Wikipedia

Beta Cancri

β Cancri
β Cancri is the bottom right star in the "crab"
Observation data
Epoch J2000      Equinox J2000
Constellation Cancer
Right ascension 08h 16m 30.92099s[1]
Declination +09° 11′ 07.9582″[1]
Apparent magnitude (V) 3.50 to 3.58[2]
Characteristics
Spectral type K4III Ba1[3]
U−B color index +1.77[4]
B−V color index +1.48[4]
Variable type Suspected[2]
Astrometry
Radial velocity (Rv)22.94[5] km/s
Proper motion (μ) RA: −46.82 mas/yr[1]
Dec.: −49.24 mas/yr[1]
Parallax (π)10.75±0.19 mas[1]
Distance303 ± 5 ly
(93 ± 2 pc)
Absolute magnitude (MV)−1.218[6]
Details
Mass1.7±0.1[7] M☉
Radius51.7±1[8] R☉
Luminosity677±41[8] L☉
Surface gravity (log g)1.28±0.04[7] cgs
Temperature4,094±53[8] K
Metallicity [Fe/H]−0.29±0.06[7] dex
Rotational velocity (v sin i)3.7±0.8[7] km/s
Age1.85±0.34[7] Gyr
Other designations
Tarf, β Cancri, 17 Cancri, BD+09°1917, FK5 312, GC 11254, HD 69267, HIP 40526, HR 3249, SAO 116569, ADS 6704, CCDM 08165+0911, WDS J08165+0911A[9]
Database references
SIMBADdata

Beta Cancri is the brightest star in the zodiacal constellation of Cancer. The star has the proper name Tarf, pronounced /ˈtɑːrf/;[10] Beta Cancri is its Bayer designation. It is visible to the naked eye with an apparent visual magnitude of +3.5,[2] and has an absolute magnitude of −1.2.[6] Based on parallax measurements, it is 303 light-years distant from the Solar System.[1] It is drifting further away with a line of sight velocity of 23 km/s.[5] An exoplanet, designated Beta Cancri b, is believed to be orbiting the star.[7]

Beta Cancri has a visual companion listed and together they are designated WDS J08165+0911. However, it is not certain if the companion is gravitationally bound or not.[11] As the primary, Beta Cancri bears the designation WDS J08165+0911A.[9] The companion is designated WDS J08165+0911B.[12]

Nomenclature

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β Cancri (Latinised to Beta Cancri) is the star's Bayer designation. This designation is Latinized from β Cancri and is abbreviated Beta Cnc or β Cnc. WDS J08165+0911A is its designation in the Washington Double Star Catalog.[9]

The star bore the traditional name of Al Tarf (anglicized as Altarf[13]), which can be translated from the Arabic as "end" or "edge".[14] In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN approved the name Tarf for Beta Cancri on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.[10]

Properties

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A light curve for Beta Cancri, plotted from Hipparcos data[16]

Beta Cancri is an orange K-type giant with a stellar classification of K4III Ba1.[3] The suffix notation indicates this is a Barium star, a type of cool giant showing enhanced abundances of barium.[17] At an estimated age of 1.9 billion years, it has 1.7 times the mass of the Sun[7] and has expanded to 52 times the Sun's radius. The star is radiating around 677 times the luminosity of the Sun from its photosphere at an effective temperature of 4,094 K.[8]

This star is suspected to vary slightly in brightness.[2] Koen and Laurent analyzed the Hipparcos data for Beta Cancri and found in that data set its brightness varied with an amplitude of 0.0054 magnitudes over a period of 6.00565 days.[18]

The co-moving companion is a red dwarf of the fourteenth magnitude.[14] From its angular separation of 29.5 arcseconds, the companion's distance from Beta Cancri is at least 2,740 AU.[11] If they form a binary system, then the orbital period is at least 76,000 years.[14]

Planetary system

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In 2014 evidence was presented of a planet orbiting Beta Cancri. Using radial velocity data from repeated observations of the star, the planet is estimated to have a minimum mass of approximately 7.8 times that of Jupiter, and an orbital period of 605 days.[7]

The Beta Cancri planetary system[19]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b 7.8±0.8 MJ 1.7±0.1 605.2±4.0 0.08±0.02 — —

See also

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References

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  1. ^ a b c d e 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.
  2. ^ a b c d Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ^ a b Lu, Phillip K. (1991). "Taxonomy of barium stars". Astronomical Journal. 101: 2229. Bibcode:1991AJ....101.2229L. doi:10.1086/115845.
  4. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. ^ a b Famaey, B.; et al. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. arXiv:astro-ph/0409579. Bibcode:2005A&A...430..165F. doi:10.1051/0004-6361:20041272. S2CID 17804304.
  6. ^ a b Cassatella, A.; et al. (2001). "On the Wilson-Bappu relationship in the Mg II k line". Astronomy and Astrophysics. 374 (3): 1085–1091. arXiv:astro-ph/0106070. Bibcode:2001A&A...374.1085C. doi:10.1051/0004-6361:20010816. S2CID 16286422.
  7. ^ a b c d e f g h Lee, B.-C.; et al. (2014). "Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris". Astronomy & Astrophysics. 566: A67. arXiv:1405.2127. Bibcode:2014A&A...566A..67L. doi:10.1051/0004-6361/201322608. S2CID 118631934.
  8. ^ a b c d Baines, Ellyn K.; et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155 (1): 30. arXiv:1712.08109. Bibcode:2018AJ....155...30B. doi:10.3847/1538-3881/aa9d8b. S2CID 119427037.{{cite journal}}: CS1 maint: postscript (link)
  9. ^ a b c "bet Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-06-26.
  10. ^ a b "Naming Stars". IAU.org. Retrieved 18 June 2018.
  11. ^ a b Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (January 2022). "Stellar and substellar companions from Gaia EDR3. Proper-motion anomaly and resolved common proper-motion pairs". Astronomy and Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. ISSN 0004-6361.
  12. ^ "UCAC4 496-050758 -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2018-06-26.
  13. ^ Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
  14. ^ a b c Kaler, James B. "AL TARF (Beta Cancri)". Stars. University of Illinois. Retrieved 2010-02-23.
  15. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  16. ^ "Light Curve". Hipparcos ESA. ESA. Retrieved 17 February 2022.
  17. ^ Gomez, A. E.; et al. (1997). "Absolute magnitudes and kinematics of barium stars". Astronomy and Astrophysics. 319: 881. Bibcode:1997A&A...319..881G.
  18. ^ Koen, Chris; Laurent, Eyer (March 2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331 (1): 45–59. arXiv:astro-ph/0112194. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x.
  19. ^ "Notes on beta Cnc b". Extrasolar Planets Encyclopaedia. Retrieved 28 February 2017.