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9 Persei
	Location of 9 Persei (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Perseus
Right ascension	02h 22m 21.43482s
Declination	55° 50′ 44.3518″
Apparent magnitude (V)	5.15 - 5.25
Characteristics
Spectral type	A2 Ia
U−B color index	−0.11
B−V color index	+0.37
Variable type	α Cyg
Astrometry
Radial velocity (Rv)	−15.20 km/s
Proper motion (μ)	RA: +0.374 mas/yr ; Dec.: −1.798 mas/yr
Parallax (π)	0.7603 ± 0.1139 mas
Distance	approx. 4,300 ly ; (approx. 1,300 pc)
Absolute magnitude (MV)	−4.73
Details
Mass	10.5 M☉
Radius	88.9+3.8; −2.8 R☉
Luminosity	12,331±2,189 L☉
Surface gravity (log g)	1.74 cgs
Temperature	9,840 K
Metallicity [Fe/H]	+0.26 dex
Rotational velocity (v sin i)	25 km/s
Other designations
	i Persei, 9 Per, V474 Per, BD+55°598, FK5 2159, GC 2836, HD 14489, HIP 11060, HR 685, SAO 23256, CCDM J02224+5551A, WDS J02224+5551A
Database references
SIMBAD	data

9 Persei is a single^[11] variable star in the northern constellation Perseus, located around 4,300 light years away from the Sun. It has the Bayer designation i Persei; 9 Persei is the Flamsteed designation. This body is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of about 5.2. It is moving closer to the Sun with a heliocentric radial velocity of −15.2 km/s.^[5] The star is a member of the Perseus OB1 association of co-moving stars.^[12]

A light curve for V474 Persei. The main plot shows the variation over a year, and the inset plot shows the same data folded over the best-fit period. The data was published by Burggraaff *et al.* (2018)^[13]

This is a blue supergiant with a stellar classification of A2 Ia,^[3] a massive star that has used up its core hydrogen and is now fusing heavier elements. It is an Alpha Cygni variable (designated V474 Persei), a type of non-radial pulsating variable. It ranges in magnitude from 5.15 down to 5.25.^[14] The star has 10.5^[7] times the mass of the Sun and has expanded to 89^[1] times the Sun's radius. It is radiating over 12,000^[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 9,840 K.^[9]

9 Persei has one visual companion, designated component B, at an angular separation of 12.3″ and magnitude 12.0.^[15]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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.
^ ^a ^b 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.
^ ^a ^b ^c Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
^ ^a ^b 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.
^ ^a ^b Wilson, R. E. (1953). "General Catalogue of Stellar Radial Velocities". Carnegie Institute Washington D.C. Publication. Carnegie Institution for Science. Bibcode:1953GCRV..C......0W. ISBN 9780598216885. LCCN 54001336.
^ Huang, W.; et al. (2012), "A catalogue of Paschen-line profiles in standard stars", Astronomy & Astrophysics, 547: A62, arXiv:1210.7893, Bibcode:2012A&A...547A..62H, doi:10.1051/0004-6361/201219804, S2CID 119286159.
^ ^a ^b Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (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. Vizier catalog entry
^ ^a ^b Wu, Yue; Singh, H. P.; Prugniel, P.; Gupta, R.; Koleva, M. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014. S2CID 53480665.
^ ^a ^b Zorec, J.; Cidale, L.; Arias, M. L.; Frémat, Y.; Muratore, M. F.; Torres, A. F.; Martayan, C. (2009). "Fundamental parameters of B supergiants from the BCD system". Astronomy and Astrophysics. 501 (1): 297–320. arXiv:0903.5134. Bibcode:2009A&A...501..297Z. doi:10.1051/0004-6361/200811147. S2CID 14969137.
^ "9 Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 26, 2019.
^ Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
^ Lee, Hsu-Tai; Lim, Jeremy (June 2008). "On the Formation of Perseus OB1 at High Galactic Latitudes". The Astrophysical Journal. 679 (2): 1352–1363. arXiv:0804.4520. Bibcode:2008ApJ...679.1352L. doi:10.1086/587801. S2CID 14252530.
^ Burggraaff, O.; Talens, G. J. J.; Spronck, J.; Lesage, A. L.; Stuik, R.; Otten, G. P. P. L.; Van Eylen, V.; Pollacco, D.; Snellen, I. A. G. (September 2018). "Studying bright variable stars with the Multi-site All-Sky CAmeRA (MASCARA)". Astronomy and Astrophysics. 617: A32. arXiv:1806.02247. Bibcode:2018A&A...617A..32B. doi:10.1051/0004-6361/201833142.
^ Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ 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. Vizier catalog entry