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42 Capricorni 
Summary
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]
| 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] |
| Distance | 108 ± 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 | |
| Mass | 1.09[9] M☉ |
| Radius | 2.6[5] R☉ |
| Surface gravity (log g) | 3.76[4] cgs |
| Temperature | 5,634[4] K |
| Metallicity [Fe/H] | −0.10[4] dex |
| Rotational velocity (v sin i) | 5.2[5] km/s |
| Age | 6.7[9] Gyr |
| 42 Cap B | |
| Rotational velocity (v sin i) | 4.4[5] km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
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 edit
- ^ 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.
- ^ a b c d e 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.
- ^ a b c d 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.
- ^ a b c d e 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.
- ^ a b c d e f g 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
- ^ a b 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.
- ^ a b 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.
- ^ a b 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.
- ^ 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.