9 Aurigae

9 Aurigae (9 Aur) is a star system in Auriga (constellation). It has an apparent magnitude of about 5, making it visible to the naked eye in many suburban skies.[15] Parallax estimates made by the Hipparcos spacecraft put it at about 86 light-years (26 parsecs) from the solar system,[1] although individual Gaia Data Release 3 parallaxes place all three components at 88 light years.

A visual band light curve for 9 Aurigae, adapted from Krisciunas et al. (1993)[16]
9 Aurigae
Location of 9 Aurigae (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Auriga
Right ascension 05h 06m 40.62967s[1]
Declination +51° 35′ 51.8025″[1]
Apparent magnitude (V) 4.93 - 5.03[2]
Characteristics
Spectral type F2V[3]
U−B color index -0.03[4]
B−V color index +0.34[4]
Variable type γ Dor[5]
Astrometry
A
Radial velocity (Rv)−0.47±0.57[6] km/s
Proper motion (μ) RA: −28.557[6] mas/yr
Dec.: −171.822[6] mas/yr
Parallax (π)37.0551 ± 0.1371 mas[6]
Distance88.0 ± 0.3 ly
(26.99 ± 0.10 pc)
B
Proper motion (μ) RA: −54.582[7] mas/yr
Dec.: −156.009[7] mas/yr
Parallax (π)37.0796 ± 0.0631 mas[7]
Distance88.0 ± 0.1 ly
(26.97 ± 0.05 pc)
C
Radial velocity (Rv)−1.88±0.17[7] km/s
Proper motion (μ) RA: −32.386[8] mas/yr
Dec.: −173.026[8] mas/yr
Parallax (π)37.2115 ± 0.0184 mas[8]
Distance87.65 ± 0.04 ly
(26.87 ± 0.01 pc)
Orbit[9]
Period (P)391.7 d
Eccentricity (e)0.37
Semi-amplitude (K1)
(primary)		5.8 km/s
Details
A
Mass1.97[10] M☉
Radius1.56[5] R☉
Luminosity6.042[11] L☉
Surface gravity (log g)4.07[5] cgs
Temperature7,023[5] K
Metallicity [Fe/H]−0.12[5] dex
Rotational velocity (v sin i)21.0[5] km/s
B
Mass0.49[10] M☉
Temperature4,947[12] K
C
Mass0.751[13] M☉
Radius0.756[13] R☉
Luminosity0.162[14] L☉
Temperature4,633[14] K
Other designations
V398 Aur, BD+51°1024, GJ 9174, HD 32537, HIP 23783, HR 1637, SAO 25019
Database references
SIMBAD9 Aur A
9 Aur B
9 Aur C

It is a well-studied Gamma Doradus variable,[5] and was one of the first stars to be so-classified.[17] This star type varies in luminosity due to non-radial pulsations.[17] Its apparent magnitude varies from 4.93 to 5.03 over a period of 1.25804 days.[2] For that reason it has been given the variable star designation V398 Aurigae.[2]

9 Aurigae is a multiple star system. The naked-eye component A is a single-lined spectroscopic binary. Only the signature of an F-type main sequence star can be seen in the spectrum, but the periodic doppler shift of the absorption lines demonstrates that there is a hidden companion in a 391.7-day orbit. The gravitational interaction of the two bodies produces variations in their respective motions, which is what creates the doppler shift.[9]

Four other companions to 9 Aurigae are listed in multiple star catalogs.[18][19] The closest companion is a 12th-magnitude red dwarf 5″ away.[5] 90″ away is component C, a 9th-magnitude star with a spectral class of K5Ve,[20] which may also be a spectroscopic binary.[10] Further-separated still is a 14th-magnitude star, component D, proposed to be a more distant red giant,[21] although Gaia astrometry places it at a similar distance and with a similar proper motion.[22] The most widely-separated companion is component E, a distant unrelated star.[21][23]

References
  1. van Leeuwen, F.; et al. (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. 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. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
  4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  5. Rachford, Brian L.; Foight, Dillon R. (2009). "Chromospheric Variability in Early F-Type Stars". The Astrophysical Journal. 698 (1): 786–802. arXiv:0904.1620. Bibcode:2009ApJ...698..786R. doi:10.1088/0004-637X/698/1/786. S2CID 693296.
  6. 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.
  7. 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.
  8. 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.
  9. Abt, Helmut A. (1965). "The Frequency of Binaries among Normal A-Type Stars". The Astrophysical Journal Supplement Series. 11: 429. Bibcode:1965ApJS...11..429A. doi:10.1086/190120.
  10. "HR 1637". Multiple Star Catalog. Archived from the original on 2020-09-16. Retrieved 2019-10-09.
  11. 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.
  12. 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.
  13. Newton, Elisabeth R.; Irwin, Jonathan; Charbonneau, David; Berlind, Perry; Calkins, Michael L.; Mink, Jessica (2017). "The Hα Emission of Nearby M Dwarfs and its Relation to Stellar Rotation". The Astrophysical Journal. 834 (1): 85. arXiv:1611.03509. Bibcode:2017ApJ...834...85N. doi:10.3847/1538-4357/834/1/85. S2CID 55000202.
  14. 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.
  15. Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 15 May 2017.
  16. Krisciunas, K.; Aspin, C.; Geballe, T. R.; Akazawa, H.; Claver, C. F.; Guinan, E. F.; Landis, H. J.; Luedeke, K. D.; Ohkura, N.; Ohshima, O.; Skillman, D. R. (August 1993). "The 9 Aurigae system". Monthly Notices of the Royal Astronomical Society. 263 (3): 781–788. arXiv:astro-ph/9304008. Bibcode:1993MNRAS.263..781K. doi:10.1093/mnras/263.3.781.
  17. Krisciunas, K.; Griffin, R. F.; Guinan, E. F.; Luedeke, K. D.; McCook, G. P. (1995). "9 Aurigae: Strong evidence for non-radial pulsations". Monthly Notices of the Royal Astronomical Society. 273 (3): 662. arXiv:astro-ph/9407094. Bibcode:1995MNRAS.273..662K. doi:10.1093/mnras/273.3.662. S2CID 117588180.
  18. Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. De l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.
  19. 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.
  20. Alonso-Floriano, F. J.; Morales, J. C.; Caballero, J. A.; Montes, D.; Klutsch, A.; Mundt, R.; Cortés-Contreras, M.; Ribas, I.; Reiners, Ansgar; Amado, P. J.; Quirrenbach, A.; Jeffers, S. V. (2015). "CARMENES input catalogue of M dwarfs". Astronomy & Astrophysics. 577: A128. arXiv:1502.07580. Bibcode:2015A&A...577A.128A. doi:10.1051/0004-6361/201525803. S2CID 53135130.
  21. Krisciunas, K.; Aspin, C.; Geballe, T. R.; Akazawa, H.; Claver, C. F.; Guinan, E. F.; Landis, H. J.; Luedeke, K. D.; Ohkura, N.; Ohshima, O.; Skillman, D. R. (1993). "The 9 Aurigae system". Monthly Notices of the Royal Astronomical Society. 263 (3): 781–788. arXiv:astro-ph/9304008. Bibcode:1993MNRAS.263..781K. doi:10.1093/mnras/263.3.781. S2CID 18596475.
  22. 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.
  23. 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.
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