 A visual band light curve of BY Capricorni, adapted from Henry et al. (1995) | |
| Observation data Epoch J2000 Equinox | |
|---|---|
| Constellation | Capricornus |
| Right ascension | 21 41 32.85882 |
| Declination | −14° 02′ 51.3964″ |
| Apparent magnitude (V) | 5.18 |
| Characteristics | |
| Spectral type | G1 IV (G1 IV + G2 V) |
| U−B color index | +0.20 |
| B−V color index | +0.65 |
| Variable type | RS CVn |
| Astrometry | |
| Radial velocity (Rv) | −1.20±0.05 km/s |
| Proper motion (μ) | RA: −123.05 mas/yr Dec.: −308.50 mas/yr |
| Parallax (π) | 30.09 ± 0.32 mas |
| Distance | 108 ± 1 ly (33.2 ± 0.4 pc) |
| Absolute magnitude (MV) | +2.73 (2.79 + 4.73) |
| Orbit | |
| 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 | |
| Mass | 1.09 M☉ |
| Radius | 2.6 R☉ |
| Surface gravity (log g) | 3.76 cgs |
| Temperature | 5,634 K |
| Metallicity | −0.10 dex |
| Rotational velocity (v sin i) | 5.2 km/s |
| Age | 6.7 Gyr |
| 42 Cap B | |
| Rotational velocity (v sin i) | 4.4 km/s |
| Other designations | |
| BY Cap, 42 Cap, BD−14° 6102, FK5 1150, HD 206301, HIP 107095, HR 8283, SAO 164580 | |
| Database references | |
| SIMBAD | data |
42 Capricorni is a binary star system in the zodiac constellation of Capricornus. It has a combined apparent visual magnitude of 5.18, 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. 42 Capricorni is 0.2 degree south of the ecliptic and so is subject to lunar occultations.
In 1995 Gregory W. Henry et al. announced that 42 Capricorni is a variable star, a discovery that was made during a survey of chromospherically active late-type stars using an automated telescope. It was given its variable star designation, BY Capricorni, in the year 2000. The star is an RS Canum Venaticorum variable, indicating the presence of an active chromosphere with star spots.
This is a double-lined close spectroscopic binary with an orbital period of 13.174 days and an eccentricity of 0.18. 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, with the individual components having estimated classes of G1 V and G2 V. The system is a source of X-ray emission.
References
- 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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
- ^ 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.
- 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.
- ^ 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.
- ^ 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.
- "42 Cap". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-27.
- 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.
- 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.
- 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 7 January 2025.
- Kazarovets, E. V.; Samus, N. N.; Durlevich, O. V. (March 2000). "The 75th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 4870: 1–47. Bibcode:2000IBVS.4870....1K. Retrieved 7 January 2025.
- 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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