astronomy & Astrophysics 579: 12. doi:10.1051/0004-6361/201525917. A68. Bibcode: 2015A&A...579A..68G. 
  16. ↑ Gallenne, A; Mérand, A; Kervella, P; Breitfelder, J; Le Bouquin, J.-B; Monnier, J. D; Gieren, W; Pilecki, B et al. (2013). "Multiplicity of Galactic Cepheids from long-baseline interferometry". Astronomy & Astrophysics 561: L3. doi:10.1051/0004-6361/201322883. Bibcode: 2014A&A...561L...3G. 



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