Iota Boötis

Iota Boötis (ι Boo, ι Boötis) is a star system in the constellation Boötes. It has the traditional name Asellus Secundus /əˈsɛləs sɪˈkʌndəs/ (Latin for "second donkey colt") and the Flamsteed designation 21 Boötis. It is approximately 95 light years from Earth.

ι Boötis
Location of ι Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension  14h 16m 09.92995s[1]
Declination +51° 22′ 02.0267″[1]
Apparent magnitude (V) 4.75[2] (4.73 - 4.78[3])
Characteristics
Spectral type A7 V[4]
U−B color index +0.06[5]
B−V color index +0.20[5]
R−I color index +0.09[5]
Variable type Delta Scuti variable[3]
Astrometry
Radial velocity (Rv)−18.7[6] km/s
Proper motion (μ) RA: -149.39[1] mas/yr
Dec.: +88.72[1] mas/yr
Parallax (π)34.40 ± 0.19[1] mas
Distance94.8 ± 0.5 ly
(29.1 ± 0.2 pc)
Absolute magnitude (MV)+2.38[7]
Details
Mass1.81[4] M☉
Radius1.6[7] R☉
Luminosity9.6[7] L☉
Surface gravity (log g)4.3[7] cgs
Temperature8,000[7] K
Metallicity [Fe/H]+0.19[8] dex
Rotational velocity (v sin i)144[9] km/s
Other designations
Asellus Secondus,[10] 21 Boötis, BD+52°1784, FK5 528, HD 125161, HIP 69713, HR 5350, SAO 29071, Wo 9474, WDS J14162+5122
Database references
SIMBADdata
Data sources:
Hipparcos Catalogue,
CCDM (2002),
Bright Star Catalogue (5th rev. ed.)

Nomenclature

This star, along with the other Aselli (θ Boo and κ Boo) and λ Boo, were Aulād al Dhiʼbah (أولاد الضّباع - aulād al dhiʼb), "the Whelps of the Hyenas".[11]

In Chinese, 天槍 (Tiān Qiāng), meaning Celestial Spear, refers to an asterism consisting of ι Boötis, κ2 Boötis and θ Boötis.[12] Consequently,the Chinese name for ι Boötis itself is 天槍二 (Tiān Qiāng èr, English: the Second Star of Celestial Spear.)[13]

Components

Iota Boötis has a companion at an angular distance of 38.6 arcseconds, easily separated with binoculars.

The primary component is a white A-type main sequence dwarf with a mean apparent magnitude of +4.75. It is classified as a Delta Scuti type variable star and its brightness varies from magnitude +4.73 to +4.78 with a stable period of 38 minutes.[7]

The companion, HD 234121, is a magnitude +8.27 main sequence star belonging to spectral class K0.[14] It is separated from ι Boo by 1,100 AU.[4]

The Washington Double Star Catalog lists a third component, a 14th magnitude star at 90 arc seconds.[14]

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
  2. Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M
  3. 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.
  4. De Rosa, R. J.; Patience, J.; Wilson, P. A.; Schneider, A.; Wiktorowicz, S. J.; Vigan, A.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Doyon, R.; Bessell, M. S.; Thomas, S.; Lai, O. (2014). "The VAST Survey - III. The multiplicity of A-type stars within 75 pc". Monthly Notices of the Royal Astronomical Society. 437 (2): 1216. arXiv:1311.7141. Bibcode:2014MNRAS.437.1216D. doi:10.1093/mnras/stt1932.
  5. 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.
  6. Evans, D. S. (1967). "The Revision of the General Catalogue of Radial Velocities". Determination of Radial Velocities and their Applications. 30: 57. Bibcode:1967IAUS...30...57E.
  7. Kiss, L. L.; Alfaro, E. J.; Bakos, G.; Csak, B.; Szatmary, K. (1999). "On the monoperiodicity of the suspected delta Scuti star Iota Bootis". Information Bulletin on Variable Stars. 4698: 1. Bibcode:1999IBVS.4698....1K.
  8. Gray, R. O.; Graham, P. W.; Hoyt, S. R. (2001). "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence". The Astronomical Journal. 121 (4): 2159. Bibcode:2001AJ....121.2159G. doi:10.1086/319957.
  9. Zorec, J.; Royer, F. (2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691.
  10. Star Name - R.H.Allen p.105
  11. Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York: Dover Publications Inc, p. 105, ISBN 0-486-21079-0, retrieved 2010-12-12
  12. (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.
  13. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-11 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  14. 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. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
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