42 Capricorni

A visual band light curve of BY Capricorni, adapted from Henry et al. (1995)[1]
Observation data
Epoch J2000      Equinox
Constellation Capricornus
Right ascension 21h 41m 32.85882s[2]
Declination −14° 02′ 51.3964″[2]
Apparent magnitude (V) 5.18[3]
Characteristics
Spectral type G1 IV[4] (G1 IV + G2 V)[5]
U−B color index +0.20[3]
B−V color index +0.65[3]
Variable type RS CVn[5]
Astrometry
Radial velocity (Rv)−1.20±0.05[6] km/s
Proper motion (μ) RA: −123.05[2] mas/yr
Dec.: −308.50[2] mas/yr
Parallax (π)30.09 ± 0.32 mas[2]
Distance108 ± 1 ly
(33.2 ± 0.4 pc)
Absolute magnitude (MV)+2.73[7] (2.79 + 4.73)[5]
Orbit[8]
Period (P)13.174 d
Eccentricity (e)0.1763±0.0025
Periastron epoch (T)2447863.626 ± 0.027 JD
Argument of periastron (ω)
(secondary)		166.45±0.83°
Semi-amplitude (K1)
(primary)		25.57±0.06 km/s
Semi-amplitude (K2)
(secondary)		35.16±0.25 km/s
Details
42 Cap A
Mass1.09[9] M☉
Radius2.6[5] R☉
Surface gravity (log g)3.76[4] cgs
Temperature5,634[4] K
Metallicity [Fe/H]−0.10[4] dex
Rotational velocity (v sin i)5.2[5] km/s
Age6.7[9] Gyr
42 Cap B
Rotational velocity (v sin i)4.4[5] km/s
Other designations
BY Cap, 42 Cap, BD−14° 6102, FK5 1150, HD 206301, HIP 107095, HR 8283, SAO 164580[10]
Database references
SIMBADdata

42 Capricorni is a binary star[11] system in the zodiac constellation of Capricornus. It has a combined apparent visual magnitude of 5.18,[3] so it is faintly visible to the naked eye. Its annual parallax shift of 30.09 mas yields a distance estimate of about 108 light years; the system is moving closer to the Sun with a radial velocity of −1.2 km/s.[6] 42 Capricorni is 0.2 degree south of the ecliptic and so is subject to lunar occultations.[12]

This is a double-lined close spectroscopic binary with an orbital period of 13.174 days and an eccentricity of 0.18.[8] The binary nature of this system was discovered in 1918 by the English astronomer Joseph Lunt. It has a combined spectrum that matches a stellar classification of G1 IV,[4] with the individual components having estimated classes of G1 V and G2 V. This is an RS Canum Venaticorum variable, indicating the presence of an active chromosphere with star spots.[5] The system is a source of X-ray emission.[13]

References

  1. ↑ Henry, Gregory W.; Fekel, Francis C.; Hall, Douglas S. (December 1995). "An Automated Search for Variability in Chromospherically Active Stars". Astronomical Journal. 110: 2926–2967. Bibcode:1995AJ....110.2926H. doi:10.1086/117740. Retrieved 18 November 2021.
  2. 1 2 3 4 5 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.
  3. 1 2 3 4 Ducati, J. R. (2002), "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system", CDS/ADC Collection of Electronic Catalogues, 2237, Bibcode:2002yCat.2237....0D.
  4. 1 2 3 4 5 Gray, R. O.; et al. (2006), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637, S2CID 119476992.
  5. 1 2 3 4 5 6 7 Fekel, Francis C. (December 1997), "Chromospherically active stars. XVI. The double-lined binary 42 Capricorni", Astronomical Journal, 114: 2747, Bibcode:1997AJ....114.2747F, doi:10.1086/118683
  6. 1 2 Karataș, Yüksel; Bilir, Selçuk; Eker, Zeki; Demircan, Osman; Liebert, James; Hawley, Suzanne L.; Fraser, Oliver J.; Covey, Kevin R.; Lowrance, Patrick; Kirkpatrick, J. Davy; Burgasser, Adam J. (2004). "Kinematics of chromospherically active binaries and evidence of an orbital period decrease in binary evolution". Monthly Notices of the Royal Astronomical Society. 349 (3): 1069–1092. arXiv:astro-ph/0404219. Bibcode:2004MNRAS.349.1069K. doi:10.1111/j.1365-2966.2004.07588.x. S2CID 15290475.
  7. ↑ 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, arXiv:1204.2459, Bibcode:2012A&A...542A.116A, doi:10.1051/0004-6361/201118724, S2CID 53666672.
  8. 1 2 Pourbaix, D.; et al. (2004), "SB9: The Ninth Catalogue of Spectroscopic Binary Orbits", Astronomy & Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213, S2CID 119387088.
  9. 1 2 Chen, Y. Q.; et al. (February 2000), "Chemical composition of 90 F and G disk dwarfs", Astronomy and Astrophysics Supplement, 141 (3): 491–506, arXiv:astro-ph/9912342, Bibcode:2000A&AS..141..491C, doi:10.1051/aas:2000124, S2CID 16273589.
  10. ↑ "42 Cap". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-27.
  11. ↑ 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.
  12. ↑ Herr, Richard B. (April 1969), "Identification List of Spectroscopic and Eclipsing Binaries Subject to Occultations by the Moon", Publications of the Astronomical Society of the Pacific, 81 (479): 105, Bibcode:1969PASP...81..105H, doi:10.1086/128748.
  13. ↑ Haakonsen, Christian Bernt; Rutledge, Robert E. (September 2009), "XID II: Statistical Cross-Association of ROSAT Bright Source Catalog X-ray Sources with 2MASS Point Source Catalog Near-Infrared Sources", The Astrophysical Journal Supplement, 184 (1): 138–151, arXiv:0910.3229, Bibcode:2009ApJS..184..138H, doi:10.1088/0067-0049/184/1/138, S2CID 119267456.
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