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KS Persei
	; A light curve for KS Persei, plotted from Hipparcos data
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Perseus
Right ascension	04h 48m 53.348s
Declination	43° 16′ 32.09″
Apparent magnitude (V)	7.70
Characteristics
Spectral type	A5Iap + B2/3Ia/Ib
B−V color index	0.423±0.019
Variable type	Semiregular
Astrometry
Proper motion (μ)	RA: 1.600 mas/yr ; Dec.: −1.781 mas/yr
Parallax (π)	0.1004 ± 0.0414 mas
Distance	< 3,200 ly ; (< 1,000 pc)
Absolute magnitude (MV)	−3.3
Orbit
Period (P)	360.47±1.07 d
Semi-major axis (a)	≥243 ± 8 Gm (1.624 ± 0.053 AU)
Eccentricity (e)	0.28±0.03
Periastron epoch (T)	2,435,141.74±5.06 JD
Argument of periastron (ω); (secondary)	268.4±4.8°
Semi-amplitude (K1); (primary)	51.4±1.6 km/s
Details
Supergiant
Mass	1.0 (assumed) M☉
Luminosity	2,000 L☉
Surface gravity (log g)	2.0±0.5 cgs
Temperature	9,500±300 K
Metallicity [Fe/H]	−0.73±0.10 dex
Companion
Mass	5 (times the primary mass) M☉
Temperature	12,500 K
Other designations
	Bidelman's Star, KS Per, AG+43 500, BD+43 1069, HD 30353, HIP 22365, SAO 39773
Database references
SIMBAD	data

KS Persei is a binary system in the equatorial constellation of Perseus. It is sometimes known as Bidelman's Star, named after William P. Bidelman.^[11]^[3] The star is invisible to the naked eye with a mean apparent visual magnitude of 7.70.^[3] As of 2018, the structure and evolutionary history of this system remain uncertain, although some form of mass transfer is likely to have occurred to explain the observed properties.^[12]

The peculiar nature of the spectra for this star was noted in the Henry Draper Catalogue and was the subject of a study by W. P. Bidelman published in 1950. He found extremely weak lines of hydrogen, similar to those for Upsilon Sagittarii but at a lower temperature. The data strongly suggested the star has an abnormally low abundance of hydrogen in the stellar atmosphere. Bidelman noted that the radial velocity of the star is variable, demonstrating that it has an unseen companion.^[13] Preliminary orbital elements for this single-lined spectroscopic binary were published in 1955 by J. F. Heard and O. Boshko, giving an orbital period of 359.7 days and with eccentricity of 0.27. They found a large mass function of 4.5, suggesting that the supergiant has lost mass and the companion is relatively massive.^[14] The mass function was revised to 3.6±0.4 in 1988, suggesting the secondary is five times more massive than the primary.^[7] Although the Gaia parallax is small (and the Hipparcos parallax is negative), KS Persei is thought to be less than 1,000 pc away. Older studies have suggested distances up to 3,900 pc.^[7]

An analysis by G. Wallerstein and associates in 1967 showed that nitrogen is the second most abundant element in the primary, likely as a result of carbon cycling.^[15] G. A. Bakos attempted to photometrically detect an eclipse but was unsuccessful. However, he did tentatively detect semiregular variation with a period of ~30 days and an amplitude of 0.1 magnitude. This variability was confirmed by K. Morrison and G. P. H. Willingale in 1987, and they discovered an additional five day cycle.^[16] In 1982, J. S. Drilling and D. Schönberner detected a hot companion from spectra collected by the International Ultraviolet Explorer.^[5] The system is an infrared source, and models of the infrared flux suggest it is being emitted by circumstellar dust heated to 1,100 K.^[7] It is possible that the companion is obscured by dust.^[9]

References

^ EAS (1997). "The HIPPARCOS and TYCHO catalogues". Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. ESA SP Series. 1200. Noordwijk, Netherlands: ESA Publications Division. Bibcode:1997ESASP1200.....E. ISBN 9290923997. Retrieved 15 October 2022.
^ ^a ^b ^c ^d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
^ ^a ^b ^c ^d Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
^ Boulon, J.; Fehrenbach, C.; Duflot, A.; Rebeirot, E.; Petit, M. (1959), "La mesure des vitesses radiales au prisme objectif - X - 4e liste de vitesses radiales déterminées au prisme objectif à vision directe", Journal des Observateurs, 42: 149, Bibcode:1959JO.....42..149B.
^ ^a ^b Drilling, J. S.; Schonberner, D. (September 1982), "The hot component of KS Per (HD 30353)", Astronomy and Astrophysics, 113: L22 – L23, Bibcode:1982A&A...113L..22D.
^ Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ ^a ^b ^c ^d ^e ^f ^g ^h Kipper, Tõnu; Klochkova, Valentina G. (2008), "Improved Parameters of the Hydrogen-Deficient Binary Star KS Per", Baltic Astronomy, 17: 195–207, arXiv:0806.2709, Bibcode:2008BaltA..17..195K.
^ Heard, John Frederick (1962), "The spectroscopic orbit of Bidelman's peculiar star H.D. 30353", Publications of the David Dunlap Observatory, 2 (9), Toronto, Canada: University of Toronto Press: 269–277, Bibcode:1962PDDO....2..269H.
^ ^a ^b ^c ^d Parthasarathy, M.; et al. (June 2007), "Progenitors of type Ia supernovae: Binary stars with white dwarf companions", New Astronomy Reviews, 51 (5–6): 524–538, arXiv:astro-ph/0703415, Bibcode:2007NewAR..51..524P, doi:10.1016/j.newar.2007.03.001, S2CID 18539861.
^ Gáspár, András; et al. (2016), "The Correlation between Metallicity and Debris Disk Mass", The Astrophysical Journal, 826 (2): 171, arXiv:1604.07403, Bibcode:2016ApJ...826..171G, doi:10.3847/0004-637X/826/2/171, S2CID 119241004.
^ ^a ^b "KS Per", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-26.
^ Hall, Philip D.; Jeffery, C. (April 2018), "The positive binding energy envelopes of low-mass helium stars", Monthly Notices of the Royal Astronomical Society, 475 (3): 3889–3895, Bibcode:2018MNRAS.475.3889H, doi:10.1093/mnras/sty055.
^ Bidelman, William P. (March 1950), "The Peculiar Star HD 30353", Astrophysical Journal, 111: 333, Bibcode:1950ApJ...111..333B, doi:10.1086/145268.
^ Heard, J. F.; Boshko, O. (June 1955), "The orbital elements of the hydrogen-poor spectroscopic binary HD 30353", Astronomical Journal, 60: 162, Bibcode:1955AJ.....60..162H, doi:10.1086/107194.
^ Wallerstein, George; et al. (October 1967), "Abundances of the Light Elements in the Hydrogen-Poor Star HD 30353", Astrophysical Journal, 150: 245, Bibcode:1967ApJ...150..245W, doi:10.1086/149326.
^ Morrison, K.; Willingale, G. P. H. (October 1987), "The photometric variability of the extremely hydrogen-deficient stars KS Persei and LSII +33 5", Monthly Notices of the Royal Astronomical Society, 228 (4): 819–825, Bibcode:1987MNRAS.228..819M, doi:10.1093/mnras/228.4.819.