Iota Aurigae

Iota Aurigae (ι Aurigae, abbreviated Iota Aur, ι Aur), officially named Hassaleh /ˈhæsəleɪ/, is a star in the northern constellation of Auriga. It has an apparent visual magnitude of 2.7,[2] which is bright enough to be readily visible to the naked eye. Parallax measurements give a distance estimate of roughly 490 light-years (150 parsecs) from the Sun.

ι Aurigae
Location of ι Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 04h 56m 59.62109s[1]
Declination +33° 09′ 57.9585″[1]
Apparent magnitude (V) 2.69[2]
Characteristics
Spectral type K3 II[3]
U−B color index +1.78[2]
B−V color index +1.53[2]
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)+17.78[5] km/s
Proper motion (μ) RA: +6.79[1] mas/yr
Dec.: −14.88[1] mas/yr
Parallax (π)6.61 ± 0.38[1] mas
Distance490 ± 30 ly
(151 ± 9 pc)
Absolute magnitude (MV)−3.20[6]
Details
Mass7.1 ± 0.7[7] M☉
Radius127[8] R☉
Luminosity4,581[6] L☉
Surface gravity (log g)1.74[9] cgs
Temperature4,160[9] K
Metallicity [Fe/H]–0.11[9] dex
Rotational velocity (v sin i)8[10] km/s
Age39.8 ± 4.9[7] Myr
Other designations
Hassaleh, Kabdhilinan, ι Aur, 3 Aurigae, BD+32°855, FK5 181, GC 6029, HD 31398, HIP 23015, HR 1577, SAO 57522[11]
Database references
SIMBADdata

Nomenclature

ι Aurigae (Latinised to Iota Aurigae) is the star's Bayer designation.

It bore the traditional name Al Kab,[12] short for Kabdhilinan /kæbˈdɪlɪnæn/, from the Arabic كعب ذي العنان kaʽb ðīl-ʽinān[13][14] "the ankle[15] of the rein holder (charioteer)".[12] Under the name Alkab, this star is a marker on the astrolabe described by Geoffrey Chaucer in his Treatise on the Astrolabe in 1391.

It bore the novel name Hassaleh in Antonín Bečvář's 1951 atlas. The origin and meaning of the name have not been discovered despite extensive search, and no connection to any language has been discovered.[16] The IAU Working Group on Star Names (WGSN)has approved the proper name Hassaleh for this star.[17]

It is known as 五車一 (the First Star of the Five Chariots) in Chinese.[18]

Properties

At Iota Aurigae's distance, extinction from interstellar dust is causing a magnitude reduction of about 0.6.[12] Examination of the spectrum yields a stellar classification of K3 II,[3] with the luminosity class of 'II' indicating this is a category of evolved star known as a bright giant. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[19] The effective temperature of the outer envelope is 4,160 K,[9] which is cooler than the Sun's effective temperature and gives Iota Aurigae the orange hue of a K-type star.[20]

It is a weak X-ray emitter with an X-ray luminosity of about 1.8 × 1027 ergs s−1. This emission is most likely coming from transient loops of plasma in Iota Aurigae's outer atmosphere, which have a temperature of around 3 million K.[21] This is a suspected variable star, although this variability remains unconfirmed.[4]

Unconfirmed substellar companions

During the Extreme Solar Systems conference held on June 25–29, 2007, in Santorini, Greece, Reffert et al. announced the detection of two substellar objects orbiting Iota Aurigae in 2:1 resonance. Such companions would be brown dwarfs with orbital periods of approximately 2 and 4 years. No minimum mass for the candidates was provided. So far the detection has not been confirmed, though Hekker et al. (2008) listed significant radial velocity variations at periods of 767 and 1586 days.[22][23]

References
  1. 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
  2. Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory, 4 (99): 99, Bibcode:1966CoLPL...4...99J
  3. Morgan, W. W.; Keenan, P. C. (1973), "Spectral Classification", Annual Review of Astronomy and Astrophysics, 11: 29, Bibcode:1973ARA&A..11...29M, doi:10.1146/annurev.aa.11.090173.000333
  4. Strassmeier, K. G. (January 2008), "Stellar Activity with BRITE: the Aurigae field", Communications in Asteroseismology, 152: 124–130, Bibcode:2008CoAst.152..124S, doi:10.1553/cia152s124
  5. Famaey, B.; et al. (January 2005), "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters", Astronomy and Astrophysics, 430 (1): 165–186, arXiv:astro-ph/0409579, Bibcode:2005A&A...430..165F, doi:10.1051/0004-6361:20041272, S2CID 17804304
  6. 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
  7. Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (January 2011), "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun", Monthly Notices of the Royal Astronomical Society, 410 (1): 190–200, arXiv:1007.4883, Bibcode:2011MNRAS.410..190T, doi:10.1111/j.1365-2966.2010.17434.x, S2CID 118629873
  8. Harper, G. M. (1992), "The outer atmospheres of the 'hybrid' bright giants - The chromospheres of Alpha TrA (K4 II), IOTA AUR (K3 II), Gamma AQL (K3 II) and Theta HER (K1 II)", Monthly Notices of the Royal Astronomical Society, 256 (1): 37–64, arXiv:0809.0359, Bibcode:1992MNRAS.256...37H, doi:10.1093/mnras/256.1.37
  9. McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527, ISSN 0067-0049
  10. Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago, 239 (1): 1, Bibcode:1970CoAsi.239....1B
  11. "iot Aur -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-19
  12. Kaler, James B., "Al Kab", Stars, University of Illinois at Urbana-Champaign, archived from the original on 2008-12-10, retrieved 2012-01-18
  13. Allen, Richard Hinckley (1899), Star-names and their meanings, G. E. Stechert, p. 91
  14. عبد الرحمن بن عمر الصوفي (ʿAbd al-Raḥmān ibn ʿUmar al-Ṣūfī). صور الكواكب الثابتة (Ṣuwar al-Kawākib al-Thābitah: Book of Fixed Stars). Manuscript from the National Library of France.
  15. Translation of the Arabic word كعب to English on the Almaany dictionaries website.
  16. Kunitzsch, Paul; Smart, Tim (2006), A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.), Cambridge, Massachusetts: Sky Pub, ISBN 978-1-931559-44-7
  17. Naming Stars, IAU.org, retrieved 16 December 2017
  18. Ian Ridpath, "Auriga", Star Tales, retrieved 2019-10-10
  19. Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society, 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
  20. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16
  21. Kashyap, V.; et al. (August 1994), "X-ray emission on hybrid stars: ROSAT observations of alpha Trianguli Australis and IOTA Aurigae", The Astrophysical Journal, 431 (1): 402–415, Bibcode:1994ApJ...431..402K, doi:10.1086/174494
  22. Hekker, S.; et al. (2008), "Precise radial velocities of giant stars. IV. A correlation between surface gravity and radial velocity variation and a statistical investigation of companion properties", Astronomy and Astrophysics, 480 (1): 215–222, arXiv:0801.0741, Bibcode:2008A&A...480..215H, doi:10.1051/0004-6361:20078321, S2CID 33442610
  23. Reffert, S.; et al. (2008), "Two brown dwarfs in resonance around a K3II giant", Extreme Solar Systems, ASP Conference Series, Vol. 398, proceedings of the conference held 25–29 June 2007, at Santorini Island, Greece (PDF), p. 115, archived from the original (PDF) on 18 July 2011, retrieved 18 November 2009
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