Iota Boötis

Iota Boötis (ι Boo, ι Boötis) is a member of a binary star system in the constellation Boötes, approximately 96 light-years from Earth. It has the traditional name Asellus Secundus /əˈsɛləs sɪˈkʌndəs/ (Latin for "second donkey colt") and the Flamsteed designation 21 Boötis. The companion is HD 234121, a K0 main sequence star.

ι Boötis
Location of ι Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes
Right ascension 14h 16m 09.92976s[1]
Declination +51° 22′ 02.0287″[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: −149.277[1] mas/yr
Dec.: +89.135[1] mas/yr
Parallax (π)33.8856 ± 0.0820 mas[1]
Distance96.3 ± 0.2 ly
(29.51 ± 0.07 pc)
Absolute magnitude (MV)+2.38[7]
Details
Mass1.81[4] M☉
Radius1.7[1] R☉
Luminosity8.8[1] L☉
Surface gravity (log g)4.14[1] cgs
Temperature7,764[1] K
Metallicity [Fe/H]+0.19[8] dex
Rotational velocity (v sin i)144[9] km/s
Age785[1] Myr
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.)

Components
ι Boötis and its nearby companion HD 234121 (the faint component C is also visible to the south)
A visual band light curve for Iota Boötis, adapted from Kiss (1995)[11]

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 7.3 main-sequence star belonging to spectral class K0V.[12][13] It is separated from ι Boo by 1,100 AU.[4] HD 234121 has a mass of 0.8 M☉, a luminosity of 0.4 L☉, a temperature of 5,090 K, and a radius of 0.8 R☉.[14]

The Washington Double Star Catalog lists a third component, a 14th-magnitude star at 90 arcseconds,[13] but it is an unrelated background star.[15]

Nomenclature

This star, along with the other Aselli (θ Boo and κ Boo) and λ Boo, were Aulād al Dhiʼbah (أولاد الضّباع - awlād al-ḍibā‘), "the Whelps of the Hyenas".[16]

In Chinese, 天槍 (Tiān Qiāng), meaning Celestial Spear, refers to an asterism consisting of ι Boötis, κ2 Boötis and θ Boötis.[17] Consequently, the Chinese name for ι Boötis itself is 天槍二 (Tiān Qiāng èr, English: the Second Star of Celestial Spear).[18]

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  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. S2CID 88503488.
  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. S2CID 55586789.
  10. Star Name - R.H. Allen p.105
  11. Kiss, L. L. (August 1995). "BV Photometry of the Delta Scuti Star iota Bootis". Information Bulletin on Variable Stars. 4237: 1. Bibcode:1995IBVS.4237....1K.
  12. Abt, H. A. (March 1981). "Visual multiples. VII - MK classifications". Astrophysical Journal Supplement Series. 45: 437–456. Bibcode:1981ApJS...45..437A. doi:10.1086/190719.
  13. 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.
  14. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  15. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  16. 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.
  17. (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.
  18. (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.
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