Lambda Cancri
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 20m 32.13630s[1] |
| Declination | +24° 01′ 20.3198″[1] |
| Apparent magnitude (V) | +5.93[2] |
| Characteristics | |
| Spectral type | B9.5 V[3][2] |
| Astrometry | |
| Radial velocity (Rv) | +23.0±4.3[4] km/s |
| Proper motion (μ) | RA: −20.29[1] mas/yr Dec.: −18.81[1] mas/yr |
| Parallax (π) | 5.9490 ± 0.1482 mas[5] |
| Distance | 550 ± 10 ly (168 ± 4 pc) |
| Absolute magnitude (MV) | +0.19[6] |
| Details[2] | |
| λ Cnc A | |
| Mass | 2.1+0.39 −0.32 M☉ |
| Luminosity | 78[7] L☉ |
| Surface gravity (log g) | 4.0±0.25 cgs |
| Temperature | 9,500±1,000 K |
| Rotational velocity (v sin i) | 188[8] km/s |
| Age | 105+287 −93 Myr |
| λ Cnc B | |
| Mass | 0.8 M☉ |
| Temperature | 4,562±154 K |
| Metallicity [Fe/H] | −0.5 dex |
| Rotational velocity (v sin i) | 10 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
Lambda Cancri (λ Cancri, abbreviated Lambda Cnc, λ Cnc) is a blue-white-hued spectroscopic binary star[2] in the zodiac constellation of Cancer. With a combined apparent visual magnitude of +5.93, it is faintly visible to the naked eye.[2] Based upon parallax measurements obtained during the Gaia mission, it is about 550 light-years distant from the Sun.[5]
The two components are designated Lambda Cancri A (formally named Piautos /piˈɔːtɒs/)[10] and B.
Nomenclature
[edit]λ Cancri (Latinised to Lambda Cancri) is the binary's Bayer designation. The designations of the two components as Lambda Cancri A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[11]
The system occurs in the lunar station that was given the name πιαυτος piautos in a Coptic manuscript list of lunar stations, nearly all of which were in "debased" Greek. Walter Crum was of the opinion that Piautos is formed from the Greek word autos "self" and the Coptic determiner pi- "that", which is automatically tacked onto Greek nouns. The combination would (in Greek) mean "the same, the very one". Given that the Greeks are not known to have used lunar stations, the origin of the names is unknown.[12]
In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN approved the name Piautos for Lambda Cancri on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.[10] The WGSN had previously stated that where a component letter (from e.g. Washington Double Star Catalog) is not explicitly listed, that the name should be understood to be attributed to the brightest component by visual brightness[14] (Lambda Cancri A in this case).
In Chinese, 爟 (Guàn), meaning Beacon Fire, refers to an asterism consisting of Lambda Cancri and Psi, Phi1 and 15 Cancri.[15] Consequently, Lambda Cancri itself is known as 爟二 (Guàn èr, English: the Second Star of Beacon Fire).[16] From this Chinese name, the name Kwan Wei meaning "the bright fire" was given.[17]
Properties
[edit]The primary, Lambda Cancri A, is a B-type main-sequence star with a stellar classification of B9.5 V.[3] It has 2.1[2] times the mass of the Sun and radiates 78[7] times the Sun's luminosity from its photosphere at an effective temperature of roughly 9,500 K.[2] Its close companion, Lambda Cancri B, has 80% of the mass of the Sun.[2]
References
[edit]- ^ a b c d 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, S2CID 18759600.
- ^ a b c d e f g h Gullikson, Kevin; et al. (August 2016), "The Close Companion Mass-ratio Distribution of Intermediate-mass Stars", The Astronomical Journal, 152 (2): 13, arXiv:1604.06456, Bibcode:2016AJ....152...40G, doi:10.3847/0004-6256/152/2/40, S2CID 119179065, 40.
- ^ a b Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
- ^ 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, S2CID 59451347, A61.
- ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
- ^ 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, S2CID 119257644.
- ^ a b McDonald, I.; et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–57, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
- ^ Royer, F.; et al. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics, 463 (2): 671–682, arXiv:astro-ph/0610785, Bibcode:2007A&A...463..671R, doi:10.1051/0004-6361:20065224, S2CID 18475298.
- ^ "lam Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-06-18.
{{cite web}}: CS1 maint: postscript (link) - ^ a b "Naming Stars". IAU.org. Retrieved 18 June 2018.
- ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
- ^ See station 10 in footnote 12 in Stefan Weinstock, "Lunar Mansions and Early Calendars", Journal of Hellenic Studies, Volume 69, November 1949, pp. 48-69.
- ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- ^ "Bulletin of the IAU Working Group on Star Names, No. 2" (PDF). Retrieved 12 October 2016.
- ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 27 日
- ^ Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc., p. 114, ISBN 0-486-21079-0, retrieved 2018-06-29.
