41 Lyncis

41 Lyncis (abbreviated 41 Lyn), also designated HD 81688 and named Intercrus /ˈɪntərkrʌs/, is a fifth magnitude star located in the northern constellation of Ursa Major. An extrasolar planet (designated 41 Lyncis b or HD 81688 b, later named Arkas) is thought to be orbiting the star.

41 Lyncis

Location of 41 Lyncis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Pronunciation /ˈɪntərkrʌs/,[1]
Right ascension 09h 28m 39.9889s[2]
Declination +45° 36′ 05.3353″[2]
Apparent magnitude (V) 5.413[3]
Characteristics
Spectral type K0 III[4]
U−B color index 0.74
B−V color index 0.983[5]
Astrometry
Radial velocity (Rv)+38.44[5] km/s
Proper motion (μ) RA: −7.297±0.140[2] mas/yr
Dec.: −129.582±0.130[2] mas/yr
Parallax (π)11.6388 ± 0.1063[2] mas
Distance280 ± 3 ly
(85.9 ± 0.8 pc)
Absolute magnitude (MV)0.675[5]
Details
Mass2.07+0.14
−0.16[6] M☉
Radius11[7] R☉
Luminosity55[7] L☉
Surface gravity (log g)2.30[5] cgs
Temperature4789[5] K
Metallicity [Fe/H]–0.23[5] dex
Rotational velocity (v sin i)[7] km/s
Age4.07±2.24[5] Gyr
Other designations
Intercrus, BD+46°1509, CCDM J09287+4536, GC 13051, HD 81688, HIP 46471, HR 3743, SAO 42876[3]
Database references
SIMBADThe star
planet b

Properties

It is estimated using parallax measurements to be approximately 280 light-years (86 parsecs) from the Sun.[2] The spectrum of this star matches a stellar classification of K0 III,[4] with the luminosity class of III suggesting it is a giant star. This star has about double the mass of the Sun, although a re-evaluation of evolutionary tracks published in 2011 gives a lower estimate of 1.1+0.3
−0.2 solar masses.[6] It has expanded to 11 times the Sun's radius and is radiating 55 times as much as the Sun from its outer atmosphere at an effective temperature of 4,789 K.[7] This temperature gives it the orange-hued glow of a K-type star.[8]

This star is following an orbit through the Milky Way with an eccentricity of 0.21. This will take it as close to the Galactic Center as 18.5 kly (5.7 kpc) and as far as 28.2 kly (8.6 kpc). The inclination of this orbit will carry it as much as 1,800 ly (550 pc) away from the galactic plane. For this reason, it is uncertain whether this star is a member of the thin disk population.[5]

41 Lyncis is listed in the Washington Double Star Catalog as having two visual companions, the 8th magnitude F-type subgiant HD 81704 72″ away, and an 11th magnitude star 84″ away.[9] Both are background objects, more distant than 41 Lyncis itself, but the two share a common proper motion and are at the same distance as each other.[10]

Nomenclature

41 Lyncis is the Flamsteed designation.[11] Typically, 'Lyncis' is the genitive for a star found in the constellation of Lynx. However, when the constellation boundaries were officially established by the International Astronomical Union in 1930, this star was located within Ursa Major. HD 81688 is the entry in the Henry Draper Catalogue. Following its discovery the planet was designated 41 Lyncis b or alternatively HD 81688 b.

In July 2014 the IAU launched a process for giving proper names to certain exoplanets and their host stars.[12] The process involved public nomination and voting for the new names.[13] In December 2015, the IAU announced the winning names were Intercrus for this star and Arkas for its planet.[14] The winning names were those submitted by the Okayama Astro Club of Japan. Intercrus means "between the legs" in Latin style, referring to the star's position in the constellation Ursa Major. Arkas was the son of Callisto (Ursa Major) in Greek mythology.[15]

The International Astronomical Union Working Group on Star Names (WGSN) has approved the proper name Intercrus for 41 Lyncis.[16]

Planetary system

On 19 February 2008 a planet was announced orbiting the star. It has a minimum mass 2.7 times that of Jupiter and completes an orbit every 184 days.[17]

The 41 Lyncis planetary system[17]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (Arkas) >2.7 MJ 0.81 184.02 ± 0.18 0 (fixed) — —

References
  1. "inter-, crus". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  2. 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. Gaia DR2 record for this source at VizieR.
  3. "* 41 Lyn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-03-25.
  4. Sato, K.; Kuji, S. (1990), "MK classification and photometry of stars used for time and latitude observations at Mizusawa and Washington", Astronomy and Astrophysics Supplement Series, 85: 1069, Bibcode:1990A&AS...85.1069S
  5. Soubiran, C.; et al. (2008), "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants", Astronomy and Astrophysics, 480 (1): 91–101, arXiv:0712.1370, Bibcode:2008A&A...480...91S, doi:10.1051/0004-6361:20078788, S2CID 16602121
  6. Kunitomo, M.; et al. (August 2011), "Planet Engulfment by ~1.5-3 M sun Red Giants", The Astrophysical Journal, 737 (2): 66, arXiv:1106.2251, Bibcode:2011ApJ...737...66K, doi:10.1088/0004-637X/737/2/66, S2CID 119208821
  7. Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209
  8. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 10, 2012, retrieved 2012-01-16
  9. Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001), "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog", The Astronomical Journal, 122 (6): 3466–3471, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
  10. 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.
  11. Kostjuk, N. D. (April 2004), "HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index (Kostjuk, 2002)", VizieR On-line Data Catalog: IV/27A, Institute of Astronomy of Russian Academy of Sciences, Bibcode:2004yCat.4027....0K
  12. NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars. IAU.org. 9 July 2014
  13. NameExoWorlds The Process
  14. Final Results of NameExoWorlds Public Vote Released, International Astronomical Union, 15 December 2015.
  15. NameExoWorlds The Approved Names
  16. "IAU Catalog of Star Names", International Astronomical Union, retrieved 28 July 2016
  17. Sato, Bun'ei; et al. (2008), "Planetary Companions around Three Intermediate-Mass G and K Giants: 18 Delphini, ξ Aquilae and HD 81688", Publications of the Astronomical Society of Japan, 60 (3): 539–550, arXiv:0802.2590, Bibcode:2008PASJ...60..539S, doi:10.1093/pasj/60.3.539, S2CID 18806627

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