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.[13] Parallax estimates made by the Hipparcos spacecraft put it at about 85.7 light-years (26.3 parsecs) from the solar system.[1]

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
Radial velocity (Rv)-0.90 ± 0.3[6] km/s
Proper motion (μ) RA: -30.49[1] mas/yr
Dec.: -172.89[1] mas/yr
Parallax (π)38.04 ± 0.34[1] mas
Distance85.7 ± 0.8 ly
(26.3 ± 0.2 pc)
Orbit[7]
Period (P)391.7 d
Eccentricity (e)0.37
Semi-amplitude (K1)
(primary)		5.8 km/s
Details
A
Mass1.97[8] M☉
Radius1.56[5] R☉
Luminosity6.042[9] 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[8] M☉
Temperature4,947[10] K
C
Mass0.751[11] M☉
Radius0.756[11] R☉
Luminosity0.162[12] L☉
Temperature4,633[12] 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.[14] This star type varies in luminosity due to non-radial pulsations.[14] 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.[7]

Four other companions to 9 Aurigae are listed in multiple star catalogs,[15][16] all thought to be common proper motion companions at the same distance from us as 9 Aurigae.[7][10][12][17] 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,[18] which may also be a spectroscopic binary.[8] Further-separated still is a 14th-magnitude star, component D, thought to be a more distant red giant.[19][17] The most widely-separated companion is component E, another distant star.[19][20]

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.
  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....1.2025S.
  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: 161. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637.
  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: 786. arXiv:0904.1620. Bibcode:2009ApJ...698..786R. doi:10.1088/0004-637X/698/1/786.
  6. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065.
  7. 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.
  8. "HR 1637". Multiple Star Catalog. Retrieved 2019-10-09.
  9. 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.
  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. Gaia DR2 record for this source at VizieR.
  11. 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.
  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. Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale". Sky & Telescope. Sky Publishing Corporation. Retrieved 15 May 2017.
  14. 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.
  15. 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.
  16. 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.
  17. 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.
  18. Alonso-Floriano, F. J.; Morales, J. C.; Caballero, J. A.; Montes, D.; Klutsch, A.; Mundt, R.; Cortés-Contreras, M.; Ribas, I.; Reiners, A.; Amado, P. J.; Quirrenbach, A.; Jeffers, S. V. (2015). "CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS". Astronomy and Astrophysics. 577: A128. arXiv:1502.07580. Bibcode:2015A&A...577A.128A. doi:10.1051/0004-6361/201525803.
  19. 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.
  20. 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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